Transcriptome and metabolite profiles reveal the role of benzothiadiazole in controlling isoprenoid synthesis and berry ripening in chardonnay grapes

Benzothiadiazole (BTH) regulates grape development, ripening, volatiles, and phenolics. This study used metabolomics and transcriptomics to understand how exogenous BTH affects Chardonnay grapes' maturation and synthesis of isoprenoids. A 0.37 mM BTH solution was sprayed during the swelling and veraison stages, and then the ripe grapes were analyzed. Our results show that BTH application significantly increased levels of important isoprenoids such as free terpinen-4-ol, bound linalool, and 8'-apo-β-carotenal. Additionally, BTH was found to modulate several signaling pathways, including those involved in ethylene biosynthesis, salicylic acid synthesis, the abscisic acid pathway, and sugar metabolism, by regulating the expression of genes like VvACO4, VvTAR, VvPLD, VvTIP1-1, VvSTKs, VvPK, VvSUC2, VvGST4, and VvSTS. BTH also promoted grapevine resistance by up-regulating the expression of VvHSP20, VvGOLS4, VvOLP, and VvPR-10. Furthermore, BTH affected isoprenoids biosynthesis by regulating the expression of VvTPS35 and VvMYB24. Moreover, 13 hub genes in the MEgreen module were identified as crucial for the biosynthesis of isoprenoids. BTH application during the swelling stage remarkably promoted isoprenoid biosynthesis more effectively than veraison. Our study provides insights into the molecular mechanisms underlying BTH-induced regulation of grape development and offers a promising approach for enhancing the quality and resistance of grapes.