Phylogenetic Analysis of β-Tubulin Sequences from Amitochondrial Protozoa

摘要: It has been proposed that certain extant anaerobic protozoa are descended from organisms diverged early in eukaryotic evolution prior to the acquisition of mitochondria. Among these extracellular parasites Giardia lamblia, Trichomonas vaginalis, and Entamoeba histolytica, obligately intracellular microsporidia. Phylogenetic analysis rRNA sequences amitochondrial suggests G. T. microsporidia near base tree, while E. histolytica clusters with mitochondria-containing species. However, since eukaryotes likely evolved by symbiotic associations, it is important analyze other which may have independent origins. Unlike ribosomes, microtubules appear be unique eukaryotes. Complete gene for beta-tubulin subunit microsporidian Encephalitozoon hellem recently determined. relationships among these, 20 additional beta-tubulins were analyzed distance matrix parsimony methods, using alpha- gamma-tubulin outgroups. All analyses placed sequence at evolutionary tree. Similar results obtained alpha-tubulin a less representative set sequences. In contrast, branched considerably higher, within lineage containing animal fungal beta-tubulins. Possible explanations considered unexpected differences between trees.