Cloning Of LeGSH1Gene And Its Function Analysis In Increasing Tomato Tolerance To Cadmium Toxicity

Glutathione, as an important antioxidant in plants, plays important roles in resistingvarious stresses. γ-glutamylcysteine synthetase (γ-ECS) plays a critical role in glutathionesynthesis of plants. The excess of cadmium in soil forms significant harm to plant growth anddevelopment.In this study, effects of the overexpression of LeGSH1gene in tomato oncadmium tolerance were studied, and the results were as follows:1. Based on tomato genome sequence, a full-length cDNA clone encoding γ-ECS wasisolated from tomato leaves. The clone, designated as LeGSH1. Semi-quantitative analysisindicated that LeGSH1was expressed in all investigated organs including root, stem, leaf,flower and fruit. In order to determine whether LeGSH1was involved in tomato tolerance tocadmium toxicity, transgenic tomato plants constitutively overexpressing LeGSH1weregenerated. Southern blot analysis showed that strong signals were detected in the DNAsamples extracted from transgenic plants, while no signal was detected in the wild type (WT)tomato, and RNA expression under Cd stress was much higher in transgenic lines than WTplants, proving that LeGSH1was successfully transferred into tomato genome andoverexpressed.2. Compared to WT plants, overexpression of LeGSH1significantly decreasedCd-induced chlorosis of tomato leaves, increased pigment contents, and alleviatedaccumulation of reactive oxygen species (ROS), resulting in lower oxidative stress. Thefunction of LeGSH1could be attributed to decreasing Cd contents in leaves, which mightgreatly depend on higher accumlation of GSH. Further analysis indicated that overexpressing-LeGSH1tomato plant leaves showed more accumulation of iron, calcium and copper than thatin WT plants, which indicated overexpressing LeGSH1also played important role incontaining nutrient balance under Cd stress.