title: Effects of chemical inhibitors and apyrase enzyme further document a role for apyrases and extracellular ATP in the opening and closing of stomates in Arabidopsis.
abstract: In Arabidopsis leaves there is a bi-phasic dose-response to applied nucleotides; i.e., lower concentrations induce stomatal opening, while higher concentrations induce closure. Two mammalian purinoceptor antagonists, PPADS and RB2, block both nucleotide-induced stomatal opening and closing. These antagonists also partially block ABA-induced stomatal closure and light-induced stomatal opening. There are two closely related Arabidopsis apyrases, AtAPY1 and AtAPY2, which are both expressed in guard cells. Here we report that low levels of apyrase chemical inhibitors can induce stomatal opening in the dark, while apyrase enzyme blocks ABA-induced stomatal closure. We also demonstrate that high concentrations of ATP induce stomatal closure in the light. Application of ATPγS and chemical apyrase inhibitors at concentrations that have no effect on stomatal closure can lower the threshold for ABA-induced closure. The closure induced by ATPγS was not observed in gpa1-3 loss-of-function mutants. These results further confirm the role of extracellular ATP in regulating stomatal apertures.
authors.affiliation: Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Clark
authors.affiliation: 1Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Cameron
authors.initials: C
authors.lastname: Darwin
authors.affiliation: 1Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Viraj
authors.initials: V
authors.lastname: Mehta
authors.affiliation: 1Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Faith
authors.initials: F
authors.lastname: Jackobs
authors.affiliation: 1Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Perry
authors.affiliation: 1Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Katia
authors.initials: K
authors.lastname: Hougaard
authors.affiliation: Section of Molecular Cell and Developmental Biology; University of Texas; Austin, TX USA.
authors.forename: Stan
authors.initials: S
authors.lastname: Roux
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D001081:Apyrase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D004791:Enzyme Inhibitors; C022571:adenosine 5'-O-(3-thiotriphosphate); D000040:Abscisic Acid; D000255:Adenosine Triphosphate; C522733:APY1 protein, Arabidopsis; C522734:APY2 protein, Arabidopsis; D001081:Apyrase
keywords: abscisic acid; apyrase; arabidopsis; extracellular ATP; stomata