Control of vacuolar dynamics and regulation of stomatal aperture by tonoplast potassium uptake

Zaida Andrés... [et al].-- 10 páginas.-- 8 figuras.-- 54 referencias.-- En Información suplementaria: 9 páginas.- 9S figuras.-- 1S tabla.-- http://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1320421111/-/DCSupplemental .-- En el archivo de acceso abierto de este Item aparecen juntos el texto y archivo suplementario.Stomatal movements rely on alterations in guard cell turgor. This requires massive K+ bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K+ into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells, the tonoplast-localized K+/H+ exchangers NHX1 and NHX2 are pivotal in the vacuolar accumulation of K+ and that nhx1 nhx2 mutant lines are dysfunctional in stomatal regulation. Hypomorphic and complete-loss-of-function double mutants exhibited significantly impaired stomatal opening and closure responses. Disruption of K+ accumulation in guard cells correlated with more acidic vacuoles and the disappearance of the highly dynamic remodelling of vacuolar structure associated with stomatal movements. Our results show that guard cell vacuolar accumulation of K+ is a requirement for stomatal opening and a critical component in the overall K+ homeostasis essential for stomatal closure, and suggest that vacuolar K+ fluxes are also of decisive importance in the regulation of vacuolar dynamics and luminal pH that underlie stomatal movements.This work was supported by Ministerio de Economia y Competitividad Grants BIO2009-08641 and BFU2012-35060, cofinanced by the European Regional Development Fund (to J.M.P.); Deutsche Forschungsgemeinschaft Grants Ku931/7-1 (to J.K.), SFB629 (to J.K.), FOR964 (to J.K.), and FOR1061 (to K.S.); Biotechnology and Biological Sciences Research Council of the United Kingdom (A.M.H.); and Junta de Ampliacion de Estudios Fellowship Program of Consejo Superior de Investigaciones Cientificas (to Z.A.).Peer reviewe

Control of vacuolar dynamics and regulation of stomatal aperture by tonoplast potassium uptake

Stomatal movements rely on alterations in guard cell turgor. This requires massive K(+) bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K(+) into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells, the tonoplast-localized K(+)/H(+) exchangers NHX1 and NHX2 are pivotal in the vacuolar accumulation of K(+) and that nhx1 nhx2 mutant lines are dysfunctional in stomatal regulation. Hypomorphic and complete-loss-of-function double mutants exhibited significantly impaired stomatal opening and closure responses. Disruption of K(+) accumulation in guard cells correlated with more acidic vacuoles and the disappearance of the highly dynamic remodelling of vacuolar structure associated with stomatal movements. Our results show that guard cell vacuolar accumulation of K(+) is a requirement for stomatal opening and a critical component in the overall K(+) homeostasis essential for stomatal closure, and suggest that vacuolar K(+) fluxes are also of decisive importance in the regulation of vacuolar dynamics and luminal pH that underlie stomatal movements