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Tuesday, March 1, 2022

Language revitalization

From Wikipedia, the free encyclopedia

Language revitalization, also referred to as language revival or reversing language shift, is an attempt to halt or reverse the decline of a language or to revive an extinct one. Those involved can include parties such as linguists, cultural or community groups, or governments. Some argue for a distinction between language revival (the resurrection of an extinct language with no existing native speakers) and language revitalization (the rescue of a "dying" language). It has been pointed out that there has only been one successful instance of a complete language revival, that of the Hebrew language, creating a new generation of native speakers without any pre-existing native speakers as a model.

Languages targeted for language revitalization include those whose use and prominence is severely limited. Sometimes various tactics of language revitalization can even be used to try to revive extinct languages. Though the goals of language revitalization vary greatly from case to case, they typically involve attempting to expand the number of speakers and use of a language, or trying to maintain the current level of use to protect the language from extinction or language death.

Reasons for revitalization vary; such as physical danger affecting those whose language is dying, economic danger such as the exploitation of indigenous natural resources, political danger such as genocide, or cultural danger/assimilation. In recent times alone, it is estimated that more than 2000 languages have already become extinct. The UN estimates that more than half of the languages spoken today have fewer than 10,000 speakers and that a quarter have fewer than 1,000 speakers and that, unless there are some efforts to maintain them, over the next hundred years most of these will become extinct. These figures are often cited as reasons why language revitalization is necessary to preserve linguistic diversity. Culture and identity are also frequently cited reasons for language revitalization, when a language is perceived as a unique "cultural treasure." A community often sees language as a unique part of their culture, connecting them with their ancestors or with the land, making up an essential part of their history and self-image.

Language revitalization is also closely tied to the linguistic field of language documentation. In this field, linguists attempt to create full records of a language's grammar, vocabulary, and linguistic features. This practice can often lead to more concern for the revitalization of a specific language on study. Furthermore, the task of documentation is often taken on with the goal of revitalization in mind.

Degrees of language endangerment

Healthy/strong
all generations use language in variety of settings
Weakening/sick
spoken by older people; not fully used in younger generations
Moribund/dying
only a few speakers (non-children) remain; no longer used as native language by children
Dead
no longer spoken as a native language
Extinct
no longer spoken and barely has written records (if at all)

Another scale for identifying degrees of language endangerment is used in a 2003 paper ("Language Vitality and Endangerment") commissioned by UNESCO from an international group of linguists. The linguists, among other goals and priorities, create a scale with six degrees for language vitality and endangerment  They also propose nine factors (six of which use the six-degree scale) to "characterizing a language’s overall sociolinguistic situation". The nine factors with their respective scales are:

  1. Intergenerational language transmission
    • safe: all generations use the language
    • unsafe: some children use the language in all settings, all children use the language in some settings
    • definitively endangered: few children speak the language; predominantly spoken by the parental generation and older
    • severely endangered: spoken by older generations; not used by the parental generation and younger
    • critically endangered: few speakers remain and are mainly from the great grandparental generation
    • extinct: no living speakers
  2. Absolute number of speakers
  3. Proportion of speakers within the total population
    • safe: the language is spoken by 100% of the population
    • unsafe: the language is spoken by nearly 100% of the population
    • definitively endangered: the language is spoken by a majority of the population
    • severely endangered: the language is spoken by less than 50% of the population
    • critically endangered: the language has very few speakers
    • extinct: no living speakers
  4. Trends in existing language domains
    • universal use (safe): spoken in all domains; for all functions
    • multilingual parity (unsafe): multiple languages (2+) are spoken in most social domains; for most functions
    • dwindling domains (definitively endangered): mainly spoken in home domains and is in competition with the dominant language; for many functions
    • limited or formal domains (severely endangered): spoken in limited social domains; for several functions
    • highly limited domains (critically endangered): spoken in highly restricted domains; for minimal functions
    • extinct: no domains; no functions
  5. Response to new domains and media
    • dynamic (safe): spoken in all new domains
    • robust/active (unsafe): spoken in most new domains
    • receptive (definitively endangered): spoken in many new domains
    • coping (severely endangered): spoken in some new domains
    • minimal (critically endangered): spoken in minimal new domains
    • inactive (extinct): spoken in no new domains
  6. Materials for language education and literacy
    • safe: established orthography and extensive access to educational materials
    • unsafe: access to educational materials; children developing literacy; not used by administration
    • definitively endangered: access to educational materials exist at school; literacy in language is not promoted
    • severely endangered: literacy materials exist however are not present in school curriculum
    • critically endangered: orthography is known and some written materials exist
    • extinct: no orthography is known
  7. Governmental and institutional language attitudes and policies (including official status and use)
    • equal support (safe): all languages are equally protected
    • differentiated support (unsafe): primarily protected for private domains
    • passive assimilation (definitively endangered): no explicit protective policy; language use dwindles in public domain
    • active assimilation (severely endangered): government discourages use of language; no governmental protection of language in any domain
    • forced assimilation (critically endangered): language is not recognized or protected; government recognized another official language
    • prohibition (extinct): use of language is banned
  8. Community members' attitudes towards their own language
    • safe: language is revered, valued, and promoted by whole community
    • unsafe: language maintenance is supported by most of the community
    • definitively endangered: language maintenance is supported by much of the community; the rest are indifferent or support language loss
    • severely endangered: language maintenance is supported by some of the community; the rest are indifferent or support language loss
    • critically endangered: language maintenance is supported by only a few members of the community; the rest are indifferent or support language loss
    • extinct: complete apathy towards language maintenance; prefer dominant language
  9. Amount and quality of documentation.
    • superlative (safe): extensive audio, video, media, and written documentation of the language
    • good (unsafe): audio, video, media, and written documentation all exist; a handful of each
    • fair (definitively endangered): some audio and video documentation exists; adequate written documentation
    • fragmentary (severely endangered): minimal audio and video documentation exits at low quality; minimal written documentation
    • inadequate (critically endangered): only a handful of written documentation exists
    • undocumented (extinct): no documentation exists

Theory

One of the most important preliminary steps in language revitalization/recovering involves establishing the degree to which a particular language has been “dislocated”. This helps involved parties find the best way to assist or revive the language.

Steps in reversing language shift

There are many different theories or models that attempt to lay out a plan for language revitalization. One of these is provided by celebrated linguist Joshua Fishman. Fishman's model for reviving threatened (or sleeping) languages, or for making them sustainable, consists of an eight-stage process. Efforts should be concentrated on the earlier stages of restoration until they have been consolidated before proceeding to the later stages. The eight stages are:

  1. Acquisition of the language by adults, who in effect act as language apprentices (recommended where most of the remaining speakers of the language are elderly and socially isolated from other speakers of the language).
  2. Create a socially integrated population of active speakers (or users) of the language (at this stage it is usually best to concentrate mainly on the spoken language rather than the written language).
  3. In localities where there are a reasonable number of people habitually using the language, encourage the informal use of the language among people of all age groups and within families and bolster its daily use through the establishment of local neighbourhood institutions in which the language is encouraged, protected and (in certain contexts at least) used exclusively.
  4. In areas where oral competence in the language has been achieved in all age groups, encourage literacy in the language, but in a way that does not depend upon assistance from (or goodwill of) the state education system.
  5. Where the state permits it, and where numbers warrant, encourage the use of the language in compulsory state education.
  6. Where the above stages have been achieved and consolidated, encourage the use of the language in the workplace.
  7. Where the above stages have been achieved and consolidated, encourage the use of the language in local government services and mass media.
  8. Where the above stages have been achieved and consolidated, encourage use of the language in higher education, government, etc.

This model of language revival is intended to direct efforts to where they are most effective and to avoid wasting energy trying to achieve the later stages of recovery when the earlier stages have not been achieved. For instance, it is probably wasteful to campaign for the use of a language on television or in government services if hardly any families are in the habit of using the language.

Additionally, Tasaku Tsunoda describes a range of different techniques or methods that speakers can use to try to revitalize a language, including techniques to revive extinct languages and maintain weak ones. The techniques he lists are often limited to the current vitality of the language.

He claims that the immersion method cannot be used to revitalize an extinct or moribund language. In contrast, the master-apprentice method of one-on-one transmission on language proficiency can be used with moribund languages. Several other methods of revitalization, including those that rely on technology such as recordings or media, can be used for languages in any state of viability.

A method's effectiveness depends on the language's viability.
Method Degree of endangerment

Weakening Moribund Dead/extinct
Immersion effective ineffective ineffective
Neighborhood effective ineffective ineffective
Bilingual effective ineffective ineffective
Master-apprentice effective effective ineffective
Total physical response effective effective ineffective
Telephone effective effective ineffective
Radio effective effective effective
Multimedia effective effective effective
Two-way effective effective effective
Formulaic effective effective effective
Artificial pidgin effective effective effective
Place name effective effective effective
Reclamation effective effective effective
Adoption effective effective effective

Factors in successful language revitalization

David Crystal, in his book Language Death, proposes that language revitalization is more likely to be successful if its speakers

  • increase the language's prestige within the dominant community;
  • increase their wealth and income;
  • increase their legitimate power in the eyes of the dominant community;
  • have a strong presence in the education system;
  • can write down the language;
  • can use electronic technology.

In her book, Endangered Languages: An Introduction, Sarah Thomason notes the success of revival efforts for modern Hebrew and the relative success of revitalizing Maori in New Zealand (see Specific Examples below). One notable factor these two examples share is that the children were raised in fully immersive environments. In the case of Hebrew, it was on early collective-communities called kibbutzim. For the Maori language In New Zealand, this was done through a language nest.

Revival linguistics

Ghil'ad Zuckermann proposes "Revival Linguistics" as a new linguistic discipline and paradigm.

Zuckermann's term 'Revival Linguistics' is modelled upon 'Contact Linguistics'. Revival linguistics inter alia explores the universal constraints and mechanisms involved in language reclamation, renewal and revitalization. It draws perspicacious comparative insights from one revival attempt to another, thus acting as an epistemological bridge between parallel discourses in various local attempts to revive sleeping tongues all over the globe.

According to Zuckermann, "revival linguistics combines scientific studies of native language acquisition and foreign language learning. After all, language reclamation is the most extreme case of second-language learning. Revival linguistics complements the established area of documentary linguistics, which records endangered languages before they fall asleep."

Zuckermann proposes that "revival linguistics changes the field of historical linguistics by, for instance, weakening the family tree model, which implies that a language has only one parent."

There are disagreements in the field of language revitalization as to the degree that revival should concentrate on maintaining the traditional language, versus allowing simplification or widespread borrowing from the majority language.

Compromise

Zuckermann acknowledges the presence of "local peculiarities and idiosyncrasies" but suggests that

"there are linguistic constraints applicable to all revival attempts. Mastering them would help revivalists and first nations' leaders to work more efficiently. For example, it is easier to resurrect basic vocabulary and verbal conjugations than sounds and word order. Revivalists should be realistic and abandon discouraging, counter-productive slogans such as "Give us authenticity or give us death!"

Nancy Dorian has pointed out that conservative attitudes toward loanwords and grammatical changes often hamper efforts to revitalize endangered languages (as with Tiwi in Australia), and that a division can exist between educated revitalizers, interested in historicity, and remaining speakers interested in locally authentic idiom (as has sometimes occurred with Irish). Some have argued that structural compromise may, in fact, enhance the prospects of survival, as may have been the case with English in the post-Norman period.

Traditionalist

Other linguists have argued that when language revitalization borrows heavily from the majority language, the result is a new language, perhaps a creole or pidgin. For example, the existence of "Neo-Hawaiian" as a separate language from "Traditional Hawaiian" has been proposed, due to the heavy influence of English on every aspect of the revived Hawaiian language. This has also been proposed for Irish, with a sharp division between "Urban Irish" (spoken by second-language speakers) and traditional Irish (as spoken as a first language in Gaeltacht areas). Ó Béarra stated: "[to] follow the syntax and idiomatic conventions of English, [would be] producing what amounts to little more than English in Irish drag." With regard to the then-moribund Manx language, the scholar T. F. O'Rahilly stated, "When a language surrenders itself to foreign idiom, and when all its speakers become bilingual, the penalty is death." Neil McRae has stated that the uses of Scottish Gaelic are becoming increasingly tokenistic, and native Gaelic idiom is being lost in favor of artificial terms created by second-language speakers.

Specific examples

The total revival of a dead language (in the sense of having no native speakers) to become the shared means of communication of a self-sustaining community of several million first language speakers has happened only once, in the case of Hebrew, now the national language of Israel. In this case, there was a unique set of historical and cultural characteristics that facilitated the revival. (See Revival of the Hebrew language.) Hebrew, once largely a liturgical language, was re-established as a means of everyday communication by Jews migrating to what is now the State of Israel and the Palestinian territories, starting in the nineteenth century. It is the world's most famous and successful example of language revitalization.

In a related development, literary languages without native speakers enjoyed great prestige and practical utility as lingua francas, often counting millions of fluent speakers at a time. In many such cases, a decline in the use of the literary language, sometimes precipitous, was later accompanied by a strong renewal. This happened, for example, in the revival of Classical Latin in the Renaissance, and the revival of Sanskrit in the early centuries AD. An analogous phenomenon in contemporary Arabic-speaking areas is the expanded use of the literary language (Modern Standard Arabic, a form of the Classical Arabic of the 6th century AD). This is taught to all educated speakers and is used in radio broadcasts, formal discussions, etc.

In addition, literary languages have sometimes risen to the level of becoming first languages of very large language communities. An example is standard Italian, which originated as a literary language based on the language of 13th-century Florence, especially as used by such important Florentine writers as Dante, Petrarch and Boccaccio. This language existed for several centuries primarily as a literary vehicle, with few native speakers; even as late as 1861, on the eve of Italian unification, the language only counted about 500,000 speakers (many non-native), out of a total population of c. 22,000,000. The subsequent success of the language has been through conscious development, where speakers of any of the numerous Italian languages were taught standard Italian as a second language and subsequently imparted it to their children, who learned it as a first language. Of course this came at the expense of local Italian languages, most of which are now endangered. Success was enjoyed in similar circumstances by High German, standard Czech, Castilian Spanish and other languages.

Africa

The Coptic language began its decline when Arabic became the predominant language in Egypt. Pope Shenouda III established the Coptic Language Institute in December 1976 in Saint Mark's Coptic Orthodox Cathedral in Cairo for the purpose of reviving the Coptic language.

Americas

North America

In recent years, a growing number of Native American tribes have been trying to revitalize their languages. For example, there are apps (including phrases, word lists and dictionaries) in many Native languages ranging from Cree, Cherokee and Chickasaw, to Lakota, Ojibway and Oneida, Massachusett, Navajo, Halq'emeylem, and Gwych'in.

Wampanoag, a language spoken by the people of the same name in Massachusetts, underwent a language revival project led by Jessie Little Doe Baird, a trained linguist. Members of the tribe use the extensive written records that exist in their language, including a translation of the Bible and legal documents, in order to learn and teach Wampanoag. The project has seen children speaking the language fluently for the first time in over 100 years. In addition, there are currently attempts at reviving the Chochenyo language of California, which had become extinct.

Tlingit

Similar to other Indigenous languages, Tlingit is critically endangered. Less than 100 fluent Elders continue to exist. From 2013 to 2014, the language activist, author, and teacher, Sʔímlaʔxw Michele K. Johnson from the Syilx Nation, attempted to teach two hopeful learners of Tlingit in the Yukon. Her methods included textbook creation, sequenced immersion curriculum, and film assessment. The aim was to assist in the creation of adult speakers that are of parent-age, so that they too can begin teaching the language. In 2020, X̱ʼunei Lance Twitchell led an Tlingit online class with Outer Coast College. Dozens of students participated. He is an associate professor of Alaska Native Languages in the School of Arts and Sciences at the University of Alaska Southeast which offers a minor in Tlingit language and an emphasis on Alaska Native Languages and Studies within a Bachelorʼs degree in Liberal Arts.

South America

Kichwa is the variety of the Quechua language spoken in Ecuador and is one of the most widely spoken indigenous languages in South America. Despite this fact, Kichwa is a threatened language, mainly because of the expansion of Spanish in South America. One community of original Kichwa speakers, Lagunas, was one of the first indigenous communities to switch to the Spanish language. According to King, this was because of the increase of trade and business with the large Spanish-speaking town nearby. The Lagunas people assert that it was not for cultural assimilation purposes, as they value their cultural identity highly. However, once this contact was made, language for the Lagunas people shifted through generations, to Kichwa and Spanish bilingualism and now is essentially Spanish monolingualism. The feelings of the Lagunas people present a dichotomy with language use, as most of the Lagunas members speak Spanish exclusively and only know a few words in Kichwa.

The prospects for Kichwa language revitalization are not promising, as parents depend on schooling for this purpose, which is not nearly as effective as continual language exposure in the home. Schooling in the Lagunas community, although having a conscious focus on teaching Kichwa, consists of mainly passive interaction, reading, and writing in Kichwa. In addition to grassroots efforts, national language revitalization organizations, like CONAIE, focus attention on non-Spanish speaking indigenous children, who represent a large minority in the country. Another national initiative, Bilingual Intercultural Education Project (PEBI), was ineffective in language revitalization because instruction was given in Kichwa and Spanish was taught as a second language to children who were almost exclusively Spanish monolinguals. Although some techniques seem ineffective, Kendall A. King provides several suggestions:

  1. Exposure to and acquisition of the language at a young age.
  2. Extreme immersion techniques.
  3. Multiple and diverse efforts to reach adults.
  4. Flexibility and coordination in planning and implementation
  5. Directly addressing different varieties of the language.
  6. Planners stressing that language revitalization is a long process
  7. Involving as many people as possible
  8. Parents using the language with their children
  9. Planners and advocates approaching the problem from all directions.

Specific suggestions include imparting an elevated perception of the language in schools, focusing on grassroots efforts both in school and the home, and maintaining national and regional attention.

Asia

Hebrew

The revival of the Hebrew language is the only truly successful example of a revived dead language. The Hebrew language survived into the medieval period as the language of Jewish liturgy and rabbinic literature. With the rise of Zionism in the 19th century, it was revived as a spoken and literary language, becoming primarily a spoken lingua franca among the early Jewish immigrants to Ottoman Palestine and received the official status in the 1922 constitution of the British Mandate for Palestine and subsequently of the State of Israel.

Sanskrit

The revival of Sanskrit happened in India. In the 2001 census of India, 14,135 people claimed Sanskrit as their mother tongue. It increased to 24,821 people in the 2011 census of India. Sanskrit has experienced a recorded growth of over 70 per cent in one decade due to the Sanskrit revival. Many Sanskrit speaking villages were also developed. However, Sanskrit speakers still account for just 0.00198 percent of India's total population.

Soyot

The Soyot language of the small-numbered Soyots in Buryatia, Russia, one of Siberian Turkic languages, has been reconstructed and a Soyot-Buryat-Russian dictionary has been published in 2002. The language is currently taught in some elementary schools.

Ainu

The Ainu language of the indigenous Ainu people of northern Japan is currently moribund, but efforts are underway to revive it. A 2006 survey of the Hokkaido Ainu indicated that only 4.6% of Ainu surveyed were able to converse in or "speak a little" Ainu. As of 2001, Ainu was not taught in any elementary or secondary schools in Japan, but was offered at numerous language centres and universities in Hokkaido, as well as at Tokyo's Chiba University.

Manchu

In China, the Manchu language is one of the most endangered languages, with speakers only in three small areas of Manchuria remaining. Some enthusiasts are trying to revive the language of their ancestors using available dictionaries and textbooks, and even occasional visits to Qapqal Xibe Autonomous County in Xinjiang, where the related Xibe language is still spoken natively.

Spanish

In the Philippines, a local variety of Spanish that was primarily based on Mexican Spanish was the lingua franca of the country since Spanish colonization in 1565 and was an official language alongside Filipino (standardized Tagalog) and English until 1987, following a ratification of a new constitution, where it was re-designated as a voluntary language. As a result of its loss as an official language and years of marginalization at the official level during and after American colonization, the use of Spanish amongst the overall populace decreased dramatically and became moribund, with the remaining native speakers left being mostly elderly people. The language has seen a gradual revival, however, due to official promotion under the administration of former President Gloria Macapagal Arroyo. Most notably, Resolution No. 2006-028 reinstated Spanish as a mandatory subject in secondary schools and universities. Results were immediate as the job demand for Spanish speakers had increased since 2008. As of 2010, the Instituto Cervantes in Manila reported the number of Spanish-speakers in the country with native or non-native knowledge at approximately 3 million, the figure albeit including those who speak the Spanish-based creole Chavacano. Complementing government efforts is a notable surge of exposure through the mainstream media and, more recently, music-streaming services.

Other Asian

The Kodrah Kristang revitalization initiative in Singapore seeks to revive the critically endangered Kristang creole.

In Thailand, there exists a Chong language revitalization project, headed by Suwilai Premsrirat.

Europe

In Europe, in the 19th and early 20th centuries, the use of both local and learned languages declined as the central governments of the different states imposed their vernacular language as the standard throughout education and official use (this was the case in the United Kingdom, France, Spain, Italy and Greece, and to some extent, in Germany and Austria-Hungary).

In the last few decades, local nationalism and human rights movements have made a more multicultural policy standard in European states; sharp condemnation of the earlier practices of suppressing regional languages was expressed in the use of such terms as "linguicide".

Irish

One of the best known European attempts at language revitalization concerns the Irish language. While English is dominant through most of Ireland, Irish, a Celtic language, is still spoken in certain areas called Gaeltachtaí, but there it is in serious decline. The challenges faced by the language over the last few centuries have included exclusion from important domains, social denigration, the death or emigration of many Irish speakers during the Irish famine of the 1840s, and continued emigration since. Efforts to revitalise Irish were being made, however, from the mid-1800s, and were associated with a desire for Irish political independence. Contemporary Irish language revitalization has chiefly involved teaching Irish as a compulsory language in mainstream English-speaking schools. But the failure to teach it in an effective and engaging way means (as linguist Andrew Carnie notes) that students do not acquire the fluency needed for the lasting viability of the language, and this leads to boredom and resentment. Carnie also noted a lack of media in Irish (2006), though this is no longer the case.

The decline of the Gaeltachtaí and the failure of state-directed revitalisation have been countered by an urban revival movement. This is largely based on an independent community-based school system, known generally as Gaelscoileanna. These schools teach entirely through Irish and their number is growing, with over thirty such schools in Dublin alone. They are an important element in the creation of a network of urban Irish speakers (known as Gaeilgeoirí), who tend to be young, well-educated and middle-class. It is now likely that this group has acquired critical mass, a fact reflected in the expansion of Irish-language media. Irish language television has enjoyed particular success. It has been argued that they tend to be better educated than monolingual English speakers and enjoy higher social status. They represent the transition of Irish to a modern urban world, with an accompanying rise in prestige.

Scottish Gaelic

There are also current attempts to revive the related language of Scottish Gaelic, which was suppressed following the formation of the United Kingdom, and entered further decline due to the Highland clearances. Currently, Gaelic is only spoken widely in the Western Isles and some relatively small areas of the Highlands and Islands. The decline in fluent Gaelic speakers has slowed; however, the population center has shifted to L2 speakers in urban areas, especially Glasgow.

Manx

Another Celtic language, Manx, lost its last native speaker in 1974 and was declared extinct by UNESCO in 2009, but never completely fell from use. The language is now taught in primary and secondary schools, including as a teaching medium at the Bunscoill Ghaelgagh, used in some public events and spoken as a second language by approximately 1800 people. Revitalization efforts include radio shows in Manx Gaelic and social media and online resources. The Manx government has also been involved in the effort by creating organizations such as the Manx Heritage Foundation (Culture Vannin) and the position of Manx Language Officer. The government has released an official Manx Language Strategy for 2017–2021.

Cornish

There have been a number of attempts to revive the Cornish language, both privately and some under the Cornish Language Partnership. Some of the activities have included translation of the Christian scriptures, a guild of bards, and the promotion of Cornish literature in modern Cornish, including novels and poetry.

Caló

The Romani arriving in the Iberian Peninsula developed an Iberian Romani dialect. As time passed, Romani ceased to be a full language and became Caló, a cant mixing Iberian Romance grammar and Romani vocabulary. With sedentarization and obligatory instruction in the official languages, Caló is used less and less. As Iberian Romani proper is extinct and as Caló is endangered, some people are trying to revitalise the language. The Spanish politician Juan de Dios Ramírez Heredia promotes Romanò-Kalò, a variant of International Romani, enriched by Caló words. His goal is to reunify the Caló and Romani roots.

Livonian

The Livonian language, a Finnic language, once spoken on about a third of modern-day Latvian territory, died in the 21st century with the death of the last native speaker Grizelda Kristiņa on 2 June 2013. Today there are about 210 people mainly living in Latvia who identify themselves as Livonian and speak the language on the A1-A2 level according to the Common European Framework of Reference for Languages and between 20 and 40 people who speak the language on level B1 and up. Today all speakers learn Livonian as a second language. There are different programs educating Latvians on the cultural and linguistic heritage of Livonians and the fact that most Latvians have common Livonian descent.

Programs worth mentioning include:

  • Livones.net with extensive information about language, history and culture
  • The Livonian Institute of the University of Latvia doing research on the Livonian language, other Finnic languages in Latvia and providing an extensive Livonian-Latvian-Estonian dictionary with declinations/conjugations
  • Virtual Livonia providing information on the Livonian language and especially its grammar
  • Mierlinkizt: An annual summer camp for children to teach children about the Livonian language, culture etc.
  • Līvõd Īt (Livonian Union)

The Livonian linguistic and cultural heritage is included in the Latvian cultural canon and the protection, revitalization and development of Livonian as an indigenous language is guaranteed by Latvian law.

Old Prussian

A few linguists and philologists are involved in reviving a reconstructed form of the extinct Old Prussian language from Luther's catechisms, the Elbing Vocabulary, place names, and Prussian loanwords in the Low Prussian dialect of German. Several dozen people use the language in Lithuania, Kaliningrad, and Poland, including a few children who are natively bilingual.

The Prusaspirā Society has published their translation of Antoine de Saint-Exupéry's The Little Prince. The book was translated by Piotr Szatkowski (Pīteris Šātkis) and released in 2015. The other efforts of Baltic Prussian societies include the development of online dictionaries, learning apps and games. There also have been several attempts to produce music with lyrics written in the revived Baltic Prussian language, most notably in the Kaliningrad Oblast by Romowe Rikoito, Kellan and Āustras Laīwan, but also in Lithuania by Kūlgrinda in their 2005 album Prūsų Giesmės (Prussian Hymns), and in Latvia by Rasa Ensemble in 1988 and Valdis Muktupāvels in his 2005 oratorio "Pārcēlātājs Pontifex" featuring several parts sung in Prussian.

Important in this revival was Vytautas Mažiulis, who died on 11 April 2009, and his pupil Letas Palmaitis, leader of the experiment and author of the website Prussian Reconstructions. Two late contributors were Prāncis Arellis (Pranciškus Erelis), Lithuania, and Dailūns Russinis (Dailonis Rusiņš), Latvia. After them, Twankstas Glabbis from Kaliningrad oblast and Nērtiks Pamedīns from East-Prussia, now Polish Warmia-Mazuria actively joined.

Yola

The Yola language revival movement has cultivated in Wexford in recent years, and the “Gabble Ing Yola” resource center for Yola materials claims there are around 140 speakers of the Yola language today.

Oceania

Australia

The European colonization of Australia, and the consequent damage sustained by Aboriginal communities, had a catastrophic effect on indigenous languages, especially in the southeast and south of the country, leaving some with no living traditional native speakers. A number of Aboriginal communities in Victoria and elsewhere are now trying to revive some of these languages. The work is typically directed by a group of Aboriginal elders and other knowledgeable people, with community language workers doing most of the research and teaching. They analyze the data, develop spelling systems and vocabulary and prepare resources. Decisions are made in collaboration. Some communities employ linguists, and there are also linguists who have worked independently, such as Luise Hercus and Peter K. Austin.

  • In the state of Queensland, an effort is being made to teach some Indigenous languages in schools and to develop workshops for adults. More than 150 languages were once spoken within the state, but today fewer than 20 are spoken as a first language, and less than two per cent of schools teach any Indigenous language. The Gunggari language is one language which is being revived, with only three native speakers left.
  • In the far north of South Australia, the Diyari language has an active programme under way, with materials available for teaching in schools and the wider community.
  • The Victorian Department of Education and Training reported 1,867 student enrollments in 14 schools offering an Aboriginal Languages Program in the state of Victoria in 2018.

New Zealand

One of the best cases of relative success in language revitalization is the case of Māori, also known as te reo Māori. It is the ancestral tongue of the indigenous Māori people of New Zealand and a vehicle for prose narrative, sung poetry, and genealogical recital. The history of the Māori people is taught in te reo Māori in sacred learning houses through oral transmission. Even after te reo Māori became a written language, the oral tradition was preserved.

Once European colonization began, many laws were enacted in order to promote the use of English over te reo Māori among indigenous people. The Education Ordinance Act of 1847 mandated school instruction in English and established boarding schools to speed up assimilation of Māori youths into European culture. The Native School Act of 1858 forbade te reo Māori from being spoken in schools.

During the 1970s, a group of young Māori people, the Ngā Tamatoa, successfully campaigned for Māori to be taught in schools. Also, Kohanga Reo, Māori language preschools, called language nests, were established. The emphasis was on teaching children the language at a young age, a very effective strategy for language learning. The Māori Language Commission was formed in 1987, leading to a number of national reforms aimed at revitalizing te reo Māori. They include media programs broadcast in te reo Māori, undergraduate college programs taught in te reo Māori, and an annual Māori language week. Each iwi, or tribe, created a language planning program catering to its specific circumstances. These efforts have resulted in a steady increase in children being taught in te reo Māori in schools since 1996.

Hawaiian

On six of the seven inhabited islands of Hawaii, Hawaiian was displaced by English and is no longer used as the daily language of communication. The one exception is Niʻihau, where Hawaiian has never been displaced, has never been endangered, and is still used almost exclusively. Efforts to revive the language have increased in recent decades. Hawaiian language immersion schools are now open to children whose families want to retain (or introduce) Hawaiian language into the next generation. The local National Public Radio station features a short segment titled "Hawaiian word of the day". Additionally, the Sunday editions of the Honolulu Star-Bulletin feature a brief article called Kauakukalahale, written entirely in Hawaiian by a student.

Current revitalization efforts

Language revitalization efforts are ongoing around the world. Revitalization teams are utilizing modern technologies to increase contact with indigenous languages and to record traditional knowledge.

In Mexico, the Mixtec people's language heavily revolves around the interaction between climate, nature, and what it means for their livelihood. UNESCO's LINKS (Local and Indigenous Knowledge) program recently underwent a project to create a glossary of Mixtec terms and phrases related to climate. UNESCO believes that the traditional knowledge of the Mixtec people via their deep connection with weather phenomena can provide insight on ways to address climate change. Their intention in creating the glossary is to "facilitate discussions between experts and the holders of traditional knowledge".

In Canada, the Wapikoni Mobile project travels to indigenous communities and provides lessons in film making. Program leaders travel across Canada with mobile audiovisual production units, and aims to provide indigenous youth with a way to connect with their culture through a film topic of their choosing. The Wapikona project submits its films to events around the world as an attempt to spread knowledge of indigenous culture and language.

Of the youth in Rapa Nui (Easter Island), ten percent learn their mother language. The rest of the community has adopted Spanish in order to communicate with the outside world and support its tourism industry. Through a collaboration between UNESCO and the Chilean Corporación Nacional de Desarrollo Indigena, the Department of Rapa Nui Language and Culture at the Lorenzo Baeza Vega School was created. Since 1990, the department has created primary education texts in the Rapa Nui language. In 2017, the Nid Rapa Nui, a non-governmental organization was also created with the goal of establishing a school that teaches courses entirely in Rapa Nui.

Health benefits of language revitalization

Language revitalisation has been linked to increased health outcomes for Indigenous communities involved in reclaiming traditional language. Benefits range from improved mental health for community members, increasing connectedness to culture, identity, and a sense of wholeness. Indigenous languages are a core element in the formation of identity, providing pathways for cultural expression, agency, spiritual and ancestral connection. Connection to culture is considered to play an important role in childhood development, and is a UN convention right. Much has been written about the connection between identity and culture being inextricably intertwined in Indigenous cultures around the world. As colonisation and subsequent linguicide was carried out through policies such as those that created Australia’s Stolen Generation have damaged this connection, language revitalization may also play an important role in countering intergenerational trauma that has been caused.

One study in the Barngarla Community in South Australia has been looking holistically at the positive benefits of language reclamation, healing mental and emotional scars, and building connections to community and country that underpin wellness and wholeness. The study identified the Barngarla peoples connection to their language is a strong component of developing a strong cultural and personal identity; the people are as connected to language as they are to culture, and culture is key to their identity. Another study in New South Wales on the Warlpiri people echoes language as life, that the survival of the language is tied to the survival of the community. Language revival is closely linked to overcoming feelings of shame and fear, which have led to poor health outcomes in the past where speaking traditional language meant the possibility of being removed from family and community. Language reclamation is a form of empowerment and builds strong connections with community and wholeness.  

Criticism

John McWhorter has argued that programs to revive indigenous languages will almost never be very effective because of the practical difficulties involved. He also argues that the death of a language does not necessarily mean the death of a culture. Indigenous expression is still possible even when the original language has disappeared, as with Native American groups and as evidenced by the vitality of black American culture in the United States, among people who speak not Yoruba but English. He argues that language death is, ironically, a sign of hitherto isolated peoples migrating and sharing space: “To maintain distinct languages across generations happens only amidst unusually tenacious self-isolation—such as that of the Amish—or brutal segregation”.

Kenan Malik has also argued that it is "irrational" to try to preserve all the world's languages, as language death is natural and in many cases inevitable, even with intervention. He proposes that language death improves communication by ensuring more people speak the same language. This may benefit the economy and reduce conflict.

The protection of minority languages from extinction is often not a concern for speakers of the dominant language. Oftentimes, there is prejudice and deliberate persecution of minority languages, in order to appropriate the cultural and economic capital of minority groups. At other times governments deem that the cost of revitalization programs and creating linguistically diverse materials is too great to take on.

RuBisCO

From Wikipedia, the free encyclopedia
 
Ribulose-1,5-bisphosphate carboxylase oxygenase
SpinachRuBisCO.png
A 3d depiction of the activated RuBisCO from spinach in open form with active site accessible. The active site Lys175 residues are marked in pink, and a close-up of the residue is provided to the right for one of the monomers composing the enzyme.
 
Identifiers
EC no.4.1.1.39
CAS no.9027-23-0
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants and other photosynthetic organisms to energy-rich molecules such as glucose. In chemical terms, it catalyzes the carboxylation of ribulose-1,5-bisphosphate (also known as RuBP). It is probably the most abundant enzyme on Earth.

Alternative carbon fixation pathways

RuBisCO is important biologically because it catalyzes the primary chemical reaction by which inorganic carbon enters the biosphere. While many autotrophic bacteria and archaea fix carbon via the reductive acetyl CoA pathway, the 3-hydroxypropionate cycle, or the reverse Krebs cycle, these pathways are relatively small contributors to global carbon fixation compared to that catalyzed by RuBisCO. Phosphoenolpyruvate carboxylase, unlike RuBisCO, only temporarily fixes carbon. Reflecting its importance, RuBisCO is the most abundant protein in leaves, accounting for 50% of soluble leaf protein in C3 plants (20–30% of total leaf nitrogen) and 30% of soluble leaf protein in C4 plants (5–9% of total leaf nitrogen). Given its important role in the biosphere, the genetic engineering of RuBisCO in crops is of continuing interest (see below).

Structure

Active site of RuBisCO of Galdieria sulphuraria with CO2: Residues involved in both the active site and stabilizing CO2 for enzyme catalysis are shown in color and labeled. Distances of the hydrogen bonding interactions are shown in angstroms. Mg2+ ion (green sphere) is shown coordinated to CO2, and is followed by three water molecules (red spheres). All other residues are placed in grayscale.
 
Location of the rbcL gene in the chloroplast genome of Arabidopsis thaliana (positions ca. 55-56.4 kb). rbcL is one of the 21 protein-coding genes involved in photosynthesis (green boxes).

In plants, algae, cyanobacteria, and phototrophic and chemoautotrophic proteobacteria, the enzyme usually consists of two types of protein subunit, called the large chain (L, about 55,000 Da) and the small chain (S, about 13,000 Da). The large-chain gene (rbcL) is encoded by the chloroplast DNA in plants. There are typically several related small-chain genes in the nucleus of plant cells, and the small chains are imported to the stromal compartment of chloroplasts from the cytosol by crossing the outer chloroplast membrane. The enzymatically active substrate (ribulose 1,5-bisphosphate) binding sites are located in the large chains that form dimers in which amino acids from each large chain contribute to the binding sites. A total of eight large-chains (= 4 dimers) and eight small chains assemble into a larger complex of about 540,000 Da. In some proteobacteria and dinoflagellates, enzymes consisting of only large subunits have been found.

Magnesium ions (Mg2+
) are needed for enzymatic activity. Correct positioning of Mg2+
in the active site of the enzyme involves addition of an "activating" carbon dioxide molecule (CO2) to a lysine in the active site (forming a carbamate). Mg2+ operates by driving deprotonation of the Lys210 residue, causing the Lys residue to rotate by 120 degrees to the trans conformer, decreasing the distance between the nitrogen of Lys and the carbon of CO2. The close proximity allows for the formation of a covalent bond, resulting in the carbamate. Mg2+ is first enabled to bind to the active site by the rotation of His335 to an alternate conformation. Mg2+ is then coordinated by the His residues of the active site (His300, His302, His335), and is partially neutralized by the coordination of three water molecules and their conversion to OH. This coordination results in an unstable complex, but produces a favorable environment for the binding of Mg2+. Formation of the carbamate is favored by an alkaline pH. The pH and the concentration of magnesium ions in the fluid compartment (in plants, the stroma of the chloroplast) increases in the light. The role of changing pH and magnesium ion levels in the regulation of RuBisCO enzyme activity is discussed below. Once the carbamate is formed, His335 finalizes the activation by returning to its initial position through thermal fluctuation.

RuBisCO large chain,
catalytic domain
Identifiers
SymbolRuBisCO_large
PfamPF00016
InterProIPR000685
PROSITEPDOC00142
SCOP23rub / SCOPe / SUPFAM
CDDcd08148
RuBisCO, N-terminal domain
Identifiers
SymbolRuBisCO_large_N
PfamPF02788
InterProIPR017444
SCOP23rub / SCOPe / SUPFAM
RuBisCO, small chain
Identifiers
SymbolRuBisCO_small
PfamPF00101
InterProIPR000894
SCOP23rub / SCOPe / SUPFAM
CDDcd03527

Enzymatic activity

Two main reactions of RuBisCo: CO2 fixation and oxygenation.

RuBisCO is one of many enzymes in the Calvin cycle. When Rubisco facilitates the attack of CO2 at the C2 carbon of RuBP and subsequent bond cleavage between the C3 and C2 carbon, 2 molecules of glycerate-3-phosphate are formed. The conversion involves these steps: enolisation, carboxylation, hydration, C-C bond cleavage, and protonation.

Substrates

Substrates for RuBisCO are ribulose-1,5-bisphosphate and carbon dioxide (distinct from the "activating" carbon dioxide). RuBisCO also catalyses a reaction of ribulose-1,5-bisphosphate and molecular oxygen (O2) instead of carbon dioxide (CO2). Discriminating between the substrates CO2 and O2 is attributed to the differing interactions of the substrate's quadrupole moments and a high electrostatic field gradient. This gradient is established by the dimer form of the minimally active RuBisCO, which with its two components provides a combination of oppositely charged domains required for the enzyme's interaction with O2 and CO2. These conditions help explain the low turnover rate found in RuBisCO: In order to increase the strength of the electric field necessary for sufficient interaction with the substrates’ quadrupole moments, the C- and N- terminal segments of the enzyme must be closed off, allowing the active site to be isolated from the solvent and lowering the dielectric constant. This isolation has a significant entropic cost, and results in the poor turnover rate.

Binding RuBP

Carbamylation of the ε-amino group of Lys201 is stabilized by coordination with the Mg2+. This reaction involves binding of the carboxylate termini of Asp203 and Glu204 to the Mg2+ ion. The substrate RuBP binds Mg2+ displacing two of the three aquo ligands.

Enolisation

Enolisation of RuBP is the conversion of the keto tautomer of RuBP to an enediol(ate). Enolisation is initiated by deprotonation at C3. The enzyme base in this step has been debated, but the steric constraints observed in crystal structures have made Lys201 the most likely candidate. Specifically, the carbamate oxygen on Lys201 that is not coordinated with the Mg ion deprotonates the C3 carbon of RuBP to form a 2,3-enediolate.

Carboxylation

A 3D image of the active site of spinach RuBisCO complexed with the inhibitor 2-Carboxyarabinitol-1,5-Bisphosphate, CO2, and Mg2+. (PDB: 1IR1; Ligand View [CAP]501:A)

Carboxylation of the 2,3-enediolate results in the intermediate 3-keto-2′-carboxyarabinitol-1,5-bisphosphate and Lys334 is positioned to facilitate the addition of the CO2 substrate as it replaces the third Mg2+-coordinated water molecule and add directly to the enediol. No Michaelis complex is formed in this process. Hydration of this ketone results in an additional hydroxy group on C3, forming a gem-diol intermediate. Carboxylation and hydration have been proposed as either a single concerted step or as two sequential steps. Concerted mechanism is supported by the proximity of the water molecule to C3 of RuBP in multiple crystal structures. Within the spinach structure, other residues are well placed to aid in the hydration step as they are within hydrogen bonding distance of the water molecule.

C-C bond cleavage

The gem-diol intermediate cleaves at the C2-C3 bond to form one molecule of glycerate-3-phosphate and a negatively charge carboxylate. Stereo specific protonation of C2 of this carbanion results in another molecule of glycerate-3-phosphate. This step is thought to be facilitated by Lys175 or potentially the carbamylated Lys201.

Products

When carbon dioxide is the substrate, the product of the carboxylase reaction is an unstable six-carbon phosphorylated intermediate known as 3-keto-2-carboxyarabinitol-1,5-bisphosphate, which decays rapidly into two molecules of glycerate-3-phosphate. The 3-phosphoglycerate can be used to produce larger molecules such as glucose.

Rubisco side activities can lead to useless or inhibitory by-products; one such product is xylulose-1,5-bisphosphate, which inhibits Rubisco activity.

When molecular oxygen is the substrate, the products of the oxygenase reaction are phosphoglycolate and 3-phosphoglycerate. Phosphoglycolate is recycled through a sequence of reactions called photorespiration, which involves enzymes and cytochromes located in the mitochondria and peroxisomes (this is a case of metabolite repair). In this process, two molecules of phosphoglycolate are converted to one molecule of carbon dioxide and one molecule of 3-phosphoglycerate, which can reenter the Calvin cycle. Some of the phosphoglycolate entering this pathway can be retained by plants to produce other molecules such as glycine. At ambient levels of carbon dioxide and oxygen, the ratio of the reactions is about 4 to 1, which results in a net carbon dioxide fixation of only 3.5. Thus, the inability of the enzyme to prevent the reaction with oxygen greatly reduces the photosynthetic capacity of many plants. Some plants, many algae, and photosynthetic bacteria have overcome this limitation by devising means to increase the concentration of carbon dioxide around the enzyme, including C4 carbon fixation, crassulacean acid metabolism, and the use of pyrenoid.

Rate of enzymatic activity

Overview of the Calvin cycle and carbon fixation.

Some enzymes can carry out thousands of chemical reactions each second. However, RuBisCO is slow, fixing only 3-10 carbon dioxide molecules each second per molecule of enzyme. The reaction catalyzed by RuBisCO is, thus, the primary rate-limiting factor of the Calvin cycle during the day. Nevertheless, under most conditions, and when light is not otherwise limiting photosynthesis, the speed of RuBisCO responds positively to increasing carbon dioxide concentration.

RuBisCO is usually only active during the day, as ribulose 1,5-bisphosphate is not regenerated in the dark. This is due to the regulation of several other enzymes in the Calvin cycle. In addition, the activity of RuBisCO is coordinated with that of the other enzymes of the Calvin cycle in several other ways:

By ions

Upon illumination of the chloroplasts, the pH of the stroma rises from 7.0 to 8.0 because of the proton (hydrogen ion, H+
) gradient created across the thylakoid membrane. The movement of protons into thylakoids is driven by light and is fundamental to ATP synthesis in chloroplasts (Further reading: Photosynthetic reaction centre; Light-dependent reactions). To balance ion potential across the membrane, magnesium ions (Mg2+
) move out of the thylakoids in response, increasing the concentration of magnesium in the stroma of the chloroplasts. RuBisCO has a high optimal pH (can be >9.0, depending on the magnesium ion concentration) and, thus, becomes "activated" by the introduction of carbon dioxide and magnesium to the active sites as described above.

By RuBisCO activase

In plants and some algae, another enzyme, RuBisCO activase (Rca, GO:0046863, P10896), is required to allow the rapid formation of the critical carbamate in the active site of RuBisCO. This is required because ribulose 1,5-bisphosphate (RuBP) binds more strongly to the active sites of RuBisCO when excess carbamate is present, preventing processes form moving forward. In the light, RuBisCO activase promotes the release of the inhibitory (or — in some views — storage) RuBP from the catalytic sites of RuBisCO. Activase is also required in some plants (e.g., tobacco and many beans) because, in darkness, RuBisCO is inhibited (or protected from hydrolysis) by a competitive inhibitor synthesized by these plants, a substrate analog 2-Carboxy-D-arabitinol 1-phosphate (CA1P). CA1P binds tightly to the active site of carbamylated RuBisCO and inhibits catalytic activity to an even greater extent. CA1P has also been shown to keep RuBisCO in a conformation that is protected from proteolysis. In the light, RuBisCO activase also promotes the release of CA1P from the catalytic sites. After the CA1P is released from RuBisCO, it is rapidly converted to a non-inhibitory form by a light-activated CA1P-phosphatase. Even without these strong inhibitors, once every several hundred reactions, the normal reactions with carbon dioxide or oxygen are not completed; other inhibitory substrate analogs are still formed in the active site. Once again, RuBisCO activase can promote the release of these analogs from the catalytic sites and maintain the enzyme in a catalytically active form. However, at high temperatures, RuBisCO activase aggregates and can no longer activate RuBisCO. This contributes to the decreased carboxylating capacity observed during heat stress.

By ATP/ADP and stromal reduction/oxidation state through the activase

The removal of the inhibitory RuBP, CA1P, and the other inhibitory substrate analogs by activase requires the consumption of ATP. This reaction is inhibited by the presence of ADP, and, thus, activase activity depends on the ratio of these compounds in the chloroplast stroma. Furthermore, in most plants, the sensitivity of activase to the ratio of ATP/ADP is modified by the stromal reduction/oxidation (redox) state through another small regulatory protein, thioredoxin. In this manner, the activity of activase and the activation state of RuBisCO can be modulated in response to light intensity and, thus, the rate of formation of the ribulose 1,5-bisphosphate substrate.

By phosphate

In cyanobacteria, inorganic phosphate (Pi) also participates in the co-ordinated regulation of photosynthesis: Pi binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. In this way, activation of bacterial RuBisCO might be particularly sensitive to Pi levels, which might cause it to act in a similar way to how RuBisCO activase functions in higher plants.

By carbon dioxide

Since carbon dioxide and oxygen compete at the active site of RuBisCO, carbon fixation by RuBisCO can be enhanced by increasing the carbon dioxide level in the compartment containing RuBisCO (chloroplast stroma). Several times during the evolution of plants, mechanisms have evolved for increasing the level of carbon dioxide in the stroma (see C4 carbon fixation). The use of oxygen as a substrate appears to be a puzzling process, since it seems to throw away captured energy. However, it may be a mechanism for preventing carbohydrate overload during periods of high light flux. This weakness in the enzyme is the cause of photorespiration, such that healthy leaves in bright light may have zero net carbon fixation when the ratio of O2 to CO2 available to RuBisCO shifts too far towards oxygen. This phenomenon is primarily temperature-dependent: High temperatures can decrease the concentration of CO2 dissolved in the moisture of leaf tissues. This phenomenon is also related to water stress: Since plant leaves are evaporatively cooled, limited water causes high leaf temperatures. C4 plants use the enzyme PEP carboxylase initially, which has a higher affinity for CO2. The process first makes a 4-carbon intermediate compound, which is shuttled into a site of C3 photosynthesis then de-carboxylated, releasing CO2 to boost the concentration of CO2, hence the name C4 plants.

Crassulacean acid metabolism (CAM) plants keep their stomata closed during the day, which conserves water but prevents the light-independent reactions (a.k.a. the Calvin Cycle) from taking place, since these reactions require CO2 to pass by gas exchange through these openings. Evaporation through the upper side of a leaf is prevented by a layer of wax.

Genetic engineering

Since RuBisCO is often rate-limiting for photosynthesis in plants, it may be possible to improve photosynthetic efficiency by modifying RuBisCO genes in plants to increase catalytic activity and/or decrease oxygenation rates. This could improve biosequestration of CO2 and be both an important climate change strategy and a strategy to increase crop yields. Approaches under investigation include transferring RuBisCO genes from one organism into another organism, engineering Rubisco activase from thermophilic cyanobacteria into temperature sensitive plants, increasing the level of expression of RuBisCO subunits, expressing RuBisCO small chains from the chloroplast DNA, and altering RuBisCO genes to increase specificity for carbon dioxide or otherwise increase the rate of carbon fixation.

Mutagenesis in plants

In general, site-directed mutagenesis of RuBisCO has been mostly unsuccessful, though mutated forms of the protein have been achieved in tobacco plants with subunit C4 species, and a RuBisCO with more C4-like kinetic characteristics have been attained in rice via nuclear transformation. Robust and reliable engineering for yield of RuBisCO and other enzymes in the C3 cycle was shown to be possible, and it was first achieved in 2019 through a synthetic biology approach.

One avenue is to introduce RuBisCO variants with naturally high specificity values such as the ones from the red alga Galdieria partita into plants. This may improve the photosynthetic efficiency of crop plants, although possible negative impacts have yet to be studied. Advances in this area include the replacement of the tobacco enzyme with that of the purple photosynthetic bacterium Rhodospirillum rubrum. In 2014, two transplastomic tobacco lines with functional RuBisCO from the cyanobacterium Synechococcus elongatus PCC7942 (Se7942) were created by replacing the RuBisCO with the large and small subunit genes of the Se7942 enzyme, in combination with either the corresponding Se7942 assembly chaperone, RbcX, or an internal carboxysomal protein, CcmM35. Both mutants had increased CO2 fixation rates when measured as carbon molecules per RuBisCO. However, the mutant plants grew more slowly than wild-type.

A recent theory explores the trade-off between the relative specificity (i.e., ability to favour CO2 fixation over O2 incorporation, which leads to the energy-wasteful process of photorespiration) and the rate at which product is formed. The authors conclude that RuBisCO may actually have evolved to reach a point of 'near-perfection' in many plants (with widely varying substrate availabilities and environmental conditions), reaching a compromise between specificity and reaction rate. It has been also suggested that the oxygenase reaction of RuBisCO prevents CO2 depletion near its active sites and provides the maintenance of the chloroplast redox state.

Since photosynthesis is the single most effective natural regulator of carbon dioxide in the Earth's atmosphere, a biochemical model of RuBisCO reaction is used as the core module of climate change models. Thus, a correct model of this reaction is essential to the basic understanding of the relations and interactions of environmental models.

Expression in bacterial hosts

There currently are very few effective methods for expressing functional plant Rubisco in bacterial hosts for genetic manipulation studies. This is largely due to Rubisco's requirement of complex cellular machinery for its biogenesis and metabolic maintenance including the nuclear-encoded RbcS subunits, which are typically imported into chloroplasts as unfolded proteins. Furthermore, sufficient expression and interaction with Rubisco activase are major challenges as well. One successful method for expression of Rubisco in E. coli involves the co-expression of multiple chloroplast chaperones, though this has only been shown for Arabidopsis thaliana Rubisco.

Depletion in proteomic studies

Due to its high abundance in plants (generally 40% of the total protein content), RuBisCO often impedes analysis of important signaling proteins such as transcription factors, kinases, and regulatory proteins found in lower abundance (10-100 molecules per cell) within plants. For example, using mass spectrometry on plant protein mixtures would result in multiple intense RuBisCO subunit peaks that interfere and hide those of other proteins.

Recently, one efficient method for precipitating out RuBisCO involves the usage of protamine sulfate solution. Other existing methods for depleting RuBisCO and studying lower abundance proteins include fractionation techniques with calcium and phytate, gel electrophoresis with polyethylene glycol, affinity chromatography, and aggregation using DTT, though these methods are more time-consuming and less efficient when compared to protamine sulfate precipitation.

Phylogenetic studies

The chloroplast gene rbcL, which codes for the large subunit of RuBisCO has been widely used as an appropriate locus for analysis of phylogenetics in plant taxonomy.

Evolution of RuBisCO

With the evolution of the C4-fixation pathway in certain species of plants, C3 RuBisCO evolved to have faster turnover of CO2 in exchange for lower specificity as a result of the greater localization of CO2 from the mesophyll cells into the bundle sheath cells. This was achieved through enhancement of conformational flexibility of the “open-closed” transition in the Calvin Cycle. Laboratory-based phylogenetic studies have shown that this evolution was constrained by the trade-off between stability and activity brought about by the series of necessary mutations for C4 RuBisCO. Moreover, in order to sustain the destabilizing mutations, the evolution to C4 RuBisCO was preceded by a period in which mutations granted the enzyme increased stability, establishing a buffer to sustain and maintain the mutations required for C4 RuBisCO. To assist with this buffering process, the newly-evolved enzyme was found to have further developed a series of stabilizing mutations. While RuBisCO has always been accumulating new mutations, most of these mutations that have survived have not had significant effects on protein stability. The destabilizing C4 mutations on RuBisCO has been sustained by environmental pressures such as low CO2 concentrations, requiring a sacrifice of stability for new adaptive functions.

History of the term

The term "RuBisCO" was coined humorously in 1979, by David Eisenberg at a seminar honouring the retirement of the early, prominent RuBisCO researcher, Sam Wildman, and also alluded to the snack food trade name "Nabisco" in reference to Wildman's attempts to create an edible protein supplement from tobacco leaves.

The capitalization of the name has been long debated. It can be capitalized for each letter of the full name (Ribulose-1,5 bisphosphate carboxylase/oxygenase), but it has also been argued that is should all be in lower case (rubisco), similar to other terms like scuba or laser.

Rejuvenation

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