Mutations in Rice (Oryza sativa) Heavy Metal ATPase 2 (OsHMA2) Restrict the Translocation of Zinc and Cadmium

Abstract

Widespread soil contamination with heavy metals has fostered the need for plant breeders to develop new crops that do not accumulate heavy metals. Metal-transporting transmembrane proteins that transport heavy metals across the plant plasma membrane are key targets for developing these new crops. Oryza sativa heavy metal ATPase 3 (OsHMA3) is known to be a useful gene for limiting cadmium (Cd) accumulation in rice. OsHMA2 is a close homolog of OsHMA3, but the function of OsHMA2 is unknown. To gain insight into the function of OsHMA2, we analyzed three Tos17 insertion mutants. The translocation ratios of zinc (Zn) and Cd were clearly lower in all mutants than in the wild type, suggesting that OsHMA2 is a major transporter of Zn and Cd from roots to shoots. By comparing each allele in the OsHMA2 protein structure and measuring the Cd translocation ratio, we identified the C-terminal region as essential for Cd translocation into shoots. Two alleles were identified as good material for breeding rice that does not contain Cd in the grain but does contain some Zn, and that grows normally.

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).…”

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

“…To analyze the expression of OsHMA3 in the T 1 plants, total RNA was extracted according to the methods of Satoh-Nagasawa et al (2012). Then, reverse transcription PCR (RT-PCR) was performed with KOD plus (Toyobo) and primers P4 and P13.…”

“…Then, reverse transcription PCR (RT-PCR) was performed with KOD plus (Toyobo) and primers P4 and P13. Actin (LOC_OS03G50885.1) cDNA amplified with Ex Taq (TaKaRa) and primers P48 and P49 were used as the standard (Sasaki et al 2012;Satoh-Nagasawa et al 2012). PCR was performed for 28 and 29 cycles for OsHMA3 and 23 and 24 cycles for Actin.…”

“…Rice seeds were surface sterilized, incubated, and cultured for 27 days according to the method of Satoh-Nagasawa et al (2012). For Cd treatment, all seedlings were grown hydroponically in a nutrient solution containing 5 µg l −1 CdCl 2 for 3 weeks.…”