Inventory and functional characterization of the HAK potassium transporters of rice.
Plants take up large amounts of K(+) from the soil solution and distribute it to the cells of all organs, where it fulfills important physiological functions. Transport of K(+) from the soil solution to its final destination is mediated by channels and transporters. To better understand K(+) movements in plants, we intended to characterize the function of the large KT-HAK-KUP family of transporters in rice (Oryza sativa cv Nipponbare). By searching in databases and cDNA cloning, we have identified 17 genes (OsHAK1-17) encoding transporters of this family and obtained evidence of the existence of other two genes. Phylogenetic analysis of the encoded transporters reveals a great diversity among them, and three distant transporters, OsHAK1, OsHAK7, and OsHAK10, were expressed in yeast (Saccharomyces cerevisiae) and bacterial mutants to determine their functions. The three transporters mediate K(+) influxes or effluxes, depending on the conditions of the experiment. A comparative kinetic analysis of HAK-mediated K(+) influx in yeast and in roots of K(+)-starved rice seedlings demonstrated the involvement of HAK transporters in root K(+) uptake. We discuss that all HAK transporters may mediate K(+) transport, but probably not only in the plasma membrane. Transient expression of the OsHAK10-green fluorescent protein fusion protein in living onion epidermal cells targeted this protein to the tonoplast.
Bañuelos
María A
MA
Departamento de Biotecnología, Universidad Politécnica de Madrid, 28040 Madrid, Spain.
Garciadeblas
Blanca
B
Cubero
Beatriz
B
Rodríguez-Navarro
Alonso
A
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008715:Methionine / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D019697:Onions / Q000166:cytology; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D019441:Plant Epidermis / Q000166:cytology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D018036:Selenium Compounds / Q000302:isolation & purification / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics
D002352:Carrier Proteins; D027682:Cation Transport Proteins; D010940:Plant Proteins; D018036:Selenium Compounds; C470696:selenium-methyl-selenium-methionine; D008715:Methionine; D011188:Potassium