Drought tolerance of cowpea is associated with rapid abscisic acid biosynthesis via VuWRKY57 in root.

Cowpea [ (L.) Walp] is more drought tolerant than other legumes, although drought still limits its productivity. Under drought stress, cowpea closes its stomata more rapidly to maintain its plant water content than soybean. The rapidly stomatal closure under drought stress in cowpea is mediated by abscisic acid (ABA), but the details of the mechanism are not yet clear. We examined the expression of an ABA-biosynthesis-related gene encoding 9--epoxycarotenoid dioxygenase (NCED) and ABA content in roots of cowpea and soybean under drought stress. Following an analysis of each gene's promoter, we investigated the expression of the genes for WRKY transcription factors VuWRKY57 and GmWRKY32. gene expression conformed with and expression, and VuWRKY57 bound to the promoter. Overexpression of in confirmed the drought stress tolerance. Thus, under drought stress, expression is rapidly induced in cowpea roots; ABA content increased via the induction of leads to stomatal closure; and drought tolerance is conferred.