UNIKONT

'Unikont' is a eukaryotic cell with a single flagellum, at least ancestrally. Current research suggests that a unikont was the ancestor of opisthokonts (animals, fungi and related forms) and amoebozoa, and a bikont (a eukaryotic cell with two flagella) was the ancestor of archaeplastida (plants and relatives), 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 origins 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, further supporting the shared ancestry of Opisthokonta and Amoebozoa.

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References

References

★ The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa, , Thomas, Cavalier-Smith, International Journal of Systematic and Evolutionary Microbiology, 2002

★ Protist phylogeny and the high-level classification of Protozoa, , Thomas, Cavalier-Smith, European Journal of Protistology, 2006

★ The root of the eukaryote tree pinpointed, , Alexandra, Stechmann, Current Biology, 2003