Unikont

Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith. The group includes eukaryotic cells with a single flagellum, at least ancestrally. Some 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 have a triple-gene fusion that is lacking in the bikonts. The three genes that are fused together in the unikonts but not bacteria or bikonts encode enzymes for synthesis of the pyrimidine nucleotides: carbamoyl phosphate synthase, dihydroorotase, aspartate carbamoyltransferase (Cavalier-Smith 2006). This must have involved a double fusion, a rare pair of events, supporting the shared ancestry of Opisthokonta and Amoebozoa.

The unikonts have 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).

References

• Cavalier-Smith, Thomas (2002). "The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa". International Journal of Systematic and Evolutionary Microbiology 52 (2): 297–354. Retrieved on 2007-06-08.
• Cavalier-Smith, Thomas (2003). "Protist phylogeny and the high-level classification of Protozoa". European Journal of Protistology 39 (4): 338–348.
• Stechmann, Alexandra; Cavalier-Smith, Thomas (2003). "The root of the eukaryote tree pinpointed". Current Biology 13 (17): R665–R666.