Overexpression of Sweet Pepper Glycerol-3-Phosphate Acyltransferase Gene Enhanced Thermotolerance of Photosynthetic Apparatus in Transgenic Tobacco

In order to investigate the relationship between the lipid composition in thylakoid membrane and thermostability of photosynthetic apparatus, tobacco transformed with sweet pepper sense glycerol-3-phosphate acyltransferase （GPAT） gene were used to analyze the lipid composition in thylakoid membrane, the net photosynthetic rate and chlorophyll fluorescence parameters under high temperature stress. The results showed that the saturated extent of monogalactosyldiacylglycerol （MGDG）, sulfoquinovosyldiacylglycerol, digalactosyldiacylglycerol and phosphatidylglycerol in thylakoid membrane of transgenic tobacco T1 lines increased generally. Particularly, the saturated extent in MGDG increased obviously by 16.2% and 12.6% in T1-2 and T1-1, respectively. With stress temperature elevating, the maximum efficiency of photosystem Ⅱ （PSⅡ） photochemistry （Fv/Fm）, actual photochemical efficiency of PSll in the light （ФPSⅡ） and net photosynthetic rate （Pn） of the two lines and wild type tobacco plants decreased gradually, but those parameters decreased much less in transgenic plants. Even though the recovery process appeared differently in the donor and acceptor side of PSⅡ in transgenic tobacco compared with wild-type plants, the entire capability of PSⅡ recovered faster in transgenic tobacco, which was shown in the parameters of PI, Fv/Fm and ФPSⅡ, as a result, the recovery of Pn was accelerated. Conclusively, we proposed that the increase in saturated extent of thylakoid membrane lipids in transgenic plants enhanced the stability of photosynthetic apparatus under high temperature stress.