Integrative transcriptome network analysis identifies SsMYB1 as a dual R2R3-MYB candidate activator of sclareol and flavonoid biosynthesis in Salvia sclarea.

Sclareol is a diterpenoid derived from Salvia sclarea (Lamiaceae) with significant economic value in the fragrance and pharmaceutical industries. Although its biosynthetic pathway has been elucidated, the transcriptional regulatory mechanisms remain unclear. Here, for the first time, we constructed a potential transcriptional regulatory network for sclareol biosynthesis using multi-tissue transcriptome data and weighted gene co-expression network analysis (WGCNA). The blue module was enriched with biosynthetic enzyme genes (SsLPPS, SsSS, and SsHDS) and highly correlated with floral tissues, where sclareol predominantly accumulates. Within this module, 28 MYB transcription factors were co-expressed with biosynthetic genes. Through expression pattern and phylogenetic analysis, we identified four candidate MYB transcription factors potentially regulating sclareol biosynthesis. Yeast one-hybrid and dual-luciferase reporter assays demonstrated that the R2R3-MYB transcription factor SsMYB1 directly binds to the promoters of SsLPPS and SsSS and activates their transcription. Furthermore, SsMYB1 was also found to activate the promoters of two putative flavonoid biosynthetic genes, g13244 (CHI) and g15856 (FLS), suggesting its dual regulatory roles in both sclareol and flavonoid biosynthesis. Subcellular localization confirmed its nuclear localization. Collectively, this study provides an initial regulatory framework for sclareol biosynthesis, offering important targets and genetic resources for metabolic engineering and molecular breeding of S. sclarea.