title: Potassium transport in developing fleshy fruits: the grapevine inward K(+) channel VvK1.2 is activated by CIPK-CBL complexes and induced in ripening berry flesh cells.
abstract: The grape berry provides a model for investigating the physiology of non-climacteric fruits. Increased K(+) accumulation in the berry has a strong negative impact on fruit acidity (and quality). In maturing berries, we identified a K(+) channel from the Shaker family, VvK1.2, and two CBL-interacting protein kinase (CIPK)/calcineurin B-like calcium sensor (CBL) pairs, VvCIPK04-VvCBL01 and VvCIPK03-VvCBL02, that may control the activity of this channel. VvCBL01 and VvCIPK04 are homologues of Arabidopsis AtCBL1 and AtCIPK23, respectively, which form a complex that controls the activity of the Shaker K(+) channel AKT1 in Arabidopsis roots. VvK1.2 remained electrically silent when expressed alone in Xenopus oocytes, but gave rise to K(+) currents when co-expressed with the pairs VvCIPK03-VvCBL02 or VvCIPK04-VvCBL01, the second pair inducing much larger currents than the first one. Other tested CIPK-CBL pairs expressed in maturing berries were found to be unable to activate VvK1.2. When activated by its CIPK-CBL partners, VvK1.2 acts as a voltage-gated inwardly rectifying K(+) channel that is activated at voltages more negative than -100 mV and is stimulated upon external acidification. This channel is specifically expressed in the berry, where it displays a very strong induction at veraison (the inception of ripening) in flesh cells, phloem tissues and perivascular cells surrounding vascular bundles. Its expression in these tissues is further greatly increased upon mild drought stress. VvK1.2 is thus likely to mediate rapid K(+) transport in the berry and to contribute to the extensive re-organization of the translocation pathways and transport mechanisms that occurs at veraison.
authors.affiliation: UMR1083, Sciences pour l'Oenologie, Institut National de la Recherche Agronomique, 2 Place Viala, F-34060, Montpellier Cedex 1, France.
authors.forename: Teresa
authors.initials: T
authors.lastname: Cuéllar
authors.forename: Farrukh
authors.initials: F
authors.lastname: Azeem
authors.forename: Mamy
authors.initials: M
authors.lastname: Andrianteranagna
authors.forename: François
authors.initials: F
authors.lastname: Pascaud
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Verdeil
authors.forename: Hervé
authors.initials: H
authors.lastname: Sentenac
authors.forename: Sabine
authors.initials: S
authors.lastname: Zimmermann
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gaillard
mesh_terms: D000818:Animals; D029681:Arabidopsis Proteins / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000235:genetics; D003001:Cloning, Molecular; D055864:Droughts; D005260:Female; D005638:Fruit / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017136:Ion Transport; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D051637:Shaker Superfamily of Potassium Channels / Q000378:metabolism; D027843:Vitis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D010940:Plant Proteins; D024661:Potassium Channels, Inwardly Rectifying; D051637:Shaker Superfamily of Potassium Channels; C483419:calcineurin B-like protein 1, Arabidopsis; C514581:CIPK23 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D011188:Potassium