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.