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Horaruang W, Klejchová M, Carroll W, Silva-Alvim FAL, Waghmare S, Papanatsiou M, Amtmann A, Hills A, Alvim JC, Blatt MR, Zhang B. Engineering a K + channel 'sensory antenna' enhances stomatal kinetics, water use efficiency and photosynthesis. NATURE PLANTS 2022; 8:1262-1274. [PMID: 36266492 DOI: 10.1038/s41477-022-01255-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
Stomata of plant leaves open to enable CO2 entry for photosynthesis and close to reduce water loss via transpiration. Compared with photosynthesis, stomata respond slowly to fluctuating light, reducing assimilation and water use efficiency. Efficiency gains are possible without a cost to photosynthesis if stomatal kinetics can be accelerated. Here we show that clustering of the GORK channel, which mediates K+ efflux for stomatal closure in the model plant Arabidopsis, arises from binding between the channel voltage sensors, creating an extended 'sensory antenna' for channel gating. Mutants altered in clustering affect channel gating to facilitate K+ flux, accelerate stomatal movements and reduce water use without a loss in biomass. Our findings identify the mechanism coupling channel clustering with gating, and they demonstrate the potential for engineering of ion channels native to the guard cell to enhance stomatal kinetics and improve water use efficiency without a cost in carbon fixation.
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Affiliation(s)
- Wijitra Horaruang
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
- Faculty of Science and Arts, Burapha University, Chanthaburi Campus, Chanthaburi, Thailand
| | - Martina Klejchová
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - William Carroll
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | | | - Sakharam Waghmare
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Maria Papanatsiou
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Anna Amtmann
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Adrian Hills
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Jonas Chaves Alvim
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK.
| | - Ben Zhang
- School of Life Sciences, Shanxi University, Taiyuan City, China
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Structural and functional approaches to studying cAMP regulation of HCN channels. Biochem Soc Trans 2021; 49:2573-2579. [PMID: 34812892 DOI: 10.1042/bst20210290] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/19/2021] [Accepted: 10/25/2021] [Indexed: 11/17/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are primarily activated by voltage and further modulated by cAMP. While cAMP binding alone does not open the channel, its presence facilitates the action of voltage, increasing channel open probability. Functional results indicate that the membrane-based voltage sensor domain (VSD) communicates with the cytosolic cyclic nucleotide-binding domain (CNBD), and vice-versa. Yet, a mechanistic explanation on how this could occur in structural terms is still lacking. In this review, we will discuss the recent advancement in understanding the molecular mechanisms connecting the VSD with the CNBD in the tetrameric organization of HCN channels unveiled by the 3D structures of HCN1 and HCN4. Data show that the HCN domain transmits cAMP signal to the VSD by bridging the cytosolic to the membrane domains. Furthermore, a metal ion coordination site connects the C-linker to the S4-S5 linker in HCN4, further facilitating cAMP signal transmission to the VSD in this isoform.
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