Na+ Sensitivity of the KAT2-Like Channel Is a Common Feature of Cucurbits and Depends on the S5-P-S6 Segment. (1st December 2021)

• Record Type: Journal Article
• Authors: Wang, Li-Min; Zhao, Li-Na; Shah, Iftikhar Hussain; Ramirez, Dora Cano; Boeglin, Martin; Véry, Anne-Aliénor; Sentenac, Hervé; Zhang, Yi-Dong
• Is Part Of: Plant & cell physiology. Volume 63:Number 2(2022)
• Page Start: 279
• Page End: 289
• Publication Date: 2021-12-01
• Subjects: Chimera channel -- Cucurbitaceae -- Electrophysiology -- Inhibition by Na+ -- KAT2-like channels -- Structure-function analysis; Plant physiology -- Periodicals; Microbiology -- Periodicals; Cytology -- Periodicals; Cell Physiology -- Periodicals; Plant Physiological Phenomena -- Periodicals; Cytology; Microbiology; Plant physiology; Periodicals; 571.205
• DOI: 10.1093/pcp/pcab170
• Languages: English
• ISSNs: 0032-0781

Abstract

Abstract: Inhibition of Shaker K + channel activity by external Na + was previously reported in the melon ( Cucumis melo L.) inwardly rectifying K + channel MIRK and was hypothesized to contribute to salt tolerance. In this study, two inward Shaker K + channels, CsKAT2 from cucumber ( Cucumis sativus ) and ClKAT2 from watermelon ( Citrullus lanatus ), were identified and characterized in Xenopus oocytes. Both channels were inwardly rectifying K + channels with higher permeability to potassium than other monovalent cations and more active when external pH was acidic. Similarly to MIRK, their activity displayed an inhibition by external Na +, thus suggesting a common feature in Cucurbitaceae ( Cucumis spp., Citrullus spp.). CsKAT2 and ClKAT2 are highly expressed in guard cells. After 24 h of plant treatment with 100 mM NaCl, the three KAT2 -like genes were significantly downregulated in leaves and guard cells. Reciprocal chimeras were obtained between MIRK and Na + -insensitive AtKAT2 cDNAs. The chimera where the MIRK S5-P-S6 segment was replaced by that from AtKAT2 no longer showed Na + sensitivity, while the inverse chimera gained Na + sensitivity. These results provide evidence that the molecular basis of the channel blockage by Na + is located in the S5-P-S6 region. Comparison of the electrostatic property in the S5-P-S6 region in AtKAT2 and MIRK revealed four key amino acid residues potentially governing Na + sensitivity.