Biochemistry

Abstract

CS-21-6 - Identification of SLAC1 anion channel residues that function in CO2 signaling in Arabidopsis guard cells

Tuesday, July 17
10:13 AM - 10:15 AM

Plants control CO2 exchange and water loss to the atmosphere in response to endogenous and environmental stimuli via stomatal pores. Atmospheric [CO2] elevation triggers stomatal closure by Cl- efflux mediated via S-type anion channels in the guard cell plasma membrane encoded by the SLAC1 gene. Previous research suggested that bicarbonate (HCO3-) can directly up-regulate reconstituted SLAC1 channel activity and that the transmembrane domain of SLAC1 is involved in the stomatal CO2/HCO3- response. The mechanism by which HCO3- regulates the SLAC1 anion channel activity and whether this regulation is relevant in planta is unknown. Here, we computationally seek to predict candidate bicarbonate binding sites within the SLAC1 anion channel through long-timescale Gaussian accelerated molecular dynamics (GaMD) simulations. Mutations of two putative HCO3- -interacting residues abolished the enhancement of the SLAC1 anion channel activity by CO2/HCO3-, while SLAC1 activation by other stimuli remained intact. Furthermore, gas exchange experiments with complemented slac1 mutant plants expressing mutated SLAC1 proteins revealed that one of these SLAC1 residues is required for the stomatal CO2 response, but not the ABA response, in planta. Patch clamp analyses of guard cells showed that activation of the S-type anion channel activity by CO2/HCO3- was impaired, while ABA activation was intact, further showing a role of this SLAC1 site for CO2 signaling. This study indicates that SLAC1 not only mediates anion efflux from guard cells, but also suggests that SLAC1 could contribute to biologically relevant CO2/HCO3- sensing. Results from this study provide important insights into how plants respond to daily Ci changes and the continuing atmospheric rise in [CO2].


 

Co-Authors

Nuo Wang – University of California, San Diego; Yinglong Miao – University of Kansas, Lawrence; Felix Hauser – University of California, San Diego; Wouter-Jan Rappel – University of California, San Diego; J. McCammon – University of California, San Diego; Julian Schroeder – University of California, San Diego

Jingbo Zhang

postdoctoral researcher
University of California, San Diego

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CS-21-6 - Identification of SLAC1 anion channel residues that function in CO2 signaling in Arabidopsis guard cells



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