Ion channels of intact young root hairs from Medicago sativa

Ion currents involved in early Nod factor response in Medicago sativa root hairs: a discontinuous single‐electrode voltage‐clamp study

“…However, during Nod-factor-induced depolarization, the IRKC could allow a K + ef¯ux for potential values positive to E K (Bouteau et al, 1999), as recently described for KAT1 currents (Bru È ggemann et al, 1999). This K + ef¯ux through IRKC channels is here in accordance with the delayed K + ef¯ux recorded with K + -selective microelectrodes (Felle et al, 1998), as they showed that external K + concentration starts to increase at the exact time that the depolarization passes E K , i.e.…”

“…Furthermore, the measurements of Felle et al (1998) were performed in the volume located between root hairs; for this reason, they concern several root hairs which did not necessarily display the same pattern of IRKC, according to our previous observations (Bouteau et al, 1999).…”

“…A previous electrophysiological and pharmacological study (Bouteau et al, 1999) identi®ed several ion channel currents in the plasma membrane of Medicago root hairs in situ: a K + inward-rectifying time-dependent current (IRKC) (also functioning as a K + ef¯ux pathway which disappears towards positive potential values); an outwardrectifying time-dependent K + current (ORKC) allowing K + ef¯ux under strong depolarizations and an instantaneous inward anion current (IIAC). In spite of the care taken to choose uniform root hairs in terms of size and morphology, several different electrical signatures were routinely recorded.…”

“…A pharmacological study using inhibitors, which are rarely speci®c for only one transport system, appeared to be of limited use to discriminate these currents which constitute variable amounts of the total current. Thus, we initially classi®ed the nature of the current displayed by each root hair using as major criteria the current kinetics and the threshold for voltage activation (near to E K or E A± , respectively, equilibrium potential for K + and anions, see Bouteau et al, 1999). To assess the role of IIAC and IRKC, we choose to work on root hairs showing predominantly one of these currents to investigate the action of Nod factor on these ion channel currents.…”

“…However, the nature of the ion channel currents underlying the dynamic functioning of the ion exchange systems has not yet been adequately studied. To address this question, we used a discontinuous single-electrode voltage-clamp technique for an in situ investigation (Bouteau et al, 1999). In this paper, we provide evidence that anion and potassium channel currents together with H + pump currents are at the origin of the electrical response induced by Nod factor.…”