A novel WRKY34-bZIP3 module regulates phenolic acid and tanshinone biosynthesis in Salvia miltiorrhiza

Phenolic acids and tanshinones are main bioactive compounds produced in Salvia miltiorrhiza widely used in treatment of cardiovascular diseases, which could be promoted by abscisic acid elicitation. However, the regulation mechanism remained to be elucidated. An ABA-inducible IIa WRKY transcription factor (TF) named SmWRKY34 exhibiting high homology with AtWRKY40 was isolated. SmWRKY34 exhibited a negative role on phenolic acids and tanshinones by directly regulating SmRAS and SmGGPPS. Moreover, ABA-responsive bZIP TF member named SmbZIP3 expressing significantly in SmWRKY34 transcriptome was screened. SmWRKY34 showed a negative regulatory role on SmbZIP3. SmbZIP3 acted as a positive regulator in the biosynthesis of phenolic acids and tanshinones by targeting SmTAT and two tanshinone-promoting TFs SmERF128 and SmMYB9b. Taken together, we identify a new module WRKY34-bZIP3 involved in ABA signaling that manipulates phenolic acid and tanshinone accumulation, shedding new insights in metabolic engineering application in S. miltiorrhiza.