Fig. 5

ZmGLK44 regulates Trp biosynthesis via activating the genes encoding enzymes involved in Trp biosynthetic pathway. a Metabolites correlated/associated with ZmGLK44. The size of circles represents fold changes of metabolite levels in drought response. Metabolites annotated as amino acid derivatives were indicated as purple circles. 1a: 1-Acetyl-3-carboxy-3,4-dihydro-β-carboline; 1b: ethyl 6-acetamido-4-hydroxyquionline-3-carboxylate; 34 N: N-Acetyl-beta-oxotryptamine. b Accumulation of ZmGLK44 correlated/associated metabolites in ZmGLK44 transgenic plants and their negative siblings grown under WW and DS conditions. c Pathways with enriched DE genes. L-tryptophan (Trp) biosynthesis pathway is highlighted. d Main enzymes (ASA2-GRMZM2G161337, PAT1-GRMZM2G051219, and TSB2-GRMZM2G005024) and metabolites involved in Trp biosynthesis process. e Expression of ASA2, PAT1, and TSB2 in ZmGLK44 transgenic plants and their negative siblings grown under DS conditions. f After DS, Indole, and Trp were enhanced in production in positive transgenic plants as compared to the negative siblings. g Diagram showing the effector (35S::ZmGLK44) and reporters (Asa2p::LUC, PAT1p::LUC and PAT1p::LUC) used in protoplast assays. The short-red lines indicate the putative GLK TF binding sites and their location in the promoters of each gene. The numbers indicate the positions relative to the translation starting site ATG (+ 1) of each gene. h Activation of TSB2p2::LUC, but not the other promoter fragments, by ZmGLK44 in maize protoplasts. Error bars: s.d, based on three biological repeats; statistical significance was determined by Student’s t test; n.s., not significant