Overexpression of a tomato carotenoid ε-hydroxylase gene alleviates sensitivity to chilling stress in transgenic tobacco.

Chilling is one of the most serious environmental stresses that disrupt the metabolic balance of cells and enhance the production of reactive oxygen species (ROS). Lutein plays important roles in dissipating excess excitation energy and eliminating ROS to maintain the normal physiological function of cells. A tomato carotenoid epsilon-ring hydroxylase gene (LeLUT1) was isolated, and the LeLUT1-GFP fusion protein was localized in the chloroplast of Arabidopsis mesophyll protoplast. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the expression of LeLUT1 was the highest in the leaves and was down-regulated by various abiotic stresses in tomato. The transgenic tobacco plants overexpressing LeLUT1 had higher lutein content, which was decreased in cold condition. Under chilling stress, the non-photochemical quenching (NPQ) values were higher in the transgenic plants than in the wild type (WT) plants. Compared with the WT plants, the transgenic plants showed lower levels of hydrogen peroxide (H2O2), superoxide radical (O2(·-)), relative electrical conductivity, and malondialdehyde content (MDA), and relatively higher values of maximal photochemical efficiency of photosystem II (Fv/Fm), oxidizable P700 of PSI, and net photosynthetic rate (Pn). Therefore, the transgenic seedlings were less suppressed in growth and lost less cotyledon chlorophyll than the WT seedlings. These results suggested that the overexpression of LeLUT1 had a key function in alleviating photoinhibition and photooxidation, and decreased the sensitivity of photosynthesis to chilling stress.