GhWRKY6 Acts as a Negative Regulator in Both Transgenic Arabidopsis and Cotton During Drought and Salt Stress

Abstract

Drought and high salinity are key limiting factors for cotton production. Therefore, research is increasingly focused on the underlying stress response mechanisms of cotton. We first identified and cloned a novel gene encoding the 525 amino acids in cotton, namely <i>GhWRKY6</i>. qRT-PCR analysis indicated that <i>GhWRKY6</i> was induced by NaCl, PEG 6000 and ABA. Analyses of germination rate and root length indicated that overexpression of <i>GhWRKY6</i> in <i>Arabidopsis</i> resulted in hypersensitivity to ABA, NaCl, and PEG 6000. In contrast, the loss-of-function mutant <i>wrky6</i> was insensitive and had slightly longer roots than the wild-type did under these treatment conditions. Furthermore, <i>GhWRKY6</i> overexpression in <i>Arabidopsis</i> modulated salt- and drought-sensitive phenotypes and stomatal aperture by regulating ABA signaling pathways, and reduced plant tolerance to abiotic stress through reactive oxygen species (ROS) enrichment, reduced proline content, and increased electrolytes and malondialdehyde (MDA). The expression levels of a series of ABA-, salt- and drought-related marker genes were altered in overexpression seedlings. Virus-induced gene silencing (VIGS) technology revealed that down-regulation of <i>GhWRKY6</i> increased salt tolerance in cotton. These results demonstrate that <i>GhWRKY6</i> is a negative regulator of plant responses to abiotic stress via the ABA signaling pathway.