Os06g0701600

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Annotated Information

Function

The family of plant membrane transporters named HKT (for high-affinity K+ transporters) can be subdivided into subfamilies 1 and 2, which, respectively, comprise Na+-selective transporters and transporters able to function as Na+-K+ symporters, at least when expressed in yeast (Saccharomyces cerevisiae) or Xenopus oocytes. Surprisingly, a subfamily 2 member from rice (Oryza sativa), OsHKT2;4, has been proposed to form cation/K+ channels or transporters permeable to Ca2+ when expressed in Xenopus oocytes. Here, OsHKT2;4 functional properties were reassessed in Xenopus oocytes. A Ca2+ permeability through OsHKT2;4 was not detected, even at very low external K+ concentration, as shown by highly negative OsHKT2;4 zero-current potential in high Ca2+ conditions and lack of sensitivity of OsHKT2;4 zero-current potential and conductance to external Ca2+. The Ca2+ permeability previously attributed to OsHKT2;4 probably resulted from activation of an endogenous oocyte conductance. OsHKT2;4 displayed a high permeability to K+ compared with that to Na+ (permeability sequence: K+ > Rb+ ≈ Cs+ > Na+ ≈ Li+ ≈ NH4+). Examination of OsHKT2;4 current sensitivity to external pH suggested that H+ is not significantly permeant through OsHKT2;4 in most physiological ionic conditions. Further analyses in media containing both Na+ and K+ indicated that OsHKT2;4 functions as K+-selective transporter at low external Na+, but transports also Na+ at high (>10 mm) Na+ concentrations. These data identify OsHKT2;4 as a new functional type in the K+ and Na+-permeable HKT transporter subfamily. Furthermore, the high permeability to K+ in OsHKT2;4 supports the hypothesis that this system is dedicated to K+ transport in the plant.

Expression

This gene is expressed in several cell types, including root hairs and vascular parenchyma cells.

Evolution

This gene is conserved in Arabidopsis

Labs working on this gene

Southwest University 
Henan University 
Zhejiang University 
Chinese Academy of Forestry 
Fujian Agriculture and Forestry University 
Shanghai Jiaotong University 
Lanzhou University

References

1. Ali Sassi;Delphine Mieulet;Imran Khan;Bertrand Moreau;Isabelle Gaillard;Hervé Sentenac;Anne-Aliénor Véry

 The Rice Monovalent Cation Transporter OsHKT2;4: Revisited Ionic Selectivity
 Plant Physiology, 2012, 160(1): 498-510

2. Wen-Zhi Lan;Wei Wang;Suo-Min Wang;Le-Gong Li;Bob B. Buchanan;Hong-Xuan Lin;Ji-Ping Gao;Sheng Luan

 A rice high-affinity potassium transporter (HKT) conceals a calcium-permeable cation channel
 Proceedings of the National Academy of Sciences, 2010, 107(15): 7089-7094