title: Rice P1B-type heavy-metal ATPase, OsHMA9, is a metal efflux protein.
abstract: P(1B)-type heavy-metal ATPases (HMAs) are transmembrane metal-transporting proteins that play a key role in metal homeostasis. Despite their importance, very little is known about their functions in monocot species. We report the characterization of rice (Oryza sativa) OsHMA9, a member of the P(1B)-type ATPase family. Semiquantitative reverse transcription-polymerase chain reaction analyses of seedlings showed that OsHMA9 expression was induced by a high concentration of copper (Cu), zinc (Zn), and cadmium. We also determined, through promoterbeta-glucuronidase analysis, that the main expression was in the vascular bundles and anthers. The OsHMA9:green fluorescence protein fusion was localized to the plasma membrane. Heterologous expression of OsHMA9 partially rescued the Cu sensitivity of the Escherichia coli copA mutant, which is defective in Cu-transporting ATPases. It did not rescue the Zn sensitivity of the zntA mutant, which is defective in Zn-transporting ATPase. To further elucidate the functional roles of OsHMA9, we isolated two independent null alleles, oshma9-1 and oshma9-2, from the T-DNA insertion population. Mutant plants exhibited the phenotype of increased sensitivity to elevated levels of Cu, Zn, and lead. These results support a role for OsHMA9 in Cu, Zn, and lead efflux from the cells. This article is the first report on the functional characterization of a P(1B)-type metal efflux transporter in monocots.
authors.affiliation: Division of Molecular and Life Science, Biotechnology Research Center, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Sichul
authors.initials: S
authors.lastname: Lee
authors.forename: Yu-Young
authors.initials: YY
authors.lastname: Kim
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Lee
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000378:metabolism; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D019216:Metals, Heavy / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D018547:Plant Stems / Q000166:cytology / Q000378:metabolism