Unveiling the Role of β-Glucosidase Genes in Bletilla striata's Secondary Metabolism: A Genome-Wide Analysis.

Abstract

β-glucosidases (BGLUs) are abundant enzymes in plants that play pivotal roles in cell wall modification, hormone signal transduction, secondary metabolism, defense against herbivores, and volatile compound release. Bletilla striata, a perennial herb revered for its therapeutic properties, lacks a comprehensive analysis of its BGLU gene family despite the critical role these genes play in plant secondary metabolism. This study aims to perform a genome-wide analysis of the BGLU gene family in B. striata (BsBGLU) to elucidate their functions and regulatory mechanisms in secondary metabolite biosynthesis. We conducted a genome-wide screening to identify BsBGLU, followed by phylogenetic analysis to classify these genes into groups. Sequence characteristics were analyzed to predict functional roles. Simple sequence repeat (SSR) markers were examined to assess conservation and polymorphism among different landraces. Expression profiles of BsBGLUs were evaluated under sodium acetate and salicylic acid elicitor treatments and across different tissues. The accumulation of phylogenetic metabolites in different treatments and tissues was also analyzed by HPLC and LCMS detection to explore the correlation between gene expression and metabolite accumulation. A total of 23 BsBGLU genes were identified and classified into eight distinct groups. Sequence analysis suggested diverse functions related to hormone responses, secondary metabolism, and stress resistance. BsBGLUs with SSR sequences were conserved yet showed polymorphism among different B. striata landraces. Under elicitor treatments, expression profiling revealed that BsBGLUs significantly modulate the synthesis of secondary metabolites such as dactylorhin A and militarine. Tissue-specific expression analysis indicated that BsBGLU15 and BsBGLU28 were highly expressed in tubers compared to other tissues, suggesting their central role and a potential negative regulatory effect in metabolite accumulation. The elicitor NaAc can regulate metabolite synthesis by modulating the expression of BsBGLUs. The BsBGLU gene family in B. striata is integral to the modulation of secondary metabolite biosynthesis and accumulation and can respond to elicitors to promote the synthesis of militarine. These findings provide a theoretical foundation for the further exploration of BsBGLU gene functions and their regulatory mechanisms, advancing the production of medicinally active compounds in B. striata.