Posttranscriptional Regulation of Chloroplast Gene Expression

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This research is analyzing the light-mediated control of expression of the RuBPCase large subunit (LSU) gene at the post-transcriptional level. The primary emphasis involves molecular and biochemical analyses of chlorplast protein synthesis in cell-free extracts. The chloroplast transcriptioanl repressionof elongation which occurs in plants shifted into darkness is being studied both in vivo, to determine how ribosomal transit times vary, and in vitro, to characterize factor(s) responsible for the altered elongation rates in dark-shifted versus light-grown plants. Initial efforts involve the continued development of a chloroplast-derived, protein synthesizing extract that is programable with exogenously added mRNA. The chimeric LSU- CAT reporter gene will be employed in developing this assay. TAhe regulation of expression of genes coded by chloroplast DNA is a fundamental problem associated with understanding growth and development in higher plants. The research in this proposal is looking at the mechanisms of regulation of chloroplast gene expression through the development of a cell-free system that responds to the same factors found in the intact chloroplast. The development of such an assay will markedly enhance the ability of workers in this field to address issues related to the control of chloroplast protein synthesis.***//