The protein kinase SmSnRK2.7 mediates abscisic acid-regulated tanshinone biosynthesis under drought stress in Salvia miltiorrhiza

Abstract

Tanshinones, the main components of Salvia miltiorrhiza, contribute significantly to the treatment of cardiovascular and cerebrovascular diseases. In this work, one protein kinase, SmSnRK2.7, was characterized through RNA sequencing. Transiently overexpressing SmSnRK2.7 increased the concentration of tanshinones in the hairy roots of S. miltiorrhiza; in contrast, RNA interference of SmSnRK2.7 had the opposite effect. The phosphatase SmPP2C24 and the abscisic acid (ABA) receptor SmPYL8 were subsequently identified using RNA sequencing in SmSnRK2.7 transgenic lines. Through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC), SmPP2C24 was subsequently confirmed to interact with SmPYL8 and SmSnRK2.7. Further investigation demonstrated that overexpressing SmPP2C24 and SmPYL8 decreased the accumulation of tanshinones by downregulating SmCPS1, SmHMGR, and SmDXS, whereas RNA interference of SmPP2C24 and SmPYL8 promoted tanshinone production. Taken together, these results initially confirmed that SmSnRK2.7 positively regulates tanshinone biosynthesis and accumulation, whereas SmPP2C24 and SmPYL8 function as negative regulators. This study offers new perspectives for establishing the groundwork for a deeper exploration of diterpenoid metabolism in S. miltiorrhiza and for the selection and cultivation of improved varieties.