Genome-wide identification of the calcium-dependent kinase CPK gene family in Salvia miltiorrhiza reveals that SmCPK24 promotes tanshinone biosynthesis

Calcium ions function as ubiquitous secondary messengers in plants, and calcium-dependent protein kinases (CPKs) are essential for decoding calcium signals into physiological responses. However, the involvement of CPKs in modulating secondary metabolic pathways, particularly in medicinal plants, remains largely unexplored. In Salvia miltiorrhiza Bunge, a renowned medicinal herb producing bioactive tanshinones, the functions of CPKs have yet to be characterized. Here, 25 CPK genes were identified in the S. miltiorrhiza genome, and SmCPK24 —a kinase exhibiting partially Ca 2+ -independent activity —was functionally characterized. In transgenic hairy roots, SmCPK24 overexpression significantly enhanced tanshinone accumulation, whereas its suppression reduced tanshinone biosynthesis. Further investigation revealed that SmCPK24 interacts with and phosphorylates SmWRKY1, resulting in enhanced transcriptional activation of SmDXS2 , a key downstream target of SmWRKY1. This study reveals a direct link between calcium signaling and terpenoid biosynthesis in a medicinal plant, uncovering a novel kinase–transcription factor module that regulates metabolic flux and enables the engineering of high-value natural products. • Twenty-five calcium-dependent kinases ( CPK s) were identified in Salvia miltiorrhiza . • SmCPK24 positively regulates tanshinone accumulation in S. miltiorrhiza . • SmCPK24 interacts with and phosphorylates SmWRKY1. • SmCPK24 promotes SmWRKY1-mediated activation of S mDXS2 .