Nramp5 Is a Major Transporter Responsible for Manganese and Cadmium Uptake in Rice

Abstract

Paddy rice (Oryza sativa) is able to accumulate high concentrations of Mn without showing toxicity; however, the molecular mechanisms underlying Mn uptake are unknown. Here, we report that a member of the Nramp (for the Natural ResistanceAssociated Macrophage Protein) family, Nramp5, is involved in Mn uptake and subsequently the accumulation of high concentrations of Mn in rice. Nramp5 was constitutively expressed in the roots and encodes a plasma membrane-localized protein. Nramp5 was polarly localized at the distal side of both exodermis and endodermis cells. Knockout of Nramp5 resulted in a significant reduction in growth and grain yield, especially when grown at low Mn concentrations. This growth reduction could be partially rescued by supplying high concentrations of Mn but not by the addition of Fe. Mineral analysis showed that the concentration of Mn and Cd in both the roots and shoots was lower in the knockout line than in wild-type rice. A short-term uptake experiment revealed that the knockout line lost the ability to take up Mn and Cd. Taken together, Nramp5 is a major transporter of Mn and Cd and is responsible for the transport of Mn and Cd from the external solution to root cells.

Zinc-Finger Transcription Factor ZAT6 Positively Regulates Cadmium Tolerance through the Glutathione-Dependent Pathway in Arabidopsis

“…In addition, a lot of key genes have been shown to be involved in Cd detoxification and tolerance in plants. These include ZNT1, OsHMA9, OsNRAMP5, ZntA, CAD2, AtPDR12, AtPDR8, AtATM3, ACBP1, Nramp5, EIN2, and MAN3 (Pence et al, 2000;Sharma et al, 2000;Shiraishi et al, 2000;Lee et al, 2003Lee et al, , 2007Kim et al, 2006Kim et al, , 2007Xiao et al, 2008;Cao et al, 2009;Lin and Aarts, 2012;Sasaki et al, 2012;Ishikawa et al, 2012;Chen et al, 2015). It was also found that Heat shock transcription factor A4a (HsfA4a) confers Cd tolerance by up-regulating MT gene expression in wheat (Triticum aestivum) and rice (Oryza sativa; Shim et al, 2009).…”

Two models of Cd uptake by common plants and Hyperaccumulators

“…OsNramp1 expression was observed mainly in roots and was higher in the roots of a high-Cdaccumulating cultivar than in those of a low-Cd-accumulating cultivar [1]. OsNramp5 was mainly expressed in the roots and localized in the plasma membrane of exodermis and endodermis cells of the roots [2]. With different Nramp gene expressions, common plants and Cd-hyperaccumulators show different Cadmium absorption rates and accumulations.…”

Uptake and Accumulation of Cadmium and Relative Gene Expression in Roots of Cd-resistant Salix matsudana Koidz

“…NRAMP5 is involved in the transportation of Cd from the soil to root cells and is also a transporter of Mn [12]. NRAMP1 is localized in the plasma membrane of root cells, functioning as a high-affinity transporter for Mn uptake [17].…”

“…The objectives of the present study were to investigate uptake and accumulation of Cd and relative gene expression (IRT1, NRAMP1, and ZIP1 genes) in roots of Cd-resistant S. matsudana exposed to 50 μM Cd over a short period of treatment (1,3,6,12, and 24 hours). The identified physiological and molecular data provide novel insight into Cd tolerance in woody plants, which can in turn play an important role in phytoremediation investigations.…”

“…in the hyperaccumulator Thlaspi caerulescens [11], the natural resistance-associated macrophage protein (NRAMP), the cation diffusion facilitator protein (CDF) family [12], and the heavy metal-transporting P1B-type ATPase (HMA) [13]. Cd is most likely crossing the plasma membrane via members of the ZIP transporter family (ZRT-IRT like protein; zinc-regulated transporter, iron-regulated transporter protein) (Guerinot, 2000).…”