Characterizing the role of rice NRAMP5 in Manganese, Iron and Cadmium Transport

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Abstract

Metals like manganese (Mn) and iron (Fe) are essential for metabolism, while cadmium (Cd) is toxic for virtually all living organisms. Understanding the transport of these metals is important for breeding better crops. We have identified that OsNRAMP5 contributes to Mn, Fe and Cd transport in rice. OsNRAMP5 expression was restricted to roots epidermis, exodermis, and outer layers of the cortex as well as in tissues around the xylem. OsNRAMP5 localized to the plasma membrane, and complemented the growth of yeast strains defective in Mn, Fe, and Cd transport. OsNRAMP5 RNAi (OsNRAMP5i) plants accumulated less Mn in the roots, and less Mn and Fe in shoots, and xylem sap. The suppression of OsNRAMP5 promoted Cd translocation to shoots, highlighting the importance of this gene for Cd phytoremediation. These data reveal that OsNRAMP5 contributes to Mn, Cd, and Fe transport in rice and is important for plant growth and development.

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IRT1, an Arabidopsis transporter essential for iron uptake from the soil and for plant growth.

Grégory Vert, Natasha Grotz, Fabienne Dédaldéchamp … (2002)

Plants are the principal source of iron in most diets, yet iron availability often limits plant growth. In response to iron deficiency, Arabidopsis roots induce the expression of the divalent cation transporter IRT1. Here, we present genetic evidence that IRT1 is essential for the uptake of iron from the soil. An Arabidopsis knockout mutant in IRT1 is chlorotic and has a severe growth defect in soil, leading to death. This defect is rescued by the exogenous application of iron. The mutant plants do not take up iron and fail to accumulate other divalent cations in low-iron conditions. IRT1-green fluorescent protein fusion, transiently expressed in culture cells, localized to the plasma membrane. We also show, through promoter::beta-glucuronidase analysis and in situ hybridization, that IRT1 is expressed in the external cell layers of the root, specifically in response to iron starvation. These results clearly demonstrate that IRT1 is the major transporter responsible for high-affinity metal uptake under iron deficiency.

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Rice plants take up iron as an Fe3+-phytosiderophore and as Fe2+.

Yasuhiro Ishimaru, Motofumi Suzuki, Takashi Tsukamoto … (2006)

Only graminaceous monocots possess the Strategy II iron (Fe)-uptake system in which Fe is absorbed by roots as an Fe3+-phytosiderophore. In spite of being a Strategy II plant, however, rice (Oryza sativa) contains the previously identified Fe2+ transporter OsIRT1. In this study, we isolated the OsIRT2 gene from rice, which is highly homologous to OsIRT1. Real-time PCR analysis revealed that OsIRT1 and OsIRT2 are expressed predominantly in roots, and these transporters are induced by low-Fe conditions. When expressed in yeast (Saccharomyces cerevisiae) cells, OsIRT2 cDNA reversed the growth defects of a yeast Fe-uptake mutant. This was similar to the effect of OsIRT1 cDNA. OsIRT1- and OsIRT2-green fluorescent protein fusion proteins localized to the plasma membrane when transiently expressed in onion (Allium cepa L.) epidermal cells. OsIRT1 promoter-GUS analysis revealed that OsIRT1 is expressed in the epidermis and exodermis of the elongating zone and in the inner layer of the cortex of the mature zone of Fe-deficient roots. OsIRT1 expression was also detected in the ccompanion cells. Analysis using the positron-emitting tracer imaging system showed that rice plants are able to take up both an Fe3+-phytosiderophore and Fe2+. This result indicates that, in addition to absorbing an Fe3+-phytosiderophore, rice possesses a novel Fe-uptake system that directly absorbs the Fe2+, a strategy that is advantageous for growth in submerged conditions.

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Gene limiting cadmium accumulation in rice.

Daisei Ueno, Naoki Yamaji, Izumi Kono … (2010)

Intake of toxic cadmium (Cd) from rice caused Itai-itai disease in the past and it is still a threat for human health. Therefore, control of the accumulation of Cd from soil is an important food-safety issue, but the molecular mechanism for the control is unknown. Herein, we report a gene (OsHMA3) responsible for low Cd accumulation in rice that was isolated from a mapping population derived from a cross between a high and low Cd-accumulating cultivar. The gene encodes a transporter belonging to the P(1B)-type ATPase family, but shares low similarity with other members. Heterologous expression in yeast showed that the transporter from the low-Cd cultivar is functional, but the transporter from the high-Cd cultivar had lost its function, probably because of the single amino acid mutation. The transporter is mainly expressed in the tonoplast of root cells at a similar level in both the low and high Cd-accumulating cultivars. Overexpression of the functional gene from the low Cd-accumulating cultivar selectively decreased accumulation of Cd, but not other micronutrients in the grain. Our results indicated that OsHMA3 from the low Cd-accumulating cultivar limits translocation of Cd from the roots to the above-ground tissues by selectively sequestrating Cd into the root vacuoles.

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Journal

Journal ID (nlm-ta): Sci Rep

Title: Scientific Reports

Publisher: Nature Publishing Group

ISSN (Electronic): 2045-2322

Publication date (Electronic): 24 February 2012

Publication date Collection: 2012

Volume: 2

Electronic Location Identifier: 286

Affiliations

[1 ]simpleGraduate School of Agricultural and Life Sciences, The University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan

[2 ]simpleDepartment of Chemistry, Tohoku University , 6-3 Aramakiaza-aoba, Aoba-ku, Sendai, Miyagi, 980-8579, Japan

[3 ]simpleAgrogenomics Research Center, National Institute of Agrobiological Sciences , 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602 Japan

[4 ]simpleDepartment of Environmental Chemistry, Heavy Metal Group, Soil Biochemistry Unit, National Institute for Agro-Environmental Sciences , 3-1-3 Kannondai, Tsukuba, Ibaraki 305–8604, Japan

[5 ]simpleResearch Institute for Bioresources and Biotechnology, Ishikawa Prefectural University , 1-308 Suematsu, Nonoichi-shi, Ishikawa 921-8836, Japan

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[a ] annaoko@ 123456mail.ecc.u-tokyo.ac.jp

Article

Publisher Item ID: srep00286

DOI: 10.1038/srep00286

PMC ID: 3285952

PubMed ID: 22368778

SO-VID: c2e3fb93-3790-4c21-9f09-49e4a6961cc8

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareALike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

Characterizing the role of rice NRAMP5 in Manganese, Iron and Cadmium Transport

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Most cited references 33

IRT1, an Arabidopsis transporter essential for iron uptake from the soil and for plant growth.

Rice plants take up iron as an Fe3+-phytosiderophore and as Fe2+.

Gene limiting cadmium accumulation in rice.

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