Bikont
| Bikonts Temporal range:
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| Aradiolarian | |
Scientific classification
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| Domain: | Eukaryota |
| (unranked): | Bikonta Cavalier-Smith,1993 |
| Subgroups | |
| Synonyms | |
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Abikont( "two flagella" ) is any of theeukaryoticorganisms classified in the groupBikonta.Many single-celled and multi-celled organisms are members of the group, and these, as well as the presumed ancestor, have twoflagella.[1]
Enzymes
[edit]Another shared trait of bikonts is the fusion of twogenesinto a single unit: the genes forthymidylate synthase(TS) anddihydrofolate reductase(DHFR) encode a single proteinwith two functions.[2]
The genes are separately translated inunikonts.
Relationships
[edit]Some research suggests that a unikont (a eukaryotic cell with a single flagellum) was the ancestor ofopisthokonts(Animals, Fungi, and related forms) andAmoebozoa,and a bikont was the ancestor ofArchaeplastida(Plants and relatives),Excavata,Rhizaria,andChromalveolata.Cavalier-Smithhas suggested thatApusozoa,which are typically consideredincertae sedis,are in fact bikonts.
Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into theCabozoaand theArchaeplastidaandChromalveolatainto theCorticata,but at least one other study has suggested that theRhizariaandChromalveolataform aclade.[3]
An alternative to the Unikont–Bikont division was suggested by Derelleet al.in 2015,[4]where they proposed theacronymsOpimoda–Diphodarespectively, as substitutes to the older terms. The name Diphoda is formed from the letters ofDIscobaanddiaPHOretickes(shown in capitals). [suggested singular forms are Opneme-Dipheme respectively]
Cladogram
[edit]A "classical" cladogram (data from 2012, 2015) is:[5][6]
| Eukaryotes |
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However, a cladogram (data from 2015, 2016) with the root in Excavata is[4][7][8]
| Eukaryotes |
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Thecorticatescorrespond roughly to the bikonts. WhileHaptophyta,Cryptophyta,Glaucophyta,Rhodophyta,theSAR supergroupandviridiplantaeare usually consideredmonophyletic,Archaeplastidamay 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 theSAR/HA supergroup.However, this seems to have fallen out of favor as the monophyly of hacrobia has come under dispute.
See also
[edit]References
[edit]- ^Burki F, Pawlowski J (October 2006)."Monophyly of Rhizaria and multigene phylogeny of unicellular bikonts".Mol. Biol. Evol.23(10): 1922–30.doi:10.1093/molbev/msl055.PMID16829542.
- ^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.
- ^Burki F, Shalchian-Tabrizi K, Minge M, Skjæveland Å, Nikolaev SI, et al. (2007). Butler G (ed.)."Phylogenomics Reshuffles the Eukaryotic Supergroups".PLOS ONE.2(8: e790): e790.Bibcode:2007PLoSO...2..790B.doi:10.1371/journal.pone.0000790.PMC1949142.PMID17726520.
- ^abDerelle, 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".Proceedings of the National Academy of Sciences.112(7): E693–E699.Bibcode:2015PNAS..112E.693D.doi:10.1073/pnas.1420657112.PMC4343179.PMID25646484.
- ^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.
- ^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.PMC3321700.PMID22298847.
- ^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.PMID26234272.
- ^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.PMC4736243.PMID26832778.
Further reading
[edit]
Data related toBikontaat Wikispecies
Media related toBikontaat Wikimedia Commons- Stechmann A, Cavalier-Smith T (September 2003)."The root of the eukaryote tree pinpointed".Curr. Biol.13(17): R665–6.doi:10.1016/S0960-9822(03)00602-X.PMID12956967.
- Tree of Life Eukaryotes
