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Analysis of drought and salt-alkali tolerance in tobacco by overexpressing WRKY39 gene from Populus trichocarpa

ABSTRACT WRKY is one of the largest families of transcription factors in plants. It not only regulates plant growth and development but also participates in the regulation of plant defense against biological and abiotic stresses. In this study, research was aimed to overexpress WRKY39 gene of P. trichocarpa (PtWRKY39) and to identify its important role played in drought and saline-alkali tolerance in tobacco model plant. Under the control of CaMV35S promoter, the overexpression of PtWRKY39 gene was increased to more than 10 times in T3 generation of transgenic tobacco plant. The drought resistance and saline-alkali tolerance were evidenced in overexpressed PtWRKY39 transgenic lines at germination/seedling stage. The overall germination rate, fresh weight, and chlorophyll contents of overexpressed lines were significantly higher while the level of malondialdehyde was significantly lower in PtWRKY39 transgenic lines than that of wild type (WT) lines. The content of H2O2 in leaves was detected by the 3, 3-Diaminobenzidine method showed that the overexpression of PtWRKY39 gene could reduce the accumulation of ROS (mainly H2O2) and enhance salt-alkali tolerance. Phenotypic analysis at 7-leaf pot transgenic seedlings stage treated with the saline-alkali soil extract and salt NaCl under root irrigation stress, revealed growth of the transgenic line was significantly higher than that of WT. This work concludes that overexpression of PtWRKY39 gene can improve the regulation of drought resistance and saline-alkali tolerance of transgenic plants during seed germination and vegetative growth.