The Gossypium hirsutum WRKY gene GhWRKY39-1 promotes pathogen infection defense responses and mediates salt stress tolerance in transgenic Nicotiana benthamiana.

KEY MESSAGE: Our results indicate that overexpression of the GhWRKY39 - 1 gene enhances resistance to pathogen infection and tolerance to high salt and oxidative stress in transgenic Nicotiana benthamiana. ABSTRACT: WRKY transcription factor genes play significant roles in the response to biotic and abiotic stresses. Cotton (Gossypium hirsutum) is an important fiber and oil crop worldwide. We isolated and characterized GhWRKY39-1, which is a group IId WRKY gene that is present as a single copy in the cotton genome. Quantitative PCR analyses indicated that GhWRKY39-1 was induced by pathogen infection, defense-related signaling molecules, and abiotic stresses, such as NaCl and methyl viologen. An analysis of the subcellular localization of the GhWRKY39-1 protein indicated that it localized to the nucleus. Furthermore, constitutive overexpression of GhWRKY39-1 in Nicotiana benthamiana conferred a greater resistance to infection by both the bacterial pathogen Ralstonia solanacearum and the fungal pathogen Rhizoctonia solani. The transgenic plants also exhibited elevated mRNA levels of several pathogen-related (PR) genes, including PR1c, PR2 and PR4. Moreover, transgenic plants displayed an enhanced tolerance to salt and oxidative stress and elevated expression of several oxidation-related genes, including APX, CAT, GST and SOD. Overall, these results indicate that GhWRKY39-1 functions as a positive regulator of plant defense against pathogen infection and responses to salt stress and reactive oxygen species.