The Mechanism Of Glycinebetaine In Protecting PS? Repair Under High Temperature Stress

High temperature stress is one of the major abiotic stresses limiting plant growth and development, in crop production, greatly affected the yield of crops. Glycine betaine(betaine)is a kind of small molecular compatible solute, some plants and microbes can accumulate betaine in response to environmental stress. As long as photosynthesis happens photosynthetic plants will inevitably occur damage of photosystem ?. When plants are under abiotic stress conditions, such as high temperature, the photosystem ? proteins' synthetic rate is often unable to compensate for the damage rate, which can lead to photoinhibition.The transgenic tomato plants with different glycinebetaine synthetic enzyme genes(BADH, cod A) can effectively improve the ability of resistance to high temperature, so the mechanism of glycinebetaine to raise the capacity of transgenic tomato plants resistance to high temperature is of great significance. The main results are as follows:(1)Through transgenic technology made the tomato plants that can not accumlate endogenous glycinebetaine accumulate betaine effectively.(2)Under high temperature stress, the photosynthetic rate of tomato plants, occurring photoinhibition, and the transgenic tomato plants or wild type tomato plants prayed exogenously betaine when reffered to wild type tomato plants the photosynthetic rate at high temperature were higher, the degree of photoinhibition were lower, actual photochemical efficiency were higher, the D1 protein content were higher, showing the higher temperature resistance.(3)Using lincomycin to inhibit chloroplast proteins' synthesis, and then detect the degree of photoinhibition at high temperature, found that the transgenic plants with higher maximum photochemical efficiency and D1 protein content was lower than of the wild type plants.(4) Under the condition of 43°C high temperature stress the tomato plant' antioxidant enzymes CAT, POD, APX and SOD enzymes ware more activity then under normal temperature 25°C. The transgenic tomato plants' antioxidant enzyme was higher than the wild type tomato plants.(5)Under high temperature stress, the accumulation of H2O2 and O2-production rate increased, wild type tomato plants H2O2 accumulation and O2-production rate were higher than the transgenic plants.(6)After 43°C high temperature stress, the soluble proteins' oxidation levels of wild type tomato plants was higher than that of the transgenic plants.(7)Under the condition of 43°C high temperature stress the D1 protein coding gene psb A and antioxidant enzymes' genes CAT1, CAT2, GR of transgenic plants had a higher expression level then the wild type plants.(8)Under the condition of 43°C high temperature stress, protease genes DEG1, DEG7,DEG8, fts H2, fts H6, fts H9, fts H12 had no too big change in the wild type, and the genes' transcriptional expression levels in transgenic plants were increased. Protease gene fts H1,DEG5 under the condition of stress had no obvious change.The above results show that under high temperature stress, the transgenic plants and the wild type plants sprayed glycinebetaine exogenously can effectively accumulate betaine,enhance the heat resistance of plants. Glycinebetaine can directly or indirectly increase the activity of antioxidant enzymes in plants under the condition of high temperature stress, the oxidation level of the soluble proteins was lower in transgenic plants, so that the translation extension factor EF-G activity inhibition degree is reduced, thus reduced the suppression of protein translational level. Betaine under high temperature stress can make part of the expression of protease genes' transcriptional levels higher than wild type plants, which may improve the damaged photosystem ? proteins' degradation rate. Using lincomycin processing plants to inhibit the synthesis of chloroplast proteins, after high temperature stress condition,transgenic plants and the wild type plants sprayed glycinebetaine exogenously had higher maximum photochemical efficiency, photoinhibition degree was lower than those of wild type plants, which indicated that betaine can protect the photosystem ? of tomato plants.Glycinebetaine can protect the synthesis of photosystem ? proteins under high temperature stress and had played an important role to accelerate the degradation of PS? damaged protein.