Abstract
The molecular mechanism of RNA degradation in Escherichia coli includes a series of sequential steps. The degradation starts with the initial endonucleolytic cleavage carried out primarily by RNase E. The cleaved products are then polyadenylated at their 3' ends and degraded exonucleolytically by polynucleotide phosphorylase (PNPase) and RNase II. In chloroplast, many characteristics of the gene expression system resemble those of bacteria because chloroplast is believed to have an evolutionally prokaryotic origin. Here, we isolated Arabidopsis mutants with disrupted homologus genes of bacterial RNases by T-DNA insertion. Based on the analysis of leaf color, growth rate and chlorophyll fluorescence, we identified putative chloroplastic RNase mutants; RNase E, PNPase and RNase II/R. PNPase mutant have etiolated leaves in proximal regions. RNase E and RNase II/R mutants could not grow photoautotrophically, indicating their essential roles in chloroplast RNA metabolism. We are now characterizing these mutants in detail.
