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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Amino Acid Polymorphisms in Strictly Conserved Domains of a P-Type ATPase HMA5 Are Involved in the Mechanism of Copper Tolerance Variation in Arabidopsis^1,[W],[OA]

Laboratory of Plant Cell Technology, Faculty of Applied Biological Sciences, Gifu University, Gifu 501–1193, Japan (Y.K., K. Kuroda, Keisuke Kimura, A.F., H.K.); Department of Farm Management, Miyagi University, Sendai, Miyagi 981–3298, Japan (Kazuhiko Kimura); Department of Biological Sciences, Faculty of Science, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 (J.L.S.-F., G.J.T.); and BioResource Center, RIKEN, Tsukuba, Ibaraki 305–0074, Japan (S.I., M.K.)

Copper (Cu) is an essential element in plant nutrition, but it inhibits the growth of roots at low concentrations. Accessions of Arabidopsis (Arabidopsis thaliana) vary in their tolerance to Cu. To understand the molecular mechanism of Cu tolerance in Arabidopsis, we performed quantitative trait locus (QTL) analysis and accession studies. One major QTL on chromosome 1 (QTL1) explained 52% of the phenotypic variation in Cu tolerance in roots in a Landsberg erecta/Cape Verde Islands (Ler/Cvi) recombinant inbred population. This QTL regulates Cu translocation capacity and involves a Cu-transporting P_1B-1-type ATPase, HMA5. The Cvi allele carries two amino acid substitutions in comparison with the Ler allele and is less functional than the Ler allele in Cu tolerance when judged by complementation assays using a T-DNA insertion mutant. Complementation assays of the ccc2 mutant of yeast using chimeric HMA5 proteins revealed that N923T of the Cvi allele, which was identified in the tightly conserved domain N(x)₆YN(x)₄P (where the former asparagine was substituted by threonine), is a cause of dysfunction of the Cvi HMA5 allele. Another dysfunctional HMA5 allele was identified in Chisdra-2, which showed Cu sensitivity and low capacity of Cu translocation from roots to shoots. A unique amino acid substitution of Chisdra-2 was identified in another strictly conserved domain, CPC(x)₆P, where the latter proline was replaced with leucine. These results indicate that a portion of the variation in Cu tolerance of Arabidopsis is regulated by the functional integrity of the Cu-translocating ATPase, HMA5, and in particular the amino acid sequence in several strictly conserved motifs.

² Present address: BioResource Center, RIKEN, 3–1–1 Koyadai, Tsukuba, Ibaraki 305–0074, Japan.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Hiroyuki Koyama (koyama{at}gifu-u.ac.jp).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.119933

^* Corresponding author; e-mail koyama{at}gifu-u.ac.jp.

Received April 8, 2008; accepted August 8, 2008; published August 13, 2008.

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