Poster 17
The Vacuolar ATPase A subunit: Implications for Early Eukaryote Evolution
Olendzenski, Lorraine, and Gogarten, J. Peter (1)
University of Connecticut
Dept. of Molecular and Cellular Biology
Storrs, CT 06269-3044
gogarten@uconnvm.uconn.edu
(1) Presented by Peter J. Gogarten
Phylogenetic analyses based on small subunit (SSU) ribosomal RNA sequences
reveal that certain unicellular amitochondriate eukaryotes consistently
group at the base of the eukaryotic lineage. These include the diplomonads,
microsporidia and trichomonads and these organisms were believed to
represent extant relatives of the oldest eukaryotes. Recently, the
phylogenetic position of microsporidia has been called into question.
Reanalysis of their meiotic life cycle, phylogenetic analysis of tubulin and
RNA polymerase sequences, suggests that microsporidia may be most closely
related to fungi. To help resolve the phylogenetic position of the
microsporidia, and to discern to what extent their position at the base of
ribosomal RNA phylogenies may be due to long branch artifacts, we have
sequenced the catalytic subunit of the V-type ATPase from the
microsporidiain Nosema locustae. Preliminary analyses of available
eukaryotic A subunits show that the Nosema sequence consistently groups with
the fungi. Our lab has also sequenced this molecule from Giardia lamblia
and is in the process of sequencing the same gene from Trichomonas
vaginalis. To investigate whether these lineages still represent likely
early branching eukaryotes, we will present molecular phylogenetic analyses
based on the vacuolar ATPase A subunit. Additionally we will analyze the
maximum likelihood landscape that results when these deep branching lineages
are moved around in the eukaryotic domain. These analyses, performed with
both the ATPase and SSU ribosomal data sets, provide confidence measures for
different tree topologies, and information regarding possible tree building
artifacts.