Genomic identification of organelle-localized PPR genes conferring resistance to Phytophthora capsici in Capsicum annuum L.

Background Pentatricopeptide repeat (PPR) gene family is one of the largest gene families in land plants. PPR genes play an important role in regulating chloroplast and mitochondrial gene expression, and participating in plant development, male sterility restoration, and biotic- and abiotic-stress responses. However, current knowledge about its exact role of Capsicum annuum in pathogens resistance remains uncharacterized. Results In this study, we identified and analyzed PPR genes in two varieties: the resistant of Zunla-1 and susceptible of Zhanshugang , with 497 and 199 PPR genes, respectively. Our finding suggested that there are distinct differences in gene abundance and duplication patterns between the two varieties. Additionally, Zunla-1 exhibited a greater number of differentially expressed PPR genes than Zhangshugang after P. capsici invasion. Generally, Zhanshugang exhibits limited adaptation to biotic stress compared to Zunla-1 . This discrepancy may attribute to the PPR genes in Zunla-1 have more complex duplication history and regulatory of stress-responsive gene expression. Conclusions These findings highlight that chloroplast- and mitochondrial-localized PPR proteins plays a critical role in resistance to biotic stresses in pepper. Thus, our study provided a novel insight into PPR-mediated biotic resistance mechanisms and identifies candidate genes for developing disease-resistant pepper varieties.