AtALMT1, which encodes a malate transporter, is identified as one of several genes critical for aluminum tolerance in Arabidopsis
- Owen A. Hoekenga*,†,
- Lyza G. Maron†,‡,
- Miguel A. Piñeros†,‡,
- Geraldo M. A. Cançado‡,§,
- Jon Shaff†,‡,
- Yuriko Kobayashi¶,
- Peter R. Ryan‖,
- Bei Dong‖,
- Emmanuel Delhaize‖,
- Takayuki Sasaki**,
- Hideaki Matsumoto**,
- Yoko Yamamoto**,
- Hiroyuki Koyama¶, and
- Leon V. Kochian†,††
- *Boyce Thompson Institute for Plant Research, Ithaca, NY 14853;
- †U.S. Plant, Soil, and Nutrition Laboratory, U.S. Department of Agriculture–Agricultural Research Service, and
- ‡Department of Plant Biology, Cornell University, Ithaca, NY 14853;
- §Center for Molecular Biology and Genetic Engineering, State University of Campinas, 13083-970, Campinas, Sao Paulo, Brazil;
- ¶Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan;
- ‖Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Canberra ACT 2601, Australia; and
- **Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan
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Communicated by Deborah P. Delmer, The Rockefeller Foundation, New York, NY, April 7, 2006 (received for review November 21, 2005)
Abstract
Aluminum (Al) tolerance in Arabidopsis is a genetically complex trait, yet it is mediated by a single physiological mechanism based on Al-activated root malate efflux. We investigated a possible molecular determinant for Al tolerance involving a homolog of the wheat Al-activated malate transporter, ALMT1. This gene, named AtALMT1 (At1g08430), was the best candidate from the 14-memberAtALMT family to be involved with Al tolerance based on expression patterns and genomic location. Physiological analysis of a transferred DNA knockout mutant for AtALMT1 as well as electrophysiological examination of the protein expressed in Xenopus oocytes showed that AtALMT1 is critical for Arabidopsis Al tolerance and encodes the Al-activated root malate efflux transporter associated with tolerance. However, gene expression and sequence analysis of AtALMT1 alleles from tolerant Columbia (Col), sensitive Landsberg erecta (Ler), and other ecotypes that varied in Al tolerance suggested that variation observed at AtALMT1 is not correlated with the differences observed in Al tolerance among these ecotypes. Genetic complementation experiments indicated that the Ler allele of AtALMT1 is equally effective as the Col allele in conferring Al tolerance and Al-activated malate release. Finally, fine-scale mapping of a quantitative trait locus (QTL) for Al tolerance on chromosome 1 indicated that AtALMT1 is located proximal to this QTL. These results indicate that AtALMT1 is an essential factor for Al tolerance in Arabidopsis but does not represent the major Al tolerance QTL also found on chromosome 1.
Footnotes
- ††To whom correspondence should be addressed. E-mail: lvk1{at}cornell.edu
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Author contributions: O.A.H., M.A.P., P.R.R., E.D., H.K., and L.V.K. designed research; O.A.H., L.G.M., M.A.P., G.M.A.C., J.S., Y.K., and B.D. performed research; T.S., H.M., and Y.Y. contributed new reagents/analytic tools; O.A.H., L.G.M., M.A.P., and L.V.K. analyzed data; and O.A.H., M.A.P., and L.V.K. wrote the paper.
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Conflict of interest statement: No conflicts declared.
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Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. DQ465038–DQ465042).
- Abbreviations:
- Col,
- Columbia;
- Ler,
- Landsberg erecta;
- MT,
- mutant;
- QTL,
- quantitative trait locus
Abbreviations:
- © 2006 by The National Academy of Sciences of the USA
