The AtDREB1A transcription factor up-regulates expression of a vernalization pathway gene, Gm VRN1-like, delaying flowering in soybean

The dehydration-responsive element binding proteins/C-repeat binding factors (i.e., DREBs/CRT) are crucial transcription factors, they can bind the cis-elements containing the A/GCCGAC sequence in the promoter region. Overexpression of DREB genes enhances the resistance to multiple abiotic stresses, but also causes dwarfism and delayed flowering in many plant species. In this study, constitutive overexpression of AtDREB1A in soybean plants caused dwarfism and delayed-flowering phenotypes. The delayed-flowering phenotype was not affected by day length and could not be reversed by exogenous gibberellic acid. The expression levels of flowering-related genes were determined by quantitative real-time RCR. The Glyma11g13220 (designated as GmVRN1-like) expression was strongly induced in transgenic plants. GmVRN1-like was homologous to the Arabidopsis thaliana VRN1 gene (At3g18990). Electrophoretic mobility shift assay showed that AtDREB1A could bind the dehydration-responsive element motif, ACCGAC, in a region -157 to -186 bp upstream of GmVRN1-like. The motif shared 100 % identity with the DRE sequence present in RD29A. Our results imply that the delayed-flowering of AtDREB1A-overexpressing plants might be caused by up-regulating of GmVRN1-like gene.