Rice shaker potassium channel OsKAT1 confers tolerance to salinity stress on yeast and rice cells.

We screened a rice ( Oryza sativa L. ‘Nipponbare’) full-length cDNA expression library through functional complementation in yeast ( Saccharomyces cerevisiae ) to find novel cation transporters involved in salt tolerance. We found that expression of a cDNA clone, encoding the rice homolog of Shaker family K + channel KAT1 (OsKAT1), suppressed the salt-sensitive phenotype of yeast strain G19 ( Δena1–4 ), which lacks a major component of Na + efflux. It also suppressed a K + -transport-defective phenotype of yeast strain CY162 ( Δtrk1Δtrk2 ), suggesting the enhancement of K + uptake by OsKAT1. By the expression of OsKAT1 , the K + contents of salt-stressed G19 cells increased during the exponential growth phase. At the linear phase, however, OsKAT1 -expressing G19 cells accumulated less Na + than nonexpressing cells, but almost the same K + . The cellular Na + to K + ratio of OsKAT1 -expressing G19 cells remained lower than nonexpressing cells under saline conditions. Rice cells overexpressing OsKAT1 also showed enhanced salt tolerance and increased cellular K + content. These functions of OsKAT1 are likely to be common among Shaker K + channels because OsAKT1 and Arabidopsis ( Arabidopsis thaliana ) KAT1 were able to complement the salt-sensitive phenotype of G19 as well as OsKAT1. The expression of OsKAT1 was restricted to internodes and rachides of wild-type rice, whereas other Shaker family genes were expressed in various organs. These results suggest that OsKAT1 is involved in salt tolerance of rice in cooperation with other K + channels by participating in maintenance of cytosolic cation homeostasis during salt stress and thus protects cells from Na + .