Genome-wide analysis of the R2R3-MYB family identifies PfMYB31 and PfMYB88 as positive regulators of floral scent biosynthesis in Primula forbesii

Floral scent plays important roles in plant-environment interactions and contributes substantially to the ornamental value of flowering plants. Although R2R3-MYB transcription factors regulate floral volatile biosynthesis in diverse plant species, their functions in Primula remain largely unknown. This study combined genome-wide characterization, candidate-gene screening, and functional validation to identify R2R3-MYB regulators of floral scent biosynthesis in the fragrant species Primula forbesii . A total of 109 R2R3-MYB genes were identified in the P. forbesii genome and unevenly distributed across nine chromosomes. Two complementary phylogenetic analyses were used: a complete-family tree containing R2R3-MYB and R3-MYB proteins, and an R2R3-specific tree that classified the 109 PfR2R3-MYB proteins into 27 subgroups. Segmental duplication was the predominant duplication type, and all calculable Ka/Ks ratios were below 1. Promoter analysis revealed numerous cis-acting elements associated with hormone signaling, stress responses, and secondary metabolism. To identify R2R3-MYB members potentially involved in floral scent regulation, we integrated transcriptomic data, a gene co-expression network, and gene expression patterns. This analysis identified PfMYB31 and PfMYB88 as key candidate regulators. The encoded PfMYB31 and PfMYB88 proteins localized to the nucleus. Silencing PfMYB31 using VIGS decreased phenylpropanoid-derived floral volatiles and the transcript abundance of associated biosynthetic genes, whereas silencing PfMYB88 decreased terpene-derived volatiles and associated pathway transcripts. These results support distinct positive regulatory roles for PfMYB31 and PfMYB88 in floral scent metabolism and provide candidate loci for further mechanistic and germplasm-based studies in Primula .