Physiological responses of transgenic tobacco plants expressing the dehydration-responsive RD22 gene of Vitis vinifera to salt stress

Abstract

Salinity is one of the most common environmental stresses affecting grapevine productivity. In order to analyze the contribution of the dehydration-responsive RD22 gene of Vitis vinifera L. (VvRD22) to salt tolerance improvement, Agrobacterium-mediated transformation in the tobacco model plant (Nicotiana benthamiana) was carried out and transgenic lines were subjected to in vitro and ex vitro salt treatments for physiological response evaluation. Under in vitro salt stress, the transgenic lines exhibited higher seed germination and growth than the wild type (WT). The ex vitro assays after salt treatment showed better growth and higher chlorophyll content in VvRD22-expressing plants than in the WT. Ion analysis revealed less increase in the levels of sodium (Na+) in leaves and chloride (Cl-) in all organs within the transgenic lines compared to the WT. Interestingly, stabilized calcium (Ca2+) contents were registered in the leaves of transgenic lines. Moreover, the occurrence of an osmotic adjustment based on an overproduction of total soluble sugars was observed within the transgenic lines. These physiological responses suggest that the protective effect of VvRD22 transgenic expression is enabling other physiological mechanisms to function and subsequently contributing to the ability to cope with salt stress. The VvRD22 transgenic expression would be useful in engineering salt stress-tolerant grapevines.