GbWRKY1 Transcription Factor Is a Key Molecular Switch for Plant Defense-to-Development Transition in Cotton

With the limitation of available resources, plants have evolved an elaborate signaling network to prioritize immune response and growth development for survival and thrive, namely the common phenomenon of growth-defense conflict. Previous research has demonstrated that the antagonistic interaction of gibberellin (GA) and jasmonate (JA) is mediated through the dynamical regulation of DELLA proteins and JASMONATE ZIM-DOMAIN1 (JAZ1) protein. In this study, we demonstrate multiple functions of cotton GbWRKY1 transcription factor in plant defense response and during development. Although the expression of GbWRKY1 is induced rapidly by methyl jasmonate and infection by Verticillium dahliae, our results show that GbWRKY1 is a negative regulator of the JA-mediated defense response and plant resistance to the pathogens Botrytis cinerea and V. dahliae. Under normal growth conditions, GbWRKY1-overexpressing lines displayed GA-associated phenotypes, including organ elongation and early flowering, coupled with the down-regulation of the putative targets of DELLA. We show that the GA-related phenotypes of GbWRKY1-overexpressing plants depend on the constitutive expression of Gossypium hirsutum GhJAZ1. We also show that GhJAZ1 can be transactivated by GbWRKY1 through TGAC core sequences, and the adjacent sequences of this binding site are essential for binding specificity and affinity to GbWRKY1, as revealed by dual-luciferase reporter assays and electrophoretic mobility shift assays. In summary, our data suggest that GbWRKY1 is a critical regulator mediating the plant defense-to-development transition during V. dahliae infection by activating JAZ1 expression.