title: Regulation of Arabidopsis leaf hydraulics involves light-dependent phosphorylation of aquaporins in veins.
abstract: The water status of plant leaves depends on the efficiency of the water supply, from the vasculature to inner tissues. This process is under hormonal and environmental regulation and involves aquaporin water channels. In Arabidopsis thaliana, the rosette hydraulic conductivity (Kros) is higher in darkness than it is during the day. Knockout plants showed that three plasma membrane intrinsic proteins (PIPs) sharing expression in veins (PIP1;2, PIP2;1, and PIP2;6) contribute to rosette water transport, and PIP2;1 can fully account for Kros responsiveness to darkness. Directed expression of PIP2;1 in veins of a pip2;1 mutant was sufficient to restore Kros. In addition, a positive correlation, in both wild-type and PIP2;1-overexpressing plants, was found between Kros and the osmotic water permeability of protoplasts from the veins but not from the mesophyll. Thus, living cells in veins form a major hydraulic resistance in leaves. Quantitative proteomic analyses showed that light-dependent regulation of Kros is linked to diphosphorylation of PIP2;1 at Ser-280 and Ser-283. Expression in pip2;1 of phosphomimetic and phosphorylation-deficient forms of PIP2;1 demonstrated that phosphorylation at these two sites is necessary for Kros enhancement under darkness. These findings establish how regulation of a single aquaporin isoform in leaf veins critically determines leaf hydraulics.
authors.affiliation: Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004, Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386, Institut National de la Recherche Agronomique/Montpellier SupAgro/Université Montpellier II, F-34060 Montpellier, cedex 2, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Prado
authors.forename: Yann
authors.initials: Y
authors.lastname: Boursiac
authors.forename: Colette
authors.initials: C
authors.lastname: Tournaire-Roux
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Monneuse
authors.forename: Olivier
authors.initials: O
authors.lastname: Postaire
authors.forename: Olivier
authors.initials: O
authors.lastname: Da Ines
authors.forename: Anton R
authors.initials: AR
authors.lastname: Schäffner
authors.forename: Sonia
authors.initials: S
authors.lastname: Hem
authors.forename: Véronique
authors.initials: V
authors.lastname: Santoni
authors.forename: Christophe
authors.initials: C
authors.lastname: Maurel
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D003624:Darkness; D018506:Gene Expression Regulation, Plant; D008027:Light; D058503:Mesophyll Cells / Q000378:metabolism; D009995:Osmosis; D010766:Phosphorylation; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018526:Plant Transpiration; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; D020033:Protein Isoforms; C491680:plasma membrane intrinsic protein 2 Arabidopsis; D014867:Water