The OsHMA2 transporter is involved in root‐to‐shoot translocation of Zn and Cd in rice

Abstract

Zinc (Zn) is an essential micronutrient for plants and humans. Cadmium (Cd) is a Zn analog and one of the most toxic heavy metals to humans. Here we investigated the role of the Zn/Cd transporter OsHMA2. OsHMA2:GFP fusion protein localized to the plasma membrane in onion epidermal cells. The yeast expressing OsHMA2 was able to reverse the growth defect in the presence of excess Zn. The expression of OsHMA2 in rice was observed mainly in the roots where OsHMA2 transcripts were abundant in vascular bundles. Furthermore, Zn and Cd concentrations of OsHMA2-suppressed rice decreased in the leaves, while the Zn concentration increased in the roots compared with the wild type (WT). These results suggest that OsHMA2 plays a role in Zn and Cd loading to the xylem and participates in root-to-shoot translocation of these metals in rice. Furthermore, the Cd concentration in the grains of OsHMA2-overexpressing rice as well as in OsSUT1-promoter OsHMA2 rice decreased to about half that of the WT, although the other metal concentrations were the same as in the WT. A phenotype that reduces only the Cd concentration in rice grains will be very useful for transgenic approaches to food safety.

Functional relationship heavy metal P-type ATPases (OsHMA 2 and OsHMA3) of rice (Oryza sativa) using RNAi

“…Thus, here, we confirmed that OsHMA3 does not transport Zn. As a whole, the phenotypes of oshma2 OsHMA3-RNAi plants in this study verified the sequential function of OsHMA3 and OsHMA2 in plant; OsHMA3 transports only Cd into vacuoles (Miyadate et al 2011;Ueno et al 2010) and OsHMA2 transports Cd and Zn into the xylem of rice roots (Nocito et al 2011;SatohNagasawa et al 2012;Takahashi et al 2012). Moreover, our results suggest the importance of the complete loss of function of OsHMA2 to minimize Cd translocation from the roots to shoots.…”

“…On the other hand, insertion mutants resulting in the loss of the function of another heavy metal P-type ATPase in rice, OsHMA2 were used to demonstrate the gene function. OsHMA2 transports Cd and zinc (Zn) into the xylem and is responsible for the translocation of Cd and Zn (Nocito et al 2011;SatohNagasawa et al 2012;Takahashi et al 2012).…”

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…Zinc is exported from root by two members of the P-type ATPase family, HMA2 (expressed in Arabidopsis, rice and barley) and HMA4 Takahashi et al, 2012;Wong and Cobbett, 2009). However, other transporters can also perform the export of Zn to vascular tissues.…”

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

“…Among rice P-type ATPases characterized, OsHMA2 transports Zn and Cd (Satoh-Nagasawa et al, 2012;Takahashi et al, 2012;Yamaji et al, 2013), OsHMA3 is involved in Cd accumulation (Ueno et al, 2010;Miyadate et al, 2011), and OsHMA9 is responsible for the transport of Zn, Cu, Pb, and Cd (Lee et al, 2007). Knockout of OsHMA5 only resulted in altered Cu concentration, but not other metals, including Zn, Fe, and Mn (Fig.…”

“…OsHMA2 was recently reported to be involved in the root-shoot translocation of Zn and Cd (Satoh-Nagasawa et al, 2012;Takahashi et al, 2012;Yamaji et al, 2013). Furthermore, OsHMA2 at the node is required for preferential distribution of Zn to young leaves and panicles (Yamaji et al, 2013).…”