Rice P1B-type heavy-metal ATPase, OsHMA9, is a metal efflux protein

Plant Physiol. 2007 Nov;145(3):831-42. doi: 10.1104/pp.107.102236. Epub 2007 Sep 7.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Flowers / metabolism
  • Gene Deletion
  • Gene Expression Regulation, Plant
  • Metals, Heavy / metabolism*
  • Oryza / enzymology*
  • Oryza / genetics
  • Plant Roots / cytology
  • Plant Roots / metabolism
  • Plant Stems / cytology
  • Plant Stems / metabolism


  • Carrier Proteins
  • Metals, Heavy
  • Adenosine Triphosphatases