RICKER, JILL M.*, JEFF D. LEWANDOWSKI, and CHARLES F. DELWICHE. Cell Biology and Molecular Genetics, University of Maryland - College Park, College Park MD 20742-5815. - Sequence diversity of the gene tufA in Coleochaete, an algal model for horizontal gene transfer.
Studying the organellar gene transfer of tufA in
Coleochaete serves as a model system for understanding the
effect of functional horizontal gene transfer on sequence conservation
and divergence. Previous work indicates that tufA, which codes
for protein synthesis elongation factor TU, is encoded only in the
chloroplast genome in most green algae, red algae, and
glaucocystophytes, but only in the nuclear genome of embryophytes. In
the charophytes, the lineage of green algae that gave rise to
embryophytes, tufA is present variously within the chloroplast
and/or nuclear genome. This implies that tufA was probably
transferred to the nucleus from the chloroplast after the charophytes
diverged from other green algae but before the diversification of the
group. The chloroplast copy has undergone three separate fates within
the charophytes: maintained in Charales, divergent in Coleochaetales,
and lost in Zygnematales. Previous research indicates the presence of
multiple nuclear copies and a highly divergent chloroplast encoded
tufA in Coleochaete orbicularis. This research aims to
isolate the chloroplast-encoded tufA from a representative
panel of Coleochaete in order to characterize patterns of
conservation in the divergent chloroplast tufA. Putative
chloroplast copies of tufA have been isolated through PCR and
subsequent molecular cloning. By comparing the DNA sequences from
copies of the chloroplast-encoded tufA from a representative
panel of Coleochaete, we hope to gain insight into patterns of
sequence conservation and from this infer the current function of the
divergent chloroplast tufA.
Key words: chloroplast, Coleochaete, EF-Tu, gene transfer, tufA