The Cotton GhWRKY91 Gene Negatively Regulates Root Elongation in Overexpressed Transgenic Arabidopsis thaliana

WRKY transcription factors play important roles in plant growth, development, and stress responses. Our previous research has shown that the GhWRKY91 gene can delay age-, abscisic acid (ABA)-, and drought-induced leaf senescence when overexpressed in transgenic Arabidopsis plants. To explore in more depth the biological functions of the GhWRKY91 gene, we further observed the root growth of overexpressing transgenic Arabidopsis thaliana under ABA and drought treatment. In this study, we transplanted the germinated seeds of wild-type (WT) and three transgenic lines (OE-12, OE-13 and OE-20) to 1/2 MS solid medium containing ABA and different concentrations of mannitol (simulated drought treatment) for culturing. The results showed that the transgenic plants had dark green leaves and short root lengths when no stress treatment was added. After ABA and mannitol treatment, the root growth of the WT and transgenic Arabidopsis was inhibited to varying degrees, and the root length downregulation of the transgenic plants was higher than that of the WT, indicating that they were more sensitive to ABA and drought. A bimolecular fluorescence complementation (BiFC) assay showed that the GhWRKY91 and GhWRKY3 proteins interact and emit yellow fluorescence in tobacco leaf cells. These results indicate that the GhWRKY91 gene negatively regulates root elongation in transgenic Arabidopsis and provide a basis for further research on the molecular mechanism of its involvement in regulating cotton root development.