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Unikont is a eukaryotic cell with a single flagellum, at least ancestrally. Current research suggests that a unikont was the ancestor of opisthokonts and Amoebozoa, and a bikont (a eukaryotic cell with two flagella) was the ancestor of Archaeplastida, Excavata, Rhizaria, and Chromalveolata. The unikonts also have a triple-gene fusion that is lacking in the bikonts, and a single centriole (Cavalier-Smith, 2002, 2006). (Some unikonts have two centrioles but their orgins are developmentally different than in the bikonts, indicating convergent evolution (Cavalier-Smith 2006). The three genes that are fused together in the unikonts but not bacteria or bikonts encode enzymes for synthesis of the pyramidine nucleotides: carbamoyl phosphate synthase, dihydroorotase, aspartate carbamoyltransferase (Cavalier-Smith 2006). This must have involved a double fusion, a rare pair of events that is unlikely to be reversed, further supporting the shared ancestry of Opisthokonta and Amoebozoa.
[edit] References
- Thomas Cavalier-Smith (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". Int. J. Syst. Evol. Microbiol. 52: 297–354.
- Thomas Cavalier-Smith (2006). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338-348.
- Alexandra Stechmann and Thomas Cavalier-Smith (2003). "The root of the eukaryote tree pinpointed". Current Biology 13 (17).
