Methyl jasmonate activates an OPR gene that regulates the β-citronellol synthesis in herbaceous peony

Floral scent is a key ornamental trait in plants, and exogenous hormonal treatments can enhance its intensity. In this study, we demonstrated that exogenous methyl jasmonate (MeJA) enhanced floral fragrance intensity in herbaceous peony ( Paeonia lactiflora ), mainly by elevating β-citronellol content. Application of MeJA at the S2 (half-opened) stage resulted in the highest fragrance intensity during the full-blooming phase. The 12-oxophytodienoate reductase (OPR) genes are involved in β-citronellol synthesis. We identified the OPR family in herbaceous peony and found five OPR genes, all of which were induced by MeJA. Functional analysis revealed that PlOPR2, PlOPR3, and PlOPR5 promote β-citronellol synthesis, among which PlOPR2 is the most potent, while PlOPR1 drives endogenous jasmonic acid biosynthesis. MeJA promoted β-citronellol synthesis via the CGTCA motif within the PlOPR2 promoter. This study provides novel insights into the regulation of β-citronellol in herbaceous peony.