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Friday, October 7, 2022

World Peace Council

From Wikipedia, the free encyclopedia

Membership in the World Peace Council:
  National affiliates
  Affiliates of the International Federation for Peace and Conciliation
  Countries with both national affiliates and the IFPC

The World Peace Council (WPC) is an international organization with the self described goals of advocating for universal disarmament, sovereignty and independence and peaceful co-existence, and campaigns against imperialism, weapons of mass destruction and all forms of discrimination. Founded from an initiative of the Information Bureau of the Communist and Workers' Parties, WPC emerged from the bureau’s worldview that divided humanity into Soviet-led "peace-loving" progressive forces and US-led "warmongering" capitalist countries. Throughout the Cold War, WPC operated as a front organization as it was controlled and largely funded by the Soviet Union, and refrained from criticizing or even defended the Soviet Union's involvement in numerous conflicts. These factors led to the decline of its influence over the peace movement in non-Communist countries. Its first president was the French physicist and activist Frédéric Joliot-Curie. It was based in Helsinki, Finland from 1968 to 1999, and since in Athens, Greece.

History

Origins

A WPC Congress in East Berlin on 1 July 1952 showing Picasso's dove above the stage, banner reading "Germany must be a land of Peace"

In August 1948 through the initiative of the Communist Information Bureau (Cominform) a "World Congress of Intellectuals for Peace" was held in Wroclaw, Poland. This gathering established a permanent organisation called the International Liaison Committee of Intellectuals for Peace—a group which joined with another international Communist organisation, the Women's International Democratic Federation to convene a second international conclave in Paris in April 1949, a meeting designated the World Congress of Partisans for Peace (Congrès Mondial des Partisans de la Paix). Some 2,000 delegates from 75 countries were in attendance at this foundation gathering in the French capital.

A new permanent organization emerged from the April 1949 conclave, the World Committee of Partisans for Peace. At a Second World Congress held in Warsaw in November 1950, this group adopted the new name World Peace Council (WPC). The origins of the WPC lay in the Cominform's doctrine that the world was divided between "peace-loving" progressive forces led by the Soviet Union and "warmongering" capitalist countries led by the United States, declaring that peace "should now become the pivot of the entire activity of the Communist Parties", and most western Communist parties followed this policy.

In 1950, Cominform adopted the report of Mikhail Suslov, a senior Soviet official, praising the Partisans for Peace and resolving that, "The Communist and Workers' Parties must utilize all means of struggle to secure a stable and lasting peace, subordinating their entire activity to this" and that "Particular attention should be devoted to drawing into the peace movement trade unions, women's, youth, cooperative, sport, cultural, education, religious and other organizations, and also scientists, writers, journalists, cultural workers, parliamentary and other political and public leaders who act in defense of peace and against war."

Lawrence Wittner, a historian of the post-war peace movement, argues that the Soviet Union devoted great efforts to the promotion of the WPC in the early post-war years because it feared an American attack and American superiority of arms at a time when the US possessed the atom bomb but the Soviet Union had not yet developed it. This was in opposition to the theory that America had no plans to attack anyone, and the purpose of the WPC was to disarm the US and the NATO alliance for a future Soviet attack.

Wroclaw 1948 and New York 1949

Session of the World Congress of Intellectuals for Peace in Wrocław in 1948

The World Congress of Intellectuals for Peace met in Wroclaw on 6 August 1948. Julian Huxley, the chair of UNESCO, chaired the meeting in the hope of bridging Cold War divisions, but later wrote that "there was no discussion in the ordinary sense of the word." Speakers delivered lengthy condemnation of the West and praises of the Soviet Union. Albert Einstein had been invited to send an address, but when the organisers found that it advocated world government and that his representative refused to change it, they substituted another document by Einstein without his consent, leaving Einstein feeling that he had been badly used.

The Congress elected a permanent International Committee of Intellectuals in Defence of Peace (also known as the International Committee of Intellectuals for Peace and the International Liaison Committee of Intellectuals for Peace) with headquarters in Paris. It called for the establishment of national branches and national meetings along the same lines as the World Congress. In accordance with this policy, a Cultural and Scientific Conference for World Peace was held in New York City in March 1949 at the Waldorf Astoria Hotel, sponsored by the National Council of Arts, Sciences and Professions.

Paris and Prague 1949

The World Congress of Partisans for Peace in Paris (20 April 1949) repeated the Cominform line that the world was divided between "a non-aggressive Soviet group and a war-minded imperialistic group, headed by the United States government". It established a World Committee of Partisans for Peace, led by a twelve-person Executive Bureau and chaired by Professor Frédéric Joliot-Curie, a Nobel Prize-winning physicist, High Commissioner for Atomic Energy and member of the French Institute. Most of the Executive were Communists. One delegate to the Congress, the Swedish artist Bo Beskow [sv], heard no spontaneous contributions or free discussions, only prepared speeches, and described the atmosphere there as "agitated", "aggressive" and "warlike". A speech given at Paris by Paul Robeson—the polyglot lawyer, folksinger, and actor son of a runaway slave—was widely quoted in the American press for stating that African Americans should not and would not fight for the United States in any prospective war against the Soviet Union; following his return, he was subsequently blacklisted and his passport confiscated for years. The Congress was disrupted by the French authorities who refused visas to so many delegates that a simultaneous Congress was held in Prague." Robeson's performance of "The March of the Volunteers" in Prague for the delegation from the incipient People's Republic of China was its earliest formal use as the country's national anthem. Picasso's lithograph, La Colombe (The Dove) was chosen as the emblem for the Congress and was subsequently adopted as the symbol of the WPC.

Sheffield and Warsaw 1950

In 1950, the World Congress of the Supporters of Peace adopted a permanent constitution for the World Peace Council, which replaced the Committee of Partisans for Peace. The opening congress of the WPC condemned the atom-bomb and the American invasion of Korea. It followed the Cominform line, recommending the creation of national peace committees in every country, and rejected pacifism and the non-aligned peace movement. It was originally scheduled for Sheffield but the British authorities, who wished to undermine the WPC, refused visas to many delegates and the Congress was forced to move to Warsaw. British Prime Minister Clement Attlee denounced the Congress as a "bogus forum of peace with the real aim of sabotaging national defence" and said there would be a "reasonable limit" on foreign delegates. Among those excluded by the government were Frédéric Joliot-Curie, Ilya Ehrenburg, Alexander Fadeyev, and Dmitri Shostakovich. The number of delegates at Sheffield was reduced from an anticipated 2,000 to 500, half of whom were British.

1950s

The WPC was directed by the International Department of the Central Committee of the Soviet Communist Party through the Soviet Peace Committee, although it tended not to present itself as an organ of Soviet foreign policy, but rather as the expression of the aspirations of the "peace loving peoples of the world".

In its early days the WPC attracted numerous "political and intellectual superstars", including W. E. B. Du Bois, Paul Robeson, Howard Fast, Pablo Picasso, Louis Aragon, Jorge Amado, Pablo Neruda, György Lukacs, Renato Guttuso, Jean-Paul Sartre, Diego Rivera, Muhammad al-Ashmar and Frédéric Joliot-Curie. Most were Communists or fellow travellers.

In the 1950s, congresses were held in Vienna, Berlin, Helsinki and Stockholm. The January 1952 World Congress of People in Vienna represented Joseph Stalin's strategy of peaceful coexistence, resulting in a more broad-based conference. Among those attending were Jean-Paul Sartre and Hervé Bazin.

In 1955, another WPC meeting in Vienna launched an "Appeal against the Preparations for Nuclear War", with grandiose claims about its success.

The WPC led the international peace movement in the decade after the Second World War, but its failure to speak out against the Soviet suppression of the 1956 Hungarian uprising and the resumption of Soviet nuclear tests in 1961 marginalised it, and in the 1960s it was eclipsed by the newer, non-aligned peace organizations like the Campaign for Nuclear Disarmament. At first, Communists denounced the Campaign for Nuclear Disarmament for "splitting the peace movement" but they were compelled to join it when they saw how popular it was.

1960s

Throughout much of the 1960s and early 1970s, the WPC campaigned against the US's role in the Vietnam War. Opposition to the Vietnam War was widespread in the mid-1960s and most of the anti-war activity had nothing to do with the WPC, which decided, under the leadership of J. D. Bernal, to take a softer line with non-aligned peace groups in order to secure their co-operation. In particular, Bernal believed that the WPC's influence with these groups was jeopardized by China's insistence that the WPC give unequivocal support to North Vietnam in the war.

In 1968, the Warsaw Pact invasion of Czechoslovakia occasioned unprecedented dissent from Soviet policy within the WPC. It brought about such a crisis in the Secretariat that in September that year only one delegate supported the invasion. However, the Soviet Union soon reasserted control, and according to the US State Department, "The WPC's eighth world assembly in East Berlin in June 1969 was widely criticized by various participants for its lack of spontaneity and carefully orchestrated Soviet supervision. As the British General Secretary of the International Confederation for Disarmament and Peace and a delegate to the 1969 assembly wrote (Tribune, 4 July 1969): 'There were a number [of delegates] who decided to vote against the general resolution for three reasons (a) it was platitudinous (b) it was one sided and (c) in protest against restrictions on minorities and the press within the assembly. This proved impossible in the end for no vote was taken.'"

Activities

Romesh Chandra (left), President of the World Peace Council, with Erich Honecker, East German head of state, 1981

Until the late 1980s, the World Peace Council's principal activity was the organization of large international congresses, nearly all of which had over 2,000 delegates representing most of the countries of the world. Most of the delegates came from pro-Communist organizations, with some observers from non-aligned bodies. There were also meetings of the WPC Assembly, its highest governing body. The congresses and assemblies issued statements, appeals and resolutions that called for world peace in general terms and condemned US weapons policy, invasions and military actions. The US Department of State described the congresses as follows: "The majority of participants in the assemblies are Soviet and East European communist party members, representatives of foreign communist parties, and representatives of other Soviet-backed international fronts. Token noncommunist participation serves to lend an element of credibility. Discussion usually is confined to the inequities of Western socioeconomic systems and attacks on the military and foreign policies of the United States and other imperialist, fascist nations. Resolutions advocating policies favored by the U.S.S.R. and other communist nations are passed by acclamation, not by vote. In most cases, delegates do not see the texts until they are published in the communist media. Attempts by noncommunist delegates to discuss Soviet actions (such as the invasion of Afghanistan) are dismissed as interference in internal affairs or anti-Soviet propaganda. Dissent among delegates often is suppressed and never acknowledged in final resolutions or communiques. All assemblies praise the U.S.S.R. and other progressive societies and endorse Soviet foreign policy positions."

The WPC was involved in demonstrations and protests especially in areas bordering US military installations in Western Europe believed to house nuclear weapons. It campaigned against US-led military operations, especially the Vietnam War, although it did not condemn similar Soviet actions in Hungary and in Afghanistan.

On 18 March 1950, the WPC launched its Stockholm Appeal at a meeting of the Permanent Committee of the World Peace Congress, calling for the absolute prohibition of nuclear weapons. The campaign won popular support, collecting, it is said, 560 million signatures in Europe, most from socialist countries, including 10 million in France (including that of the young Jacques Chirac), and 155 million signatures in the Soviet Union – the entire adult population. Several non-aligned peace groups who had distanced themselves from the WPC advised their supporters not to sign the Appeal.

In June 1975 the WPC launched a second Stockholm Appeal during a period of détente between East and West. It declared that, "The victories of peace and détente have created a new international climate, new hopes, new confidence, new optimism among the peoples."

In the 1980s it campaigned against the deployment of U.S. missiles in Europe.

It published two magazines, New Perspectives and Peace Courier. Its current magazine is Peace Messenger.

Associated groups

In accordance with the Comniform's 1950 resolution to draw into the peace movement trade unions, women's and youth organisations, scientists, writers and journalists, etc., several Communist mass organisations supported the WPC, for example:

Relations with non-aligned peace groups

The WPC has been described as caught in contradictions as "it sought to become a broad world movement while being instrumentalized increasingly to serve foreign policy in the Soviet Union and nominally socialist countries." From the 1950s until the late 1980s it tried to use non-aligned peace organizations to spread the Soviet point of view, alternately wooing and attacking them, either for their pacifism or their refusal to support the Soviet Union. Until the early 1960s there was limited co-operation between such groups and the WPC, but they gradually dissociated themselves as they discovered it was impossible to criticize the Soviet Union at WPC conferences.

From the late 1940s to the late 1950s the WPC, with its large budget and high-profile conferences, dominated the peace movement, to the extent that the movement became identified with the Communist cause. The formation of the Campaign for Nuclear Disarmament in Britain in 1957 sparked a rapid growth in the unaligned peace movement and its detachment from the WPC. However, the public and some Western leaders still tended to regard all peace activists as Communists. For example, US President Ronald Reagan said that the big peace demonstrations in Europe in 1981 were "all sponsored by a thing called the World Peace Council, which is bought and paid for by the Soviet Union", and Soviet defector Vladimir Bukovsky claimed that they were co-ordinated at the WPC's 1980 World Parliament of Peoples for Peace in Sofia. The FBI reported to the United States House Permanent Select Committee on Intelligence that the WPC-affiliated U.S. Peace Council was one of the organizers of a large 1982 peace protest in New York City, but said that the KGB had not manipulated the American movement "significantly." International Physicians for the Prevention of Nuclear War was said to have had "overlapping membership and similar policies" to the WPC. and the Pugwash Conferences on Science and World Affairs and the Dartmouth Conferences were said to have been used by Soviet delegates to promote Soviet propaganda. Joseph Rotblat, one of the leaders of the Pugwash movement, said that although a few participants in Pugwash conferences from the Soviet Union "were obviously sent to push the party line ... the majority were genuine scientists and behaved as such".

As the non-aligned peace movement "was constantly under threat of being tarnished by association with avowedly pro-Soviet groups", many individuals and organizations "studiously avoided contact with Communists and fellow-travellers." Some western delegates walked out of the Wroclaw conference of 1948, and in 1949 the World Pacifist Meeting warned against active collaboration with Communists. In the same year, several members of the British Peace Pledge Union, including Vera Brittain, Michael Tippett, and Sybil Morrison, criticised the WPC-affiliated British Peace Committee for what they saw as its "unquestioning hero-worship" of the Soviet Union. In 1950, several Swedish peace organizations warned their supporters against signing the WPC's Stockholm Appeal. In 1953, the International Liaison Committee of Organizations for Peace stated that it had "no association with the World Peace Council". In 1956, a year in which the WPC condemned the Suez war but not the Russian suppression of the 1956 Hungarian uprising, the German section of War Resisters International condemned it for its failure to respond to Soviet H-bomb tests. In Sweden, Aktionsgruppen Mot Svensk Atombomb discouraged its members from participating in Communist-led peace committees. The WPC attempted to co-opt the eminent peace campaigner Bertrand Russell, much to his annoyance, and in 1957 he refused the award of the WPC's International Peace Prize. In Britain, CND advised local groups in 1958 not to participate in a forthcoming WPC conference. In the US, SANE rejected WPC appeals for co-operation. A final break occurred during the WPC's 1962 World Congress for Peace and Disarmament in Moscow. The WPC had invited non-aligned peace groups, who were permitted to criticize Soviet nuclear testing, but when western activists including the British Committee of 100 tried to demonstrate in Red Square against Soviet weapons and the Communist system, their banners were confiscated and they were threatened with deportation. As a result of this confrontation, 40 non-aligned organizations decided to form a new international body, the International Confederation for Disarmament and Peace, which was not to have Soviet members.

From about 1982, following the proclamation of martial law in Poland, the Soviet Union adopted a harder line with non-aligned groups, apparently because their failure to prevent the deployment of Cruise and Pershing missiles. In December 1982, the Soviet Peace Committee President, Yuri Zhukov, returning to the rhetoric of the mid-1950s, wrote to several hundred non-communist peace groups in Western Europe accusing the Bertrand Russell Peace Foundation of "fueling the cold war by claiming that both NATO and the Warsaw Pact bear equal responsibility for the arms race and international tension. Zhukov denounced the West Berlin Working Group for a Nuclear-Free Europe, organizers of a May 1983 European disarmament conference in Berlin, for allegedly siding with NATO, attempting to split the peace movement, and distracting the peaceloving public from the main source of the deadly threat posed against the peoples of Europe-the plans for stationing a new generation of nuclear missiles in Europe in 1983." In 1983, the British peace campaigner E. P. Thompson, a leader of European Nuclear Disarmament, attended the World Peace Council's World Assembly for Peace and Life Against Nuclear War in Prague at the suggestion of the Czech dissident group Charter 77 and raised the issue of democracy and civil liberties in the Communist states, only for Assembly to respond by loudly applauding a delegate who said that "the so-called dissident issue was not a matter for the international peace movement, but something that had been injected into it artificially by anti-communists." The Hungarian student peace group, Dialogue, also tried to attend the 1983 Assembly but were met with tear gas, arrests, and deportation to Hungary; the following year the authorities banned it.

Rainer Santi, in his history of the International Peace Bureau, said that the WPC "always had difficulty in securing cooperation from West European and North American peace organisations because of its obvious affiliation with Socialist countries and the foreign policy of the Soviet Union. Especially difficult to digest, was that instead of criticising the Soviet Union's unilaterally resumed atmospheric nuclear testing in 1961, the WPC issued a statement rationalizing it. In 1979 the World Peace Council explained the Soviet invasion of Afghanistan as an act of solidarity in the face of Chinese and US aggression against Afghanistan." Rob Prince, a former secretary of the WPC, suggested that it simply failed to connect with the western peace movement because it used most of its funds on international travel and lavish conferences. It had poor intelligence on Western peace groups, and, even though its HQ was in Helsinki, had no contact with Finnish peace organizations.

After the demise of the Soviet Union

By the mid-1980s the Soviet Peace Committee "concluded that the WPC was a politically expendable and spent force," although it continued to provide funds until 1991. As the Soviet Peace Committee was the conduit for Soviet direction of the WPC, this judgement represented a downgrading of the WPC by the Soviet Communist Party. Under Mikhail Gorbachev, the Soviet Peace Committee developed bilateral international contacts "in which the WPC not only played no role, but was a liability." Gorbachev never even met WPC President Romesh Chandra and excluded him from many Moscow international forums. Following the 1991 breakup of the Soviet Union, the WPC lost most of its support, income and staff and dwindled to a small core group. Its international conferences now attract only a tenth of the delegates that its Soviet-backed conferences could attract (see below), although it still issues statements couched in similar terms to those of its historic appeals.

Location

The WPC first set up its offices in Paris, but was accused by the French government of engaging in "fifth column" activities and was expelled in 1952. It moved to Prague and then to Vienna. In 1957 it was banned by the Austrian government. It was invited to Prague but did not move there, had no official HQ but continued to operate in Vienna under cover of the International Institute for Peace. In 1968 it re-assumed its name and moved to Helsinki, Finland, where it remained until 1999. In 2000 it re-located to Athens, Greece.

Funding

According to the WPC, 90 percent of its funding came from the Soviet Union, which was said to have given it $49 million. Its current income is believed to derive mainly from the interest on a $10m payment made by the Soviet Peace Committee in around 1991, although its finances remain shrouded in mystery.

Allegations of CIA measures against the WPC

The Congress for Cultural Freedom was founded in 1950 with the support of the CIA to counter the propaganda of the emerging WPC, and Phillip Agee claimed that the WPC was a Soviet front for propaganda which CIA covertly tried to neutralize and to prevent the WPC from organizing outside the Communist bloc.

Current organisation

The WPC currently states its goals as: Actions against imperialist wars and occupation of sovereign countries and nations; prohibition of all weapons of mass destruction; abolition of foreign military bases; universal disarmament under effective international control; elimination of all forms of colonialism, neo-colonialism, racism, sexism and other forms of discrimination; respect for the right of peoples to sovereignty and independence, essential for the establishment of peace; non-interference in the internal affairs of nations; peaceful co-existence between states with different political systems; negotiations instead of use of force in the settlement of differences between nations.

The WPC is a registered NGO at the United Nations and co-operates primarily with the Non-Aligned Movement. It cooperates with United Nations Educational, Scientific and Cultural Organization (UNESCO), United Nations Conference on Trade and Development (UNCTAD), United Nations Industrial Development Organization (UNIDO), International Labour Organization (ILO), and other UN specialized agencies, special committees and departments. It is said to have successfully influenced their agendas, the terms of discussion and the orientations of their resolutions. It also cooperates with the African Union, the League of Arab States, and other inter-governmental bodies.

Leadership

  • President: Socorro Gomes, Brazilian Center for Solidarity with the People and the Struggle for Peace (CEBRAPAZ)
  • General Secretary: Thanasis Pafilis, Greek Committee for International Détente and Peace (EEDYE)
  • Executive Secretary: Iraklis Tsavdaridis, Greek Committee for International Détente and Peace (EEDYE)

Secretariat

The members of the Secretariat of the WPC are:

Peace prizes

The WPC awards several peace prizes, some of which, it has been said, were awarded to politicians who funded the organization.

Congresses and assemblies

The highest WPC body, the Assembly, meets every three years.

Year Event Location Country No. of delegates Countries represented Comments
1948 World Congress of Intellectuals in Defense of Peace Wrocław Poland 600 46
1949 World Congress of Advocates of Peace Paris France 2,200 72 Established the World Committee of Partisans for Peace, chaired by Frédéric Joliot-Curie.
Prague Czechoslovakia
1950 World Congress of the Supporters of Peace Sheffield United Kingdom

Moved from Sheffield to Warsaw as a result of the British government refusing visas to delegates.
Warsaw Poland

1951
Stockholm Sweden


1952 Congress of the People for Peace Vienna Austria

Presiding committee included Jean-Paul Sartre, Paul Robeson, Pablo Neruda, Diego Rivera, and Louis Aragon. Also attended by Madame Sun Yat Sen, Ilya Ehrenburg and Hewlett Johnson.
1952
East Berlin East Germany


1953
Budapest Hungary

15-20 June
1954
East Berlin East Germany

23–28 May
1955
Helsinki Finland

June
1958 World Congress on Disarmament and International Cooperation Stockholm Sweden

Bertrand Russell withdrew his sponsorship of the congress and denounced the WPC for its refusal to condemn the Soviet invasion of Hungary in 1956 and the kidnapping and murder of Hungarian prime minister, Imre Nagy.
1962 World Conference for General Disarmament and Peace Moscow Soviet Union

Addressed by Nikita Khrushchev, General Secretary of the Communist Party of the Soviet Union. Attended by delegates from non-aligned groups. Sponsors include Bertrand Russell and Canon John Collins of CND. As a result of confrontation between western and Soviet delegates, 40 non-aligned organizations form the International Confederation for Disarmament and Peace, without Soviet membership.
1965 World Congress for Peace, National Independence and General disarmament Helsinki Finland 1,470 98 Called for withdrawal of all U.S. armed forces from Vietnam.
1971 Assembly Budapest Hungary

1973 World Congress of Peace Forces Moscow Soviet Union 3,200
Chaired by Romesh Chandra, general secretary of the WPC. The main speaker was Leonid Brezhnev
1977
Warsaw Poland


1980 World Parliament of Peoples for Peace Sofia Bulgaria 2,230 134 Launched campaigns against stationing of new US nuclear weapons in Western Europe, against Camp David Accords between Egypt and Israel, and campaigns of solidarity with Vietnam, Syria, Cuba, the PLO and the Soviet-backed regime in Afghanistan.
1983 World Assembly for Peace and Life Against Nuclear War Prague Czechoslovakia 2,635 132 Noted that "An especially acute danger is represented by plans to deploy first-strike nuclear missiles in Western Europe." Members of Charter 77 not permitted to attend. Members of the unofficial Hungarian student peace movement Dialógus (Dialogue) who attempted to attend "were met with tear gas, arrests, and later deportation back to Hungary."
1986 World Congress for the International Year of Peace Copenhagen Denmark 2,648
15-19 October
The International Year of Peace was declared by the United Nations. This was said to be the first WPC-sponsored congress to be held in a NATO country. The Coalition for Peace through Security demonstrated against the Soviet occupation of Afghanistan, giving rise to worldwide media coverage.
1990
Athens Greece


1996
México City Mexico


2000
Athens Greece
186
2004
Athens 150 50+
2005
Seoul South Korea


2008 World Congress of the World Peace Council Caracas, Venezuela 120 76
2009
New York United States 400 194
2012 World Peace Assembly and Conference Kathmandu Nepal

2016 Anti-Nato Conference Warsaw Poland 85 22

Past presidents

Current members

Under its current rules, WPC members are national and international organizations that agree with its main principles and any of its objectives and pay membership fees. Other organizations may join at the discretion of the Executive Committee or become associate members. Distinguished individuals may become honorary members at the discretion of the Executive Committee.

As of March 2014, the WPC lists the following organizations among its "members and friends".

Current Communist States

Former Soviet Union

Former Eastern bloc

Europe

Asia

Africa

Americas

Oceania

Other

Plant evolutionary developmental biology

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

Evolutionary developmental biology (evo-devo) is the study of developmental programs and patterns from an evolutionary perspective. It seeks to understand the various influences shaping the form and nature of life on the planet. Evo-devo arose as a separate branch of science rather recently. An early sign of this occurred in 1999.

Most of the synthesis in evo-devo has been in the field of animal evolution, one reason being the presence of model systems like Drosophila melanogaster, C. elegans, zebrafish and Xenopus laevis. However, since 1980, a wealth of information on plant morphology, coupled with modern molecular techniques has helped shed light on the conserved and unique developmental patterns in the plant kingdom also.

Historical perspective

Before 1900

Johann Wolfgang von Goethe first used the word morphology.

The origin of the term "morphology" is generally attributed to Johann Wolfgang von Goethe (1749–1832). He was of the opinion that there is an underlying fundamental organisation (Bauplan) in the diversity of flowering plants. In his book The Metamorphosis of Plants, he proposed that the Bauplan enabled us to predict the forms of plants that had not yet been discovered. Goethe was the first to make the perceptive suggestion that flowers consist of modified leaves. He also entertained different complementary interpretations.

In the middle centuries, several basic foundations of our current understanding of plant morphology were laid down. Nehemiah Grew, Marcello Malpighi, Robert Hooke, Antonie van Leeuwenhoek, Wilhelm von Nageli were just some of the people who helped build knowledge on plant morphology at various levels of organisation. It was the taxonomical classification of Carl Linnaeus in the eighteenth century though, that generated a firm base for the knowledge to stand on and expand. The introduction of the concept of Darwinism in contemporary scientific discourse also had had an effect on the thinking on plant forms and their evolution.

Wilhelm Hofmeister, one of the most brilliant botanists of his times, was the one to diverge away from the idealist way of pursuing botany. Over the course of his life, he brought an interdisciplinary outlook into botanical thinking. He came up with biophysical explanations on phenomena like phototaxis and geotaxis, and also discovered the alternation of generations in the plant life cycle.

1900 to the present

Arabidopsis thaliana, a flowering plant that has been a model system for most of plant molecular studies

The past century witnessed a rapid progress in the study of plant anatomy. The focus shifted from the population level to more reductionist levels. While the first half of the century saw expansion in developmental knowledge at the tissue and the organ level, in the latter half, especially since the 1990s, there has also been a strong impetus on gaining molecular information.

Edward Charles Jeffrey was one of the early evo-devo researchers of the 20th century. He performed a comparative analyses of the vasculatures of living and fossil gymnosperms and came to the conclusion that the storage parenchyma has been derived from tracheids. His research focussed primarily on plant anatomy in the context of phylogeny. This tradition of evolutionary analyses of plant architectures was further advanced by Katherine Esau, best known for her book The Plant Anatomy. Her work focussed on the origin and development of various tissues in different plants. Working with Vernon Cheadle, she also explained the evolutionary specialization of the phloem tissue with respect to its function.

In 1959 Walter Zimmermann published a revised edition of Die Phylogenie der Planzen. This very comprehensive work, which has not been translated into English, has no equal in the literature. It presents plant evolution as the evolution of plant development (hologeny). In this sense it is plant evolutionary developmental biology (plant evo-devo). According to Zimmermann, diversity in plant evolution occurs though various developmental processes. Three very basic processes are heterochrony (changes in the timing of developmental processes), heterotopy (changes in the relative positioning of processes), and heteromorphy (changes in form processes).

In the meantime, by the beginning of the latter half of the 1900s, Arabidopsis thaliana had begun to be used in some developmental studies. The first collection of Arabidopsis thaliana mutants were made around 1945. However it formally became established as a model organism only in 1998.

The recent spurt in information on various plant-related processes has largely been a result of the revolution in molecular biology. Powerful techniques like mutagenesis and complementation were made possible in Arabidopsis thaliana via generation of T-DNA containing mutant lines, recombinant plasmids, techniques like transposon tagging etc. Availability of complete physical and genetic maps, RNAi vectors, and rapid transformation protocols are some of the technologies that have significantly altered the scope of the field. Recently, there has also been a massive increase in the genome and EST sequences of various non-model species, which, coupled with the bioinformatics tools existing today, generate opportunities in the field of plant evo-devo research.

Gérard Cusset provided a detailed in-depth analysis of the history of plant morphology, including plant development and evolution, from its beginnings to the end of the 20th century. Rolf Sattler discussed fundamental principles of plant morphology.

Organisms, databases and tools

The sampling of the Floral Genome Project

The most important model systems in plant development have been arabidopsis and maize. Maize has traditionally been the favorite of plant geneticists, while extensive resources in almost every area of plant physiology and development are available for Arabidopsis thaliana. Apart from these, rice, Antirrhinum majus, Brassica, and tomato are also being used in a variety of studies. The genomes of Arabidopsis thaliana and rice have been completely sequenced, while the others are in process. It must be emphasized here that the information from these "model" organisms form the basis of our developmental knowledge. While Brassica has been used primarily because of its convenient location in the phylogenetic tree in the mustard family, Antirrhinum majus is a convenient system for studying leaf architecture. Rice has been traditionally used for studying responses to hormones like abscissic acid and gibberelin as well as responses to stress. However, recently, not just the domesticated rice strain, but also the wild strains have been studied for their underlying genetic architectures.

Some people have objected against extending the results of model organisms to the plant world. One argument is that the effect of gene knockouts in lab conditions wouldn't truly reflect even the same plant's response in the natural world. Also, these supposedly crucial genes might not be responsible for the evolutionary origin of that character. For these reasons, a comparative study of plant traits has been proposed as the way to go now.

Since the past few years, researchers have indeed begun looking at non-model, "non-conventional" organisms using modern genetic tools. One example of this is the Floral Genome Project, which envisages to study the evolution of the current patterns in the genetic architecture of the flower through comparative genetic analyses, with a focus on EST sequences. Like the FGP, there are several such ongoing projects that aim to find out conserved and diverse patterns in evolution of the plant shape. Expressed sequence tag (EST) sequences of quite a few non-model plants like sugarcane, apple, barley, cycas, coffee, to name a few, are available freely online. The Cycad Genomics Project, for example, aims to understand the differences in structure and function of genes between gymnosperms and angiosperms through sampling in the order Cycadales. In the process, it intends to make available information for the study of evolution of seeds, cones and evolution of life cycle patterns. Presently the most important sequenced genomes from an evo-devo point of view include those of A. thaliana (a flowering plant), poplar (a woody plant), Physcomitrella patens (a bryophyte), Maize (extensive genetic information), and Chlamydomonas reinhardtii (a green alga). The impact of such a vast amount of information on understanding common underlying developmental mechanisms can easily be realised.

Apart from EST and genome sequences, several other tools like PCR, yeast two-hybrid system, microarrays, RNA Interference, SAGE, QTL mapping etc. permit the rapid study of plant developmental patterns. Recently, cross-species hybridization has begun to be employed on microarray chips, to study the conservation and divergence in mRNA expression patterns between closely related species.[25] Techniques for analyzing this kind of data have also progressed over the past decade. We now have better models for molecular evolution, more refined analysis algorithms and better computing power as a result of advances in computer sciences.

Evolution of plant morphology

Overview of plant evolution

Evidence suggests that an algal scum formed on the land 1,200 million years ago, but it was not until the Ordovician period, around 500 million years ago, that land plants appeared. These began to diversify in the late Silurian period, around 420 million years ago, and the fruits of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage known as the Rhynie chert. This chert preserved early plants in cellular detail, petrified in volcanic springs. By the middle of the Devonian period most of the features recognised in plants today are present, including roots and leaves. By the late Devonian, plants had reached a degree of sophistication that allowed them to form forests of tall trees. Evolutionary innovation continued after the Devonian period. Most plant groups were relatively unscathed by the Permo-Triassic extinction event, although the structures of communities changed. This may have set the scene for the evolution of flowering plants in the Triassic (~200 million years ago), which exploded the Cretaceous and Tertiary. The latest major group of plants to evolve were the grasses, which became important in the mid Tertiary, from around 40 million years ago. The grasses, as well as many other groups, evolved new mechanisms of metabolism to survive the low CO2 and warm, dry conditions of the tropics over the last 10 million years. Although animals and plants evolved their bodyplan independently, they both express a developmental constraint during mid-embryogenesis that limits their morphological diversification.

Meristems

The meristem architectures differ between angiosperms, gymnosperms and pteridophytes. The gymnosperm vegetative meristem lacks organization into distinct tunica and corpus layers. They possess large cells called central mother cells. In angiosperms, the outermost layer of cells divides anticlinally to generate the new cells, while in gymnosperms, the plane of division in the meristem differs for different cells. However, the apical cells do contain organelles like large vacuoles and starch grains, like the angiosperm meristematic cells.

Pteridophytes, like fern, on the other hand, do not possess a multicellular apical meristem. They possess a tetrahedral apical cell, which goes on to form the plant body. Any somatic mutation in this cell can lead to hereditary transmission of that mutation. The earliest meristem-like organization is seen in an algal organism from group Charales that has a single dividing cell at the tip, much like the pteridophytes, yet simpler. One can thus see a clear pattern in evolution of the meristematic tissue, from pteridophytes to angiosperms: Pteridophytes, with a single meristematic cell; gymnosperms with a multicellular, but less defined organization; and finally, angiosperms, with the highest degree of organization.

Evolution of plant transcriptional regulation

Transcription factors and transcriptional regulatory networks play key roles in plant development and stress responses, as well as their evolution. During plant landing, many novel transcription factor families emerged and are preferentially wired into the networks of multicellular development, reproduction, and organ development, contributing to more complex morphogenesis of land plants.

Evolution of leaves

Origins of the leaf

Leaf lamina. The leaf architecture probably arose multiple times in the plant lineage

Leaves are the primary photosynthetic organs of a plant. Based on their structure, they are classified into two types - microphylls, that lack complex venation patterns and megaphylls, that are large and with a complex venation. It has been proposed that these structures arose independently. Megaphylls, according to the telome theory, have evolved from plants that showed a three-dimensional branching architecture, through three transformations: planation, which involved formation of a planar architecture, webbing, or formation of the outgrowths between the planar branches and fusion, where these webbed outgrowths fused to form a proper leaf lamina. Studies have revealed that these three steps happened multiple times in the evolution of today's leaves.

Contrary to the telome theory, developmental studies of compound leaves have shown that, unlike simple leaves, compound leaves branch in three dimensions. Consequently, they appear partially homologous with shoots as postulated by Agnes Arber in her partial-shoot theory of the leaf. They appear to be part of a continuum between morphological categories, especially those of leaf and shoot. Molecular genetics confirmed these conclusions (see below).

It has been proposed that the before the evolution of leaves, plants had the photosynthetic apparatus on the stems. Today's megaphyll leaves probably became commonplace some 360 mya, about 40 my after the simple leafless plants had colonized the land in the early Devonian period. This spread has been linked to the fall in the atmospheric carbon dioxide concentrations in the late Paleozoic era associated with a rise in density of stomata on leaf surface. This must have allowed for better transpiration rates and gas exchange. Large leaves with less stomata would have heated up in the sun's rays, but an increased stomatal density allowed for a better-cooled leaf, thus making its spread feasible.

Factors influencing leaf architectures

Various physical and physiological forces like light intensity, humidity, temperature, wind speeds etc. are thought to have influenced evolution of leaf shape and size. It is observed that high trees rarely have large leaves, owing to the obstruction they generate for winds. This obstruction can eventually lead to the tearing of leaves, if they are large. Similarly, trees that grow in temperate or taiga regions have pointed leaves, presumably to prevent nucleation of ice onto the leaf surface and reduce water loss due to transpiration. Herbivory, not only by large mammals, but also small insects has been implicated as a driving force in leaf evolution, an example being plants of the genus Aciphylla, that are commonly found in New Zealand. The now-extinct moas (birds) fed upon these plants, and the spines on the leaves probably discouraged the moas from feeding on them. Other members of Aciphylla that did not co-exist with the moas were spineless.

Genetic evidences for leaf evolution

At the genetic level, developmental studies have shown that repression of the KNOX genes is required for initiation of the leaf primordium. This is brought about by ARP genes, which encode transcription factors. Genes of this type have been found in many plants studied till now, and the mechanism i.e. repression of KNOX genes in leaf primordia, seems to be quite conserved. Expression of KNOX genes in leaves produces complex leaves. It is speculated that the ARP function arose quite early in vascular plant evolution, because members of the primitive group lycophytes also have a functionally similar gene  Other players that have a conserved role in defining leaf primordia are the phytohormone auxin, gibberelin and cytokinin.

The diversity of leaves

One feature of a plant is its phyllotaxy. The arrangement of leaves on the plant body is such that the plant can maximally harvest light under the given constraints, and hence, one might expect the trait to be genetically robust. However, it may not be so. In maize, a mutation in only one gene called abphyl (abnormal phyllotaxy) was enough to change the phyllotaxy of the leaves. It implies that sometimes, mutational tweaking of a single locus on the genome is enough to generate diversity. The abphyl gene was later on shown to encode a cytokinin response regulator protein.

Once the leaf primordial cells are established from the SAM cells, the new axes for leaf growth are defined, one important (and more studied) among them being the abaxial-adaxial (lower-upper surface) axes. The genes involved in defining this, and the other axes seem to be more or less conserved among higher plants. Proteins of the HD-ZIPIII family have been implicated in defining the adaxial identity. These proteins deviate some cells in the leaf primordium from the default abaxial state, and make them adaxial. It is believed that in early plants with leaves, the leaves just had one type of surface - the abaxial one. This is the underside of today's leaves. The definition of the adaxial identity occurred some 200 million years after the abaxial identity was established. One can thus imagine the early leaves as an intermediate stage in evolution of today's leaves, having just arisen from spiny stem-like outgrowths of their leafless ancestors, covered with stomata all over, and not optimized as much for light harvesting.

How the infinite variety of plant leaves is generated is a subject of intense research. Some common themes have emerged. One of the most significant is the involvement of KNOX genes in generating compound leaves, as in tomato (see above). But this again is not universal. For example, pea uses a different mechanism for doing the same thing. Mutations in genes affecting leaf curvature can also change leaf form, by changing the leaf from flat, to a crinkly shape, like the shape of cabbage leaves. There also exist different morphogen gradients in a developing leaf which define the leaf's axis. Changes in these morphogen gradients may also affect the leaf form. Another very important class of regulators of leaf development are the microRNAs, whose role in this process has just begun to be documented. The coming years should see a rapid development in comparative studies on leaf development, with many EST sequences involved in the process coming online.

Molecular genetics has also shed light on the relation between radial symmetry (characteristic of stems) and dorsiventral symmetry (typical for leaves). James (2009) stated that "it is now widely accepted that... radiality [characteristic of most shoots] and dorsiventrality [characteristic of leaves] are but extremes of a continuous spectrum. In fact, it is simply the timing of the KNOX gene expression!" In fact there is evidence for this continuum already at the beginning of land plant evolution. Furthermore, studies in molecular genetics confirmed that compound leaves are intermediate between simple leaves and shoots, that is, they are partially homologous with simple leaves and shoots, since "it is now generally accepted that compound leaves express both leaf and shoot properties”. This conclusion was reached by several authors on purely morphological grounds.

Evolution of flowers

The pollen-bearing organs of the early flower Crossotheca

Flower-like structures first appear in the fossil records some ~130 mya, in the Cretaceous era.

The flowering plants have long been assumed to have evolved from within the gymnosperms; according to the traditional morphological view, they are closely allied to the gnetales. However, recent molecular evidence is at odds to this hypothesis, and further suggests that gnetales are more closely related to some gymnosperm groups than angiosperms, and that gymnosperms form a distinct clade to the angiosperms. Molecular clock analysis predicts the divergence of flowering plants (anthophytes) and gymnosperms to ~300 mya.

The main function of a flower is reproduction, which, before the evolution of the flower and angiosperms, was the job of microsporophylls and megasporophylls. A flower can be considered a powerful evolutionary innovation, because its presence allowed the plant world to access new means and mechanisms for reproduction.

Origins of the flower

It seems that on the level of the organ, the leaf may be the ancestor of the flower, or at least some floral organs. When we mutate some crucial genes involved in flower development, we end up with a cluster of leaf-like structures. Thus, sometime in history, the developmental program leading to formation of a leaf must have been altered to generate a flower. There probably also exists an overall robust framework within which the floral diversity has been generated. An example of that is a gene called LEAFY (LFY), which is involved in flower development in Arabidopsis thaliana. The homologs of this gene are found in angiosperms as diverse as tomato, snapdragon, pea, maize and even gymnosperms. Expression of Arabidopsis thaliana LFY in distant plants like poplar and citrus also results in flower-production in these plants. The LFY gene regulates the expression of some gene belonging to the MADS-box family. These genes, in turn, act as direct controllers of flower development.

Evolution of the MADS-box family

The members of the MADS-box family of transcription factors play a very important and evolutionarily conserved role in flower development. According to the ABC model of flower development, three zones - A, B and C - are generated within the developing flower primordium, by the action of some transcription factors, that are members of the MADS-box family. Among these, the functions of the B and C domain genes have been evolutionarily more conserved than the A domain gene. Many of these genes have arisen through gene duplications of ancestral members of this family. Quite a few of them show redundant functions.

The evolution of the MADS-box family has been extensively studied. These genes are present even in pteridophytes, but the spread and diversity is many times higher in angiosperms. There appears to be quite a bit of pattern into how this family has evolved. Consider the evolution of the C-region gene AGAMOUS (AG). It is expressed in today's flowers in the stamens, and the carpel, which are reproductive organs. It's ancestor in gymnosperms also has the same expression pattern. Here, it is expressed in the strobili, an organ that produces pollens or ovules. Similarly, the B-genes' (AP3 and PI) ancestors are expressed only in the male organs in gymnosperms. Their descendants in the modern angiosperms also are expressed only in the stamens, the male reproductive organ. Thus, the same, then-existing components were used by the plants in a novel manner to generate the first flower. This is a recurring pattern in evolution.

Factors influencing floral diversity

The various shapes and colors of flowers

How is the enormous diversity in the shape, color and sizes of flowers established? There is enormous variation in the developmental program in different plants. For example, monocots possess structures like lodicules and palea, that were believed to be analogous to the dicot petals and carpels respectively. It turns out that this is true, and the variation is due to slight changes in the MADS-box genes and their expression pattern in the monocots. Another example is that of the toad-flax, Linaria vulgaris, which has two kinds of flower symmetries: radial and bilateral. These symmetries are due to changes in copy number, timing, and location of expression in CYCLOIDEA, which is related to TCP1 in Arabidopsis. 

The large number of petals in roses has probably been a result of human selection.

Arabidopsis thaliana has a gene called AGAMOUS that plays an important role in defining how many petals and sepals and other organs are generated. Mutations in this gene give rise to the floral meristem obtaining an indeterminate fate, and many floral organs keep on getting produced. We have flowers like roses, carnations and morning glory, for example, that have very dense floral organs. These flowers have been selected by horticulturists since long for increased number of petals. Researchers have found that the morphology of these flowers is because of strong mutations in the AGAMOUS homolog in these plants, which leads to them making a large number of petals and sepals. Several studies on diverse plants like petunia, tomato, impatiens, maize etc. have suggested that the enormous diversity of flowers is a result of small changes in genes controlling their development.

Some of these changes also cause changes in expression patterns of the developmental genes, resulting in different phenotypes. The Floral Genome Project looked at the EST data from various tissues of many flowering plants. The researchers confirmed that the ABC Model of flower development is not conserved across all angiosperms. Sometimes expression domains change, as in the case of many monocots, and also in some basal angiosperms like Amborella. Different models of flower development like the fading boundaries model, or the overlapping-boundaries model which propose non-rigid domains of expression, may explain these architectures. There is a possibility that from the basal to the modern angiosperms, the domains of floral architecture have gotten more and more fixed through evolution.

Flowering time

Another floral feature that has been a subject of natural selection is flowering time. Some plants flower early in their life cycle, others require a period of vernalization before flowering. This decision is based on factors like temperature, light intensity, presence of pollinators and other environmental signals. In Arabidopsis thaliana it is known that genes like CONSTANS (CO), FRIGIDA, Flowering Locus C (FLC) and FLOWERING LOCUS T (FT) integrate the environmental signals and initiate the flower development pathway. Allelic variation in these loci have been associated with flowering time variations between plants. For example, Arabidopsis thaliana ecotypes that grow in the cold temperate regions require prolonged vernalization before they flower, while the tropical varieties and common lab strains, do not. Much of this variation is due to mutations in the FLC and FRIGIDA genes, rendering them non-functional.

Many genes in the flowering time pathway are conserved across all plants studied to date. However, this does not mean that the mechanism of action is similarly conserved. For example, the monocot rice accelerates its flowering in short-day conditions, while Arabidopsis thaliana, a eudicot, responds to long-day conditions. In both plants, the proteins CO and FT are present but in Arabidopsis thaliana CO enhances FT production, while in rice the CO homolog represses FT production, resulting in completely opposite downstream effects.

Theories of flower evolution

There are many theories that propose how flowers evolved. Some of them are described below.

The Anthophyte Theory was based on the observation that a gymnospermic family Gnetaceae has a flower-like ovule. It has partially developed vessels as found in the angiosperms, and the megasporangium is covered by three envelopes, like the ovary structure of angiosperm flowers. However, many other lines of evidence show that gnetophytes are not related to angiosperms.

The Mostly Male Theory has a more genetic basis. Proponents of this theory point out that the gymnosperms have two very similar copies of the gene LFY while angiosperms only have one. Molecular clock analysis has shown that the other LFY paralog was lost in angiosperms around the same time as flower fossils become abundant, suggesting that this event might have led to floral evolution. According to this theory, loss of one of the LFY paralog led to flowers that were more male, with the ovules being expressed ectopically. These ovules initially performed the function of attracting pollinators, but sometime later, may have been integrated into the core flower.

Evolution of secondary metabolism

Structure of azadirachtin, a terpenoid produced by the neem plant, which helps ward off microbes and insects. Many secondary metabolites have complex structures.

Plant secondary metabolites are low molecular weight compounds, sometimes with complex structures that have no essential role in primary metabolism. They function in processes such as anti-herbivory, pollinator attraction, communication between plants, allelopathy, maintenance of symbiotic associations with soil flora and enhancing the rate of fertilization. Secondary metabolites have great structural and functional diversity and many thousands of enzymes may be involved in their synthesis, coded for by as much as 15–25% of the genome. Many plant secondary metabolites such as the colour and flavor components of saffron and the chemotherapeutic drug taxol are of culinary and medical significance to humans and are therefore of commercial importance. In plants they seem to have diversified using mechanisms such as gene duplications, evolution of novel genes and the development of novel biosynthetic pathways. Studies have shown that diversity in some of these compounds may be positively selected for. Cyanogenic glycosides may have been proposed to have evolved multiple times in different plant lineages, and there are several other instances of convergent evolution. For example, the enzymes for synthesis of limonene – a terpene – are more similar between angiosperms and gymnosperms than to their own terpene synthesis enzymes. This suggests independent evolution of the limonene biosynthetic pathway in these two lineages.

Mechanisms and players in evolution

While environmental factors are significantly responsible for evolutionary change, they act merely as agents for natural selection. Some of the changes develop through interactions with pathogens. Change is inherently brought about via phenomena at the genetic level – mutations, chromosomal rearrangements and epigenetic changes. While the general types of mutations hold true across the living world, in plants, some other mechanisms have been implicated as highly significant.

Polyploidy is a very common feature in plants. It is believed that at least half plants are or have been polyploids. Polyploidy leads to genome doubling, thus generating functional redundancy in most genes. The duplicated genes may attain new function, either by changes in expression pattern or changes in activity. Polyploidy and gene duplication are believed to be among the most powerful forces in evolution of plant form. It is not known though, why genome doubling is such a frequent process in plants. One possible reason is the production of large amounts of secondary metabolites in plant cells. Some of them might interfere in the normal process of chromosomal segregation, leading to polypoidy.

Top: teosinte; bottom: maize; middle: maize-teosinte hybrid

In recent times, plants have been shown to possess significant microRNA families, which are conserved across many plant lineages. In comparison to animals, while the number of plant miRNA families is less, the size of each family is much larger. The miRNA genes are also much more spread out in the genome than those in animals, where they are found clustered. It has been proposed that these miRNA families have expanded by duplications of chromosomal regions. Many miRNA genes involved in regulation of plant development have been found to be quite conserved between plants studied.

Domestication of plants such as maize, rice, barley, wheat etc. has also been a significant driving force in their evolution. Some studies have looked at the origins of the maize plant and found that maize is a domesticated derivative of a wild plant from Mexico called teosinte. Teosinte belongs to the genus Zea, just as maize, but bears very small inflorescence, 5–10 hard cobs, and a highly branched and spread-out stem.

CauliflowerBrassica oleracea var. botrytis

Crosses between a particular teosinte variety and maize yield fertile offspring that are intermediate in phenotype between maize and teosinte. QTL analysis has also revealed some loci that when mutated in maize yield a teosinte-like stem or teosinte-like cobs. Molecular clock analysis of these genes estimates their origins to some 9000 years ago, well in accordance with other records of maize domestication. It is believed that a small group of farmers must have selected some maize-like natural mutant of teosinte some 9000 years ago in Mexico, and subjected it to continuous selection to yield the maize plant as known today.

Another case is that of cauliflower. The edible cauliflower is a domesticated version of the wild plant Brassica oleracea, which does not possess the dense undifferentiated inflorescence, called the curd, that cauliflower possesses.

Cauliflower possesses a single mutation in a gene called CAL, controlling meristem differentiation into inflorescence. This causes the cells at the floral meristem to gain an undifferentiated identity, and instead of growing into a flower, they grow into a lump of undifferentiated cells. This mutation has been selected through domestication at least since the Greek empire.

Operator (computer programming)

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