Prison abolition movement

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https://en.wikipedia.org/wiki/Prison_abolition_movement

The prison abolition movement is a network of groups and activists that seek to reduce or eliminate prisons and the prison system, and replace them with systems of rehabilitation and education that do not place a focus on punishment and government institutionalization. The prison abolitionist movement is distinct from conventional prison reform, which is the attempt to improve conditions inside prisons.

Some supporters of decarceration and prison abolition also work to end solitary confinement, the death penalty, and the construction of new prisons through non-reformist reform. Others support books-to-prisoner projects and defend the rights of prisoners to have access to information and library services. Some organizations, such as the Anarchist Black Cross, seek total abolishment of the prison system, without any intention to replace it with other government-controlled systems. Many anarchist organizations believe that the best form of justice arises naturally out of social contracts, restorative justice, or transformative justice.

Definition

Scholar Dorothy Roberts takes the prison abolition movement in the United States to endorse three basic theses:

1. "[T]oday’s carceral punishment system can be traced back to slavery and the racial capitalist regime it relied on and sustained."
2. "[T]he expanding criminal punishment system functions to oppress black people and other politically marginalized groups in order to maintain a racial capitalist regime."
3. "[W]e can imagine and build a more humane and democratic society that no longer relies on caging people to meet human needs and solve social problems."

Thus, Roberts situates the theory of prison abolition within an intellectual tradition including scholars such as Cedric Robinson, who developed the concept of racial capitalism, and characterizes the movement as a response to a long history of oppressive treatment of black people in the United States. In Canada, many abolitionists have called Canada's prisons the "new residential schools", which were designed as a cultural genocide of Indigenous people.

Legal scholar Allegra McLeod notes that prison abolition is not merely a negative project of "opening … prison doors", but rather "may be understood instead as a gradual project of decarceration, in which radically different legal and institutional regulatory forms supplant criminal law enforcement." Prison abolition, in McLeod's view, involves a positive agenda that reimagines how societies might deal with social problems in the absence of prisons, using techniques such as decriminalization and improved welfare provision.

Like Roberts, McLeod sees the contemporary theory of prison abolition as linked to theories regarding the abolition of slavery. McLeod notes that W. E. B. Du Bois—particularly in his Black Reconstruction in America—saw abolitionism not only as a movement to end the legal institution of property in human beings, but also as a means of bringing about a "different future" wherein former slaves could enjoy full participation in society. (Angela Davis explicitly took inspiration from Du Bois's concept of "abolition democracy" in her book Abolition Democracy: Beyond Empire, Prisons, and Torture.) Similarly, on McLeod's view, prison abolition implies broad changes to social institutions: "[a]n abolitionist framework", she writes, "requires positive forms of social integration and collective security that are not organized around criminal law enforcement, confinement, criminal surveillance, punitive policing, or punishment."

The abolition of prisons is not only about the closure of prisons. Abolitionist views is also a way to counter the hegemonic discourse, and gives an alternative ways of thinking. It is a way to reconceptualize basic notions like crime, innocence, punishment etc.

Historical development

Anarchism and prison abolition

Anarchist opposition to incarceration can be found in articles written as early as 1851, and is elucidated by major anarchist thinkers such as Proudhon, Bakunin, Berkman, Goldman, Malatesta, Bonano, and Kropotkin.

Personal experiences in prison because of revolutionary activity prompted many anarchists who were “deeply affected by their experiences” to publish their criticisms. In 1886, the trial of eight anarchists following the Haymarket riots brought state repression to public attention. Lucy Parsons, an anarchist and wife of one of the Haymarket eight, embarked on a speaking tour through 17 different states speaking to a total of almost 200,000 people. A single rally in Havana, Cuba, to support the families of the eight accused anarchists raised nearly $1000. Speaking at his trial, in a widely disseminated speech, one of the co-accused, August Spies, stated:

It is not likely that the honorable Bonfield and Grinnell can conceive of a social order not held intact by the policeman's club and pistol, nor of a free society without prisons, gallows, and State's attorneys. In such a society they probably fail to find a place for themselves. And is this the reason why Anarchism is such a "pernicious and damnable doctrine?"

The Anarchist Red Cross, a prisoner support group and the precursor to the Anarchist Black Cross, was founded roughly in 1906. By that year, groups existed in Kiev, Odessa, Bialystok, and trials of its members, led to its spread across Europe and North America. A 2018 guide to starting an Anarchist Black Cross group states that "we need to destroy all the prisons, and free all the prisoners. Our position is an abolitionist stance against the state and it’s prisons."

In 1917, the Anarchist Red Cross would disband and members joined the revolution in Russia. Following the February revolution, political prisoners were released from Russian jails, in a massive wave of amnesties. The Anarchist Red Cross reorganised in 1919 as the Anarchist Black Cross, with some members joining the anarchist insurgent, Nestor Makhno.

Makhno, a Ukrainian anarchist who was freed in 1917 from a life sentence in prison, organised a revolutionary insurgent army along anarchist principles that would come to control a territory of seven-and-a-half million people. Upon taking control of a town, Makhnovists would destroy “all remnants and symbols of slavery: prisons, police and gendarmerie posts were blown up with dynamite or put to the torch.” Prisoners in battle who were not officers were typically welcomed into the ranks of Makhnovists or freed. The Makhnovist revolutionary insurgent army adopted a declaration in 1919, stating

we are against all rigid judicial and police machinery, against any legislative code prescribed once and for all time, for these involve gross violations of genuine justice and of the real protections of the population. These ought not to be organized but should be instead the living, free and creative act of the community. Which is why all obsolete forms of justice — court administration, revolutionary tribunals, repressive laws, police or militia, Cheka, prisons and all other sterile and useless anachronisms — must disappear of themselves or be abolished from the very first breath of the free life, right from the very first steps of the free and living organization of society and the economy.

The Anarchist Black Cross was reconstituted in the aftermath of the Spanish Civil War and Anarchist Revolution. The pressure from the number of anarchist prisoners in need of aid led to the closing of “most of the chapters in the United States and Europe.” Alternative groups, such as the Alexander Berkman Aid Fund and the Society to Aid Anarchist Prisoners in Russia would take their place. Another resurgence was felt in 1967, and, again, in 1979 owing to the efforts of Lorenzo Kom’boa Ervin, whose writings on prison and anarchism are credited as having spread and been foundational to Black anarchism.

Anarchists agitation against prisons in Canada has included Bulldozer, an anti-prison anarchist project founded in Toronto in 1980. Bulldozer was closed after being raided and charged with sedition. The End the Prison Industrial Complex (Epic) was formed in 2009, and Anarchist Black Cross projects emerged throughout the 2000s. Anarchists and abolitionists within Québec organise yearly noise demonstrations outside of prison facilities on New Year's Eve. A campaign to stop the construction of a migrant prison involved anarchists unloading thousands of crickets into the offices of an architectural firm in 2018.

Campaigns to free anarchist prisoners have served as the basis for calling for freedom for all prisoners. June 11, 2011, international solidarity actions for anarchist prisoners Marie Mason and Eric McDavid triggered the start of an international day and week of solidarity with all anarchist prisoners in 2015. 2022's week of solidarity included actions in Poland, Russia, Ukraine, Uruguay, Greece, the UK, and other countries. The 2022-2023 hunger strike of anarchist prisoner Alfredo Cospito led to police skirmishes with protesters in Rome, a Turin cell tower being lit on fire, and a letter with bullets was sent to a newspaper stating "if Alfredo Cospito dies judges will all be targets, two months without food, burn down the prisons." International actions to free Cospito, included the burning of a Strabag excavator in Germany. The Italian placed their embassies on "alert" in response to mobilizations.

The Rojavan Revolution, which many have considered illustrative of, and rooted in, anarchist theory, involved the mass liquidation of prisons and freeing of political prisoners and nonviolent offenders. Neighbourhood based "peace committees," composed of elected community members with, largely, no formal legal education, were created to resolve conflicts using a model of consensus and restorative justice.

Prison Abolition and the New Left

Angela Davis traces the roots of contemporary prison abolition theory at least to Thomas Mathiesen's 1974 book The Politics of Abolition, which had been published in the wake of the Attica Prison uprising and unrest in European prisons around the same time. She also cites activist Fay Honey Knopp's 1976 work Instead of Prisons: A Handbook for Abolitionists as significant in the movement.

Eduardo Bautista Duran and Jonathan Simon point out that George Jackson's 1970 text Soledad Brother drew global attention to the conditions of prisons in the United States and made prison abolition a tenet of the New Left.

Liz Samuels observes that, following the Attica Prison uprising, activists began to coalesce around a vision of abolition, whereas previously they had endorsed a program of reform.

1973 Walpole Prison uprising

Main article: Walpole prison strike

In 1973, two years after the Attica Prison uprising, the inmates of Walpole prison, in Massachusetts, formed a prisoners' union to protect themselves from guards, end behavioral modification programs, advocate for the prisoner's right for education and healthcare, gain more visitation rights, work assignments, and to be able to send money to their families.

The union also created a general truce within the prison and race-related violence sharply declined. During the Kwanzaa celebration, black prisoners were placed under lockdown, angering the whole facility and leading to a general strike. Prisoners refused to work or leave their cells for three months, to which the guards responded by beating prisoners, putting prisoners in solitary confinement, and denying prisoners medical care and food.

The strike ended in the prisoners' favour as the superintendent of the prison resigned. The prisoners were granted more visitation rights and work programs. Angered by this, the prison guards went on strike and abandoned the prison, hoping that this would create chaos and violence throughout the prison. But the prisoners were able to create an anarchist community where recidivism dropped dramatically and murders and rapes fell to zero. Prisoners volunteered to cook meals. Vietnam veterans who had been trained as medics took charge of the pharmacy and distribution of medication. Decisions were made in community assemblies.

Guards retook the prison after two months, leading to many prison administrators and bureaucrats quitting their jobs and embracing the prison abolition movement.

Advocates of prison abolition

Anarchist banner in Melbourne Australia, on 16 June 2017

Angela Davis writes: "Mass incarceration is not a solution to unemployment, nor is it a solution to the vast array of social problems that are hidden away in a rapidly growing network of prisons and jails. However, the great majority of people have been tricked into believing in the efficacy of imprisonment, even though the historical record clearly demonstrates that prisons do not work."

Angela Davis and Ruth Wilson Gilmore co-founded Critical Resistance, which is an organization working to "build an international movement to end the Prison Industrial Complex by challenging the belief that caging and controlling people makes us safe." Other similarly motivated groups such as the Prison Activist Resource Center (PARC), a group "committed to exposing and challenging all forms of institutionalized racism, sexism, able-ism, heterosexism, and classism, specifically within the Prison Industrial Complex," and Black & Pink, an abolitionist organization that focuses around LGBTQ rights, all broadly advocate for prison abolition. Furthermore, the Human Rights Coalition, a 2001 group that aims to abolish prisons, and the California Coalition for Women Prisoners, a grassroots organization dedicated to dismantling the PIC, can all be added to the long list of organizations that desire a different form of justice system.

Since 1983, the International Conference on Penal Abolition (ICOPA) gathers activists, academics, journalists, and "others from across the world who are working towards the abolition of imprisonment, the penal system, carceral controls and the prison industrial complex (PIC)," to discuss three important questions surrounding the reality of prison abolition ICOPA was one of the first penal abolitionist conference movements, similar to Critical Resistance in America, but "with an explicitly international scope and agenda-setting ambition."

Anarchists wish to eliminate all forms of state control, of which imprisonment is seen as one of the more obvious examples. Anarchists also oppose prisons given that statistics show incarceration rates affect mainly poor people and ethnic minorities, and do not generally rehabilitate criminals, in many cases making them worse. As a result, the prison abolition movement often is associated with humanistic socialism, anarchism and anti-authoritarianism.

In October 2015, members at a plenary session of the National Lawyers Guild (NLG) released and adopted a resolution in favor of prison abolition.

In Canada, a number of organizations support prison abolition, which includes the Saskatchewan Manitoba Alberta Abolition Organization (SMAAC) or the Toronto Prisoners’ Rights Project. These organizations collaborate and organize on issues of prison abolition and work towards prison abolition.

Disability, mental illness and prison

Further information: Mentally ill people in United States jails and prisons

Prison abolitionists such as Amanda Pustilnik take issue with the fact that prisons are used as a "default asylum" for many individuals with mental illness:

Why do governmental units choose to spend billions of dollars a year to concentrate people with serious illnesses in a system designed to punish intentional lawbreaking, when doing so matches neither the putative purposes of that system nor most effectively addresses the issues posed by that population?

In the United States, there are more people with mental illness in prisons than in psychiatric hospitals. In Canada, mental health issues are 2 to 3 times more prevalent in prisons than in the general population. This statistic is one of the major pieces of evidence that prison abolitionists claim highlights the depravity of the penal system.

Prison abolitionists contend that prisons violate the Constitutional rights (5th and 6th Amendment rights) of mentally ill prisoners on the grounds that these individuals will not be receiving the same potential for rehabilitation as the non-mentally ill prison population. This injustice is sufficient grounds to argue for the abolishment of prisons. Prisons were not designed to be used to house the mentally ill, and prison practices like solitary confinement are damaging to mental health. Additionally, individuals with mental illnesses have a much higher chance of committing suicide while in prison.

In response to the fear that prisons are needed for the most serious cases of mentally ill, Liat Ben-Mosh describe prison abolitionist's' view on the issue: "Many prison abolitionists advocate for transformative justice and healing practices in which no one will be restrained or segregated, while some, like PREAP, believe that there will always be a small percentage of those whose behavior is so unacceptable or harmful that they will need to be incapacitated, socially exiled, or restrained and that this should be done humanely, temporarily, and not in a carceral or punitive manner." Another point raised is that the current focus in criminal justice reform on nonviolent, nonserious and nonsexual offences shrinks the borders and understandings of innocence and guilt.

Aging in prison

The prison abolition movement and prison abolitionists, like Liat Ben-Moshe have taken issue with the treatment of the aging population in prisons. Prolonged sentencing policies have resulted in an increased aging population in prisons as well as the harsh conditions of imprisonment. A number of reasons can contribute to older adult's risk for illness while in prison. Prisons are not intended to be used as nursing homes, hospice or long-term care facilities for the aging prison population.

In Canada, individuals 50 years of age and older in federal custody account for 25% of the federal prison population. Investigations into the Canadian federal penitentiary have found that there is a general failure of the Correctional Service of Canada to meet safe and humane custody and assisting in the rehabilitation and reintegration of offenders into the community. The conditions of confinement of older individuals jeopardize the protection of their human rights. The conditions of the aging population in Canada has been denounced by persons who are incarcerated.

Proposed reforms and alternatives

2022 Spanish-language graffiti in Vallcarca i els Penitents (Barcelona) advocating for the freeing of prisoners.

2022 Catalan-language graffiti in Vallcarca i els Penitents (Barcelona) deeming prisons as torture.

Proposals for prison reform and alternatives to prisons differ significantly depending on the political beliefs behind them. Often they fall in one of three categories from the "Attrition Model", a model proposed by the Prison Research Education Action Project in 1976: moratorium, decarceration, and excarceration. Proposals and tactics often include:

• Penal system reforms:
  • Substituting, for incarceration, supervised release, probation, restitution to victims, and/or community work.
  • Decreasing terms of imprisonment by abolishing mandatory minimum sentencing
  • Decreasing ethnic disparity in prison populations
• Prison condition reforms
• Crime prevention rather than punishment
• Abolition of specific programs which increase prison population, such as the prohibition of drugs (e.g., the American War on Drugs) and prohibition of prostitution.
• Education programs to inform people who have never been in prison about the problems
• Fighting individual cases of wrongful conviction

The United Nations Office on Drugs and Crime published a series of handbooks on criminal justice. Among them is Alternatives to Imprisonment which identifies how the overuse of imprisonment impacts fundamental human rights, especially those convicted for lesser crimes.

Social justice and advocacy organizations such as Students Against Mass Incarceration (SAMI) at the University of California, San Diego often look to Scandinavian countries Sweden and Norway for guidance in regard to successful prison reform because both countries have an emphasis on rehabilitation rather than punishment. According to Sweden's former Prison and Probation Service Director-General, Nils Öberg, this emphasis is popular among the Swedish because the act of imprisonment is considered punishment enough. This focus on rehabilitation includes an emphasis on promoting normalcy for inmates, a charge lead by experienced criminologists and psychologists. In Norway a focus on preparation for societal re-entry has yielded "one of the lowest recidivism rates in the world at 20%, [while] the US has one of the highest: 76.6% of [American] prisoners are re-arrested within five years". The Scandinavian method of incarceration seems to be successful: the Swedish incarceration rate decreased by 6% between 2011 and 2012.

Abolitionist views

Many prison reform organizations and abolitionists in the United States advocate community accountability practices, such as community-controlled courts, councils, or assemblies as an alternative to the criminal justice system.

Abolitionists like Angela Davis recommend four measures as a way to deal with violent and other serious crimes: (1) make mental health care available to all (2) everyone should have access to affordable treatment for substance use disorders (3) make a stronger effort to rehabilitate those who commit criminal offences and (4) employ reparative or restorative justice measures as an accountability tool to reconcile offenders with their victims and undo or compensate the harm done.

Organizations such as INCITE! and Sista II Sista that support women of color who are survivors of interpersonal violence argue that the criminal justice system does not protect marginalized people who are victims in relationships. Instead, victims, especially those who are poor, minorities, transgender or gender non-conforming can experience additional violence at the hands of the state. Instead of relying on the criminal justice system, these organizations work to implement community accountability practices, which often involve collectively-run processes of intervention initiated by a survivor of violence to try to hold the person who committed violence accountable by working to meet a set of demands. For organizations outside the United States see, e.g. Justice Action, Australia.

Some anarchists and socialists contend that a large part of the problem is the way the judicial system deals with prisoners, people, and capital. According to Marxists, in capitalist economies incentives are in place to expand the prison system and increase the prison population. This is evidenced by the creation of private prisons in America and corporations like CoreCivic, formerly known as Correction Corporation of America (CCA). Its shareholders benefit from the expansion of prisons and tougher laws on crime. More prisoners is seen as beneficial for business. Some anarchists contend that with the destruction of capitalism, and the development of social structures that would allow for the self-management of communities, property crimes would largely vanish. There would be fewer prisoners, they assert, if society treated people more fairly, regardless of gender, color, ethnic background, sexual orientation, education, etc.

The demand for prison abolition is a feature of anarchist criminology, which argues that prisons encourage recidivism and should be replaced by efforts to rehabilitate offenders and reintegrate them into communities.

“Nine perspectives for prison abolitionists”

Instead of prisons: a handbook for abolitionists, republished by Critical Resistance in 2005, outlines what they identify as the nine main perspectives for prison abolitionists:

Perspective 1

The imprisonment of a human being is inherently immoral, and while total abolition of the current prison system is not an easy task, it is possible. The first step towards abolition is admitting that prisons cannot be reformed, as a carceral system is founded on brutality and contempt for those imprisoned. Additionally, the current system works to disproportionally imprison poor and working-class people, so its abolition would ensure progress towards equality. Abolitionists see many similarities between today's carceral system and the slavery establishment of the past, and would in fact say that the current system is simply reformed enslavement which perpetuates the same oppressive and discriminatory patterns. But just as superficial reforms could not alter the brutality of the slave system, reforms cannot change a system rooted in racism.

Perspective 2

The abolitionist message requires changing our language and definitions of punishment “treatment” and “inmates”. In order to break away from the prison system, we must use honest language and take back the power of our vocabulary.

Perspective 3

Imprisonment is not a proper response to deviance. Abolitionists promote reconciliation rather than punishment, a perspective seeking to restore both the criminal and the victim while limiting the disruption of their lives in the process.

Perspective 4

Abolitionists advocate for changes beneficial to the prisoner but do so while remaining a non-member of the system. In a similar fashion, abolitionists respect the personhood of system managers but oppose their role in the perpetuation of an oppressive system.

Perspective 5

The abolitionist message extends farther than the traditional helping relationship; Abolitionists identify themselves as allies of the imprisoned, respecting their perspectives as well as the requirements for abolition.

Perspective 6

The empowerment of prisoners and ex-prisoners is crucial to the abolitionist movement. Programs and resources dedicated to reinstating that which has been stripped from them by the prison system are fundamental in putting power back in their own hands.

Perspective 7

Abolitionists believe that citizens are the true source of institutional power which can lead to the abolition of the prison system. Giving or limiting support from certain policies and practices will enable the progression of the abolitionist movement.

Perspective 8

Abolitionists believe that crime is a consequence of a broken society, and recourses must be used towards social programs instead of the funding of prisons. They advocate for public solutions to public problems, producing effects which will benefit everyone in society.

Perspective 9

An emphasis is placed on the correction of society rather than the correction of an individual. It is only in a corrected or caring community that individual redemption and rehabilitation can be achieved. Thus, abolitionists see that the only adequate alternative to the prison system is building a kind of society which has no need for prisons.

Ovule

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Ovule

For animal ovules, see Ovum.

Location of ovules inside a Helleborus foetidus flower

In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. The female gametophyte — specifically termed a megagametophyte— is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization. The ovule is a small structure present in the ovary. It is attached to the placenta by a stalk called a funicle. The funicle provides nourishment to the ovule.

Location within the plant

In flowering plants, the ovule is located inside the portion of the flower called the gynoecium. The ovary of the gynoecium produces one or more ovules and ultimately becomes the fruit wall. Ovules are attached to the placenta in the ovary through a stalk-like structure known as a funiculus (plural, funiculi). Different patterns of ovule attachment, or placentation, can be found among plant species, these include:

• Apical placentation: The placenta is at the apex (top) of the ovary. Simple or compound ovary.
• Axile placentation: The ovary is divided into radial segments, with placentas in separate locules. Ventral sutures of carpels meet at the centre of the ovary. Placentae are along fused margins of carpels. Two or more carpels. (e.g. Hibiscus, Citrus, Solanum)
• Basal placentation: The placenta is at the base (bottom) of the ovary on a protrusion of the thalamus (receptacle). Simple or compound carpel, unilocular ovary. (e.g. Sonchus, Helianthus, Asteraceae)
• Free-central placentation: Derived from axile as partitions are absorbed, leaving ovules at the central axis. Compound unilocular ovary. (e.g. Stellaria, Dianthus)
• Marginal placentation: Simplest type. There is only one elongated placenta on one side of the ovary, as ovules are attached at the fusion line of the carpel's margins . This is conspicuous in legumes. Simple carpel, unilocular ovary. (e.g. Pisum)
• Parietal placentation: Placentae on inner ovary wall within a non-sectioned ovary, corresponding to fused carpel margins. Two or more carpels, unilocular ovary. (e.g. Brassica)
• Superficial: Similar to axile, but placentae are on inner surfaces of multilocular ovary (e.g. Nymphaea)

In gymnosperms such as conifers, ovules are borne on the surface of an ovuliferous (ovule-bearing) scale, usually within an ovulate cone (also called megastrobilus). In the early extinct seed ferns, ovules were borne on the surface of leaves. In the most recent of these taxa, a cupule (a modified branch or group of branches) surrounded the ovule (e.g. Caytonia or Glossopteris).

Parts and development

Ovule structure (anatropous) 1: nucellus 2: chalaza 3: funiculus 4: raphe

Ovule orientation may be anatropous, such that when inverted the micropyle faces the placenta (this is the most common ovule orientation in flowering plants), amphitropous, campylotropous, or orthotropous (anatropous are common and micropyle is in downward position and chalazal end in on the upper position hence, in amphitropous the anatropous arrangement is tilted 90 degrees and in orthotropus it is completely inverted) . The ovule appears to be a megasporangium with integuments surrounding it. Ovules are initially composed of diploid maternal tissue, which includes a megasporocyte (a cell that will undergo meiosis to produce megaspores). Megaspores remain inside the ovule and divide by mitosis to produce the haploid female gametophyte or megagametophyte, which also remains inside the ovule. The remnants of the megasporangium tissue (the nucellus) surround the megagametophyte. Megagametophytes produce archegonia (lost in some groups such as flowering plants), which produce egg cells. After fertilization, the ovule contains a diploid zygote and then, after cell division begins, an embryo of the next sporophyte generation. In flowering plants, a second sperm nucleus fuses with other nuclei in the megagametophyte forming a typically polyploid (often triploid) endosperm tissue, which serves as nourishment for the young sporophyte.

Integuments, micropyle, chalaza and hilum

Plant ovules: Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right

Models of different ovules, Botanical Museum Greifswald

An integument is a protective layer of cells surrounding the ovule. Gymnosperms typically have one integument (unitegmic) while angiosperms typically have two integuments (bitegmic). The evolutionary origin of the inner integument (which is integral to the formation of ovules from megasporangia) has been proposed to be by enclosure of a megasporangium by sterile branches (telomes). Elkinsia, a preovulate taxon, has a lobed structure fused to the lower third of the megasporangium, with the lobes extending upwards in a ring around the megasporangium. This might, through fusion between lobes and between the structure and the megasporangium, have produced an integument.

The origin of the second or outer integument has been an area of active contention for some time. The cupules of some extinct taxa have been suggested as the origin of the outer integument. A few angiosperms produce vascular tissue in the outer integument, the orientation of which suggests that the outer surface is morphologically abaxial. This suggests that cupules of the kind produced by the Caytoniales or Glossopteridales may have evolved into the outer integument of angiosperms.

The integuments develop into the seed coat when the ovule matures after fertilization.

The integuments do not enclose the nucellus completely but retain an opening at the apex referred to as the micropyle. The micropyle opening allows the pollen (a male gametophyte) to enter the ovule for fertilization. In gymnosperms (e.g., conifers), the pollen is drawn into the ovule on a drop of fluid that exudes out of the micropyle, the so-called pollination drop mechanism. Subsequently, the micropyle closes. In angiosperms, only a pollen tube enters the micropyle. During germination, the seedling's radicle emerges through the micropyle.

Located opposite from the micropyle is the chalaza where the nucellus is joined to the integuments. Nutrients from the plant travel through the phloem of the vascular system to the funiculus and outer integument and from there apoplastically and symplastically through the chalaza to the nucellus inside the ovule. In chalazogamous plants, the pollen tubes enter the ovule through the chalaza instead of the micropyle opening.

Nucellus, megaspore and perisperm

The nucellus (plural: nucelli) is part of the inner structure of the ovule, forming a layer of diploid (sporophytic) cells immediately inside the integuments. It is structurally and functionally equivalent to the megasporangium. In immature ovules, the nucellus contains a megasporocyte (megaspore mother cell), which undergoes sporogenesis via meiosis. In the megasporocyte of Arabidopsis thaliana, meiosis depends on the expression of genes that facilitate DNA repair and homologous recombination.

In gymnosperms, three of the four haploid spores produced in meiosis typically degenerate, leaving one surviving megaspore inside the nucellus. Among angiosperms, however, a wide range of variation exists in what happens next. The number (and position) of surviving megaspores, the total number of cell divisions, whether nuclear fusions occur, and the final number, position and ploidy of the cells or nuclei all vary. A common pattern of embryo sac development (the Polygonum type maturation pattern) includes a single functional megaspore followed by three rounds of mitosis. In some cases, however, two megaspores survive (for example, in Allium and Endymion). In some cases all four megaspores survive, for example in the Fritillaria type of development (illustrated by Lilium in the figure) there is no separation of the megaspores following meiosis, then the nuclei fuse to form a triploid nucleus and a haploid nucleus. The subsequent arrangement of cells is similar to the Polygonum pattern, but the ploidy of the nuclei is different.

After fertilization, the nucellus may develop into the perisperm that feeds the embryo. In some plants, the diploid tissue of the nucellus can give rise to the embryo within the seed through a mechanism of asexual reproduction called nucellar embryony.

Megagametophyte

Megagametophyte formation of the genera Polygonum and Lilium. Triploid nuclei are shown as ellipses with three white dots. The first three columns show the meiosis of the megaspore, followed by 1-2 mitoses.

Ovule with megagametophyte: egg cell (yellow), synergids (orange), central cell with two polar nuclei (bright green), and antipodals (dark green)

The haploid megaspore inside the nucellus gives rise to the female gametophyte, called the megagametophyte.

In gymnosperms, the megagametophyte consists of around 2000 nuclei and forms archegonia, which produce egg cells for fertilization.

In flowering plants, the megagametophyte (also referred to as the embryo sac) is much smaller and typically consists of only seven cells and eight nuclei. This type of megagametophyte develops from the megaspore through three rounds of mitotic divisions. The cell closest to the micropyle opening of the integuments differentiates into the egg cell, with two synergid cells by its side that are involved in the production of signals that guide the pollen tube. Three antipodal cells form on the opposite (chalazal) end of the ovule and later degenerate. The large central cell of the embryo sac contains two polar nuclei.

Zygote, embryo and endosperm

The pollen tube releases two sperm nuclei into the ovule. In gymnosperms, fertilization occurs within the archegonia produced by the female gametophyte. While it is possible that several egg cells are present and fertilized, typically only one zygote will develop into a mature embryo as the resources within the seed are limited.

In flowering plants, one sperm nucleus fuses with the egg cell to produce a zygote, the other fuses with the two polar nuclei of the central cell to give rise to the polyploid (typically triploid) endosperm. This double fertilization is unique to flowering plants, although in some other groups the second sperm cell does fuse with another cell in the megagametophyte to produce a second embryo. The plant stores nutrients such as starch, proteins, and oils in the endosperm as a food source for the developing embryo and seedling, serving a similar function to the yolk of animal eggs. The endosperm is also called the albumen of the seed. the zygote then develops into a megasporophyte, which in turn produces one or more megasporangia. The ovule, with the developing megasporophyte, may be described as either tenuinucellate or crassinucellate. The former has either no cells or a single cell layer between the megasporophyte and the epidermal cells, while the latter has multiple cell layers between.

Embryos may be described by a number of terms including Linear (embryos have axile placentation and are longer than broad), or rudimentary (embryos are basal in which the embryo is tiny in relation to the endosperm).

Types of gametophytes

Megagametophytes of flowering plants may be described according to the number of megaspores developing, as either monosporic, bisporic, or tetrasporic.

Maternal effect

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Maternal_effect

A maternal effect is a situation where the phenotype of an organism is determined not only by the environment it experiences and its genotype, but also by the environment and genotype of its mother. In genetics, maternal effects occur when an organism shows the phenotype expected from the genotype of the mother, irrespective of its own genotype, often due to the mother supplying messenger RNA or proteins to the egg. Maternal effects can also be caused by the maternal environment independent of genotype, sometimes controlling the size, sex, or behaviour of the offspring. These adaptive maternal effects lead to phenotypes of offspring that increase their fitness. Further, it introduces the concept of phenotypic plasticity, an important evolutionary concept. It has been proposed that maternal effects are important for the evolution of adaptive responses to environmental heterogeneity.

In genetics

In genetics, a maternal effect occurs when the phenotype of an organism is determined by the genotype of its mother. For example, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation.

Genetic crosses involving a maternal effect recessive mutation, m. The maternal genotype determines the phenotype of the offspring.

Maternal effect
All offspring show the wild-type phenotype		All offspring show the mutant phenotype

Maternal effects often occur because the mother supplies a particular mRNA or protein to the oocyte, hence the maternal genome determines whether the molecule is functional. Maternal supply of mRNAs to the early embryo is important, as in many organisms the embryo is initially transcriptionally inactive. Because of the inheritance pattern of maternal effect mutations, special genetic screens are required to identify them. These typically involve examining the phenotype of the organisms one generation later than in a conventional (zygotic) screen, as their mothers will be potentially homozygous for maternal effect mutations that arise.

In Drosophila early embryogenesis

Protein and RNA are transported in particles (white dots) from the nurse cells (maternal) to the developing oocyte in Drosophila melanogaster. Scale bar shows 10µm.

Further information: Drosophila embryogenesis

A Drosophila melanogaster oocyte develops in an egg chamber in close association with a set of cells called nurse cells. Both the oocyte and the nurse cells are descended from a single germline stem cell, however cytokinesis is incomplete in these cell divisions, and the cytoplasm of the nurse cells and the oocyte is connected by structures known as ring canals. Only the oocyte undergoes meiosis and contributes DNA to the next generation.

Many maternal effect Drosophila mutants have been found that affect the early steps in embryogenesis such as axis determination, including bicoid, dorsal, gurken and oskar. For example, embryos from homozygous bicoid mothers fail to produce head and thorax structures.

Once the gene that is disrupted in the bicoid mutant was identified, it was shown that bicoid mRNA is transcribed in the nurse cells and then relocalized to the oocyte. Other maternal effect mutants either affect products that are similarly produced in the nurse cells and act in the oocyte, or parts of the transportation machinery that are required for this relocalization. Since these genes are expressed in the (maternal) nurse cells and not in the oocyte or fertilised embryo, the maternal genotype determines whether they can function.

Maternal effect genes are expressed during oogenesis by the mother (expressed prior to fertilization) and develop the anterior-posterior and dorsal ventral polarity of the egg. The anterior end of the egg becomes the head; posterior end becomes the tail. the dorsal side is on the top; the ventral side is in underneath. The products of maternal effect genes called maternal mRNAs are produced by nurse cell and follicle cells and deposited in the egg cells (oocytes). At the start of development process, mRNA gradients are formed in oocytes along anterior-posterior and dorsal ventral axes.

About thirty maternal genes are involved in pattern formation have been identified. In particular, products of four maternal effect genes are critical to the formation of anterior-posterior axis. The product of two maternal effect gene, bicoid and hunchback, regulates formation of anterior structure while another pair nanos and caudal, specifies protein that regulates formation of posterior part of embryo.

The transcript of all four genes-bicoid, hunchback, caudal, nanos are synthesized by nurse and follicle cells and transported into the oocytes.

In birds

In birds, mothers may pass down hormones in their eggs that affect an offspring's growth and behavior. Experiments in domestic canaries have shown that eggs that contain more yolk androgens develop into chicks that display more social dominance. Similar variation in yolk androgen levels has been seen in bird species like the American coot, though the mechanism of effect has yet to be established.

In humans

In 2015, obesity theorist Edward Archer published "The Childhood Obesity Epidemic as a Result of Nongenetic Evolution: The Maternal Resources Hypothesis" and a series of works on maternal effects in human obesity and health. In this body of work, Archer argued that accumulative maternal effects via the non-genetic evolution of matrilineal nutrient metabolism is responsible for the increased global prevalence of obesity and diabetes mellitus type 2. Archer posited that decrements in maternal metabolic control altered fetal pancreatic beta cell, adipocyte (fat cell) and myocyte (muscle cell) development thereby inducing an enduring competitive advantage of adipocytes in the acquisition and sequestering on nutrient energy.

In plants

The environmental cues such as light, temperature, soil moisture and nutrients that the mother plant encounters can cause variations in seed quality, even within the same genotype. Thus, the mother plant greatly influences seed traits such as seed size, germination rate, and viability.

Environmental maternal effects

The environment or condition of the mother can also in some situations influence the phenotype of her offspring, independent of the offspring's genotype.

Paternal effect genes

In contrast, a paternal effect is when a phenotype results from the genotype of the father, rather than the genotype of the individual. The genes responsible for these effects are components of sperm that are involved in fertilization and early development. An example of a paternal-effect gene is the ms(3)sneaky in Drosophila. Males with a mutant allele of this gene produce sperm that are able to fertilize an egg, but the sneaky-inseminated eggs do not develop normally. However, females with this mutation produce eggs that undergo normal development when fertilized.

Adaptive maternal effects

Adaptive maternal effects induce phenotypic changes in offspring that result in an increase in fitness. These changes arise from mothers sensing environmental cues that work to reduce offspring fitness, and then responding to them in a way that then “prepares” offspring for their future environments. A key characteristic of “adaptive maternal effects” phenotypes is their plasticity. Phenotypic plasticity gives organisms the ability to respond to different environments by altering their phenotype. With these “altered” phenotypes increasing fitness it becomes important to look at the likelihood that adaptive maternal effects will evolve and become a significant phenotypic adaptation to an environment.

Defining adaptive maternal effects

When traits are influenced by either the maternal environment or the maternal phenotype, it is said to be influenced by maternal effects. Maternal effects work to alter the phenotypes of the offspring through pathways other than DNA. Adaptive maternal effects are when these maternal influences lead to a phenotypic change that increases the fitness of the offspring. In general, adaptive maternal effects are a mechanism to cope with factors that work to reduce offspring fitness; they are also environment specific.

It can sometimes be difficult to differentiate between maternal and adaptive maternal effects. Consider the following: Gypsy moths reared on foliage of black oak, rather than chestnut oak, had offspring that developed faster. This is a maternal, not an adaptive maternal effect. In order to be an adaptive maternal effect, the mother's environment would have to have led to a change in the eating habits or behavior of the offspring. The key difference between the two therefore, is that adaptive maternal effects are environment specific. The phenotypes that arise are in response to the mother sensing an environment that would reduce the fitness of her offspring. By accounting for this environment she is then able to alter the phenotypes to actually increase the offspring's fitness. Maternal effects are not in response to an environmental cue, and further they have the potential to increase offspring fitness, but they may not.

When looking at the likelihood of these “altered” phenotypes evolving there are many factors and cues involved. Adaptive maternal effects evolve only when offspring can face many potential environments; when a mother can “predict” the environment into which her offspring will be born; and when a mother can influence her offspring's phenotype, thereby increasing their fitness. The summation of all of these factors can then lead to these “altered” traits becoming favorable for evolution.

The phenotypic changes that arise from adaptive maternal effects are a result of the mother sensing that a certain aspect of the environment may decrease the survival of her offspring. When sensing a cue the mother “relays” information to the developing offspring and therefore induces adaptive maternal effects. This tends to then cause the offspring to have a higher fitness because they are “prepared” for the environment they are likely to experience. These cues can include responses to predators, habitat, high population density, and food availability.

The increase in size of Northern American red squirrels is a great example of an adaptive maternal effect producing a phenotype that resulted in an increased fitness. The adaptive maternal effect was induced by the mothers sensing the high population density and correlating it to low food availability per individual. Her offspring were on average larger than other squirrels of the same species; they also grew faster. Ultimately, the squirrels born during this period of high population density showed an increased survival rate (and therefore fitness) during their first winter.

Phenotypic plasticity

When analyzing the types of changes that can occur to a phenotype, we can see changes that are behavioral, morphological, or physiological. A characteristic of the phenotype that arises through adaptive maternal effects, is the plasticity of this phenotype. Phenotypic plasticity allows organisms to adjust their phenotype to various environments, thereby enhancing their fitness to changing environmental conditions. Ultimately it is a key attribute to an organism's, and a population's, ability to adapt to short term environmental change.

Phenotypic plasticity can be seen in many organisms, one species that exemplifies this concept is the seed beetle Stator limbatus. This seed beetle reproduces on different host plants, two of the more common ones being Cercidium floridum and Acacia greggii. When C. floridum is the host plant, there is selection for a large egg size; when A. greggii is the host plant, there is a selection for a smaller egg size. In an experiment it was seen that when a beetle who usually laid eggs on A. greggii was put onto C. floridum, the survivorship of the laid eggs was lower compared to those eggs produced by a beetle that was conditioned and remained on the C. florium host plant. Ultimately these experiments showed the plasticity of egg size production in the beetle, as well as the influence of the maternal environment on the survivorship of the offspring.

Further examples of adaptive maternal effects

In many insects:

• Cues such as rapidly cooling temperatures or decreasing daylight can result in offspring that enter into a dormant state. They therefore will better survive the cooling temperatures and preserve energy.
• When parents are forced to lay eggs on environments with low nutrients, offspring will be provided with more resources, such as higher nutrients, through an increased egg size.
• Cues such as poor habitat or crowding can lead to offspring with wings. The wings allow the offspring to move away from poor environments to ones that will provide better resources.

Maternal diet and environment influence epigenetic effects

Further information: Epigenetics

Related to adaptive maternal effects are epigenetic effects. Epigenetics is the study of long lasting changes in gene expression that are produced by modifications to chromatin instead of changes in DNA sequence, as is seen in DNA mutation. This "change" refers to DNA methylation, histone acetylation, or the interaction of non-coding RNAs with DNA. DNA methylation is the addition of methyl groups to the DNA. When DNA is methylated in mammals, the transcription of the gene at that location is turned down or turned off entirely. The induction of DNA methylation is highly influenced by the maternal environment. Some maternal environments can lead to a higher methylation of an offspring's DNA, while others lower methylation. The fact that methylation can be influenced by the maternal environment, makes it similar to adaptive maternal effects. Further similarities are seen by the fact that methylation can often increase the fitness of the offspring. Additionally, epigenetics can refer to histone modifications or non-coding RNAs that create a sort of cellular memory. Cellular memory refers to a cell's ability to pass nongenetic information to its daughter cell during replication. For example, after differentiation, a liver cell performs different functions than a brain cell; cellular memory allows these cells to "remember" what functions they are supposed to perform after replication. Some of these epigenetic changes can be passed down to future generations, while others are reversible within a particular individual's lifetime. This can explain why individuals with identical DNA can differ in their susceptibility to certain chronic diseases.

Currently, researchers are examining the correlations between maternal diet during pregnancy and its effect on the offspring's susceptibility for chronic diseases later in life. The fetal programming hypothesis highlights the idea that environmental stimuli during critical periods of fetal development can have lifelong effects on body structure and health and in a sense they prepare offspring for the environment they will be born into. Many of these variations are thought to be due to epigenetic mechanisms brought on by maternal environment such as stress, diet, gestational diabetes, and exposure to tobacco and alcohol. These factors are thought to be contributing factors to obesity and cardiovascular disease, neural tube defects, cancer, diabetes, etc. Studies to determine these epigenetic mechanisms are usually performed through laboratory studies of rodents and epidemiological studies of humans.

Importance for the general population

Knowledge of maternal diet induced epigenetic changes is important not only for scientists, but for the general public. Perhaps the most obvious place of importance for maternal dietary effects is within the medical field. In the United States and worldwide, many non-communicable diseases, such as cancer, obesity, and heart disease, have reached epidemic proportions. The medical field is working on methods to detect these diseases, some of which have been discovered to be heavily driven by epigenetic alterations due to maternal dietary effects. Once the genomic markers for these diseases are identified, research can begin to be implemented to identify the early onset of these diseases and possibly reverse the epigenetic effects of maternal diet in later life stages. The reversal of epigenetic effects will utilize the pharmaceutical field in an attempt to create drugs which target the specific genes and genomic alterations. The creation of drugs to cure these non-communicable diseases could be used to treat individuals who already have these illnesses. General knowledge of the mechanisms behind maternal dietary epigenetic effects is also beneficial in terms of awareness. The general public can be aware of the risks of certain dietary behaviors during pregnancy in an attempt to curb the negative consequences which may arise in offspring later in their lives. Epigenetic knowledge can lead to an overall healthier lifestyle for the billions of people worldwide.

The effect of maternal diet in species other than humans is also relevant. Many of the long term effects of global climate change are unknown. Knowledge of epigenetic mechanisms can help scientists better predict the impacts of changing community structures on species which are ecologically, economically, and/or culturally important around the world. Since many ecosystems will see changes in species structures, the nutrient availability will also be altered, ultimately affecting the available food choices for reproducing females. Maternal dietary effects may also be used to improve agricultural and aquaculture practices. Breeders may be able to utilize scientific data to create more sustainable practices, saving money for themselves, as well as the consumers.

Maternal diet and environment epigenetically influences susceptibility for adult diseases

Hyperglycemia during gestation correlated with obesity and heart disease in adulthood

Hyperglycemia during pregnancy is thought to cause epigenetic changes in the leptin gene of newborns leading to a potential increased risk for obesity and heart disease. Leptin is sometimes known as the “satiety hormone” because it is released by fat cells to inhibit hunger. By studying both animal models and human observational studies, it has been suggested that a leptin surge in the perinatal period plays a critical role in contributing to long-term risk of obesity. The perinatal period begins at 22 weeks gestation and ends a week after birth. DNA methylation near the leptin locus has been examined to determine if there was a correlation between maternal glycemia and neonatal leptin levels. Results showed that glycemia was inversely associated with the methylation states of LEP gene, which controls the production of the leptin hormone. Therefore, higher glycemic levels in mothers corresponded to lower methylation states in LEP gene in their children. With this lower methylation state, the LEP gene is transcribed more often, thereby inducing higher blood leptin levels. These higher blood leptin levels during the perinatal period were linked to obesity in adulthood, perhaps due to the fact that a higher “normal” level of leptin was set during gestation. Because obesity is a large contributor to heart disease, this leptin surge is not only correlated with obesity but also heart disease.

High fat diets during gestation correlated with metabolic syndrome

High fat diets in utero are believed to cause metabolic syndrome. Metabolic syndrome is a set of symptoms including obesity and insulin resistance that appear to be related. This syndrome is often associated with type II diabetes as well as hypertension and atherosclerosis. Using mice models, researchers have shown that high fat diets in utero cause modifications to the adiponectin and leptin genes that alter gene expression; these changes contribute to metabolic syndrome. The adiponectin genes regulate glucose metabolism as well as fatty acid breakdown; however, the exact mechanisms are not entirely understood. In both human and mice models, adiponectin has been shown to add insulin-sensitizing and anti-inflammatory properties to different types of tissue, specifically muscle and liver tissue. Adiponectin has also been shown to increase the rate of fatty acid transport and oxidation in mice, which causes an increase in fatty acid metabolism. With a high fat diet during gestation, there was an increase in methylation in the promoter of the adiponectin gene accompanied by a decrease in acetylation. These changes likely inhibit the transcription of the adiponectin genes because increases in methylation and decreases in acetylation usually repress transcription. Additionally, there was an increase in methylation of the leptin promoter, which turns down the production of the leptin gene. Therefore, there was less adiponectin to help cells take up glucose and break down fat, as well as less leptin to cause a feeling of satiety. The decrease in these hormones caused fat mass gain, glucose intolerance, hypertriglyceridemia, abnormal adiponectin and leptin levels, and hypertension throughout the animal's lifetime. However, the effect was abolished after three subsequent generations with normal diets. This study highlights the fact that these epigenetic marks can be altered in as many as one generation and can even be completely eliminated over time. This study highlighted the connection between high fat diets to the adiponectin and leptin in mice. In contrast, few studies have been done in humans to show the specific effects of high fat diets in utero on humans. However, it has been shown that decreased adiponectin levels are associated with obesity, insulin resistance, type II diabetes, and coronary artery disease in humans. It is postulated that a similar mechanism as the one described in mice may also contribute to metabolic syndrome in humans.

High fat diets during gestation correlated with chronic inflammation

In addition, high fat diets cause chronic low-grade inflammation in the placenta, adipose, liver, brain, and vascular system. Inflammation is an important aspect of the bodies’ natural defense system after injury, trauma, or disease. During an inflammatory response, a series of physiological reactions, such as increased blood flow, increased cellular metabolism, and vasodilation, occur in order to help treat the wounded or infected area. However, chronic low-grade inflammation has been linked to long-term consequences such as cardiovascular disease, renal failure, aging, diabetes, etc. This chronic low-grade inflammation is commonly seen in obese individuals on high fat diets. In a mice model, excessive cytokines were detected in mice fed on a high fat diet. Cytokines aid in cell signaling during immune responses, specifically sending cells towards sites of inflammation, infection, or trauma. The mRNA of proinflammatory cytokines was induced in the placenta of mothers on high fat diets. The high fat diets also caused changes in microbiotic composition, which led to hyperinflammatory colonic responses in offspring. This hyperinflammatory response can lead to inflammatory bowel diseases such as Crohn's disease or ulcerative colitis. As previously mentioned, high fat diets in utero contribute to obesity; however, some proinflammatory factors, like IL-6 and MCP-1, are also linked to body fat deposition. It has been suggested that histone acetylation is closely associated with inflammation because the addition of histone deacetylase inhibitors has been shown to reduce the expression of proinflammatory mediators in glial cells. This reduction in inflammation resulted in improved neural cell function and survival. This inflammation is also often associated with obesity, cardiovascular disease, fatty liver, brain damage, as well as preeclampsia and preterm birth. Although it has been shown that high fat diets induce inflammation, which contribute to all these chronic diseases; it is unclear as to how this inflammation acts as a mediator between diet and chronic disease.

Undernutrition during gestation correlated with cardiovascular disease

A study done after the Dutch Hunger Winter of 1944-1945 showed that undernutrition during the early stages of pregnancy are associated with hypomethylation of the insulin-like growth factor II (IGF2) gene even after six decades. These individuals had significantly lower methylation rates as compared to their same sex sibling who had not been conceived during the famine. A comparison was done with children conceived prior to the famine so that their mothers were nutrient deprived during the later stages of gestation; these children had normal methylation patterns. The IGF2 stands for insulin-like growth factor II; this gene is a key contributor in human growth and development. IGF2 gene is also maternally imprinted meaning that the mother's gene is silenced. The mother's gene is typically methylated at the differentially methylated region (DMR); however, when hypomethylated, the gene is bi-allelically expressed. Thus, individuals with lower methylation states likely lost some of the imprinting effect. Similar results have been demonstrated in the Nr3c1 and Ppara genes of the offspring of rats fed on an isocaloric protein-deficient diet before starting pregnancy. This further implies that the undernutrition was the cause of the epigenetic changes. Surprisingly, there was not a correlation between methylation states and birth weight. This displayed that birth weight may not be an adequate way to determine nutritional status during gestation. This study stressed that epigenetic effects vary depending on the timing of exposure and that early stages of mammalian development are crucial periods for establishing epigenetic marks. Those exposed earlier in gestation had decreased methylation while those who were exposed at the end of gestation had relatively normal methylation levels. The offspring and descendants of mothers with hypomethylation were more likely to develop cardiovascular disease. Epigenetic alterations that occur during embryogenesis and early fetal development have greater physiologic and metabolic effects because they are transmitted over more mitotic divisions. In other words, the epigenetic changes that occur earlier are more likely to persist in more cells.

Nutrient restriction during gestation correlated with diabetes mellitus type 2

In another study, researchers discovered that perinatal nutrient restriction resulting in intrauterine growth restriction (IUGR) contributes to diabetes mellitus type 2 (DM2). IUGR refers to the poor growth of the baby in utero. In the pancreas, IUGR caused a reduction in the expression of the promoter of the gene encoding a critical transcription factor for beta cell function and development. Pancreatic beta cells are responsible for making insulin; decreased beta cell activity is associated with DM2 in adulthood. In skeletal muscle, IUGR caused a decrease in expression of the Glut-4 gene. The Glut-4 gene controls the production of the Glut-4 transporter; this transporter is specifically sensitive to insulin. Thus, when insulin levels rise, more glut-4 transporters are brought to the cell membrane to increase the uptake of glucose into the cell. This change is caused by histone modifications in the cells of skeletal muscle that decrease the effectiveness of the glucose transport system into the muscle. Because the main glucose transporters are not operating at optimal capacity, these individuals are more likely to develop insulin resistance with energy rich diets later in life, contributing to DM2.

High protein diet during gestation correlated with higher blood pressure and adiposity

Further studies have examined the epigenetic changes resulting from a high protein/low carbohydrate diet during pregnancy. This diet caused epigenetic changes that were associated with higher blood pressure, higher cortisol levels, and a heightened Hypothalamic-pituitary-adrenal (HPA) axis response to stress. Increased methylation in the 11β-hydroxysteroid dehydrogenase type 2 (HSD2), glucocorticoid receptor (GR), and H19 ICR were positively correlated with adiposity and blood pressure in adulthood. Glucocorticoids play a vital role in tissue development and maturation as well as having effects on metabolism. Glucocorticoids’ access to GR is regulated by HSD1 and HSD2. H19 is an imprinted gene for a long coding RNA (lncRNA), which has limiting effects on body weight and cell proliferation. Therefore, higher methylation rates in H19 ICR repress transcription and prevent the lncRNA from regulating body weight. Mothers who reported higher meat/fish and vegetable intake and lower bread/potato intake in late pregnancy had a higher average methylation in GR and HSD2. However, one common challenge of these types of studies is that many epigenetic modifications have tissue and cell-type specificity DNA methylation patterns. Thus, epigenetic modification patterns of accessible tissues, like peripheral blood, may not represent the epigenetic patterns of the tissue involved in a particular disease.

Neonatal estrogen exposure correlated with prostate cancer

Strong evidence in rats supports the conclusion that neonatal estrogen exposure plays a role in the development of prostate cancer. Using a human fetal prostate xenograft model, researchers studied the effects of early exposure to estrogen with and without secondary estrogen and testosterone treatment. A xenograft model is a graft of tissue transplanted between organisms of different species. In this case, human tissue was transplanted into rats; therefore, there was no need to extrapolate from rodents to humans. Histopathological lesions, proliferation, and serum hormone levels were measured at various time-points after xenografting. At day 200, the xenograft that had been exposed to two treatments of estrogen showed the most severe changes. Additionally, researchers looked at key genes involved in prostatic glandular and stromal growth, cell-cycle progression, apoptosis, hormone receptors, and tumor suppressors using a custom PCR array. Analysis of DNA methylation showed methylation differences in CpG sites of the stromal compartment after estrogen treatment. These variations in methylation are likely a contributing cause to the changes in the cellular events in the KEGG prostate cancer pathway that inhibit apoptosis and increase cell cycle progression that contribute to the development of cancer.

Supplementation may reverse epigenetic changes

In utero or neonatal exposure to bisphenol A (BPA), a chemical used in manufacturing polycarbonate plastic, is correlated with higher body weight, breast cancer, prostate cancer, and an altered reproductive function. In a mice model, the mice fed on a BPA diet were more likely to have a yellow coat corresponding to their lower methylation state in the promoter regions of the retrotransposon upstream of the Agouti gene. The Agouti gene is responsible for determining whether an animal's coat will be banded (agouti) or solid (non-agouti). However, supplementation with methyl donors like folic acid or phytoestrogen abolished the hypomethylating effect. This demonstrates that the epigenetic changes can be reversed through diet and supplementation.

Maternal diet effects and ecology

Maternal dietary effects are not just seen in humans, but throughout many taxa in the animal kingdom. These maternal dietary effects can result in ecological changes on a larger scale throughout populations and from generation to generation. The plasticity involved in these epigenetic changes due to maternal diet represents the environment into which the offspring will be born. Many times, epigenetic effects on offspring from the maternal diet during development will genetically prepare the offspring to be better adapted for the environment in which they will first encounter. The epigenetic effects of maternal diet can be seen in many species, utilizing different ecological cues and epigenetic mechanisms to provide an adaptive advantage to future generations.

Within the field of ecology, there are many examples of maternal dietary effects. Unfortunately, the epigenetic mechanisms underlying these phenotypic changes are rarely investigated. In the future, it would be beneficial for ecological scientists as well as epigenetic and genomic scientists to work together to fill the holes within the ecology field to produce a complete picture of environmental cues and epigenetic alterations producing phenotypic diversity.

Parental diet affects offspring immunity

A pyralid moth species, Plodia interpunctella, commonly found in food storage areas, exhibits maternal dietary effects, as well as paternal dietary effects, on its offspring. Epigenetic changes in moth offspring affect the production of phenoloxidase, an enzyme involved with melanization and correlated with resistance of certain pathogens in many invertebrate species. In this study, parent moths were housed in food rich or food poor environments during their reproductive period. Moths who were housed in food poor environments produced offspring with less phenoloxidase, and thus had a weaker immune system, than moths who reproduced in food rich environments. This is believed to be adaptive because the offspring develop while receiving cues of scarce nutritional opportunities. These cues allow the moth to allocate energy differentially, decreasing energy allocated for the immune system and devoting more energy towards growth and reproduction to increase fitness and insure future generations. One explanation for this effect may be imprinting, the expression of only one parental gene over the other, but further research has yet to be done.

Parental-mediated dietary epigenetic effects on immunity has a broader significance on wild organisms. Changes in immunity throughout an entire population may make the population more susceptible to an environmental disturbance, such as the introduction of a pathogen. Therefore, these transgenerational epigenetic effects can influence the population dynamics by decreasing the stability of populations who inhabit environments different from the parental environment that offspring are epigenetically modified for.

Maternal diet affects offspring growth rate

Food availability also influences the epigenetic mechanisms driving growth rate in the mouthbrooding cichlid, Simochromis pleurospilus. When nutrient availability is high, reproducing females will produce many small eggs, versus fewer, larger eggs in nutrient poor environments. Egg size often correlates with fish larvae body size at hatching: smaller larvae hatch from smaller eggs. In the case of the cichlid, small larvae grow at a faster rate than their larger egg counterparts. This is due to the increased expression of GHR, the growth hormone receptor. Increased transcription levels of GHR genes increase the receptors available to bind with growth hormone, GH, leading to an increased growth rate in smaller fish. Fish of larger size are less likely to be eaten by predators, therefore it is advantageous to grow quickly in early life stages to insure survival. The mechanism by which GHR transcription is regulated is unknown, but it may be due to hormones within the yolk produced by the mother, or just by the yolk quantity itself. This may lead to DNA methylation or histone modifications which control genic transcription levels.

Ecologically, this is an example of the mother utilizing her environment and determining the best method to maximize offspring survival, without actually making a conscious effort to do so. Ecology is generally driven by the ability of an organism to compete to obtain nutrients and successfully reproduce. If a mother is able to gather a plentiful amount of resources, she will have a higher fecundity and produce offspring who are able to grow quickly to avoid predation. Mothers who are unable to obtain as many nutrients will produce fewer offspring, but the offspring will be larger in hopes that their large size will help insure survival into sexual maturation. Unlike the moth example, the maternal effects provided to the cichlid offspring do not prepare the cichlids for the environment that they will be born into; this is because mouth brooding cichlids provide parental care to their offspring, providing a stable environment for the offspring to develop. Offspring who have a greater growth rate can become independent more quickly than slow growing counterparts, therefore decreasing the amount of energy spent by the parents during the parental care period.

A similar phenomenon occurs in the sea urchin, Strongylocentrotus droebachiensis. Urchin mothers in nutrient rich environments produce a large number of small eggs. Offspring from these small eggs grow at a faster rate than their large egg counterparts from nutrient poor mothers. Again, it is beneficial for sea urchin larvae, known as planula, to grow quickly to decrease the duration of their larval phase and metamorphose into a juvenile to decrease predation risks. Sea urchin larvae have the ability to develop into one of two phenotypes, based on their maternal and larval nutrition. Larvae who grow at a fast rate from high nutrition, are able to devote more of their energy towards development into the juvenile phenotype. Larvae who grow at a slower rate with low nutrition, devote more energy towards growing spine-like appendages to protect themselves from predators in an attempt to increase survival into the juvenile phase. The determination of these phenotypes is based on both the maternal and the juvenile nutrition. The epigenetic mechanisms behind these phenotypic changes is unknown, but it is believed that there may be a nutritional threshold that triggers epigenetic changes affecting development and, ultimately, the larval phenotype.

Baldwin effect

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Baldwin_effect

The Baldwin effect compared to Lamarck's theory of evolution, Darwinian evolution, and Waddington's genetic assimilation. All the theories offer explanations of how organisms respond to a changed environment with adaptive inherited change.

In evolutionary biology, the Baldwin effect describes an effect of learned behaviour on evolution. James Mark Baldwin and others suggested that an organism's ability to learn new behaviours (e.g. to acclimatise to a new stressor) will affect its reproductive success and will therefore have an effect on the genetic makeup of its species through natural selection. It posits that subsequent selection might reinforce the originally learned behaviors, if adaptive, into more in-born, instinctive ones. Though this process appears similar to Lamarckism, that view proposes that living things inherited their parents' acquired characteristics. The Baldwin effect only posits that learning ability, which is genetically based, is another variable in / contributor to environmental adaptation. First proposed during the Eclipse of Darwinism in the late 19th century, this effect has been independently proposed several times, and today it is generally recognized as part of the modern synthesis.

"A New Factor in Evolution"

The effect, then unnamed, was put forward in 1896 in a paper "A New Factor in Evolution" by the American psychologist James Mark Baldwin, with a second paper in 1897. The paper proposed a mechanism for specific selection for general learning ability. As the historian of science Robert Richards explains:

If animals entered a new environment—or their old environment rapidly changed—those that could flexibly respond by learning new behaviours or by ontogenetically adapting would be naturally preserved. This saved remnant would, over several generations, have the opportunity to exhibit spontaneously congenital variations similar to their acquired traits and have these variations naturally selected. It would look as though the acquired traits had sunk into the hereditary substance in a Lamarckian fashion, but the process would really be neo-Darwinian.

Selected offspring would tend to have an increased capacity for learning new skills rather than being confined to genetically coded, relatively fixed abilities. In effect, it places emphasis on the fact that the sustained behaviour of a species or group can shape the evolution of that species. The "Baldwin effect" is better understood in evolutionary developmental biology literature as a scenario in which a character or trait change occurring in an organism as a result of its interaction with its environment becomes gradually assimilated into its developmental genetic or epigenetic repertoire. In the words of the philosopher of science Daniel Dennett:

Thanks to the Baldwin effect, species can be said to pretest the efficacy of particular different designs by phenotypic (individual) exploration of the space of nearby possibilities. If a particularly winning setting is thereby discovered, this discovery will create a new selection pressure: organisms that are closer in the adaptive landscape to that discovery will have a clear advantage over those more distant.

An update to the Baldwin effect was developed by Jean Piaget, Paul Weiss, and Conrad Waddington in the 1960s–1970s. This new version included an explicit role for the social in shaping subsequent natural change in humans (both evolutionary and developmental), with reference to alterations of selection pressures.

Subsequent research shows that Baldwin was not the first to identify the process; Douglas Spalding mentioned it in 1873.

Controversy and acceptance

Initially Baldwin's ideas were not incompatible with the prevailing, but uncertain, ideas about the mechanism of transmission of hereditary information and at least two other biologists put forward very similar ideas in 1896. In 1901, Maurice Maeterlinck referred to behavioural adaptations to prevailing climates in different species of bees as "what had merely been an idea, therefore, and opposed to instinct, has thus by slow degrees become an instinctive habit". The Baldwin effect theory subsequently became more controversial, with scholars divided between "Baldwin boosters" and "Baldwin skeptics". The theory was first called the "Baldwin effect" by George Gaylord Simpson in 1953. Simpson "admitted that the idea was theoretically consistent, that is, not inconsistent with the modern synthesis", but he doubted that the phenomenon occurred very often, or if so, could be proven to occur. In his discussion of the reception of the Baldwin-effect theory Simpson points out that the theory appears to provide a reconciliation between a neo-Darwinian and a neo-Lamarckian approach and that "Mendelism and later genetic theory so conclusively ruled out the extreme neo-Lamarckian position that reconciliation came to seem unnecessary". In 1942, the evolutionary biologist Julian Huxley promoted the Baldwin effect as part of the modern synthesis, saying the concept had been unduly neglected by evolutionists.

In the 1960s, the evolutionary biologist Ernst Mayr contended that the Baldwin effect theory was untenable because

1. the argument is stated in terms of the individual genotype, whereas what is really exposed to the selection pressure is a phenotypically and genetically variable population;
2. it is not sufficiently emphasized that the degree of modification of the phenotype is in itself genetically controlled;
3. it is assumed that phenotypic rigidity is selectively superior to phenotypic flexibility.

In 1987 Geoffrey Hinton and Steven Nowlan demonstrated by computer simulation that learning can accelerate evolution, and they associated this with the Baldwin effect.

Paul Griffiths suggests two reasons for the continuing interest in the Baldwin effect. The first is the role mind is understood to play in the effect. The second is the connection between development and evolution in the effect. Baldwin's account of how neurophysiological and conscious mental factors may contribute to the effect brings into focus the question of the possible survival value of consciousness.

The house finch's colonisation of North America has provided empirical evidence of the Baldwin effect.

Still, David Depew observed in 2003, "it is striking that a rather diverse lot of contemporary evolutionary theorists, most of whom regard themselves as supporters of the Modern Synthesis, have of late become 'Baldwin boosters'". These

are typically evolutionary psychologists who are searching for scenarios in which a population can get itself by behavioral trial and error onto a "hard to find" part of the fitness landscape in which human brain, language, and mind can rapidly coevolve. They are searching for what Daniel Dennett, himself a Baldwin booster, calls an "evolutionary crane," an instrument to do some heavy lifting fast.

According to Dennett, also in 2003, recent work has rendered the Baldwin effect "no longer a controversial wrinkle in orthodox Darwinism". Potential genetic mechanisms underlying the Baldwin effect have been proposed for the evolution of natural (genetically determinant) antibodies. In 2009, empirical evidence for the Baldwin effect was provided from the colonisation of North America by the house finch.

The Baldwin effect has been incorporated into the extended evolutionary synthesis.

Comparison with genetic assimilation

Further information: Genetic assimilation

The Baldwin effect has been confused with, and sometimes conflated with, a different evolutionary theory also based on phenotypic plasticity, C. H. Waddington's genetic assimilation. The Baldwin effect includes genetic accommodation, of which one type is genetic assimilation. Science historian Laurent Loison has written that "the Baldwin effect and genetic assimilation, even if they are quite close, should not be conflated".