OsPPR8-1 is essential for early chloroplast development at 30 ℃

Abstract Pentatricopeptide repeat (PPR) proteins regulate the expression of organelle genes in plants by participating in RNA metabolism. In this study, we identified a PPR gene OsPPR8-1 which encodes a typical P subfamily PPR protein with 9 PPR motifs. Compared to dicots, the OsPPR8-1 has a more closer relationship with monocots, such as brachypodium, sorghum, maize, and so on. Expression specificity analysis shows that OsPPR8-1 is highly expressed in green tissues and OsPPR8-1 was localized in chloroplasts. Phenotypic observation revealed that when the OsPPR8-1 gene undergone heterozygous mutations or lacking the one hundred and third (103rd) and one hundred and fourth (104th) amino acids, no significant phenotypic changes were observed. However, when the homozygous deletion of 1 bp, 2 bps or 38 bps in the CDS region of OsPPR8-1 which caused frameshift mutations, the rice seedlings show an albino phenotype from germination to the third-leaf stage, and then gradually died at 30 ℃. All chlorophyll a (Chla), chlorophyll b (Chlb), carotenoid (Car) and total chlorophyll (Chl) significantly decreased in osppr8-1 homozygous mutants, and ultrathin section shows that OsPPR8-1 participates in regulating the generation of chloroplasts. Loss-of-function of OsPPR8-1 resulted in severe defects in the intron splicing of PetB, atpF, trnG and rps12. These results indicate that OsPPR8-1 is indispensable for early chloroplast development and seedling growth in rice by influencing the intron splicing of multiple chloroplast group II introns at 30 ℃.