Paclobutrazol induces triterpenoid biosynthesis via downregulation of the negative transcriptional regulator SlMYB in Sanghuangporus lonicericola

Triterpenoids are well-known pharmacological components of Sanghuangporus fungi, such as Sanghuangporus lonicericola. This study investigates the inductive effects of paclobutrazol (PBZ) on triterpenoid biosynthesis in the submerged fermentation of S. lonicericola and explores the induction mechanisms via multi-omics and genetic methods. The addition of 100 mg/L PBZ significantly increases the triterpenoid yield by 151.39%. A total of 29 triterpenoids are tentatively identified, of which 18 are newly presented only under PBZ induction. Moreover, 30 genes involved in the MVA pathway and 31 genes encoding cytochrome P450 monooxygenases assumed to be responsible for decoration are identified. Finally, a MYB transcription factor (SlMYB) is identified and found to be downregulated under paclobutrazol induction. Genetic manipulation of SlMYB demonstrates its negative regulatory effect on four putative target genes, including ACAT, MVD, IDI, and FDPS. Electrophoretic mobility gel shift assays verify the direct interactions with the promoters of MVD, IDI, and FDPS. Taken together, PBZ acts as an effective inducer of triterpenoid biosynthesis in S. lonicericola, and the transcription factor SlMYB is negatively regulated.