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  • Published Article: Identification of SLAC1 anion channel residues required for CO 2 /bicarbonate sensing and regulation of stomatal movements
Title: Identification of SLAC1 anion channel residues required for CO 2 /bicarbonate sensing and regulation of stomatal movements

Increases in CO2concentration in plant leaves due to respiration in the dark and the continuing atmospheric [CO2] rise cause closing of stomatal pores, thus affecting plant–water relations globally. However, the underlying CO2/bicarbonate (CO2/HCO3−) sensing mechanisms remain unknown. [CO2] elevation in leaves triggers stomatal closure by anion efflux mediated via the SLAC1 anion channel localized in the plasma membrane of guard cells. Previous reconstitution analysis has suggested that intracellular bicarbonate ions might directly up-regulate SLAC1 channel activity. However, whether such a CO2/HCO3−regulation of SLAC1 is relevant for CO2control of stomatal movements in planta remains unknown. Here, we computationally probe for candidate bicarbonate-interacting sites within the SLAC1 anion channel via long-timescale Gaussian accelerated molecular dynamics (GaMD) simulations. Mutations of two putative bicarbonate-interacting residues, R256 and R321, impaired the enhancement of the SLAC1 anion channel activity by CO2/HCO3−inXenopusoocytes. Mutations of the neighboring charged amino acid K255 and residue R432 and the predicted gate residue F450 did not affect HCO3−regulation of SLAC1. Notably, gas-exchange experiments withslac1-transformed plants expressing mutated SLAC1 proteins revealed that the SLAC1 residue R256 is required for CO2regulation of stomatal movements in planta, but not for abscisic acid (ABA)-induced stomatal closing. Patch clamp analyses of guard cells show that activation of more » S-type anion channels by CO2/HCO3−, but not by ABA, was impaired, indicating the relevance of R256 for CO2signal transduction. Together, these analyses suggest that the SLAC1 anion channel is one of the physiologically relevant CO2/HCO3−sensors in guard cells.

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Authors:
; ; ; ; ; ;
Publication Date:
NSF-PAR ID:
10077074
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
115
Issue:
44
Page Range or eLocation-ID:
p. 11129-11137
ISSN:
0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Sponsoring Org:
National Science Foundation
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