Poster: Regulation of gene expression

Abs # 775: Characterization of Chlamydomonas reinhardtii nuclear mutants affected in the translation of chloroplast mRNA

Presenter:	Fortson, Derek , fortsde@auburn.edu
Authors	Fortson, Derek  (A)   Liu, Bin  (A)   Somanchi, Aravind  (A)
Affiliations:	(A): Auburn University

It is widely known and accepted that the chloroplast, a prokaryotic-like organelle, is highly regulated by signals from the nucleus. Yet, the vital constituents that make up this regulatory mechanism remain an enigma. Nuclear-encoded proteins have been shown to be essential for the translation of several chloroplast mRNAs. One method, insertional mutagenesis, has become an invaluable approach in the identification and characterization of Chlamydomonas reinhardtii nuclear-encoded genes that affect a variety of physiological processes. An insertional mutant library has been generated in order to identify nuclear genes that affect translation of chloroplast mRNAs. Screening of this library has identified several mutants that show deficiencies in the accumulation of specific photosynthetic proteins, despite accumulating wt levels of corresponding mRNAs. Here we present the characterization of four such mutants that show high chlorophyll fluorescence, inability to photosynthesize and lack specific photosynthetic proteins. We are in the process of identifying the site of integration of the marker and the sequences flanking the insertion by using a combination of molecular approaches (marker mapping, genome walking and vectorette PCR). Screening of an indexed WT cosmid library will facilitate the identification of the disrupted genes in the mutants. We also present our efforts at biochemical characterization and analysis of the role of these genes in the translation of specific chloroplast mRNAs.