Overexpression of violaxanthin de-epoxidase gene alleviates photoinhibition of PSII and PSI in tomato during high light and chilling stress

A tomato (Lycopersicon esculentum) violaxanthin de-epoxidase gene (LeVDE) was isolated. The deduced amino acid sequence of LeVDE showed high identities with violaxanthin de-epoxidase in other plant species. RNA gel blot analysis showed that the mRNA accumulation of LeVDE in the wild-type (WT) was regulated by diurnal rhythm and temperature. RNA and protein gel blot analyses confirmed that the sense LeVDE was transferred into the tomato genome and overexpressed under the control of 35S-CaMV. The ratio of (A+Z)/(V+A+Z) and the values of non-photochemical quenching (NPQ) were higher in transgenic plants than those in WT under high light and chilling stress (4 °C). The net photosynthetic rate (Pn) decreased markedly in WT compared to transgenic lines under high light stress. The maximum quantum yield of primary photochemistry of PSII (Fv/Fm) in transgenic plants decreased more slowly during stresses and recovered faster than that in WT under optimal conditions. The oxidizable P700 in transgenic plants was higher than that in WT under chilling stress. These results suggest that overexpression of LeVDE increased the function of the xanthophyll cycle and alleviated photoinhibition of PSII and PSI in tomato during high light and chilling stress with low irradiance.