Inhibition of root plasma membrane H+-ATPase by drought is mediated by the abscisic acid signalling pathway

Abstract

The plasma membrane H+-ATPase of stomata gueard cells is inhibited by abscisisc acid (ABA) during drought stress and this is important for stomata closure (Merlot et al, 2007, EMBO J 26: 3216). In the present work we have investigated the regulation of the enzyme by drought and ABA in wheat and Arabidopsis roots. Root H+-ATPase is inhibited by drought. Addition of ABA was also inhibitory and no inhibition by drought was observed in an ABA-insensitive Arabidopsis mutant. Inhibition of H+-ATPase correlates with neither decreased phosphorylation of the penultimate threonine nor decreased amount of the enzyme. An inhibitory phosphorylation mediated by ABA-activated protein kinases (SnRK2) is proposed.