PfbHLH131 Mediates the Biosynthesis of Fragrance Compounds in Primula forbesii Franch

Objectives: This study aims to provide a theoretical basis for a deeper understanding of the transcriptional regulatory network underlying the formation of Primula forbesii floral scent, and also offers important genetic resources for the molecular improvement of floral scent traits in Primula species. Methods: Using the P. forbesii cultivar 'Pink violet' as experimental material, we cloned PfbHLH131 and analyzed its expression pattern. We also validated its function via virus-induced gene silencing (VIGS) and used gas chromatography-mass spectrometry (GC-MS) to analyze changes in floral aroma components in silenced plants. Additionally, we detected the expression levels of key structural genes involved in floral aroma biosynthesis in silenced plants via qRT-PCR to elucidate the regulatory role of PfbHLH131 in the biosynthesis of P. forbesii floral aroma. Results: The cloned PfbHLH131 open reading frame is 922 bp in length, encoding a total of 307 amino acids, and contains a bHLH_AtBPE_like domain characteristic of the bHLH gene family. Quantitative real-time PCR (qRT-PCR) revealed that PfbHLH131 is highly expressed in floral organs, peaking during full bloom. Subcellular localization studies indicated that it is localized to the nucleus. VIGS-mediated transient silencing of PfbHLH131 significantly reduced the release of terpenoid and phenylpropanoid floral odor compounds and suppressed the expression of multiple key structural genes in both synthetic pathways. Conclusions: PfbHLH131 is a positive regulator of scent biosynthesis in P. forbesii.