Abstract

Floral fragrance is a crucial biological and ornamental trait in plants. Flare tree peony (FTP), originating from Paeonia rockii ( S.G.Haw & Lauener) T.Hong & J.J.Li ex D.Y.Hong, exhibits diverse flower scents, which enhance its ornamental and ecological value. However, the regulatory mechanisms governing floral volatile compounds biosynthesis in FTP remain elusive. In this study, we identified geraniol as the most abundant volatile compound and found its accumulation to be strongly correlated with the expression of an R2R3-MYB transcription factor, PrMYB5b. Transient silencing of PrMYB5b in FTP petals resulted in a significant reduction in geraniol accumulation and downregulated the expression of PrDXS and PrGES genes. In contrast, stable overexpression of PrMYB5b in tobacco ( Nicotiana tabacum L.) remarkably upregulated the transcript levels of endogenous NtDXS and heterologous PrGES genes, thereby leading to a substantial increase in geraniol production. Electrophoretic mobility shift assay (EMSA), yeast one-hybrid (Y1H), and dual-luciferase (Dual-LUC) assays revealed that PrMYB5b directly binds to and activates the promoters of PrDXS and PrGES . These findings confirm PrMYB5b as a core regulator of geraniol biosynthesis in FTP, providing both mechanistic insights and direct genetic targets for breeding fragrant varieties and engineering geraniol production.