Mutational reconstructed ferric chelate reductase confers enhanced tolerance in rice to iron deficiency in calcareous soil
- Yasuhiro Ishimaru*,
- Suyeon Kim*,
- Takashi Tsukamoto*,
- Hiroyuki Oki†,
- Takanori Kobayashi*,†,
- Satoshi Watanabe‡,
- Shinpei Matsuhashi‡,
- Michiko Takahashi*,
- Hiromi Nakanishi†,
- Satoshi Mori†, and
- Naoko K. Nishizawa*,§,¶
- Departments of *Global Agricultural Sciences and
- †Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1–1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; and
- §Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation, and
- ‡Department of Radiation Research for Environment and Resources, Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, Takasaki, Gunma 370-1292, Japan
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Edited by Maarten J. Chrispeels, University of California at San Diego, La Jolla, CA, and approved March 1, 2007 (received for review November 29, 2006)
Abstract
Iron (Fe) deficiency is a worldwide agricultural problem on calcareous soils with low-Fe availability due to high soil pH. Rice plants use a well documented phytosiderophore-based system (Strategy II) to take up Fe from the soil and also possess a direct Fe2+ transport system. Rice plants are extremely susceptible to low-Fe supply, however, because of low phytosiderophore secretion and low Fe3+ reduction activity. A yeast Fe3+ chelate-reductase gene refre1/372, selected for better performance at high pH, was fused to the promoter of the Fe-regulated transporter, OsIRT1, and introduced into rice plants. The transgene was expressed in response to a low-Fe nutritional status in roots of transformants. Transgenic rice plants expressing the refre1/372 gene showed higher Fe3+ chelate-reductase activity and a higher Fe-uptake rate than vector controls under Fe-deficient conditions. Consequently, transgenic rice plants exhibited an enhanced tolerance to low-Fe availability and 7.9× the grain yield of nontransformed plants in calcareous soils. This report shows that enhancing the Fe3+ chelate-reductase activity of rice plants that normally have low endogenous levels confers resistance to Fe deficiency.
Footnotes
- ¶To whom correspondence should be addressed. E-mail: annaoko{at}mail.ecc.u-tokyo.ac.jp
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Author contributions: Y.I., S.K., T.T., M.T., H.N., S. Mori, and N.K.N. designed research; Y.I. and T.T. performed research; H.O., S.W., and S. Matsuhashi contributed new reagents/analytic tools; Y.I. analyzed data; and Y.I. and T.K. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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See Commentary on page 7311.
- Abbreviations:
- IRT1,
- Fe-regulated transporter;
- FRE1,
- yeast Fe3+ chelate reductase;
- MA,
- mugineic acid;
- PETIS,
- positron-emitting tracer imaging system;
- PMPS,
- positron multiprobe system;
- refre1/372,
- reconstructed yeast Fe3+ chelate reductase.
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Freely available online through the PNAS open access option.
- © 2007 by The National Academy of Sciences of the USA
