title: The grapevine tonoplast aquaporin TIP2;1 is a pressure gated water channel.
abstract: In plants, the vacuole is a multifunctional organelle with an important role in the maintenance of the intracellular space. Tonoplast membranes are highly permeable to water due to their content in aquaporins TIPs (Tonoplast Intrinsic Proteins) that allow the rapid water influx creating an internal turgor pressure responsible for cell expansion, elongation and shape. The aim of the present study was to evaluate if the grapevine Vitis vinifera TIP2;1 would operate as a possible volume regulator gated by membrane surface tension. For that, the wild type VvTIP2;1 and a non-functional mutated form were heterologous expressed in yeast. Using an experimental strategy in which cells are incubated in external media that induce an increase in internal hydrostatic pressure and consequently membrane surface tension, we were able to compare the osmotic permeability (Pf) and the activation energy for water transport (Ea) of yeast strains expressing the functional and a non-functional TIP2;1. We found Pf and Ea dependence on internal turgor pressure only for the strain harboring the functional aquaporin indicating that TIP2;1 activity is regulated by membrane tension changing from an open to a closed state in an internal pressure dependent manner. This turgor dependent gating of TIP2;1 might be a mechanism to regulate vacuolar size and shape in plants withstanding hostile drought conditions such as grapevine.
authors.affiliation: CBAA, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal; Institut d'Ecologie et des Sciences de l'Environnement (iEES Paris), UMR 7618, département SOLéO, équipe IPE, Université Paris Est Créteil, 61, Avenue du Général De Gaulle, 94010 Créteil cedex, France.
authors.forename: Luís
authors.initials: L
authors.lastname: Leitão
authors.affiliation: CBAA, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Prista
authors.affiliation: CBAA, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Loureiro-Dias
authors.affiliation: Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, 1649-003 Lisboa, Portugal; Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal.
authors.forename: Teresa F
authors.initials: TF
authors.lastname: Moura
authors.affiliation: Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, 1649-003 Lisboa, Portugal; Dep. Bioquímica e Biologia Humana, Faculdade de Farmácia, Universidade de Lisboa, 1649-003 Lisboa, Portugal. Electronic address: gsoveral@ff.ul.pt.
authors.forename: Graça
authors.initials: G
authors.lastname: Soveral
mesh_terms: D020346:Aquaporins / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008560:Membrane Fluidity / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D064587:Osmoregulation / Q000502:physiology*; D009997:Osmotic Pressure / Q000502:physiology; D010940:Plant Proteins / Q000502:physiology*; D011312:Pressure; D013718:Tensile Strength; D027843:Vitis / Q000502:physiology*; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D008565:Membrane Proteins; D010940:Plant Proteins; C077491:tonoplast intrinsic protein, plant; D014867:Water
keywords: Membrane tension; Tonoplast aquaporin; Turgor; Vitis vinifera; Water permeability; Yeast