Transformation of Choline Dehydrogenase Gene and Identification of Salt-tolerance in Transgenic Tomato

The betA gene which encodes choline dehydrogenase that converts choline into glycinebetaine has been cloned from Escherichia coli TG1. Agrobacterium-mediated transformation has been used to introduce the betA gene under the control of the 35S promoter of cauliflower mosaic virus as well as the nptⅡ marker gene into tomato (Lycopersicon esculentum). Salt tolerance assays were performed on two independent transgenic plants. Under salt stress, the osmotic adjustment ability of the transgenic tomato was higher than that of the control plant(Fig.6). At 200 mmol/L NaCl, there is no visible symptoms of salt damage in transgenic tomato whereas the lower leaves of the control plant turned yellow and exhibited necrosis. The results suggest a positive effect of the betA gene on the level of salt tolerance in transgenic plants.