The SmNPR4-SmTGA5 module regulates SA-mediated phenolic acid biosynthesis in Salvia miltiorrhiza hairy roots

Abstract

Phenolic acids are the main bioactive compounds in Salvia miltiorrhiza, which can be increased by salicylic acid (SA) elicitation. However, the specific molecular mechanism remains unclear. The nonexpresser of PR genes 1 (NPR1) and its family members are essential components of the SA signaling pathway. Here, we report an NPR protein, SmNPR4, that showed strong expression in hairy root after SA treatment, acting as a negative moderator of SA-induced phenolic acid biosynthesis in S. miltiorrhiza (S. miltiorrhiza). Moreover, a basic leucine zipper family transcription factor SmTGA5 was identified and was found to interact with SmNPR4. SmTGA5 activates the expression of phenolic acid biosynthesis gene SmTAT1 through binding to the as-1 element. Finally, a series of biochemical assays and dual gene overexpression analysis demonstrated that the SmNPR4 significantly inhibited the function of SmTGA5, and SA can alleviate the inhibitory effect of SmNPR4 on SmTGA5. Overall, our results reveal the molecular mechanism of salicylic acid regulating phenolic acid biosynthesis in S. miltiorrhiza and provide new insights for SA signaling to regulate secondary metabolic biosynthesis.

Acknowledgements

We are grateful to the Molecular Platform at Northwest A&F University’s College of Life Sciences. Thanks to YongFeng Xie from Weinan Normal University (Shaanxi, China) for her help with the instruction of experiment. The research was financially supported by the National Natural Science Foundation of China (31670301, 32270278), the Natural Science Foundation of Shaanxi Province (2022JM-099), and the Innovation Training Program for College Students (202210712222).

Author contributions

J.D. and P.M. designed the research. M.D., S.Z., R.H., and Y.X. performed the experiments. M.D. analysed the data and wrote the manuscript. B.Z. revised the paper.

Data availability

The data that support the results of this paper are available in this paper and its supplementary materials.

Conflict of interest

The authors declare that they have no conflict of interests.

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