Heterology expression of the tomato LeLhcb2 gene confers elevated tolerance 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). Light harvesting complex (LHC) proteins had a function in dissipating excess excitation energy and eliminating ROS to maintain the normal physiological function of cells. A tomato (Lycopersicon esculentum) LHC antenna protein gene (LeLhcb2) was isolated. The LeLhcb2-green fluorescent protein (GFP) fusion protein was targeted to the chloroplast of Arabidopsis mesophyll protoplast. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the expression of LeLhcb2 was markedly abundant in leaves and was induced by chilling (4 °C). qRT-PCR analysis and western blot confirmed that the sense gene LeLhcb2 was transferred into tobacco genome and overexpressed. Under chilling stress, the transgenic plants showed not only better growth, higher fresh weight, chlorophyll content, but also lower malondialdehyde (MDA) accumulation and relative electrical conductivity (REC), compared with the wild type (WT). The maximal photochemical efficiency of PSII (Fv/Fm), non-photochemical quenching (NPQ) and D1 protein content were also higher in the transgenic plants. Furthermore, the relatively lower hydrogen peroxide (H2O2) and superoxide radical (O2(-)) levels in the sense plants were not considered to due to the higher activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD). These results suggested that the overexpression of LeLhcb2 had a key function in alleviating photo-oxidation of PSII and enhanced transgenic tobacco tolerance to chilling stress.