Studies On Overexpression Of Vitamin C Metabolism Related Genes In Rice

Vitamins C (Vc) is antioxidants which is synthesized in plants and plays an important physiological roles in plant growth and development. The lack of vitamin C will seriously affect human body health. But human and some primates are due to lack of the last enzyme which is used to synthesis of Vc, so they must obtain Vc from the diet. Thus, the research about improving the content of Vc in the food and using Vc to enhance crop resistance is particularly important. Rice is the most important model plant for cereals, which is also one of the important food crops in the world, it is important to raise the content of Vc by transgenic approach in order to improve the nutrition quality and the ability of resisting adversity stress.In this study, with the aim to improve the content of vitamin C in rice, we carried out the following works. Firstly, we screened several transgenic lines containing the homozygous target gene(s) through in vitro test of hygromycin resistance and PCR analysis. Secondly, we analyzed the expression of target gene(s) in both the developing seed and leaf in selected transgenic rice by using the semi-quantitative and real-time fluorescence quantitative RT-PCR with the purpose of providing the basis for the determination of Vc content in the next work. Thirdly, we measured the content of Vc in the transgenic rice by using the high performance liquid chromatography in order to obtain transgenic materials with high vitamin C content. Last, we analyzed the phenotype of the transgenic rice seedlings under treatment with salt. The main results are as followings:1. After careful screen of transgenic offspring materials, we obtained a number of transgenic rice with homozygous transgene(s), such as GLDH, OsDHAR, GGP, DHAR, GME, GMP, GDH, GPP, and the number are10,10,9,9,6,7,7,8, respectively. In addition, we also selected a transgenic rice line with both transgenes (GPP and GDH).2. The expression results showed that the expression of exogenous gene in transgenic rice had a bigger difference among the transgenic rice with different target gene. It was implied that the expression between endogenous and exogenous genes might be competitive within the leaf of transgenic plant.3. It was showed that overexpression of GGP, GME or GDH had the largest contribution to the accumulation of vitamin C according to the determination result of Vc content in transgenic rice. Compared with the untransformed wild type or transgenic rice with empty vector, the highest content of AsA in the transgenic lines with the above transgene was raised to2.74,1.89and1.81times, respectively.4. The results from salt treatment of rice seedling showed that the increase of Vc content could enhance the ability of resistance to salt stress, and overexpression of GGP might have better contribution to stress resistance than others.