CodA Transgenic Tomato Plants Enhance Tolerance to High Temperature Stress

Abstract

The effects of codA gene on photosynthesis,activities of antioxidative enzymes,the expression of the heat response genes and the accumulation of D1 protein in tomato leaf under different temperature stresses were investigated to reveal the mechanism of thermotolerance in codA-transgenic tomato plants.The wild type(cv.Moneymaker)and codA transgenic tomato plants were treated with 25,30,35,40,45,and 50℃ respectively for two hours,then net photosynthetic rate(Pn),the maximal efficiency of PSII photochemistry(Fv/Fm),hydrogen peroxide(H2O2)content,malondialdehyde(MDA)content,relative electric conductivity(REC)and activities of antioxidative enzymes were detected.After 42℃ heat stress for 0,3,6 hours,the expressions of antioxidant enzyme genes and heat stress genes and the accumulation of the D1 protein were also determined.The results demonstrated that under high temperature stress,the inhibition degree of Pn and Fv/Fm in codA transgenic tomato plants was lower than that in wild type plants.The accumulation of H2O2,MDA and REC in codA transgenic tomato plants was less than that in wild type plants.And codA transgenic tomato plants also greatly enhanced the activities of catalase(CAT),superoxide dismutase(SOD),peroxidase(POD),and ascorbate peroxidase(APX).Moreover,the expression levels of antioxidant genes and heat response genes in codA transgenic tomato plants was higher than those in wild type plants and the degradation degree of D1 protein in codA transgenic tomato plants were lower than that in wild type plants.It indicated that codA transgenic tomato plants enhance thermotolerance via maintaining higher activities of antioxidant enzymes,accelerating the expression of heat response genes and reducing the degradation of D1 protein.