Sodium transport and HKT transporters:: the rice model

被引:300
作者
Garciadeblás, B [1 ]
Senn, ME [1 ]
Bañuelos, MA [1 ]
Rodríguez-Navarro, A [1 ]
机构
[1] Univ Politecn Madrid, Escuela Tecn Super Ingn Agron, Dept Biotecnol, E-28040 Madrid, Spain
关键词
rice; HKT transporters; sodium; potassium;
D O I
10.1046/j.1365-313X.2003.01764.x
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
Na+ uptake in the roots of K+ -starved seedlings of barley, rice, and wheat was found to exhibit fast rate, low K (m) , and high sensitivity to K+ . Sunflower plants responded in a similar manner but the uptake was not K+ sensitive. Ba2+ inhibited Na+ uptake, but not K+ uptake in rice roots. This demonstrated that Na+ and K+ uptake are mediated by different transporters, and that K+ blocked but was not transported by the Na+ transporter. The genome of rice cv. Nipponbare contains seven HKT genes, which may encode Na+ transporters, plus two HKT pseudogenes. Yeast expressions of OsHKT1 and OsHKT4 proved that they are Na+ transporters of high and low affinity, respectively, which are sensitive to K+ and Ba2+ . Parallel experiments of K+ and Na+ uptake in yeast expressing the wheat or rice HKT1 transporters proved that they were very different; TaHKT1 transported K+ and Na+ , and OsHKT1 only Na+ . Transcript expressions in shoots of the OsHKT genes were fairly constant and insensitive to changes in the K+ and Na+ concentrations of the nutrient solution. In roots, the expressions were much lower than in shoots, except for OsHKT4 and OsHKT1 in K+ -starved plants. We propose that OsHKT transporters are involved in Na+ movements in rice, and that OsHKT1 specifically mediates Na+ uptake in rice roots when the plants are K+ deficient. The incidence of HKT ESTs in several plant species suggests that the rice model with many HKT genes applies to other plants.
引用
收藏
页码:788 / 801
页数:14
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