Characterization of wheat TaSnRK2.7 promoter in Arabidopsis

Abstract

Expression of TaSnRK2.7 promoter is strongly induced under abiotic stress and could be used as a valuable tool for improving plant stress resistance via transgenic techniques. The sucrose non-fermenting 1-related protein kinase 2 (SnRK2) gene family plays pivotal roles in response to abiotic stresses (drought, salinity and cold). Here, we studied the expression of five wheat TaSnRK2.7 promoter-5'-deletion constructs (-2547, -1621, -806, -599, and -254) fused to beta-glucuronidase (GUS) in Arabidopsis. Tissue-expression analysis revealed that the -254 to ATG fragment was sufficient for inducing GUS expression in hypocotyls. Additionally, the -806 to -599 and -2547 to -1621 fragments contained leaf- and root-specific elements, respectively. Deletion analysis showed that these fragments were unresponsive to ABA treatment, suggesting that TaSnRK2.7 participates in an ABA-independent signaling pathway. Assays examining stress responses of constructs demonstrated that the -599 to -254 and -806 to -599 fragments contained elements responsive to abiotic and osmotic stress, respectively. The TaSnRK2.7 promoter contained enhancers from -806 to -254 and -2547 to -1621, while the -1621 to -806 fragment contained negative regulatory elements that restrict root and leaf gene expression in response to abiotic stress. Furthermore, under drought and salt stress, the TaSnRK2.7 promoter conferred greater gene expression in leaves than the rd29A promoter, even though both were induced by abiotic stress. These findings enhance our understanding of the molecular mechanisms behind TaSnRK2.7 action, which should prove useful in transgenic studies investigating stress-induced gene expression.