The increase in unsaturation of fatty acids of phosphatidylglycerol in thylakoid membrane enhanced salt tolerance in tomato
Overexpression of chloroplastic glycerol-3-phosphate acyltransferase gene (LeGPAT) in tomato increased cis-unsaturated fatty acid content in phosphatidylglycerol (PG) of thylakoid membrane. By contrast, suppressing the expression of LeGPAT decreased the content of cis-unsaturated fatty acid in PG. Under salt stress, sense transgenic plants exhibited higher activities of chloroplastic antioxidant enzymes, lower content of reactive oxygen species (ROS) and less ion leakage compared with the wild type (WT) plants. The net photosynthetic rate (P N) and the maximal photochemical efficiency (Fv/Fm) of photosystem II (PSII) decreased more slightly in sense lines but more markedly in the antisense ones, compared to WT. D1 protein, located in the reactive center of the PSII, is the primary target of photodamage and has the highest turnover rate in the chloroplast. Under salt stress, compared with WT, the content of D1 protein decreased slightly in sense lines and significantly in the antisense ones. In the presence of streptomycin (SM), the net degradation of the damaged D1 protein was faster in sense lines than in other plants. These results suggested that, under salt-stress conditions, increasing cis-unsaturated fatty acids in PG by overexpression of LeGPAT can alleviate PSII photoinhibition by accelerating the repair of D1 protein and improving the activity of antioxidant enzymes in chloroplasts.
Additional key wordsascorbate peroxidase D1 protein glycerol-3-phosphate acyltransferase phosphatidylglycerol salt stress
the maximal photochemical efficiency of PSII
Lycopersicon esculentum glycerol-3-phosphate acyltransferase gene
net photosynthetic rate
photosynthetic photon flux density
photosystem I (II)
reactive oxygen species
sodium dodecyl sulfate polyacrylamide gel electrophoresis
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We thank professor Lixin Zhang, Institute of Botany, Chinese Academy of Sciences, for the D1-specific antibodies. This research was supported by the State Key Basic Research and Development Plan of China (2009CB118500), the Natural Science Foundation of China (30871458), Program for Changjiang Scholars and Innovative Research Team in University (Grant IRT0635) and the Natural Science Foundation of Shandong province (Y2007D50).
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