title: Drought and abscisic acid effects on aquaporin content translate into changes in hydraulic conductivity and leaf growth rate: a trans-scale approach.
abstract: The effects of abscisic acid (ABA) on aquaporin content, root hydraulic conductivity (Lpr), whole plant hydraulic conductance, and leaf growth are controversial. We addressed these effects via a combination of experiments at different scales of plant organization and tested their consistency via a model. We analyzed under moderate water deficit a series of transformed maize (Zea mays) lines, one sense and three antisense, affected in NCED (for 9-cis-epoxycarotenoid dioxygenase) gene expression and that differed in the concentration of ABA in the xylem sap. In roots, the mRNA expression of most aquaporin PIP (for plasma membrane intrinsic protein) genes was increased in sense plants and decreased in antisense plants. The same pattern was observed for the protein contents of four PIPs. This resulted in more than 6-fold differences between lines in Lpr under both hydrostatic and osmotic gradients of water potential. This effect was probably due to differences in aquaporin activity, because it was nearly abolished by a hydrogen peroxide treatment, which blocks the water channel activity of aquaporins. The hydraulic conductance of intact whole plants was affected in the same way when measured either in steady-state conditions or via the rate of recovery of leaf water potential after rewatering. The recoveries of leaf water potential and elongation upon rehydration differed between lines and were accounted for by the experimentally measured Lpr in a model of water transfer. Overall, these results suggest that ABA has long-lasting effects on plant hydraulic properties via aquaporin activity, which contributes to the maintenance of a favorable plant water status.
authors.affiliation: INRA, UMR 759 Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, F-34060 Montpellier, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Parent
authors.forename: Charles
authors.initials: C
authors.lastname: Hachez
authors.forename: Elise
authors.initials: E
authors.lastname: Redondo
authors.forename: Thierry
authors.initials: T
authors.lastname: Simonneau
authors.forename: François
authors.initials: F
authors.lastname: Chaumont
authors.forename: François
authors.initials: F
authors.lastname: Tardieu
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis / Q000494:pharmacology*; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018527:Hydroponics; D008954:Models, Biological; D053147:Plant Exudates / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects* / Q000254:growth & development*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects; D030821:Plants, Genetically Modified; D012987:Soil; D013997:Time Factors; D014170:Transformation, Genetic / Q000187:drug effects; D052584:Xylem / Q000187:drug effects / Q000502:physiology; D003313:Zea mays / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D020346:Aquaporins; D053147:Plant Exudates; D010940:Plant Proteins; D012987:Soil; D000040:Abscisic Acid; D006861:Hydrogen Peroxide