title: Rice OsHKT2;1 transporter mediates large Na+ influx component into K+-starved roots for growth.
abstract: Excessive accumulation of sodium in plants causes toxicity. No mutation that greatly diminishes sodium (Na+) influx into plant roots has been isolated. The OsHKT2;1 (previously named OsHKT1) transporter from rice functions as a relatively Na+-selective transporter in heterologous expression systems, but the in vivo function of OsHKT2;1 remains unknown. Here, we analyzed transposon-insertion rice lines disrupted in OsHKT2;1. Interestingly, three independent oshkt2;1-null alleles exhibited significantly reduced growth compared with wild-type plants under low Na+ and K+ starvation conditions. The mutant alleles accumulated less Na+, but not less K+, in roots and shoots. OsHKT2;1 was mainly expressed in the cortex and endodermis of roots. (22)Na+ tracer influx experiments revealed that Na+ influx into oshkt2;1-null roots was dramatically reduced compared with wild-type plants. A rapid repression of OsHKT2;1-mediated Na+ influx and mRNA reduction were found when wild-type plants were exposed to 30 mM NaCl. These analyses demonstrate that Na+ can enhance growth of rice under K+ starvation conditions, and that OsHKT2;1 is the central transporter for nutritional Na+ uptake into K+-starved rice roots.
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, and Center for Molecular Genetics, University of California-San Diego, 9500 Gilman Street, La Jolla, CA 92093, USA.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Horie
authors.forename: Alex
authors.initials: A
authors.lastname: Costa
authors.forename: Tae Houn
authors.initials: TH
authors.lastname: Kim
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Han
authors.forename: Rie
authors.initials: R
authors.lastname: Horie
authors.forename: Ho-Yin
authors.initials: HY
authors.lastname: Leung
authors.forename: Akio
authors.initials: A
authors.lastname: Miyao
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Hirochika
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
authors.forename: Julian I
authors.initials: JI
authors.lastname: Schroeder
mesh_terms: D027682:Cation Transport Proteins / Q000378:metabolism*; D017136:Ion Transport; D012275:Oryza / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; C434985:HKT2 protein, Oryza sativa; D010940:Plant Proteins; D012964:Sodium; D011188:Potassium