In transgenic (TG) tomato (Lycopersicon esculentum Mill.) overexpressed ω-3 fatty acid desaturase gene (LeFAD7) was identified, which was controlled by the cauliflower mosaic virus 35S promoter and induced increased contents of unsaturated fatty acids in thylakoid membrane. Under chilling stress at low irradiance (4 °C, 100 µmol m-2 s-1) TG plants with higher linolenic acids (18: 3) content maintained a higher O2 evolution rate, oxidizable P700 content, and maximal photochemical efficiency (Fv/Fm) than wild type (WT) plants. Low temperature treatment for 6 h resulted in extensive changes of chloroplast ultrastructure: in WT plants most chloroplasts became circular, the number of amyloids increased, appressed granum stacks were dissolved, grana disappeared, and the number of grana decreased, while only a few grana were found in leaves of TG plants. Hence the overexpression of LeFAD7 could increase the content of
18 : 3 in thylakoid membrane, and this increase alleviated the photoinhibition of photosystem (PS) 1 and PS2 under chilling at low irradiance. and X.-Y. Liu ... [et al.].
Over-expression of chloroplastic glycerol-3-phosphate acyltransferase gene (LeGPAT) increased unsaturated fatty acid contents in phosphatidylglycerol (PG) of thylakoid membrane in tomato. The effect of this increase on the xanthophyll cycle and chloroplast antioxidant enzymes was examined by comparing wild type (WT) tomato with the transgenic (TG) lines at chilling temperature (4 °C) under low irradiance (100 µmol m-2 s-1). Net photosynthetic rate and the maximal photochemical efficiency of photosystem (PS) 2 (Fv/Fm) in TG plants decreased more slowly during chilling stress and Fv/Fm recovered faster than that in WT plants under optimal conditions. The oxidizable P700 in both WT and TG plants decreased during chilling stress under low irradiance, but recovered faster in TG plants than in the WT ones. During chilling stress, non-photochemical quenching (NPQ) and the de-epoxidized ratio of xanthophyll cycle in WT plants were lower than those of TG tomatoes. The higher activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in TG plants resulted in the reduction of O2-. and H2O2 contents during chilling stress. Hence the increase in content of unsaturated fatty acids in PG by the over-expression of LeGPAT could alleviate photoinhibition of PS2 and PS1 by improving the de-epoxidized ratio of xanthophyll cycle and activities of SOD and APX in chloroplast. and N. Sui ... [et al.].