GmPHD6 regulates gene expression and binds to the promoter regions of target genes. A, Expression of downstream genes in G6-OE, G6-RNAi, LHP1-RNAi, and G6M (V34M, E35V)-OE transgenic hairy roots. B, Expression of ASR, CYP75B1, and CYP82C4 genes in their transgenic hairy roots. C, Performance of soybean plants with ASR-OE, CYP75B1-OE, or CYP82C4-OE transgenic roots after salt stress. Plants in water were used as control. Enlargement of the parts is given in the middle photo to show the performance of soybean leaves and roots after salt stress. D, Relative growth rate of transgenic hairy roots after salt stress. Bars indicate se (n = 30). Asterisks indicate significant difference (**P < 0.01) compared to control hairy roots (K599). E, Relative electrolyte leakage in leaves of soybean with transgenic hairy roots. Bars indicate sd (n = 10). Asterisks indicate significant difference (*P < 0.05 and **P < 0.01) compared to leaves of control plants (K599). F, Promoter-LUC activity mediated by GmPHD6 binding. The ability with which GmPHD6 bound to the promoter regions of downstream genes was determined by the DLR assay. Bars indicate sd (n = 3). In the left panel, asterisks indicate significant difference (*P < 0.05 and **P < 0.01) compared to control samples (LUC). In the right panel, asterisks indicate significant difference (*P < 0.05) compared to control samples (LUC plus G6-VP16 or P_CYP82C4-LUC plus BD-VP16 or P_CYP82C4-LUC plus Actin-VP16) and mutated protein (P_CYP82C4-LUC plus G6M-VP16).