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The opisthokonts (Greek: ὀπίσθιος (opísthios) = "rear, posterior" + κοντός (kontós) = "pole" i.e. "flagellum") or Choanozoa are a broad group of eukaryotes, including both the animal and fungus kingdoms,[5] together with the eukaryotic microorganisms that are sometimes grouped in the paraphyletic phylum Choanozoa (conventionally assigned to the protist "kingdom").[6] The opisthokonts, previously called the "Fungi/Metazoa group",[7] are generally recognized as a clade. Opisthokonts together with Apusomonadida and Breviata comprise the larger clade Obazoa.[6][8][9][10][11]

Flagella

A common characteristic of opisthokonts is that flagellate cells, such as the sperm of most animals and the spores of the chytrid fungi, propel themselves with a single posterior flagellum. It is this feature that gives the group its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more anterior flagella. However, in some opisthokont groups, including most of the fungi, flagellate cells have been lost.[6]

History

The close relationship between animals and fungi was suggested by Thomas Cavalier-Smith in 1987,[3] who used the informal name opisthokonta (the formal name has been used for the chytrids by Copeland in 1956), and was supported by later genetic studies.[12]

Early phylogenies placed fungi near the plants and other groups that have mitochondria with flat cristae, but this character varies. More recently, it has been said that holozoa (animals) and holomycota (fungi) are much more closely related to each other than either is to plants, because opisthokonts have a triple fusion of carbamoyl phosphate synthetase, dihydroorotase, and aspartate carbamoyltransferase that is not present in plants, and plants have a fusion of thymidylate synthase and dihydrofolate reductase not present in the opisthokonts. Animals and fungi are also more closely related to amoebas than they are to plants, and plants are more closely related to the SAR supergroup of protists than they are to animals or fungi.[citation needed] Animals and fungi are both heterotrophs, unlike plants, and while fungi are sessile like plants, there are also sessile animals.

Cavalier-Smith and Stechmann[13] argue that the uniciliate eukaryotes such as opisthokonts and Amoebozoa, collectively called unikonts, split off from the other biciliate eukaryotes, called bikonts, shortly after they evolved.

Taxonomy

Opisthokonts are divided into Holomycota or Nucletmycea (fungi and all organisms more closely related to fungi than to animals) and Holozoa (animals and all organisms more closely related to animals than to fungi); no opisthokonts basal to the Holomycota/Holozoa split have yet been identified.[citation needed] The Opisthokonts was largely resolved by Torriella et al.[14] Holomycota and Holozoa are composed of the following groups.

Phylogeny

The paraphyletic taxon Choanozoa includes either non-animal holozoans, or non-animal, non-fungal opisthokonts.

The choanoflagellates have a circular mitochondrial DNA genome with long intergenic regions. This is four times as large as animal mitochondrial genomes and contains twice as many protein coding genes.

Corallochytrium seem likely to be more closely related to the fungi than to the animals on the basis of the presence of ergosterol in their membranes and being capable of synthesis of lysine via the AAA pathway.

The ichthyosporeans have a two amino acid deletion in their EEF1A1 gene that is considered characteristic of fungi.[citation needed]

The ichthyosporean genome is >200 kilobase pairs in length and consists of several hundred linear chromosomes that share elaborate terminal-specific sequence patterns.[citation needed]

In the following phylogenetic tree it is indicated how many millions of years ago (Mya) the clades diverged into newer clades.

Eukaryotes
Bikonta

Archaeplastida (Plantae sensu lato) Pediastrum (cropped).jpg



Hacrobia Coccolithus pelagicus.jpg



SAR supergroup Ochromonas.png




Excavata Euglena mutabilis - 400x - 1 (10388739803) (cropped).jpg


Podiata

Varisulca Collodictyon anterior view, showing sulcus, nucleus, blepharoplast, rhizoplast, and four flagella..jpg


Amorphea/

Amoebozoa Chaos carolinensis Wilson 1900.jpg


Obazoa

Breviatea Mastigamoeba invertens.jpg




Apusomonadida Apusomonas.png


Opisthokonts
Holomycota


Opisthosporidia Fibrillanosema spore.jpg



Fungi Asco1013.jpg



Cristidiscoidea

Nucleariida Nuclearia sp Nikko.jpg



Fonticulida




Holozoa

Ichthyosporea Abeoforma whisleri-2.jpg



Pluriformea

Syssomonas



Corallochytrium Corallochytrium limacisporum.png



Filozoa

Filasterea Ministeria vibrans.jpeg


Apoikozoa

Choanoflagellatea Desmarella moniliformis.jpg



Animalia Comb jelly.jpg


950 mya



1300 mya


Unikonts


One view of the great kingdoms and their stem groups.[16]

Gallery

References

  1. ^ Parfrey, Laura Wegener; Lahr, Daniel J. G.; Knoll, Andrew H.; Katz, Laura A. (August 16, 2011). "Estimating the timing of early eukaryotic diversification with multigene molecular clocks". Proceedings of the National Academy of Sciences of the United States of America. 108 (33): 13624–13629. doi:10.1073/pnas.1110633108. PMC 3158185Freely accessible. PMID 21810989. 
  2. ^ Copeland, H. F. (1956). The Classification of Lower Organisms. Palo Alto: Pacific Books.
  3. ^ a b Cavalier-Smith, T. (1987). "The origin of fungi and pseudofungi". In Rayner, Alan D. M. (ed.). Evolutionary biology of Fungi. Cambridge: Cambridge Univ. Press. pp. 339–353. ISBN 0-521-33050-5. 
  4. ^ Adl, S.M.; et al. (September–October 2005). "The new higher level classification of eukaryotes with emphasis on the taxonomy of protists". Journal of eukaryotic microbiology. 52: 399–451. doi:10.1111/j.1550-7408.2005.00053.x. PMID 16248873. 
  5. ^ Shalchian-Tabrizi K, Minge MA, Espelund M, et al. (7 May 2008). Aramayo R, ed. "Multigene phylogeny of choanozoa and the origin of animals". PLoS ONE. 3 (5): e2098. Bibcode:2008PLoSO...3.2098S. doi:10.1371/journal.pone.0002098. PMC 2346548Freely accessible. PMID 18461162. 
  6. ^ a b c Steenkamp ET, Wright J, Baldauf SL (January 2006). "The protistan origins of animals and fungi". Mol. Biol. Evol. 23 (1): 93–106. doi:10.1093/molbev/msj011. PMID 16151185. 
  7. ^ "Fungi/Metazoa group". Retrieved 2009-03-08. 
  8. ^ Huang, Jinling; Xu, Ying; Gogarten, Johann Peter (November 2005). "The presence of a haloarchaeal type tyrosyl-tRNA synthetase marks the opisthokonts as monophyletic". Molecular Biology and Evolution. 22 (11): 2142–2146. doi:10.1093/molbev/msi221. PMID 16049196. 
  9. ^ Parfrey, Laura Wegener; et al. (December 2006). "Evaluating support for the current classification of eukaryotic diversity". PLOS Genetics. 2 (12): e220. doi:10.1371/journal.pgen.0020220. PMC 1713255Freely accessible. PMID 17194223. 
  10. ^ Torruella, Guifré; et al. (February 2012). "Phylogenetic relationships within the Opisthokonta based on phylogenomic analyses of conserved single-copy protein domains". Molecular Biology and Evolution. 29 (2): 531–544. doi:10.1093/molbev/msr185. PMC 3350318Freely accessible. PMID 21771718. 
  11. ^ Eme, Laura; Sharpe, Susan C.; Brown, Matthew W.; Roger, Andrew J. (2014-08-01). "On the Age of Eukaryotes: Evaluating Evidence from Fossils and Molecular Clocks". Cold Spring Harbor Perspectives in Biology. 6 (8): a016139. doi:10.1101/cshperspect.a016139. ISSN 1943-0264. PMC 4107988Freely accessible. PMID 25085908. 
  12. ^ Wainright PO, Hinkle G, Sogin ML, Stickel SK (April 1993). "Monophyletic origins of the metazoa: an evolutionary link with fungi". Science. 260 (5106): 340–2. Bibcode:1993Sci...260..340W. doi:10.1126/science.8469985. PMID 8469985. 
  13. ^ Stechmann, A.; Cavalier-Smith, T. (5 July 2002). "Rooting the eukaryote tree by using a derived gene fusion". Science. 297 (5578): 89–91. Bibcode:2002Sci...297...89S. doi:10.1126/science.1071196. PMID 12098695. 
  14. ^ Torruella, Guifré; Mendoza, Alex de; Grau-Bové, Xavier; Antó, Meritxell; Chaplin, Mark A.; Campo, Javier del; Eme, Laura; Pérez-Cordón, Gregorio; Whipps, Christopher M. (2015). "Phylogenomics Reveals Convergent Evolution of Lifestyles in Close Relatives of Animals and Fungi". Current Biology. 25 (18): 2404–2410. doi:10.1016/j.cub.2015.07.053. 
  15. ^ Matthew W. Brown, Frederick W. Spiegel and Jeffrey D. Silberman (2009), "Phylogeny of the "Forgotten" Cellular Slime Mold, Fonticula alba, Reveals a Key Evolutionary Branch within Opisthokonta", Molecular Biology and Evolution, 26 (12): 2699–2709, doi:10.1093/molbev/msp185, PMID 19692665 
  16. ^ Phylogeny based on:

External links