title: The role of plasma membrane aquaporins in regulating the bundle sheath-mesophyll continuum and leaf hydraulics.
abstract: Our understanding of the cellular role of aquaporins (AQPs) in the regulation of whole-plant hydraulics, in general, and extravascular, radial hydraulic conductance in leaves (K(leaf)), in particular, is still fairly limited. We hypothesized that the AQPs of the vascular bundle sheath (BS) cells regulate K(leaf). To examine this hypothesis, AQP genes were silenced using artificial microRNAs that were expressed constitutively or specifically targeted to the BS. MicroRNA sequences were designed to target all five AQP genes from the PLASMA MEMBRANE-INTRINSIC PROTEIN1 (PIP1) subfamily. Our results show that the constitutively silenced PIP1 (35S promoter) plants had decreased PIP1 transcript and protein levels and decreased mesophyll and BS osmotic water permeability (P(f)), mesophyll conductance of CO2, photosynthesis, K(leaf), transpiration, and shoot biomass. Plants in which the PIP1 subfamily was silenced only in the BS (SCARECROW:microRNA plants) exhibited decreased mesophyll and BS Pf and decreased K(leaf) but no decreases in the rest of the parameters listed above, with the net result of increased shoot biomass. We excluded the possibility of SCARECROW promoter activity in the mesophyll. Hence, the fact that SCARECROW:microRNA mesophyll exhibited reduced P(f), but not reduced mesophyll conductance of CO2, suggests that the BS-mesophyll hydraulic continuum acts as a feed-forward control signal. The role of AQPs in the hierarchy of the hydraulic signal pathway controlling leaf water status under normal and limited-water conditions is discussed.
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Nir
authors.initials: N
authors.lastname: Sade
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Arava
authors.initials: A
authors.lastname: Shatil-Cohen
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Ziv
authors.initials: Z
authors.lastname: Attia
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Christophe
authors.initials: C
authors.lastname: Maurel
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Yann
authors.initials: Y
authors.lastname: Boursiac
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Gilor
authors.initials: G
authors.lastname: Kelly
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: David
authors.initials: D
authors.lastname: Granot
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Adi
authors.initials: A
authors.lastname: Yaaran
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.).
authors.forename: Stephen
authors.initials: S
authors.lastname: Lerner
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel (N.S., A.S.-C., Z.A., G.K., A.Y., S.L., M.M.);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 (C.M., Y.B.); andInstitute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel (G.K., D.G.) moshelio@agri.huji.ac.il.
authors.forename: Menachem
authors.initials: M
authors.lastname: Moshelion
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D058503:Mesophyll Cells / Q000378:metabolism; D010539:Permeability; D018515:Plant Leaves / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; C100978:SCR protein, Arabidopsis; C491680:plasma membrane intrinsic protein 2 Arabidopsis