Effects Of Unsaturation Of Thylakoid Membrane On Salt Tolerance In Tomato Plants

Tomato (Lycopersicon esculentum mill.) originating in the western highland of South America is an important economic crop, and also a world-wide distribution, more consumption and major vegetables. In order to investigate the correlation of fatty acid composition in thylakoid membrane and the tolerance to salt stress,WT, antisense- transgenic lines T2-8(-)and sense- transgenic lines T2-7(+) of tomato were used to measure the fatty acid composition of thylakoid membrane, photosynthetic and chlorophyll fluorescence parameters, chloroplastic reactive oxygen species and activities of antioxidant enzymes under salt stress. The results showed as follows:1. The results showed that linolenic acid (18:3) obviously increased and the content of oleic acid (18:2) concomitantly decreased in the sense-transgenic lines, resulting in the increase of the unsaturation of thylakoid membrane. In contrast, the decreased unsaturation of thylakoid membrane in antisense-transgenic plants was observed.2. In order to investigate the correlation of fatty acid composition in thylakoid membrane and the tolerance of photosystem to salt stress, photosynthetic and chlorophyll fluorescence parameters were measured. The maximal photochemical efficiency of PSII(Fv/Fm) and photosynthetic rates(Pn) in T2-7(+) lines with higher 18:3 decreased less under salt stress, while Fv/Fm and Pn in T2-8(-) lines decreased obviously.3. Compared to WT, the sense-transgenic lines could maintain higher activities of chloroplastic SOD and APX, lower content of chloroplastic O2 and H2O2 under salt stress. In contrast, the activities of chloroplastic SOD and APX were lower in the antisense-transgenic plants T2-8(-), so the contents of chloroplastic O2 and H2O2 were higher. 4. Compared to WT, sense-transgenic lines could accumulate more solute sugars and free proline under salt stress, so the osmotic adjustment ability increased. In contrast, under salt stress, the saturated osmotic potential in T2-8(-) was higher and osmotic adjustment ability were lower than that in WT. The results showed that the increase in unsaturation of thylakoid membrane enhanced osmotic adjustment ability in tomato plants under salt stress.