Chlorophyta Explained

Chlorophyta is a taxon of green algae informally called chlorophytes.[1] The name is used in two very different senses, so care is needed to determine the use by a particular author. In older classification systems, it is a highly paraphyletic group of all the green algae within the green plants (Viridiplantae) and thus includes about 7,000 species[2] [3] of mostly aquatic photosynthetic eukaryotic organisms. In newer classifications, it is the sister clade of the streptophytes/charophytes. The clade Streptophyta consists of the Charophyta in which the Embryophyta (land plants) emerged.[4] [5] In this latter sense the Chlorophyta includes only about 4,300 species. About 90% of all known species live in freshwater.[6] Like the land plants (embryophytes: bryophytes and tracheophytes), green algae (chlorophytes and charophytes besides embryophytes) contain chlorophyll a and chlorophyll b and store food as starch in their plastids.

With the exception of the three classes Ulvophyceae, Trebouxiophyceae and Chlorophyceae in the UTC clade, which show various degrees of multicellularity, all the Chlorophyta lineages are unicellular.[7] Some members of the group form symbiotic relationships with protozoa, sponges, and cnidarians. Others form symbiotic relationships with fungi to form lichens, but the majority of species are free-living. Some conduct sexual reproduction, which is oogamous or isogamous. All members of the clade have motile flagellated swimming cells.[8] While most species live in freshwater habitats and a large number in marine habitats, other species are adapted to a wide range of land environments. For example, Chlamydomonas nivalis, which causes Watermelon snow, lives on summer alpine snowfields. Others, such as Trentepohlia species, live attached to rocks or woody parts of trees. Monostroma kuroshiense, an edible green alga cultivated worldwide and most expensive among green algae, belongs to this group.

Ecology

Species of Chlorophyta (treated as what is now considered one of the two main clades of Viridiplantae) are common inhabitants of marine, freshwater and terrestrial environments.[9] [10] Several species have adapted to specialised and extreme environments, such as deserts, arctic environments, hypersaline habitats, marine deep waters, deep-sea hydrothermal vents and habitats that experiences extreme changes in temperature, light and salinity.[11] [12] [13] [14] Some groups, such as the Trentepohliales are exclusively found on land.[15] Several species of Chlorophyta live in symbiosis with a diverse range of eukaryotes, including fungi (to form lichens), ciliates, forams, cnidarians and molluscs. Some species of Chlorophyta are heterotrophic, either free-living or parasitic.[16] [17] Others are mixotrophic bacterivores through phagocytosis.[18] Two common species of the heterotrophic green alga Prototheca are pathogenic and can cause the disease protothecosis in humans and animals.[19]

Classifications

Characteristics used for the classification of Chlorophyta are: type of zoid, mitosis (karyokinesis), cytokinesis, organization level, life cycle, type of gametes, cell wall polysaccharides[20] and more recently genetic data.

Phylogeny

Leliaert et al. 2012 proposed the following phylogeny. He marked the "prasinophytes" as paraphyletic, with the remaining Chlorophyta groups as "core chlorophytes". He described all Streptophyta except the land plants as paraphyletic "charophytes".[10]

A 2020 paper places the "Prasinodermophyta" (i.e. Prasinodermophyceae + Palmophyllophyceae) as the basal Viridiplantae clade.[21]

Leliaert et al. 2012

Simplified phylogeny of the Chlorophyta, according to Leliaert et al. 2012. Note that many algae previously classified in Chlorophyta are placed here in Streptophyta.

Pombert et al. 2005

A possible classification when Chlorophyta refers to one of the two clades of the Viridiplantae is shown below.[22]

Lewis & McCourt 2004

Hoek, Mann and Jahns 1995

Classification of the Chlorophyta, treated as all green algae, according to Hoek, Mann and Jahns 1995.[2]

In a note added in proof, an alternative classification is presented for the algae of the class Chlorophyceae:

Bold and Wynne 1985

Classification of the Chlorophyta and Charophyta according to Bold and Wynne 1985.[23]

Mattox & Stewart 1984

Classification of the Chlorophyta according to Mattox & Stewart 1984:[24]

Fott 1971

Classification of the Chlorophyta according to Fott 1971.

Round 1971

Classification of the Chlorophyta and related algae according to Round 1971.[25]

Smith 1938

Classification of the Chlorophyta according to Smith 1938:

Research and discoveries

In February 2020, the fossilized remains of green algae, named Proterocladus antiquus were discovered in the northern province of Liaoning, China.[26] At around a billion years old, it is believed to be one of the oldest examples of a multicellular chlorophyte.[27]

Further reading

Notes and References

  1. Rockwell NC, Martin SS, Li FW, Mathews S, Lagarias JC . The phycocyanobilin chromophore of streptophyte algal phytochromes is synthesized by HY2 . The New Phytologist . 214 . 3 . 1145–1157 . May 2017 . 28106912 . 5388591 . 10.1111/nph.14422 .
  2. Book: van den Hoek C, Mann DG, Jahns HM . 1995 . Algae An Introduction to Phycology . Cambridge University Press . Cambridge . 978-0-521-30419-1 .
  3. Web site: Major Algae Phyla - Table - MSN Encarta . https://web.archive.org/web/20091029105234/http://encarta.msn.com/media_461543986/Major_Algae_Phyla.html . 2009-10-29 . dead .
  4. Lewis LA, McCourt RM . Green algae and the origin of land plants . American Journal of Botany . 91 . 10 . 1535–56 . October 2004 . 21652308 . 10.3732/ajb.91.10.1535 .
  5. Becker B, Marin B . Streptophyte algae and the origin of embryophytes . Annals of Botany . 103 . 7 . 999–1004 . May 2009 . 19273476 . 2707909 . 10.1093/aob/mcp044 .
  6. Book: Chlorophyta (Chapter 5) - Phycology - Cambridge University Press. 2018. 10.1017/9781316407219. Lee. Robert Edward. 9781316407219.
  7. Umen JG . Green algae and the origins of multicellularity in the plant kingdom . Cold Spring Harbor Perspectives in Biology . 6 . 11 . a016170 . October 2014 . 25324214 . 4413236 . 10.1101/cshperspect.a016170 .
  8. Kapraun DF . Nuclear DNA content estimates in green algal lineages: chlorophyta and streptophyta . Annals of Botany . 99 . 4 . 677–701 . April 2007 . 17272304 . 2802934 . 10.1093/aob/mcl294 .
  9. Graham LE, Graham JM, Wilcox LW (2009) Algae. 2nd Edition. Benjamin Cummings (Pearson), San Francisco, CA
  10. Leliaert F, Smith DR, Moreau H, Herron MD, Verbruggen H, Delwiche CF, De Clerck O . 2012 . Phylogeny and molecular evolution of the green algae . https://web.archive.org/web/20150626102452/http://images.algaebase.org/pdf/5628E58F0ecc431F0CsJm2B04CAD/49951.pdf . 2015-06-26 . live . 10.1080/07352689.2011.615705 . Critical Reviews in Plant Sciences . 31 . 1–46 . 17603352 .
  11. Lewis LA, Lewis PO . Unearthing the molecular phylodiversity of desert soil green algae (Chlorophyta) . Systematic Biology . 54 . 6 . 936–47 . December 2005 . 16338765 . 10.1080/10635150500354852 . free .
  12. De Wever A, Leliaert F, Verleyen E, Vanormelingen P, Van der Gucht K, Hodgson DA, Sabbe K, Vyverman W . Hidden levels of phylodiversity in Antarctic green algae: further evidence for the existence of glacial refugia . Proceedings. Biological Sciences . 276 . 1673 . 3591–9 . October 2009 . 19625320 . 2817313 . 10.1098/rspb.2009.0994 .
  13. Leliaert F, Verbruggen H, Zechman FW . Into the deep: new discoveries at the base of the green plant phylogeny . BioEssays . 33 . 9 . 683–92 . September 2011 . 21744372 . 10.1002/bies.201100035 . 40459076 .
  14. Foflonker F, Ananyev G, Qiu H, Morrison A, Palenik B, Dismukes GC, Bhattacharya D . The unexpected extremophile: Tolerance to fluctuating salinity in the green alga Picochlorum . Algal Research . June 2016 . 16 . 465–472 . 10.1016/j.algal.2016.04.003 . free .
  15. López-Bautista JM, Rindi F, Guiry MD . Molecular systematics of the subaerial green algal order Trentepohliales: an assessment based on morphological and molecular data . International Journal of Systematic and Evolutionary Microbiology . 56 . Pt 7 . 1709–15 . July 2006 . 16825655 . 10.1099/ijs.0.63990-0 . free . 10379/9448 . free .
  16. Joubert JJ, Rijkenberg FH . Parasitic green algae . Annu. Rev. Phytopathol. . 9 . 45–64 . 1971 . 10.1146/annurev.py.09.090171.000401.
  17. Nedelcu AM . Complex patterns of plastid 16S rRNA gene evolution in nonphotosynthetic green algae . Journal of Molecular Evolution . 53 . 6 . 670–9 . December 2001 . 11677627 . 10.1007/s002390010254 . 2001JMolE..53..670N . 21151223 .
  18. Mixotrophy in Chlorophytes and Haptophytes—Effect of Irradiance, Macronutrient, Micronutrient and Vitamin Limitation - NCBI - NIH. 2018. 6080504. Anderson. R.. Charvet. S.. Hansen. P. J.. Frontiers in Microbiology. 9. 1704. 10.3389/fmicb.2018.01704. 30108563. free.
  19. Tartar A, Boucias DG, Adams BJ, Becnel JJ . Phylogenetic analysis identifies the invertebrate pathogen Helicosporidium sp. as a green alga (Chlorophyta) . International Journal of Systematic and Evolutionary Microbiology . 52 . Pt 1 . 273–9 . January 2002 . 11837312 . 10.1099/00207713-52-1-273 . free .
  20. Book: Lobban . Christopher S. . Wynne . Michael James . vanc . 1981 . The Biology of Seaweeds. . Botanical Monograph Series 17. . . 88 . 9780520045859.
  21. Li L, Wang S, Wang H, Sahu SK, Marin B, Li H, Xu Y, Liang H, Li Z, Cheng S, Reder T, Çebi Z, Wittek S, Petersen M, Melkonian B, Du H, Yang H, Wang J, Wong GK, Xu X, Liu X, Van de Peer Y, Melkonian M, Liu H . 6 . The genome of Prasinoderma coloniale unveils the existence of a third phylum within green plants . Nature Ecology & Evolution . 4 . 9 . 1220–1231 . September 2020 . 32572216 . 7455551 . 10.1038/s41559-020-1221-7 .
  22. Pombert JF, Otis C, Lemieux C, Turmel M . The chloroplast genome sequence of the green alga Pseudendoclonium akinetum (Ulvophyceae) reveals unusual structural features and new insights into the branching order of chlorophyte lineages . Molecular Biology and Evolution . 22 . 9 . 1903–18 . September 2005 . 15930151 . 10.1093/molbev/msi182 . free .
  23. Book: Bold HC, Wynne MJ . 1985 . Introduction to the algae : structure and reproduction . 2nd . Englewood Cliffs, N.J. . Prentice-Hall . 978-0-13-477746-7 .
  24. Book: Mattox KR, Stewart KD . 1984 . Classification of the green algae: a concept based on comparative cytology.. 29–72 . Irvine DE, John DM . The systematics of Green Algae . The Systematics Association . 27 . Academic Press . London .
  25. Round FE . 1971 . The taxonomy of the Chlorophyta, 2 . Br. Phycol. J. . 6 . 2. 235–264 . 10.1080/00071617100650261. free .
  26. Web site: Billion-year-old green algae found in China is the oldest ever discovered . McCall R . 2020-02-24. Newsweek. en. 2020-02-25.
  27. Web site: Scientists discover world's oldest green algae fossil in China. Sandhya Ramesh . 2020-02-25. ThePrint. en-US. 2020-02-25.

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