PALE-GREEN LEAF12 Encodes a Novel Pentatricopeptide Repeat Protein Required for Chloroplast Development and 16S rRNA Processing in Rice. (3rd December 2018) - Chen, Long
Abstract: Pentatricopeptide repeat (PPR) proteins regulate organellar gene expression in plants, through their involvement in organellar RNA metabolism. In rice ( Oryza sativa ), 477 genes are predicted to encode PPR proteins; however, the majority of their functions remain unknown. In this study, we identified and characterized a rice mutant, pale-green leaf12 ( pgl12 ); at the seedling stage, pgl12 mutants had yellow-green leaves, which gradually turned pale green as the plants grew. The pgl12 mutant had significantly reduced Chl contents and increased sensitivity to changes in temperature. A genetic analysis revealed that the pgl12 mutation is recessive and located within a single nuclear gene. Map-based cloning of PGL12, including a transgenic complementation test, confirmed the presence of a base substitution (C to T), generating a stop codon, within LOC_Os12g10184 in the pgl12 mutant. LOC_Os12g10184 encodes a novel PLS-type PPR protein containing 17 PPR motifs and targeted to the chloroplasts. A quantitative real-time PCR analysis showed that PGL12 was expressed in various tissues, especially the leaves. We also showed that the transcript levels of several nuclear- and plastid-encoded genes associated with chloroplast development and photosynthesis were significantly altered in pgl12 mutants. The mutant exhibited defects in the 16S rRNA processing and splicing of the plastid transcript ndhA . Our results indicate that PGL12 is a new PLS-type PPR protein required for proper chloroplast development and 16S rRNA processing in rice.