Constitutive activation of a plasma membrane H(+)-ATPase prevents abscisic acid-mediated stomatal closure.
Light activates proton (H(+))-ATPases in guard cells, to drive hyperpolarization of the plasma membrane to initiate stomatal opening, allowing diffusion of ambient CO(2) to photosynthetic tissues. Light to darkness transition, high CO(2) levels and the stress hormone abscisic acid (ABA) promote stomatal closing. The overall H(+)-ATPase activity is diminished by ABA treatments, but the significance of this phenomenon in relationship to stomatal closure is still debated. We report two dominant mutations in the OPEN STOMATA2 (OST2) locus of Arabidopsis that completely abolish stomatal response to ABA, but importantly, to a much lesser extent the responses to CO(2) and darkness. The OST2 gene encodes the major plasma membrane H(+)-ATPase AHA1, and both mutations cause constitutive activity of this pump, leading to necrotic lesions. H(+)-ATPases have been traditionally assumed to be general endpoints of all signaling pathways affecting membrane polarization and transport. Our results provide evidence that AHA1 is a distinct component of an ABA-directed signaling pathway, and that dynamic downregulation of this pump during drought is an essential step in membrane depolarization to initiate stomatal closure.
Merlot
Sylvain
S
Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France.
Leonhardt
Nathalie
N
Fenzi
Francesca
F
Valon
Christiane
C
Costa
Miguel
M
Piette
Laurie
L
Vavasseur
Alain
A
Genty
Bernard
B
Boivin
Karine
K
Müller
Axel
A
Giraudat
Jérôme
J
Leung
Jeffrey
J
D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D002462:Cell Membrane / Q000201:enzymology*; D048429:Cell Size; D018506:Gene Expression Regulation, Plant; D009154:Mutation / Q000235:genetics; D009336:Necrosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D010935:Plant Diseases / Q000235:genetics; D030821:Plants, Genetically Modified; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
D011522:Protons; D000040:Abscisic Acid; D006180:Proton-Translocating ATPases