title: Disruption of AtMRP4, a guard cell plasma membrane ABCC-type ABC transporter, leads to deregulation of stomatal opening and increased drought susceptibility.
abstract: ATP-binding cassette (ABC) transporters are membrane proteins responsible for cellular detoxification processes in plants and animals. Recent evidence shows that this class of transporters may also be involved in many other cellular processes. Because of their homology with human multidrug resistance-associated proteins (MRP), cystic fibrosis transmembrane conductance regulator (CFTR) and sulfonylurea receptor (SUR), some plant ABC transporters have been implicated in the regulation of ion channel activities. This paper describes an investigation of the AtMRP4 gene and its role in stomatal regulation. Reporter gene studies showed that AtMRP4 is highly expressed in stomata and that the protein is localized to the plasma membrane. Stomatal aperture in three independent atmrp4 mutant alleles was larger than in wild-type plants, both in the light and in the dark, resulting in increased water loss but no change in the photosynthetic rate. In baker's yeast, AtMRP4 shows ATP-dependent, vanadate-sensitive transport of methotrexate (MTX), an antifolate and a substrate of mammalian MRPs. Treatment with MTX reduced stomatal opening in wild-type plants, but had no effect in atmrp4 mutants. These results indicate the involvement of AtMRP4 in the complex regulation of stomatal aperture.
authors.affiliation: Zurich Basel Plant Science Center, University of Zurich, Plant Biology, Zollikerstrasse 107, CH-8008 Zurich, Switzerland. markus.klein@botinst.unizh.ch
authors.forename: Markus
authors.initials: M
authors.lastname: Klein
authors.forename: Markus
authors.initials: M
authors.lastname: Geisler
authors.forename: Su Jeoung
authors.initials: SJ
authors.lastname: Suh
authors.forename: H Uner
authors.initials: HU
authors.lastname: Kolukisaoglu
authors.forename: Louis
authors.initials: L
authors.lastname: Azevedo
authors.forename: Sonia
authors.initials: S
authors.lastname: Plaza
authors.forename: Mark D
authors.initials: MD
authors.lastname: Curtis
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
authors.forename: Barbara
authors.initials: B
authors.lastname: Weder
authors.forename: Burkhard
authors.initials: B
authors.lastname: Schulz
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D002245:Carbon Dioxide / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D004190:Disasters; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D017930:Genes, Reporter; D007700:Kinetics; D008027:Light; D008727:Methotrexate / Q000494:pharmacology; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D018526:Plant Transpiration; D021381:Protein Transport; D017154:Stromal Cells
chemical_list: D002245:Carbon Dioxide; D008727:Methotrexate; D027425:ATP-Binding Cassette, Sub-Family C Proteins