Salinity causes billion dollar losses in annual crop production. So far, the main avenue in breeding crops for salt tolerance has been to reduce Na(+) uptake and transport from roots to shoots. Recently we have demonstrated that retention of cytosolic K(+) could be considered as another key factor in conferring salt tolerance in plants. A subsequent study has shown that Na(+)-induced K(+) efflux in barley root epidermis occurs primarily via outward rectifying K(+) channels (KORC). Surprisingly, expression of KORC was similar in salt- tolerant and sensitive genotypes. However, the former were able to better oppose Na(+)-induced depolarization via enhanced activity of plasma membrane H(+)-ATPase (thus minimizing K(+) leak from the cytosol). In addition to highly K(+)-selective KORC channels, activities of several types of non-selective cation channels were detected at depolarizing potentials. Here we show that the expression of one of them, NORC, was significantly lower in salt-tolerant genotypes. As NORC is capable of mediating K(+) efflux coupled to Na(+) influx, we suggest that the restriction of its activity could be beneficial for plants under salt stress.
Keywords: K+ homeostasis; KOR; barley; ion flux; non-selective channels; patch-clamp; salinity tolerance.