Abstract
PGR3 is a pentatrico-peptide repeat (PPR) protein containing 27 PPR motifs and belongs to the P-subfamily. Previous studies have suggested that PGR3 functions in stabilization and translation of petL operon RNA in chloroplasts, and is also required for the accumulation of chloroplast NAD(P)H dehydrogenase (NDH). To gain new insights of multiple functions of PGR3, polysome assembly of 11 ndh transcripts was compared between the wild type and pgr3-3 that was suggested to be specifically defective in translation. The majority of ndhA and petL transcripts were detected in the non-polysomal fractions in pgr3-3, suggesting the translational defects in both genes. Comparison of the 5 UTR sequences of two genes identified two conserved sequences as candidates for target sites of PGR3. These results suggest that PGR3 is involved in the translation of ndhA and petL, as well as stabilizing petL operon RNA, by binding to these putative cis-elements.
