A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

Abstract

ORCID ID: 0000-0003-3411-827X (J.F.M.).Heavy metal-transporting P-type ATPase (HMA) has been implicated in the transport of heavy metals in plants. Here, we report the function and role of an uncharacterized member of HMA, OsHMA5 in rice (Oryza sativa). Knockout of OsHMA5 resulted in a decreased copper (Cu) concentration in the shoots but an increased Cu concentration in the roots at the vegetative stage. At the reproductive stage, the concentration of Cu in the brown rice was significantly lower in the mutants than in the wild-type rice; however, there was no difference in the concentrations of iron, manganese, and zinc between two independent mutants and the wild type. The Cu concentration of xylem sap was lower in the mutants than in the wild-type rice. OsHMA5 was mainly expressed in the roots at the vegetative stage but also in nodes, peduncle, rachis, and husk at the reproductive stage. The expression was up-regulated by excess Cu but not by the deficiency of Cu and other metals, including zinc, iron, and manganese, at the vegetative stage. Analysis of the transgenic rice carrying the OsHMA5 promoter fused with green fluorescent protein revealed that it was localized at the root pericycle cells and xylem region of diffuse vascular bundles in node I, vascular tissues of peduncle, rachis, and husk. Furthermore, immunostaining with an antibody against OsHMA5 revealed that it was localized to the plasma membrane. Expression of OsHMA5 in a Cu transport-defective mutant yeast (Saccharomyces cerevisiae) strain restored the growth. Taken together, OsHMA5 is involved in loading Cu to the xylem of the roots and other organs.

Functional and Biochemical Characterization of Cucumber Genes Encoding Two Copper ATPases CsHMA5.1 and CsHMA5.2

“…A similar function has been recently reported for the homologous protein OsHMA5 in rice (18). The athma5 knock-out mutant is hypersensitive to copper, whereas rice knock-out lines for OsHMA5 accumulated more copper in roots and less in shoots, when compared with wild type plants (17,18). In addition, OsHMA5 was shown to be localized in the plasma membrane (18).…”

“…The athma5 knock-out mutant is hypersensitive to copper, whereas rice knock-out lines for OsHMA5 accumulated more copper in roots and less in shoots, when compared with wild type plants (17,18). In addition, OsHMA5 was shown to be localized in the plasma membrane (18). These observations suggest that in plants HMA5 is involved in root-to-shoot translocation of copper and thus protects plant roots from copper toxicity (17).…”

“…Contrary to AtHMA6 -AtHMA8, which deliver copper to the target proteins, AtHMA5 appears to be involved in detoxification of Arabidopsis roots from copper excess (17). A similar function has been recently reported for the homologous protein OsHMA5 in rice (18). The athma5 knock-out mutant is hypersensitive to copper, whereas rice knock-out lines for OsHMA5 accumulated more copper in roots and less in shoots, when compared with wild type plants (17,18).…”

Orchestration of three transporters and distinct vascular structures in node for intervascular transfer of silicon in rice

“…Recently, identification of mineral nutrient transporters in node and physiological studies shed a new light on the importance of node for preferential distribution of mineral nutrients to developing and reproductive organs (2,14,(18)(19)(20)(21)(22)(23). The xylem flow in EVBs and DVBs, which are connected by nodal vascular anastomosis (NVA) at the base of the node, are simply divided following the transpiration rate of each upper organ.…”

“…Although different transporters are supposed to be involved in these steps, only a few of them in some steps have been identified. For instance, Lsi6 is involved in Si unloading from EVB (14, 18); OsHMA5 and OsYSL16 are involved in Cu exclusion from xylem and loading to phloem of DVB, respectively (19,20), whereas OsHMA2 is required for Zn/Cd reloading to phloem of DVB (21); and OsNramp3 has a dual role for both xylem unloading from EVB and phloem reloading to DVB of Mn (22). In the present study, by integrating in vivo experiments with mathematical modeling, we were able to identify all factors involved in the intervascular transfer for preferential distribution of Si in node (Fig.…”