The PPR protein PDM1 is involved in the processing of rpoA pre-mRNA in Arabidopsis thaliana

Pentatricopeptide repeat (PPR) proteins, containing tandem repeats of degenerate 35 amino acid motifs, are important for post-transcriptional chloroplast gene expression. In this study, we report the characterization of a pigment-deficient mutant 1 (pdm1) in Arabidopsis, which displays the albino phenotype. PDM1 contains 5 PPR motifs followed by a PLS domain. The levels of plastid-encoded polymerase-dependent chloroplast genes were reduced dramatically, whereas those of nucleus-encoded polymerase-dependent chloroplast genes increased in the mutant. In addition, the pattern of rpoA pre-mRNA was altered and the rpoA transcript was absent in pdm1. Thus, these results suggest that PDM1 is required for processing of rpoA pre-mRNA in Arabidopsis.