Genome-wide identification and expression analysis of wall-associated kinases (WAK/WAKLs) in Salvia miltiorrhiza with novel insights into tanshinone regulation in response to fungal elicitors

Wall-associated kinases (WAKs) are transmembrane proteins involved in growth, cell wall expansion, and defence responses, particularly through antimicrobial metabolite accumulation. Salvia militorrhiza Bunge, a deciduous perennial, is used as a traditional Chinese medicine and is known for its antimicrobial tanshinones. Tanshinone accumulation in S. miltiorrhiza is induced in response to fungal elicitors, but the role of WAKs in this process has not been explored. In this study, 22 WAKs and 18 wall-associated kinase-like (WAKLs) genes were identified from the genome of S. miltiorrhiza, which are distributed across nine chromosomes. Phylogenetic analysis classified SmWAKs/WAKLs into three clades. Cis-regulatory element analysis showed a considerable number of growth, phytohormones, and defence-responsive elements. The differential expression analysis showed that 23 SmWAKs/WAKLs were up-regulated in response to fungal elicitors, whereas 17 SmWAKs/WAKLs were down-regulated. Notably, the expression levels of SmWAK5, SmWAK16, SmWAKL6, SmWAKL13, and SmWAKL18 showed a significant increase. Moreover, Pearson correlation analysis showed a very high positive correlation between the expression level of these genes and tanshinones content, suggesting their role in regulating tanshinone accumulation. This work reveals insights into the regulatory roles of SmWAKs/WAKLs in tanshinone accumulation and offers a foundation for biological function studies of WAKs/WAKLs and enhancing tanshinones production.