Title: Presentaci
1Inhibition of root plasma membrane H-ATPase by
drought is mediated by the abscisic acid
signalling pathway
M. Dolores Planes1, Hassan M. Younis2 and Ramón
Serrano1 1Instituto de Biología Molecular y
Celular de Plantas, Universidad Politécnica de
Valencia-C.S.I.C., Camino de Vera s/n, 46022
Valencia, Spain 2Department of Pesticide
Chemistry, Faculty of Agriculture, El-Shatby,
21545 Alexandria, Egypt
BACKGROUND AND SUMMARY 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.
The hypothesis to explain these results is that
ABA, via PYR/PYL receptors, PP2Cs and SnRK2s,
triggers phosphorylation of the plasma membrane
H-ATPase in an inhibitory site different from
the activating phosphorylation of the penultimate
threonine. Inhibition of root plasma membrane
H-ATPase by ABA may participate in the
inhibition of root and general plant functions
under stress conditions.