SmGRAS5 acts as a positive regulator in GA-induced biosynthesis of
tanshinones in Salvia miltiorrhiza hairy roots
Abstract
GA is an important phytohormone that regulates root growth and secondary
metabolism. GRAS family transcription factors (TFs) are the key
regulators of GA signaling. Here, we found that SmGRAS5 was co-expressed
in the root periderm with tanshinones in Salvia miltiorrhiza.
Overexpression (OE) of SmGRAS5 increased tanshinones accumulation and
upregulated the biosynthetic genes. Antisense expression (AE) of SmGRAS5
reduced tanshinones accumulation and downregulated the biosynthetic
genes. Yeast one-hybrid (Y1H), dual-luciferase (Dual-LUC) and
electrophoretic mobility shift assays (EMSA) showed that SmGRAS5
promoted tanshinones biosynthesis by directly binding to the GARE motif
in the promoter of SmKSL1 to induce its expression. However,
overexpressing SmGRAS5 reduced GA content through downregulating
biosynthetic genes. GA treatment further increased tanshinones
accumulation and restored the accumulation of GA inhibited by
overexpressing SmGRAS5. SmGRAS5 could not directly bind to the GA
biosynthetic genes. Transcriptome analysis revealed the potential
functions of SmGRAS5 in regulating secondary metabolism. Taken together,
SmGRAS5 regulated GA-promoted tanshinones biosynthesis by directly
activating the expression of SmKSL1, which suggested that SmGRAS5 may be
a potential target for further metabolic engineering of tanshinones
biosynthesis in S. miltiorrhiza.