Structure and activity of SLAC1 channels for stomatal signaling in leaves.

Proceedings of the National Academy of Sciences of the United States of America 2021 May 04

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Stomata in leaves regulate gas exchange between the plant and its atmosphere. Various environmental stimuli elicit abscisic acid (ABA); ABA leads to phosphoactivation of slow anion channel 1 (SLAC1); SLAC1 activity reduces turgor pressure in aperture-defining guard cells; and stomatal closure ensues. We used electrophysiology for functional characterizations of Arabidopsis thaliana SLAC1 (AtSLAC1) and cryoelectron microscopy (cryo-EM) for structural analysis of Brachypodium distachyon SLAC1 (BdSLAC1), at 2.97-Å resolution. We identified 14 phosphorylation sites in AtSLAC1 and showed nearly 330-fold channel-activity enhancement with 4 to 6 of these phosphorylated. Seven SLAC1-conserved arginines are poised in BdSLAC1 for regulatory interaction with the N-terminal extension. This BdSLAC1 structure has its pores closed, in a basal state, spring loaded by phenylalanyl residues in high-energy conformations. SLAC1 phosphorylation fine-tunes an equilibrium between basal and activated SLAC1 trimers, thereby controlling the degree of stomatal opening.

Citation

Ya-Nan Deng, Hamdy Kashtoh, Quan Wang, Guang-Xiao Zhen, Qi-Yu Li, Ling-Hui Tang, Hai-Long Gao, Chun-Rui Zhang, Li Qin, Min Su, Fei Li, Xia-He Huang, Ying-Chun Wang, Qi Xie, Oliver B Clarke, Wayne A Hendrickson, Yu-Hang Chen. Structure and activity of SLAC1 channels for stomatal signaling in leaves. Proceedings of the National Academy of Sciences of the United States of America. 2021 May 04;118(18)