Overexpression of W6 Gene Increases Salt Tolerance in Transgenic Tobacco Plants

An ethylene responsive factor (ERF) gene W6, which belongs to ERF IV subfamily, was isolated from the cDNA library of wheat (Triticum aestivum L.) landrace Xiaobaimai. The full-length cDNA of W6 encoded an ERF protein containing a conserved ERF DNA-binding motif, 2 putative nuclear localization sequences, and a C-terminal acidic transcription activation domain. The expression of W6 in wheat was induced by various treatments, such as cold, drought, salt, abscisic acid (ABA), and fungal pathogens. To identify the function of the W6 gene, a transgenic vector (35S::pBI121::W6) containing CaMV 35S promoter was constructed and the W6-overexpresed tobacco (Nicotiana tabacum) plants by Agrobacterium-mediated transformation was obtained. Under the treatment with 200 mmol L−1 NaCl for 50 d, the transgenic plants grew well but the control plants almost died. The root length of the transgenic tobacco plants ranged from 1.40 to 3.93 cm but that of control was only 0.20 cm. The root weight of the transgenic tobacco plants ranged from 2.41 to 7.79 g compared with the control of 0.06 g. The superoxide dismutase activity and chlorophyll content in the transgenic plants were obviously higher than those of the control. The results showed that the overexpression of W6 improved the salt tolerance of tobacco, and W6 probably acted as a connector among different signal transduction pathways. The overexpression of W6 activated the expression of GCC box-containing genes PR2, PR3, PR5, and drought-responsive element/C-repeat (DRE/CRT) genes (NtERD10A and NtERD10C) under normal growth conditions. This improvement of the transgenic tobacco plants to salt stress suggested that W6 regulates osmotic tolerance by activation of downstream gene expression through interaction with the GCC box or DRE elements.