A Cyclic Nucleotide-Gated Channel, HvCNGC2-3, Is Activated by the Co-Presence of Na⁺ and K⁺ and Permeable to Na⁺ and K⁺ Non-Selectively.

PLANTS-BASEL(2018)

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摘要
Cyclic nucleotide-gated channels (CNGCs) have been postulated to contribute significantly in plant development and stress resistance. However, their electrophysiological properties remain poorly understood. Here, we characterized barley CNGC2-3 (HvCNGC2-3) by the two-electrode voltage-clamp technique in the Xenopus laevis oocyte heterologous expression system. Current was not observed in X. laevis oocytes injected with HvCNGC2-3 complementary RNA (cRNA) in a bathing solution containing either Na+ or K+ solely, even in the presence of 8-bromoadenosine 3,5-cyclic monophosphate (8Br-cAMP) or 8-bromoguanosine 3,5-cyclic monophosphate (8Br-cGMP). A weakly voltage-dependent slow hyperpolarization-activated ion current was observed in the co-presence of Na+ and K+ in the bathing solution and in the presence of 10 mu M 8Br-cAMP, but not 8Br-cGMP. Permeability ratios of HvCNGC2-3 to K+, Na+ and Cl- were determined as 1:0.63:0.03 according to reversal-potential analyses. Amino-acid replacement of the unique ion-selective motif of HvCNGC2-3, AQGL, with the canonical motif, GQGL, resulted in the abolition of the current. This study reports a unique two-ion-dependent activation characteristic of the barley CNGC, HvCNGC2-3.
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关键词
cyclic nucleotide-gated channel,barley,sodium,potassium,roots
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