A POSSIBLE MITOCHONDRIAL GENE IN THE EARLY-BRANCHING AMITOCHONDRIATE PROTIST TRICHOMONAS-VAGINALIS

Trichomonads are anaerobic flagellated protists that, based on analyse s of ribosomal. RNA sequences, represent one of the earliest branching lineages among the eukaryotes. The absence of mitochondria in these o rganisms coupled with their deep phylogenetic position has prompted se veral authors to suggest that trichomonads, along with other deeply-br anching amitochondriate protist groups, diverged from the main eukaryo tic lineage prior to the endosymbiotic origin of mitochondria. In this report we describe the presence of a gene in Trichomonas vaginalis sp ecifically related to mitochondrial chaperonin 60 (cpn60). A recent st udy indicates that a protein immunologically related to cpn60 is locat ed in trichomonad hydrogenosomes. Together, these data provide evidenc e that ancestors of trichomonads perhaps harbored the endosymbiotic pr ogenitors of mitochondria, but that these evolved into hydrogenosomes early in trichomonad evolution.