Study On The Thermotolerance Of Transgenic Rice Plants With COD Gene

In natural environment, plants are continuously exposed to biotic and abiotic stress conditions during their whole life cycles. High temperature which affects the growth and the production of crops is a common abiotic stress during summer. In the process of involving, plants have evolved mechanisms to overcome environmental stresses. One mechanism is the accumulation of compatible solutes such as glycinebetaine (GB). GB is one of the organic compatible solutes that can accumulate rapidly in many plants under salinity stress, drought and low temperature, and enhanced the tolerance to adverse conditions. Genetically engineered rice with the ability to synthesize glycinebetaine was established by introducing the codA gene for choline oxidase. The main results are as follow:(1) Under normal condition, codA transgenic rice showed higher CO2 assimilation rate, apparent quantum yield and carboxylation efficiency by contrast with wild-type plant;(2) After High temperature treatment, Pn and AQY of wild-type rice plants decreased more than that of codA transgenic rice plants. Transgenic rice plants maintained higher thermotolerance;(3) Fo is sencitive to high temperature. After high temperature treatment, Fo was higher in wild-type plants than that of transgenic rice plants.ΦPS II and Fv/Fm of transgenic plants were higher than that of wild-type plants after high temperature treatment. Transgenic plants maintained higher photoreaction activity under heat stress condition;(4) Heat stress increased the accumulation of H2O2 and accelerated the production of O2-in the wild-type and transgenic rice plants, but this accumulation and production were less in transgenic plant;(5) GB decreased the accumulation of ROS through maintaining relatively higher antioxidant enzyme activities in codA transgenic rice plants;(6) During high temperature, the transcript of gene for HSP70 was lower in codA transgenic plant than that in the wild-type plant than in wild-type plants. The accumulation of HSP70 was less in the codA transgenic plants than that in the wild-type plants. The results demonstrated that the codA transgenic plants showed higher tolerance to high temperature. Transgenic rices have the ability to synthetize and accumulate GB, maintained higher activity of antioxidase and stabilized protein conformation, increased heat stress tolerance.