Biology:Bikont
A bikont ("two flagella") is any of the eukaryotic organisms classified in the group Bikonta. Many single-celled and multi-celled organisms are members of the group, and these, as well as the presumed ancestor, have two flagella.[1]
Enzymes
Another shared trait of bikonts is the fusion of two genes into a single unit: the genes for thymidylate synthase (TS) and dihydrofolate reductase (DHFR) encode a single protein with two functions.[2]
The genes are separately translated in unikonts.
Relationships
Some research suggests that a unikont (a eukaryotic cell with a single flagellum) was the ancestor of opisthokonts (Animals, Fungi, and related forms) and Amoebozoa, and a bikont was the ancestor of Archaeplastida (Plants and relatives), Excavata, Rhizaria, and Chromalveolata. Cavalier-Smith has suggested that Apusozoa, which are typically considered incertae sedis, are in fact bikonts.[3]
Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into the Cabozoa and the Archaeplastida and Chromalveolata into the Corticata, but at least one other study has suggested that the Rhizaria and Chromalveolata form a clade.[4]
An alternative to the Unikont–Bikont division was suggested by Derelle et al. in 2015,[5] where they proposed the acronyms Opimoda–Diphoda respectively, as substitutes to the older terms. The name Diphoda is formed from the letters of DIscoba and diaPHOretickes (shown in capitals). [suggested singular forms are Opneme-Dipheme respectively][citation needed]
Cladogram
A "classical" cladogram (data from 2012, 2015) is:[6][7]
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However, a cladogram (data from 2015, 2016) with the root in Excavata is[5][8][9]
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The corticates correspond roughly to the bikonts. While Haptophyta, Cryptophyta, Glaucophyta, Rhodophyta, the SAR supergroup and Viridiplantae are usually considered monophyletic, Archaeplastida may be paraphyletic, and the mutual relationships between these phyla are still to be fully resolved.
Recent reconstructions placed Archaeplastida and Hacrobia together in an "HA supergroup" or "AH supergroup", which was a sister clade to the SAR supergroup within the SAR/HA supergroup. However, this seems to have fallen out of favor as the monophyly of hacrobia has come under dispute.
See also
References
- ↑ "Monophyly of Rhizaria and multigene phylogeny of unicellular bikonts". Mol. Biol. Evol. 23 (10): 1922–30. October 2006. doi:10.1093/molbev/msl055. PMID 16829542.
- ↑ Thomas Cavalier-Smith (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348. doi:10.1078/0932-4739-00002.
- ↑ Cavalier-Smith, Thomas (1 January 2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348. doi:10.1078/0932-4739-00002.
- ↑ Butler, Geraldine, ed (2007). "Phylogenomics Reshuffles the Eukaryotic Supergroups". PLOS ONE 2 (8: e790): e790. doi:10.1371/journal.pone.0000790. PMID 17726520. Bibcode: 2007PLoSO...2..790B.
- ↑ 5.0 5.1 Derelle, Romain; Torruella, Guifré; Klimeš, Vladimír; Brinkmann, Henner; Kim, Eunsoo; Vlček, Čestmír; Lang, B. Franz; Eliáš, Marek (17 February 2015). "Bacterial proteins pinpoint a single eukaryotic root" (in en). Proceedings of the National Academy of Sciences 112 (7): E693–E699. doi:10.1073/pnas.1420657112. PMID 25646484. Bibcode: 2015PNAS..112E.693D.
- ↑ Jackson, Christopher; Clayden, Susan; Reyes-Prieto, Adrian (2015). "The Glaucophyta: the blue-green plants in a nutshell". Acta Societatis Botanicorum Poloniae 84 (2): 149–165. doi:10.5586/asbp.2015.020. Bibcode: 2015AcSBP..84..149J.
- ↑ Burki, Fabien; Okamoto, Noriko; Pombert, Jean-François; Keeling, Patrick J. (7 June 2012). "The evolutionary history of haptophytes and cryptophytes: phylogenomic evidence for separate origins". Proceedings of the Royal Society of London B: Biological Sciences 279 (1736): 2246–2254. doi:10.1098/rspb.2011.2301. PMID 22298847.
- ↑ Cavalier-Smith, Thomas; Chao, Ema E.; Lewis, Rhodri (December 2015). "Multiple origins of Heliozoa from flagellate ancestors: New cryptist subphylum Corbihelia, superclass Corbistoma, and monophyly of Haptista, Cryptista, Hacrobia and Chromista". Molecular Phylogenetics and Evolution 93: 331–362. doi:10.1016/j.ympev.2015.07.004. PMID 26234272. Bibcode: 2015MolPE..93..331C.
- ↑ Eliáš, Marek; Klimeš, Vladimír; Derelle, Romain; Petrželková, Romana; Tachezy, Jan (2016). "A paneukaryotic genomic analysis of the small GTPase RABL2 underscores the significance of recurrent gene loss in eukaryote evolution". Biology Direct 11 (1): 5. doi:10.1186/s13062-016-0107-8. PMID 26832778.
Further reading
Data related to Bikonta at Wikispecies- "The root of the eukaryote tree pinpointed". Curr. Biol. 13 (17): R665–6. September 2003. doi:10.1016/S0960-9822(03)00602-X. PMID 12956967. Bibcode: 2003CBio...13.R665S.
- Tree of Life Eukaryotes
Wikidata ☰ Q860203 entry
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