Overexpression Of IbOr And IbMYB Gene Confers Enhanced Tolerance To Stress In Sweet Potato (Ipomoes Batats L.)

Environmental problem is increasingly serious in recent years, water deficit condition, such as drought, salinity, may limit the growth and yield of sweet potato as well as other crops.Therefore, better understanding the adaptation mechanism of sweet potato to drought and salinity stress, and improving existing varieties by transgenic technology, then choosing strong resistant varieties to stress, have important significance on improving the production potential of sweet potato. Transgenic sweet potato lines(TS) overexpressing IbMYB or IbOr, and non-transgenic line(NT) were used as experimental materials and were analyzed the collaborative response mechanism of photosynthetic system, membrane lipid peroxidation, antioxidant defense system under PEG and different degrees of drought stress condition, which was mediated by adding 15% polyethylene glycol(PEG 6000) into 1/2 hoagland solution and potted experiment of soil drought. Then, through the 150 mM NaCl stress of 1/2 hoagland solution treatment, response of photosynthetic system and antioxidants in transgenic sweet potato lines and non-transgenic line at different times, were studied to explore the physiological mechanism of transferring genes increase the salt stress tolerance of sweet potato. And then we got these results as following:1. Under PEG stress conditions, photosynthetic rate(Pn), stomatal conductance(Gs), Intercellular CO2 concentration(Ci), transpiration rate(Tr) decreased evidently in all sweet potato lines, but Pn, Gs and Tr of IbOr TS were higher than NS. The chlorophyll content(Chl) and carotenoid content in TS decreased evidently after PEG stress, but it was significantly higher than NT. The results suggested that overexpression of IbOr gene enhanced tolerance of sweet potato to PEG, because it may delay the photosynthetic function decline by maintaining a higher level of chlorophyll and carotenoid.2. After 24 h PEG, O2—· and MDA content of IbOr TS were significantly lower than NT, APX activity and higher levels of carotenoids content timely removed the excessive production of reactive oxygen species.3. Under salt stress, Pn, Gs and Tr of IbOr TS were higher than NT, 24 h later, Pn, Ci, Tr of TS rose slightly, and Gs had no obvious change. It demonstrated that stomatal limitation caused by decreased stomatal conductance was the main reason of photosynthesis declining at early stage of salt stress. In addition, chlorophyll and carotenoid content of TS were always higher than NT, and carotenoid content of TS increased at 48 h under salt stress, with modest Ps increasing, showed that the structure and function of photosynthetic organ were damaged lightly, so it can maintain higher chlorophyll and carotenoid content to maintain higher photosynthetic capacity.4. With the method of potted experiment, Pn drop extent of IbMYB TS was smaller than NT under long-term drought stress. After drought stress, anthocyanin content of TS increased significantly, and the chlorophyll content was always higher than NT, therefore, anthocyanins can protect chloroplast, then improve photosynthetic ability.5. After soil drought stress, O2—· and MDA content of IbMYB TS were always lower than NT, but enzyme activity was higher than NT, and the anthocyanin in leaves and storage roots of TS were significantly higher than that of NT, indicating that plant protected themselves from damage by adjusting the antioxidant system, and anthocyanin played an important role.