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 peroxida tion, 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. Further more, 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.
In this study, the experimental vapor?liquid equilibria data of the ternary Pb?Sn?Sb alloy system are determined using a new experimental method. The experimental VLE data passed the thermodynamic consistency test (Van Ness test), suggesting that the experimental results are reliable. The activities of the components of Pb?Sn?Sb ternary alloy and those of the corresponding three constituent binaries were calculated using the Wilson equation. The predicted values are in good agreement with the data determined from the experiments, and the average relative deviation and average standard deviation were smaller than ? 4.00% and ? 0.03 for all constituent binaries, respectively, which indicates that the Wilson equation is reliable for calculating the activity of the components of the Pb?Sn?Sb ternary alloy. The VLE data of the Pb? Sn and Sb?Sn binary alloys and Pb?Sn?Sb ternary alloy were calculated based on the VLE theory and the Wilson equation. The calculated VLE data were in good agreement with the data determined from the experiments, indicating that this method is reliable for calculating the VLE of alloy systems. The proposed study offers a valid method for analyzing the composition of products that are dependent on the distillation temperature and system pressure during vacuum distillation, which is of great significance to the experimental design of this process.
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