A tomato (Lycopersicon esculentum Mill.) zeaxanthin epoxidase gene (LeZE) was isolated and antisense transgenic tomato plants were produced. Northern, southern, and western blot analyses demonstrated that antisense LeZE was transferred into the tomato genome and the expression of LeZE was inhibited. The ratio of (A+Z)/(V+A+Z) in antisense transgenic plants was maintained at a higher level than in the wild type (WT) plants under high light and chilling stress with low irradiance. The value of non-photochemical quenching (NPQ) in WT and transgenic plants was not affected during the stresses. The oxidizable P700 and the maximal photochemical efficiency of PSII (Fv/Fm) in transgenic plants decreased more slowly at chilling temperature under low irradiance. These results suggested that suppression of LeZE caused zeaxanthin accumulation, which was helpful in alleviating photoinhibition of PSI and PSII in tomato plants under chilling stress. and N. Wang ... [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.].