The cyclic nucleotide-gated channel AtCNGC10 transports Ca²⁺and Mg²⁺in<i>Arabidopsis</i>

The suppression of the cyclic nucleotide-gated channel (CNGC) AtCNGC10 alters K(+) transport in Arabidopsis plants. Other CNGCs have been shown to transport Ca(2+), K(+), Li(+), Cs(+) and Rb(+) across the plasma membrane when expressed in heterologous systems; however, the ability of the AtCNGC10 channel to transport nutrients other than K(+) in plants has not been previously tested. The ion fluxes along different zones of the seedling roots, as estimated by the non-invasive ion-specific microelectrode technique, were significantly different in two AtCNGC10 antisense lines (A2 and A3) in comparison to the wild type (WT). Most notably, the influxes of H(+), Ca(2+) and Mg(2+) in the meristem and distal elongation zones of the antisense A2 and A3 lines were significantly lower than in the WT. The lower Ca(2+) influx from the external media corresponded to a lower intracellular Ca(2+) activity, which was estimated by fluorescence lifetime imaging measurements (FLIM). On the other hand, the intracellular pH values in the meristem zone of the roots of A2 and A3 seedlings were significantly lower (more acidic) than that of the WT, which might indicate a feedback block of H(+) influx into meristematic cells caused by low intracellular pH. Under the control conditions, mature plants from the A2 and A3 lines contained significantly higher K(+) and lower Ca(2+) and Mg(2+) content in the shoots, indicating disturbed long-distance ion transport of these cations, possibly because of changes in xylem loading/retrieval and/or phloem loading. Exposing the plants in the flowering stage to various K(+), Ca(2+) and Mg(2+) concentrations in the solution led to altered K(+), Ca(2+) and Mg(2+) content in the shoots of A2 and A3 plants in comparison with the WT, suggesting a primary role of AtCNGC10 in Ca(2+) (and probably Mg(2+)) transport in plants, which in turn regulates K(+) transporters' activities.