Biology of SLAC1‐type anion channels – from nutrient uptake to stomatal closure. Issue 1 (19th July 2017)

• Record Type: Journal Article
• Authors: Hedrich, Rainer; Geiger, Dietmar
• Is Part Of: New phytologist. Volume 216:Issue 1(2017)
• Page Start: 46
• Page End: 61
• Publication Date: 2017-07-19
• Subjects: abscisic acid (ABA) signalling -- guard cell -- SLAC1 -- stomata -- S‐type anion channel; Botany -- Periodicals; 580
• DOI: 10.1111/nph.14685
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: Stomatal guard cells control leaf CO2 intake and concomitant water loss to the atmosphere. When photosynthetic CO2 assimilation is limited and the ratio of CO2 intake to transpiration becomes suboptimal, guard cells, sensing the rise in CO2 concentration in the substomatal cavity, deflate and the stomata close. Screens for mutants that do not close in response to experimentally imposed high CO2 atmospheres identified the guard cell‐expressed Slowly activating anion channel, SLAC1, as the key player in the regulation of stomatal closure. SLAC1 evolved, though, before the emergence of guard cells. In Arabidopsis, SLAC1 is the founder member of a family of anion channels, which comprises four homologues. SLAC1 and SLAH3 mediate chloride and nitrate transport in guard cells, while SLAH1, SLAH2 and SLAH3 are engaged in root nitrate and chloride acquisition, and anion translocation to the shoot. The signal transduction pathways involved in CO2, water stress and nutrient‐sensing activate SLAC/SLAH via distinct protein kinase/phosphatase pairs. In this review, we discuss the role that SLAC/SLAH channels play in guard cell closure, on the one hand, and in the root–shoot continuum on the other, along with the molecular basis of the channels' anion selectivity and gating. Contents Summary 46 I. Introduction 46 II. SLAC1 evolved before stomata 47 III. Multisensory guard cells integrate abiotic and biotic signals (Fig. 3) 50 IV. Anion channels in shoot and root 53 V. Structural basis for selectivity and gating 56 VI. Future opportunities 57 Accession numbers 58 Acknowledgements 58 References 58