Overexpression of the glutathione S-transferase gene from Pyrus pyrifolia fruit improves tolerance to abiotic stress in transgenic tobacco plants

Glutathione S-transferases (GSTs) are ubiquitous enzymes in animals and plants, and they are multifunctional proteins encoded by a large gene family. GSTs are involved in response to the oxidative stress including drought, salt, heavy metals, and so on. Under oxidative stress, the excessive reactive oxygen species (ROS) induce an increase in GST levels, and then the GSTs metabolize the toxic products of lipid peroxidation, damaged DNA and other molecules. Previously, a full-length cDNA of a novel zeta GST gene, PpGST, was characterized from fruit of Pyrus pyrifolia Nakai cv. Huobali. In the present study, a constitutive plant expression vector of PpGST was constructed and transferred into tobacco (Nicotiana tabacum L. cv Xanthi) to verify the function of PpGST. As a result, the PpGST gene was successfully integrated into the genome of the transgenic tobacco lines and expressed as expected in the transformants through Southern blotting and quantitative reverse transcription-polymerase chain reaction (QRT-PCR) analysis. Growth of T1 generation plants of PpGST transgenic lines and WT under non-stressful conditions was similar, however, the transgenic tobacco lines showed relatively normal growth under drought, NaCl, and cadmium (Cd) stresses. Furthermore, the T1 transgenic tobacco lines showed significantly slower superoxide anion production rate than the WT under abiotic stress. Simultaneously, the MDA content of each T1 transgenic tobacco plant was only slightly increased and significantly lower than that of the WT under drought, salt and Cd stress. Together with the GST activity of the transgenic tobacco lines, which was significantly increased under stressful conditions, as compared with that in WT, overexpression of PpGST in tobacco enhanced the tolerance of transgenic tobacco lines to oxidative damage caused by drought, NaCl, and Cd stresses.