Sequence Diversity of the Gene tufA in Coleochaete: An Algal Model for Horizontal Gene Transfer

Abstract

AbstractStudying 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.