Identification of the 12-oxophytoeienoic acid reductase (OPR) gene family in pepper (Capsicum annuum L.) and functional characterization of CaOPR6 in pepper fruit development and stress response

The 12-oxophytoeienoic acid reductase (OPR) is a kind of enzyme in the octadecanoid biosynthesis pathway that determines the biosynthesis of jasmonic acid. Although the roles of OPRs have been extensively studied in several crop plants, little is known about the biological functions of OPR-encoding genes in Capsicum annuum plants. In this study, seven OPR family genes (CaOPR1-7) were identified from the C. annuum genome. The physical and chemical properties of CaOPR1-7 were further analyzed, including gene expression patterns, promoter elements, and chromosomal locations. The results showed that the seven CaOPR homologues could be divided into two subgroups, and CaOPR6 was highly similar to AtOPR3 in Arabidopsis. The expression of CaOPR6 was significantly induced by various stresses such as cold, salt, and pathogen infection, indicating that CaOPR6 plays important roles in response to abiotic and biotic stresses. Overall, these findings improve the understanding of the biological functions of CaOPR6 in the development of pepper fruit and stress response of pepper plants, and facilitate further studies on the molecular biology of OPR proteins in Solanaceae vegetables.