Ion currents involved in early Nod factor response in Medicago sativa root hairs: a discontinuous single-electrode voltage-clamp study.
Nod factor [NodRm-IV(Ac,S)], isolated from the bacterium Rhizobium meliloti, induces a well-known depolarization in Medicago sativa (cv Sitel) root hairs. Analysis of this membrane response using the discontinuous single-electrode voltage-clamp technique (dSEVC) shows that anion channel, K+ channel and H+-ATPase pump currents are involved in young growing root hairs. The early Nod-factor-induced depolarization is due to increase of the inward ion current and inhibition of the H+ pump. It involved an instantaneous inward anion current (IIAC) and/or a time-dependent inward K+ current (IRKC). These two ion currents are then down-regulated while the H+ pump is stimulated, allowing long-term rectification of the membrane potential (Em). Our results support the idea that the regulation of inward current plays a primary role in the Nod-factor-induced electrical response, the nature of the ions carried by these currents depending on the activated anion and/or K+ channels at the plasma membrane.
Kurkdjian
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A
Institut des Sciences Végétales, Centre National de la Recherche Scientifique, Bât 22, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France. armen@isv.cnrs-gif.fr
Bouteau
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F
Pennarun
A M
AM
Convert
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M
Cornel
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D
Rona
J P
JP
Bousquet
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U
D020013:Calcium Signaling / Q000187:drug effects; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism*; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D000455:Medicago sativa / Q000187:drug effects* / Q000378:metabolism* / Q000382:microbiology; D008564:Membrane Potentials / Q000187:drug effects; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D017494:Proton Pumps / Q000187:drug effects / Q000378:metabolism; D016962:Sinorhizobium meliloti / Q000378:metabolism
D007473:Ion Channels; D008070:Lipopolysaccharides; C092082:Nod factor IV, Rhizobium meliloti; D015221:Potassium Channels; D017494:Proton Pumps