GbWRKY1, a member of the WRKY transcription factor family identified from Gossypium barbadense, is involved in resistance to Verticillium wilt

Abstract

WRKY transcription factors are involved in complex signalling processes that occur during stress responses. However, in contrast to the exploration of such mechanisms in model plants, far less research has focussed on the WRKY family in cotton. We previously identified GbWRKY1 in cotton (Gossypium barbadense), the expression of which is induced upon infection by Verticillium dahliae. Our current results indicate that this gene with three introns, has a group of cis-acting elements in its promoter that are associated with plant growth and development as well as responses to environmental stresses. Here, we used virus-induced gene silencing to characterize the role of GbWRKY1. Silencing in cotton simultaneously up-regulated salicylic acid (SA)-mediated responses and inhibited jasmonate (JA)-inducible and ethylene (ET)-inducible defences, resulting in an increased susceptibility to V. dahliae. However, when compared with wild-type Arabidopsis, transgenic plants exhibited more resistance to infection with V. dahliae. In the latter genotype, expression was increased for pathogen-related PR4 and ACS2, two genes involved in the JA pathway and ET biosynthesis, while expression of PR5, involved in the SA pathway, decreased after V. dahliae infection. Moreover, POD activity and lignin content related to ethylene synthesis in transgenic Arabidopsis were higher than those in wild-type Arabidopsis after V. dahliae infection. Collectively, these findings suggest that GbWRKY1 is regulated by signalling pathways for SA, JA and ET, and mainly involved in resistance to V. dahliae attack by ET signalling pathway the response. This highlights the importance of WRKYs in regulating pathogen-induced responses and plant development.