Overexpression of NbWRKY79 enhances salt stress tolerance in Nicotiana benthamiana

Main conclusion A WRKY transcription factor encoding NbWRKY79, which was induced by salt and ABA was isolated from Nicotiana benthamiana . Overexpression of NbWRKY79 resulted in enhanced tolerance to salt stress. In plants, there are many families of transcriptional regulators, one of which is WRKY transcription factors, which have a significant effect on the adaptation to abiotic stress. Nevertheless, most of the mechanisms in plant to which WRKY genes are concerned to tolerate salinity are still undiscovered. In this study, a gene from Nicotiana benthamiana , NbWRKY79, was isolated and characterized. NbWRKY79 contains one WRKY domain and localizes in the nucleus. NbWRKY79 was induced after the plant was exposed to salinity and abscisic acid (ABA). The overexpression of NbWRKY79 remarkably enhanced the tolerance of tobacco plant to salinity, which was confirmed when the plant growth, root growth and chlorophyll content were studied through physiological analyses. The sensitivity to ABA-mediated seed germination and seedling root growth of NbWRKY79 transgenic lines were increasing. In addition, the reduced accumulation of reactive oxygen species and malondialdehyde content as well as an increase in proline content and the activity of antioxidant enzymes such as superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase during salt treatment were found, and these indicated that the transgenic plants enhanced tolerance to oxidative stress when comparing to the wild-type plants. Furthermore, it was found that ABA content and transcript levels of ABA-inducible genes, including NbAREB , NbDREB and NbNCED , were significantly increased in the salt stress conditions. These results recommend that NbWRKY79 holds the key to salt stress response.