Rice OsHKT2;1 transporter mediates large Na+ influx component into K+-starved roots for growth.
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.
Horie
Tomoaki
T
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.
Costa
Alex
A
Kim
Tae Houn
TH
Han
Min Jung
MJ
Horie
Rie
R
Leung
Ho-Yin
HY
Miyao
Akio
A
Hirochika
Hirohiko
H
An
Gynheung
G
Schroeder
Julian I
JI
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*
D027682:Cation Transport Proteins; C434985:HKT2 protein, Oryza sativa; D010940:Plant Proteins; D012964:Sodium; D011188:Potassium