SmGRAS3 negatively responds to GA signaling while promotes tanshinones biosynthesis in Salvia miltiorrhiza

Abstract

Salvia miltiorrhiza Bunge is the origin plant of traditional Chinese medicine, Danshen. Demand of high-quality S. miltiorrhiza is increasing because of its excellent pharmaceutical value. Tanshinones and salvianolic acids (SAs) are the main active ingredients of S. miltiorrhiza. GA was reported to induce tanshinones and SAs accumulation, however, its mechanism was unclear. Here, we got a GA responsive protein, SmGRAS3. SmGRAS3 expressed highest in the periderm where tanshinones produced and accumulated. Results of SmGRAS3 over and antisense expression indicated that SmGRAS3 is a positive regulator of tanshinones biosynthesis in S. miltiorrhiza hairy roots. But overexpression of SmGRAS3 depressed SAs and GA biosynthesis as well as hairy roots growth, and application of GA could partially recover these depressions. Pathway enzyme genes expressions of tanshinones, SAs and GA biosynthesis were comprehensively changed in SmGRAS3 transgenic hairy roots. SmGRAS3 acted as a transcription factor that located in nucleus and has the transcription activation activity. Yeast one-hybrid (Y1H) and electrophoretic mobility shift assay (EMSA) showed that SmGRAS3 directly bound to GARE-motif in promoter of KSL1 and activated KSL1 transcription. Our study suggested that the SmGRAS3 may be a good potential target for further metabolic engineering of bioactive components biosynthesis in S. miltiorrhiza.