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{{Short description|Eukaryotic biological kingdom}}
{{Short description|Eukaryotic biological kingdom}}
{{Automatic taxobox
{{Automatic taxobox
| image = Chromista collage 2.jpg
| image=Chromista collage 2.jpg
| image_caption = Chromista collage
| image_caption=Chromista collage
| display_parents = 2
| display_parents=2
| taxon = Chromista
| taxon=Chromista
| authority = [[Cavalier-Smith]] 1981
| authority=[[Cavalier-Smith]] 1981
| subdivision_ranks = Phyla
| subdivision_ranks=Phyla
| subdivision =
| subdivision=
* [[Corbihelia]]
* [[Corbihelia]]
* [[Cryptophyta]]
* [[Cryptophyta]]
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}}
}}


'''Chromista''' is a proposed but seemingly polyphyletic<ref name="pmid7972066"/><ref name="Burki Roger Brown Simpson 2020 pp. 43–55"/> [[kingdom (biology)|biological kingdom]] consisting of single-celled and multicellular [[eukaryotic]] species that share similar features in their [[Photosynthesis|photosynthetic]] organelles ([[plastid]]s).<ref name="parfrey" /> It includes all [[protists]] whose plastids contain [[chlorophyll c|chlorophyll ''c'']], such as some [[algae]], [[diatoms]], [[oomycetes]], and [[protozoans]]. It is probably a [[polyphyletic]] group whose members independently arose as a separate evolutionary group from the common ancestor of all eukaryotes.<ref name="pmid7972066">{{cite journal | vauthors = Cavalier-Smith T, Allsopp MT, Chao EE | title = Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic? | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 91 | issue = 24 | pages = 11368–11372 | date = November 1994 | pmid = 7972066 | pmc = 45232 | doi = 10.1073/pnas.91.24.11368 | bibcode = 1994PNAS...9111368C | doi-access = free }}</ref> As it is assumed the [[Most recent common ancestor|last common ancestor]] already possessed [[Chloroplast|chloroplasts]] of [[Red algae|red algal]] origin, the non-photosynthetic forms evolved from ancestors able to perform photosynthesis. Their plastids are surrounded by four [[Cell membrane|membranes]], and are believed to have been acquired from some red algae.
'''Chromista''' is a proposed but seemingly polyphyletic<ref name="pmid7972066"/><ref name="Burki Roger Brown Simpson 2020 pp. 43–55"/> [[kingdom (biology)|biological kingdom]] consisting of single-celled and multicellular [[eukaryotic]] species that share similar features in their [[Photosynthesis|photosynthetic]] organelles ([[plastid]]s).<ref name="parfrey" /> It includes all [[protists]] whose plastids contain [[chlorophyll c|chlorophyll ''c'']], such as some [[algae]], [[diatoms]], [[oomycetes]], and [[protozoans]]. It is probably a [[polyphyletic]] group whose members independently arose as a separate evolutionary group from the common ancestor of all eukaryotes.<ref name="pmid7972066">{{cite journal | vauthors=Cavalier-Smith T, Allsopp MT, Chao EE | title=Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic? | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=91 | issue=24 | pages=11368–11372 | date=November 1994 | pmid=7972066 | pmc=45232 | doi=10.1073/pnas.91.24.11368 | bibcode=1994PNAS...9111368C | doi-access=free }}</ref> As it is assumed the [[Most recent common ancestor|last common ancestor]] already possessed [[Chloroplast|chloroplasts]] of [[Red algae|red algal]] origin, the non-photosynthetic forms evolved from ancestors able to perform photosynthesis. Their plastids are surrounded by four [[Cell membrane|membranes]], and are believed to have been acquired from some red algae.


Chromista as a biological kingdom was created by British biologist [[Thomas Cavalier-Smith]] in 1981 to differentiate some protists from typical protozoans and plants.<ref name=bio1981>{{cite journal | vauthors = Cavalier-Smith T | title = Eukaryote kingdoms: seven or nine? | journal = Bio Systems | volume = 14 | issue = 3–4 | pages = 461–81 | year = 1981 | pmid = 7337818 | doi = 10.1016/0303-2647(81)90050-2 }}</ref> According to Cavalier-Smith, the kingdom originally included only algae, but his later analysis indicated that many protozoa also belong to the new group. As of 2018, the kingdom is as diverse as kingdoms Plantae and Animalia, consisting of eight phyla. Notable members include marine algae, [[potato blight]], [[dinoflagellates]], ''[[Paramecium]]'', the brain parasite ''[[Toxoplasma]],'' and the malarial parasite ''[[Plasmodium]]''.<ref name="protoplasma18">{{cite journal |last1=Cavalier-Smith |first1=Thomas |title=Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences |journal=Protoplasma |date=2018 |volume=255 |issue=1 |pages=297–357 |doi=10.1007/s00709-017-1147-3 |pmid=28875267 |pmc=5756292}}</ref>
Chromista as a biological kingdom was created by British biologist [[Thomas Cavalier-Smith]] in 1981 to differentiate some protists from typical protozoans and plants.<ref name=bio1981>{{cite journal | vauthors=Cavalier-Smith T | title=Eukaryote kingdoms: seven or nine? | journal=Bio Systems | volume=14 | issue=3–4 | pages=461–81 | year=1981 | pmid=7337818 | doi=10.1016/0303-2647(81)90050-2 }}</ref> According to Cavalier-Smith, the kingdom originally included only algae, but his later analysis indicated that many protozoa also belong to the new group. As of 2018, the kingdom is as diverse as kingdoms Plantae and Animalia, consisting of eight phyla. Notable members include marine algae, [[potato blight]], [[dinoflagellates]], ''[[Paramecium]]'', the brain parasite ''[[Toxoplasma]],'' and the malarial parasite ''[[Plasmodium]]''.<ref name="protoplasma18">{{cite journal |last1=Cavalier-Smith |first1=Thomas |title=Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences |journal=Protoplasma |date=2018 |volume=255 |issue=1 |pages=297–357 |doi=10.1007/s00709-017-1147-3 |pmid=28875267 |pmc=5756292}}</ref>


==Biology==
==Biology==
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==History and groups==
==History and groups==


Some examples of classification of the groups involved, which have overlapping but non-identical memberships, are shown below.<ref>{{cite book | vauthors = de Reviers B | date = 2006 | url = https://books.google.com/books?id=6fw4AgAAQBAJ&pg=PA156 | title = Biologia e Filogenia das Algas | publisher = Editora Artmed | location = Porto Alegre | pages = 156–157 | isbn = 9788536315102 }}</ref><ref>{{cite journal | vauthors = Blackwell W | title = Chromista revisited: a dilemma of overlapping putative kingdoms, and the attempted application of the botanical code of nomenclature. | journal = Phytologia | date = 2009 | volume = 91 | issue = 2 | pages = 191–225 | url = http://www.phytologia.org/uploads/2/3/4/2/23422706/912191-225blackwellchromistarevisted.pdf }}</ref>
Some examples of classification of the groups involved, which have overlapping but non-identical memberships, are shown below.<ref>{{cite book | vauthors=de Reviers B | date=2006 | url=https://books.google.com/books?id=6fw4AgAAQBAJ&pg=PA156 | title=Biologia e Filogenia das Algas | publisher=Editora Artmed | location=Porto Alegre | pages=156–157 | isbn=9788536315102 }}</ref><ref>{{cite journal | vauthors=Blackwell W | title=Chromista revisited: a dilemma of overlapping putative kingdoms, and the attempted application of the botanical code of nomenclature. | journal=Phytologia | date=2009 | volume=91 | issue=2 | pages=191–225 | url=http://www.phytologia.org/uploads/2/3/4/2/23422706/912191-225blackwellchromistarevisted.pdf }}</ref>


===Chromophycées (Chadefaud, 1950)===
===Chromophycées (Chadefaud, 1950)===


The Chromophycées (Chadefaud, 1950),<ref>{{cite journal | vauthors = Chadefaud M | date = 1950 | title = Les cellules nageuses des Algues dans l'embranchement des Chromophycées | trans-title = Seaweed swimming cells in the branch of Chromophyceae | language = French | journal = Comptes rendus hebdomadaires des séances de l'Académie des Sciences | volume = 231 | pages = 788–790 }}</ref> renamed Chromophycota (Chadefaud, 1960),<ref>{{cite book | vauthors = Chadefaud M | date = 1960 | chapter = Les végétaux non vasculaires (Cryptogamie) | veditors = Chadefaud M, Emberger L | title = Traité de Botanique Systématique | publisher = Tome I | location = Paris }}</ref> included the current [[Ochrophyta]] (autotrophic [[Stramenopile]]s), [[Haptophyta]] (included in Chrysophyceae until Christensen, 1962), [[Cryptophyta]], [[Dinophyta]], [[Euglenophyceae]] and [[Choanoflagellida]] (included in Chrysophyceae until Hibberd, 1975).
The Chromophycées (Chadefaud, 1950),<ref>{{cite journal | vauthors=Chadefaud M | date=1950 | title=Les cellules nageuses des Algues dans l'embranchement des Chromophycées | trans-title=Seaweed swimming cells in the branch of Chromophyceae | language=French | journal=Comptes rendus hebdomadaires des séances de l'Académie des Sciences | volume=231 | pages=788–790 }}</ref> renamed Chromophycota (Chadefaud, 1960),<ref>{{cite book | vauthors=Chadefaud M | date=1960 | chapter=Les végétaux non vasculaires (Cryptogamie) | veditors=Chadefaud M, Emberger L | title=Traité de Botanique Systématique | publisher=Tome I | location=Paris }}</ref> included the current [[Ochrophyta]] (autotrophic [[Stramenopile]]s), [[Haptophyta]] (included in Chrysophyceae until Christensen, 1962), [[Cryptophyta]], [[Dinophyta]], [[Euglenophyceae]] and [[Choanoflagellida]] (included in Chrysophyceae until Hibberd, 1975).


===Chromophyta (Christensen 1962, 1989)===
===Chromophyta (Christensen 1962, 1989)===
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===Chromista (Cavalier-Smith, 1981)===
===Chromista (Cavalier-Smith, 1981)===


The name Chromista was first introduced by [[Thomas Cavalier-Smith|Cavalier-Smith]] in 1981;<ref name=bio1981/> the earlier names Chromophyta, Chromobiota and Chromobionta correspond to roughly the same group. It has been described as consisting of three different groups:<ref name="pmid18296415">{{cite journal | vauthors = Csurös M, Rogozin IB, Koonin EV | title = Extremely intron-rich genes in the alveolate ancestors inferred with a flexible maximum-likelihood approach | journal = Molecular Biology and Evolution | volume = 25 | issue = 5 | pages = 903–11 | date = May 2008 | pmid = 18296415 | doi = 10.1093/molbev/msn039 | doi-access = free }}</ref> It includes all protists whose plastids contain [[chlorophyll c|chlorophyll ''c'']].<ref name="pmid7972066"/>
The name Chromista was first introduced by [[Thomas Cavalier-Smith|Cavalier-Smith]] in 1981;<ref name=bio1981/> the earlier names Chromophyta, Chromobiota and Chromobionta correspond to roughly the same group. It has been described as consisting of three different groups:<ref name="pmid18296415">{{cite journal | vauthors=Csurös M, Rogozin IB, Koonin EV | title=Extremely intron-rich genes in the alveolate ancestors inferred with a flexible maximum-likelihood approach | journal=Molecular Biology and Evolution | volume=25 | issue=5 | pages=903–11 | date=May 2008 | pmid=18296415 | doi=10.1093/molbev/msn039 | doi-access=free }}</ref> It includes all protists whose plastids contain [[chlorophyll c|chlorophyll ''c'']].<ref name="pmid7972066"/>


* [[Heterokont]]s or stramenopiles: [[brown alga]]e, [[diatom]]s, [[water mould]]s, etc.
* [[Heterokont]]s or stramenopiles: [[brown alga]]e, [[diatom]]s, [[water mould]]s, etc.
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===Chromalveolata (Adl ''et al''., 2005)===
===Chromalveolata (Adl ''et al''., 2005)===


The [[Chromalveolata]] (Cavalier-Smith, 1981) included [[Stramenopile]]s, [[Haptophyta]], [[Cryptophyta]] and [[Alveolata]].<ref name=Adl2005> {{cite journal |first = Sina M. |last = Adl |title = The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists |journal = Journal of Eukaryotic Microbiology |year=2005 |volume=52 |issue=5 |pages=399–451 |doi=10.1111/j.1550-7408.2005.00053.x |pmid=16248873 |s2cid = 8060916 |display-authors=etal |doi-access=free }}</ref>
The [[Chromalveolata]] (Cavalier-Smith, 1981) included [[Stramenopile]]s, [[Haptophyta]], [[Cryptophyta]] and [[Alveolata]].<ref name=Adl2005> {{cite journal |last=Adl |first=Sina M. |title=The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists |journal=Journal of Eukaryotic Microbiology |year=2005 |volume=52 |issue=5 |pages=399–451 |doi=10.1111/j.1550-7408.2005.00053.x |pmid=16248873 |s2cid=8060916 |display-authors=etal |doi-access=free }}</ref> However, in 2008 the group was found not to be monophyletic,<ref name=Burki2008a>{{Cite journal |last1=Burki |first1=Fabien |last2=Shalchian-Tabrizi |first2=Kamran |last3=Pawlowski |first3=Jan |year=2008 |title=Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes |journal=Biology Letters |volume=4 |pages=366–369 |doi=10.1098/rsbl.2008.0224 |name-list-style=amp |pmid=18522922 |issue=4 |pmc=2610160 }}</ref><ref name=KimGraham2008>{{cite journal | doi=10.1371/journal.pone.0002621 |date=July 2008 |last1=Kim |first1=E. |last2=Graham |first2=L. E. | editor1-last=Redfield | editor1-first=Rosemary Jeanne | title=EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata. | volume=3 | issue=7 | pages=e2621 | pmid=18612431 | pmc=2440802 | journal=PLOS ONE |bibcode=2008PLoSO...3.2621K |doi-access=free }}</ref> and later studies confirmed this.<ref name="Burki Kaplan 2016 Untangling"/><ref name="Burki Okamoto 2012 Separate origins">{{cite journal|last1=Burki |first1=F. |last2=Okamoto |first2=N. |last3=Pombert |first3= J.F. |last4=Keeling |first4=P.J. |year=2012 |title=The evolutionary history of haptophytes and cryptophytes: phylogenomic evidence for separate origins |journal=Proc. Biol. Sci. |doi=10.1098/rspb.2011.2301 |name-list-style=amp |volume=279 |issue=1736 |pages=2246–2254 |pmid=22298847 |pmc=3321700}}</ref>


==Classification==
==Classification==
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{{further|Diaphoretickes}}
{{further|Diaphoretickes}}


Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the [[alveolate]]s (see [[chromalveolate]]s), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts or the SAR clade, but may be associated with the [[Archaeplastida]].<ref name="parfrey">{{cite journal |vauthors=Parfrey LW, Barbero E, Lasser E, Dunthorn M, Bhattacharya D, Patterson DJ, Katz LA |title=Evaluating support for the current classification of eukaryotic diversity |journal=PLOS Genetics |volume=2 |issue=12 |pages=e220 |date=December 2006 |pmid=17194223 |pmc=1713255 |doi=10.1371/journal.pgen.0020220 |name-list-style=amp }}</ref><ref name="pmid17726520">{{cite journal |vauthors=Burki F, Shalchian-Tabrizi K, Minge M, Skjaeveland A, Nikolaev SI, Jakobsen KS, Pawlowski J |title=Phylogenomics reshuffles the eukaryotic supergroups |journal=PLOS ONE |volume=2 |issue=8 |pages=e790 |date=August 2007 |pmid=17726520 |pmc=1949142 |doi=10.1371/journal.pone.0000790 |bibcode=2007PLoSO...2..790B |doi-access=free }}</ref> Cryptista specifically may be sister or part of Archaeplastida.<ref>{{cite journal |vauthors=Burki F, Kaplan M, Tikhonenkov DV, Zlatogursky V, Minh BQ, Radaykina LV, Smirnov A, Mylnikov AP, Keeling PJ |title=Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista |journal=Proceedings. Biological Sciences |volume=283 |issue=1823 |pages=20152802 |date=January 2016 |pmid=26817772 |pmc=4795036 |doi=10.1098/rspb.2015.2802 }}</ref> A 2020 phylogeny of the eukaryotes states that "the chromalveolate hypothesis is not widely accepted" (noting Cavalier-Smith et al 2018<ref name="Cavalier-Smith Chao Lewis 2018 pp. 1517–1574">{{cite journal | last=Cavalier-Smith | first=Thomas | last2=Chao | first2=Ema E. | last3=Lewis | first3=Rhodri | title=Multigene phylogeny and cell evolution of chromist infrakingdom Rhizaria: contrasting cell organisation of sister phyla Cercozoa and Retaria | journal=Protoplasma | volume=255 | issue=5 | date=17 April 2018 | issn=0033-183X | doi=10.1007/s00709-018-1241-1 | pages=1517–1574}}</ref> as an exception), explaining that the host lineages do not appear to be closely related in "most phylogenetic analyses".<ref name="Burki Roger Brown Simpson 2020 pp. 43–55"/><ref>{{cite book |last=Burki |first=F. |chapter=The convoluted evolution of eukaryotes with complex plastids |editor-last=Hirakawa |editor-first=Y. |title=Advances in Botanical Research |volume=84 |publisher=Academic Press |year=2017 |pages=1-30}}</ref> Further, none of TSAR, Cryptista, and Haptista, groups formerly within Chromalveolata, appear "likely to be ancestrally defined by red secondary plastids".<ref name="Burki Roger Brown Simpson 2020 pp. 43–55">{{cite journal |last=Burki |first=Fabien |last2=Roger |first2=Andrew J. |last3=Brown |first3=Matthew W. |last4=Simpson |first4=Alastair G.B. |title=The New Tree of Eukaryotes |journal=Trends in Ecology & Evolution |publisher=Elsevier BV |volume=35 |issue=1 |year=2020 |issn=0169-5347 |doi=10.1016/j.tree.2019.08.008 |pages=43–55}}</ref>
Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the [[alveolate]]s (see [[chromalveolate]]s), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts or the SAR clade, but may be associated with the [[Archaeplastida]].<ref name="parfrey">{{cite journal |vauthors=Parfrey LW, Barbero E, Lasser E, Dunthorn M, Bhattacharya D, Patterson DJ, Katz LA |title=Evaluating support for the current classification of eukaryotic diversity |journal=PLOS Genetics |volume=2 |issue=12 |pages=e220 |date=December 2006 |pmid=17194223 |pmc=1713255 |doi=10.1371/journal.pgen.0020220 |name-list-style=amp }}</ref><ref name="pmid17726520">{{cite journal |vauthors=Burki F, Shalchian-Tabrizi K, Minge M, Skjaeveland A, Nikolaev SI, Jakobsen KS, Pawlowski J |title=Phylogenomics reshuffles the eukaryotic supergroups |journal=PLOS ONE |volume=2 |issue=8 |pages=e790 |date=August 2007 |pmid=17726520 |pmc=1949142 |doi=10.1371/journal.pone.0000790 |bibcode=2007PLoSO...2..790B |doi-access=free }}</ref> Cryptista specifically may be sister or part of Archaeplastida.<ref name="Burki Kaplan 2016 Untangling">{{cite journal |vauthors=Burki F, Kaplan M, Tikhonenkov DV, Zlatogursky V, Minh BQ, Radaykina LV, Smirnov A, Mylnikov AP, Keeling PJ |title=Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista |journal=Proceedings. Biological Sciences |volume=283 |issue=1823 |pages=20152802 |date=January 2016 |pmid=26817772 |pmc=4795036 |doi=10.1098/rspb.2015.2802 }}</ref> A 2020 phylogeny of the eukaryotes states that "the chromalveolate hypothesis is not widely accepted" (noting Cavalier-Smith et al 2018<ref name="Cavalier-Smith Chao Lewis 2018 pp. 1517–1574">{{cite journal | last=Cavalier-Smith | first=Thomas | last2=Chao | first2=Ema E. | last3=Lewis | first3=Rhodri | title=Multigene phylogeny and cell evolution of chromist infrakingdom Rhizaria: contrasting cell organisation of sister phyla Cercozoa and Retaria | journal=Protoplasma | volume=255 | issue=5 | date=17 April 2018 | issn=0033-183X | doi=10.1007/s00709-018-1241-1 | pages=1517–1574}}</ref> as an exception), explaining that the host lineages do not appear to be closely related in "most phylogenetic analyses".<ref name="Burki Roger Brown Simpson 2020 pp. 43–55"/><ref>{{cite book |last=Burki |first=F. |chapter=The convoluted evolution of eukaryotes with complex plastids |editor-last=Hirakawa |editor-first=Y. |title=Advances in Botanical Research |volume=84 |publisher=Academic Press |year=2017 |pages=1-30}}</ref> Further, none of TSAR, Cryptista, and Haptista, groups formerly within Chromalveolata, appear "likely to be ancestrally defined by red secondary plastids".<ref name="Burki Roger Brown Simpson 2020 pp. 43–55">{{cite journal |last=Burki |first=Fabien |last2=Roger |first2=Andrew J. |last3=Brown |first3=Matthew W. |last4=Simpson |first4=Alastair G.B. |title=The New Tree of Eukaryotes |journal=Trends in Ecology & Evolution |publisher=Elsevier BV |volume=35 |issue=1 |year=2020 |issn=0169-5347 |doi=10.1016/j.tree.2019.08.008 |pages=43–55}}</ref>


== See also ==
== See also ==

Revision as of 20:43, 16 March 2023

Chromista
Chromista collage
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Kingdom: Chromista
Cavalier-Smith 1981
Phyla

Chromista is a proposed but seemingly polyphyletic[1][2] biological kingdom consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids).[3] It includes all protists whose plastids contain chlorophyll c, such as some algae, diatoms, oomycetes, and protozoans. It is probably a polyphyletic group whose members independently arose as a separate evolutionary group from the common ancestor of all eukaryotes.[1] As it is assumed the last common ancestor already possessed chloroplasts of red algal origin, the non-photosynthetic forms evolved from ancestors able to perform photosynthesis. Their plastids are surrounded by four membranes, and are believed to have been acquired from some red algae.

Chromista as a biological kingdom was created by British biologist Thomas Cavalier-Smith in 1981 to differentiate some protists from typical protozoans and plants.[4] According to Cavalier-Smith, the kingdom originally included only algae, but his later analysis indicated that many protozoa also belong to the new group. As of 2018, the kingdom is as diverse as kingdoms Plantae and Animalia, consisting of eight phyla. Notable members include marine algae, potato blight, dinoflagellates, Paramecium, the brain parasite Toxoplasma, and the malarial parasite Plasmodium.[5]

Biology

Structure of typical chromists compared with plant cell (left)

Members of Chromista are single-celled and multicellular eukaryotes having basically either or both features:[4]

  1. plastid(s) that contain chlorophyll c and lie within an extra (periplastid) membrane in the lumen of the rough endoplasmic reticulum (typically within the perinuclear cisterna);
  2. cilia with tripartite or bipartite rigid tubular hairs.

The kingdom includes diverse organisms from algae to malarial parasites (Plasmodium).[6] Molecular evidence indicates that the plastids in chromists were derived from red algae through secondary symbiogenesis in a single event.[7] (In contrast, plants acquired their plastids from cyanobacteria through primary symbiogenesis.)[8] These plastids are now enclosed in two extra cell membranes, making a four-membrane envelope, as a result of which they acquired many other membrane proteins for transporting molecules in and out of the organelles. The diversity of chromists is hypothesised to have arisen from degeneration, loss or replacement of the plastids in some lineages.[9] Additional symbiogenesis of green algae has provided genes retained in some members (such as heterokonts),[10] and bacterial chlorophyll (indicated by the presence of ribosomal protein L36 gene, rpl36) in haptophytes and cryptophytes.[11]

History and groups

Some examples of classification of the groups involved, which have overlapping but non-identical memberships, are shown below.[12][13]

Chromophycées (Chadefaud, 1950)

The Chromophycées (Chadefaud, 1950),[14] renamed Chromophycota (Chadefaud, 1960),[15] included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta (included in Chrysophyceae until Christensen, 1962), Cryptophyta, Dinophyta, Euglenophyceae and Choanoflagellida (included in Chrysophyceae until Hibberd, 1975).

Chromophyta (Christensen 1962, 1989)

The Chromophyta (Christensen 1962, 2008), defined as algae with chlorophyll c, included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta, Cryptophyta, Dinophyta and Choanoflagellida. The Euglenophyceae were transferred to the Chlorophyta.

Chromophyta (Bourrelly, 1968)

The Chromophyta (Bourrelly, 1968) included the current Ochrophyta (autotrophic Stramenopiles), Haptophyta and Choanoflagellida. The Cryptophyceae and the Dinophyceae were part of Pyrrhophyta (= Dinophyta).

Chromista (Cavalier-Smith, 1981)

The name Chromista was first introduced by Cavalier-Smith in 1981;[4] the earlier names Chromophyta, Chromobiota and Chromobionta correspond to roughly the same group. It has been described as consisting of three different groups:[16] It includes all protists whose plastids contain chlorophyll c.[1]

In 1994, Cavalier-Smith and colleagues indicated that the Chromista is probably a polyphyletic group whose members arose independently, sharing no more than descent from the common ancestor of all eukaryotes:[1]

The four phyla that contain chromophyte algae (those with chlorophyll c--i.e., Cryptista, Heterokonta, Haptophyta, Dinozoa) are distantly related to each other and to Chlorarachniophyta on our trees. However, all of the photosynthetic taxa within each of these four phyla radiate from each other very substantially after the radiation of the four phyla themselves. This favors the view that the common ancestor of these four phyla was not photosynthetic and that chloroplasts were implanted separately into each much more recently. This probable polyphyly of the chromophyte algae, if confirmed, would make it desirable to treat Cryptista, Heterokonta, and Haptophyta as separate kingdoms, rather than to group them together in the single kingdom Chromista.[1]

In 2009, Cavalier-Smith gave his reason for making a new kingdom, saying:[6]

I established Chromista as a kingdom distinct from Plantae and Protozoa because of the evidence that chromist chloroplasts were acquired secondarily by enslavement of a red alga, itself a member of kingdom Plantae, and their unique membrane topology.[6]

Since then Chromista has been defined in different ways at different times. In 2010, Cavalier-Smith reorganised Chromista to include the SAR supergroup (named for the included groups Stramenopiles, Alveolata and Rhizaria) and Hacrobia (Haptista and Cryptista).[6]

Chromalveolata (Adl et al., 2005)

The Chromalveolata (Cavalier-Smith, 1981) included Stramenopiles, Haptophyta, Cryptophyta and Alveolata.[17] However, in 2008 the group was found not to be monophyletic,[18][19] and later studies confirmed this.[20][21]

Classification

Cavalier-Smith et al 2015

In 2015, Cavalier-Smith and his colleagues made a new higher-level grouping of all organisms as a revision of the seven kingdoms model. In it, they classified the kingdom Chromista into 2 subkingdoms and 11 phyla, namely:[22]

Chromista
2015

Cavalier-Smith 2018

Chromista classification according to Cavalier-Smith, 2018

Cavalier-Smith made a new analysis of Chromista in 2018 in which he classified all chromists into 8 phyla (Gyrista corresponds to the above phyla Ochrophyta and Pseudofungi, Cryptista corresponds to the above phyla Cryptista and "N.N.", Haptista corresponds to the above phyla Haptophyta and Heliozoa):[5]

Chromista
2018

Paraphyly

Further information: Diaphoretickes

Molecular trees have had some difficulty resolving relationships between the different groups. All three may share a common ancestor with the alveolates (see chromalveolates), but there is evidence that suggests that the haptophytes and cryptomonads do not belong together with the heterokonts or the SAR clade, but may be associated with the Archaeplastida.[3][23] Cryptista specifically may be sister or part of Archaeplastida.[20] A 2020 phylogeny of the eukaryotes states that "the chromalveolate hypothesis is not widely accepted" (noting Cavalier-Smith et al 2018[24] as an exception), explaining that the host lineages do not appear to be closely related in "most phylogenetic analyses".[2][25] Further, none of TSAR, Cryptista, and Haptista, groups formerly within Chromalveolata, appear "likely to be ancestrally defined by red secondary plastids".[2]

See also

References

  1. ^ a b c d e Cavalier-Smith T, Allsopp MT, Chao EE (November 1994). "Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic?". Proceedings of the National Academy of Sciences of the United States of America. 91 (24): 11368–11372. Bibcode:1994PNAS...9111368C. doi:10.1073/pnas.91.24.11368. PMC 45232. PMID 7972066.
  2. ^ a b c Burki, Fabien; Roger, Andrew J.; Brown, Matthew W.; Simpson, Alastair G.B. (2020). "The New Tree of Eukaryotes". Trends in Ecology & Evolution. 35 (1). Elsevier BV: 43–55. doi:10.1016/j.tree.2019.08.008. ISSN 0169-5347.
  3. ^ a b Parfrey LW, Barbero E, Lasser E, Dunthorn M, Bhattacharya D, Patterson DJ, Katz LA (December 2006). "Evaluating support for the current classification of eukaryotic diversity". PLOS Genetics. 2 (12): e220. doi:10.1371/journal.pgen.0020220. PMC 1713255. PMID 17194223.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  4. ^ a b c Cavalier-Smith T (1981). "Eukaryote kingdoms: seven or nine?". Bio Systems. 14 (3–4): 461–81. doi:10.1016/0303-2647(81)90050-2. PMID 7337818.
  5. ^ a b Cavalier-Smith, Thomas (2018). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma. 255 (1): 297–357. doi:10.1007/s00709-017-1147-3. PMC 5756292. PMID 28875267.
  6. ^ a b c d Cavalier-Smith, Thomas (2009). "Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree". Biology Letters. 6 (3): 342–345. doi:10.1098/rsbl.2009.0948. PMC 2880060. PMID 20031978.
  7. ^ Keeling, Patrick J. (2009). "Chromalveolates and the Evolution of Plastids by Secondary Endosymbiosis". Journal of Eukaryotic Microbiology. 56 (1): 1–8. doi:10.1111/j.1550-7408.2008.00371.x. PMID 19335769. S2CID 34259721.
  8. ^ Ponce-Toledo, Rafael I.; Deschamps, Philippe; López-García, Purificación; Zivanovic, Yvan; Benzerara, Karim; Moreira, David (2017). "An Early-Branching Freshwater Cyanobacterium at the Origin of Plastids". Current Biology. 27 (3): 386–391. doi:10.1016/j.cub.2016.11.056. PMC 5650054. PMID 28132810.
  9. ^ Keeling, Patrick J. (2010). "The endosymbiotic origin, diversification and fate of plastids". Philosophical Transactions of the Royal Society B: Biological Sciences. 365 (1541): 729–748. doi:10.1098/rstb.2009.0103. PMC 2817223. PMID 20124341.
  10. ^ Morozov, A.A.; Galachyants, Yuri P. (2019). "Diatom genes originating from red and green algae: Implications for the secondary endosymbiosis models". Marine Genomics. 45: 72–78. doi:10.1016/j.margen.2019.02.003. PMID 30792089.
  11. ^ Rice, Danny W; Palmer, Jeffrey D (2006). "An exceptional horizontal gene transfer in plastids: gene replacement by a distant bacterial paralog and evidence that haptophyte and cryptophyte plastids are sisters". BMC Biology. 4 (1): 31. doi:10.1186/1741-7007-4-31. PMC 1570145. PMID 16956407.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  12. ^ de Reviers B (2006). Biologia e Filogenia das Algas. Porto Alegre: Editora Artmed. pp. 156–157. ISBN 9788536315102.
  13. ^ Blackwell W (2009). "Chromista revisited: a dilemma of overlapping putative kingdoms, and the attempted application of the botanical code of nomenclature" (PDF). Phytologia. 91 (2): 191–225.
  14. ^ Chadefaud M (1950). "Les cellules nageuses des Algues dans l'embranchement des Chromophycées" [Seaweed swimming cells in the branch of Chromophyceae]. Comptes rendus hebdomadaires des séances de l'Académie des Sciences (in French). 231: 788–790.
  15. ^ Chadefaud M (1960). "Les végétaux non vasculaires (Cryptogamie)". In Chadefaud M, Emberger L (eds.). Traité de Botanique Systématique. Paris: Tome I.
  16. ^ Csurös M, Rogozin IB, Koonin EV (May 2008). "Extremely intron-rich genes in the alveolate ancestors inferred with a flexible maximum-likelihood approach". Molecular Biology and Evolution. 25 (5): 903–11. doi:10.1093/molbev/msn039. PMID 18296415.
  17. ^ Adl, Sina M.; et al. (2005). "The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists". Journal of Eukaryotic Microbiology. 52 (5): 399–451. doi:10.1111/j.1550-7408.2005.00053.x. PMID 16248873. S2CID 8060916.
  18. ^ Burki, Fabien; Shalchian-Tabrizi, Kamran & Pawlowski, Jan (2008). "Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes". Biology Letters. 4 (4): 366–369. doi:10.1098/rsbl.2008.0224. PMC 2610160. PMID 18522922.
  19. ^ Kim, E.; Graham, L. E. (July 2008). Redfield, Rosemary Jeanne (ed.). "EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata". PLOS ONE. 3 (7): e2621. Bibcode:2008PLoSO...3.2621K. doi:10.1371/journal.pone.0002621. PMC 2440802. PMID 18612431.
  20. ^ a b Burki F, Kaplan M, Tikhonenkov DV, Zlatogursky V, Minh BQ, Radaykina LV, Smirnov A, Mylnikov AP, Keeling PJ (January 2016). "Untangling the early diversification of eukaryotes: a phylogenomic study of the evolutionary origins of Centrohelida, Haptophyta and Cryptista". Proceedings. Biological Sciences. 283 (1823): 20152802. doi:10.1098/rspb.2015.2802. PMC 4795036. PMID 26817772.
  21. ^ Burki, F.; Okamoto, N.; Pombert, J.F. & Keeling, P.J. (2012). "The evolutionary history of haptophytes and cryptophytes: phylogenomic evidence for separate origins". Proc. Biol. Sci. 279 (1736): 2246–2254. doi:10.1098/rspb.2011.2301. PMC 3321700. PMID 22298847.
  22. ^ Ruggiero, Michael A.; Gordon, Dennis P.; Orrell, Thomas M.; Bailly, Nicolas; Bourgoin, Thierry; Brusca, Richard C.; Cavalier-Smith, Thomas; Guiry, Michael D.; Kirk, Paul M.; Thuesen, Erik V. (2015). "A higher level classification of all living organisms". PLOS ONE. 10 (4): e0119248. Bibcode:2015PLoSO..1019248R. doi:10.1371/journal.pone.0119248. PMC 4418965. PMID 25923521.
  23. ^ Burki F, Shalchian-Tabrizi K, Minge M, Skjaeveland A, Nikolaev SI, Jakobsen KS, Pawlowski J (August 2007). "Phylogenomics reshuffles the eukaryotic supergroups". PLOS ONE. 2 (8): e790. Bibcode:2007PLoSO...2..790B. doi:10.1371/journal.pone.0000790. PMC 1949142. PMID 17726520.
  24. ^ Cavalier-Smith, Thomas; Chao, Ema E.; Lewis, Rhodri (17 April 2018). "Multigene phylogeny and cell evolution of chromist infrakingdom Rhizaria: contrasting cell organisation of sister phyla Cercozoa and Retaria". Protoplasma. 255 (5): 1517–1574. doi:10.1007/s00709-018-1241-1. ISSN 0033-183X.
  25. ^ Burki, F. (2017). "The convoluted evolution of eukaryotes with complex plastids". In Hirakawa, Y. (ed.). Advances in Botanical Research. Vol. 84. Academic Press. pp. 1–30.

External links

Wikispecies has information related to Chromista.
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