title: Rice shaker potassium channel OsKAT1 confers tolerance to salinity stress on yeast and rice cells.
abstract: 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 (Deltaena1-4), which lacks a major component of Na(+) efflux. It also suppressed a K(+)-transport-defective phenotype of yeast strain CY162 (Deltatrk1Deltatrk2), 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(+).
authors.affiliation: Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Obata
authors.forename: Hiroko K
authors.initials: HK
authors.lastname: Kitamoto
authors.forename: Atsuko
authors.initials: A
authors.lastname: Nakamura
authors.forename: Atsunori
authors.initials: A
authors.lastname: Fukuda
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D000468:Alkalies / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D002412:Cations / Q000378:metabolism; D002460:Cell Line; D015870:Gene Expression; D005816:Genetic Complementation Test; D006706:Homeostasis / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D051637:Shaker Superfamily of Potassium Channels / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*
chemical_list: D000468:Alkalies; D002412:Cations; D051637:Shaker Superfamily of Potassium Channels; D012965:Sodium Chloride; D012964:Sodium; D011188:Potassium