title: A vesicle-trafficking protein commandeers Kv channel voltage sensors for voltage-dependent secretion.
abstract: Growth in plants depends on ion transport for osmotic solute uptake and secretory membrane trafficking to deliver material for wall remodelling and cell expansion. The coordination of these processes lies at the heart of the question, unresolved for more than a century, of how plants regulate cell volume and turgor. Here we report that the SNARE protein SYP121 (SYR1/PEN1), which mediates vesicle fusion at the Arabidopsis plasma membrane, binds the voltage sensor domains (VSDs) of K(+) channels to confer a voltage dependence on secretory traffic in parallel with K(+) uptake. VSD binding enhances secretion in vivo subject to voltage, and mutations affecting VSD conformation alter binding and secretion in parallel with channel gating, net K(+) concentration, osmotic content and growth. These results demonstrate a new and unexpected mechanism for secretory control, in which a subset of plant SNAREs commandeer K(+) channel VSDs to coordinate membrane trafficking with K(+) uptake for growth.
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Christopher
authors.identifier: http://orcid.org/0000-0002-5820-4466
authors.initials: C
authors.lastname: Grefen
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Rucha
authors.initials: R
authors.lastname: Karnik
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Emily
authors.initials: E
authors.lastname: Larson
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Cécile
authors.initials: C
authors.lastname: Lefoulon
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Sakharam
authors.initials: S
authors.lastname: Waghmare
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Adrian
authors.initials: A
authors.lastname: Hills
authors.affiliation: Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Blatt