Selection And Functional Analysis Of Poplar WRKY Transcription Factor Gene In Response To Salt Stress

The adaptive responses commonly use transcriptional activation or repression of genes upon signal perception and transduction of the external stimuli. Plant adaptability is mainly operated by the regulation of various transcription factors. Significant progress has been made in understanding the genes response to various stresses, numerous transcription factors in plants have been identified. WRKY transcription factors are one of the largest groups of plant-specific transcriptional factors familys, and play diverse roles in various plant development processes and abiotic stress response.The 119 poplar WRKY genes full cDNA sequences were obtained from plant transcription factor database, and the expression patten of poplar WRKY genes in di-haploid Populus simonii×P.nigra were investigated by quantitative real-time PCR (qRT-PCR). The results indicated that the expression of 51 poplar WRKY genes were introduced by salt stress, including 17 upregulated genes and 34 downregulated genes. To understand the expression patterns of poplar WRKY genes under salinity stress,13 poplar WRKY genes responed to salt stress were selected. All of 13 poplar WRKY genes were expressed in root, stem, and leaf tissues, but their expression levels and overall patterns varied notably in these tissues. Regarding overall gene expression in roots, the 13 genes were significantly highly expressed at all six time points after the treatment, reaching the plateau of expression at hour 9. In leaves, the 13 genes were similarly up-regulated from 3 to 12 h in response to NaCl treatment. In stems, however, expression levels of the 13 genes did not show significant changes after the NaCl treatment. The poplar WRKY56, poplar WRKY 116 gene was constructed into plant expression vector and transformed to Arabidopsis by floral dip method. The root length, fresh weight and seed germination were compared between transgenic plants and wild type plants under NaCl treatment. The results indicated that the transgenic plants significantly improved the salt tolerance. The physiological traits such as MDA content, SOD actibity, POD actibity and proline content in transgenic plants and wild type plants were detected. The results indicated that proline content, SOD and POD actibity in transgenic Arabidopsis overexpressing WRKY56 gene were higher, and MDA content were lower than that of wild type Arabidopsis under salt stress conditions. The MDA content, SOD actibity in WRKY116 transgenic Arabidopsis were lower than that of non- transformants under salt stress conditions, but proline containt and POD actibity higher than that of non- transformants.