The metal ion transporter IRT1 is necessary for iron homeostasis and efficient photosynthesis in Arabidopsis thaliana

Authors

  • Claudio Varotto,

    1. Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (ZIGIA), Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany,
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  • Daniela Maiwald,

    1. Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (ZIGIA), Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany,
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  • Paolo Pesaresi,

    1. Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (ZIGIA), Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany,
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  • Peter Jahns,

    1. Institut fu¨r Biochemie der Pflanzen, Heinrich-Heine-Universita¨t Du¨sseldorf, Universita¨tsstraße 1, 40225 Du¨sseldorf, Germany
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  • Francesco Salamini,

    1. Abteilung fu¨r Pflanzenzu¨chtung und Ertragsphysiologie, Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany.
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  • Dario Leister

    Corresponding author
    1. Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (ZIGIA), Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany,
    2. Abteilung fu¨r Pflanzenzu¨chtung und Ertragsphysiologie, Max-Planck-Institut fu¨r Zu¨chtungsforschung, Carl-von-Linné-Weg 10, 50829 Ko¨ln, Germany.
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* For correspondence (fax +49 221 5062 413; e-mail: leister@mpiz-koeln.mpg.de).

Summary

The mutants irt1-1 and irt1-2 of Arabidopsis thaliana were identified among a collection of T-DNA-tagged lines on the basis of a decrease in the effective quantum yield of photosystem II. The mutations responsible interfere with expression of IRT1, a nuclear gene that encodes the metal ion transporter IRT1. In irt1 mutants, photosensitivity and chlorophyll fluorescence parameters, as well as abundance and composition of the photosynthetic apparatus, are significantly altered. Additional effects of the mutation under greenhouse conditions, including chlorosis and a drastic reduction in growth rate and fertility, are compatible with a deficiency in iron transport. Propagation of irt1 plants on media supplemented with additional quantities of iron salts restores almost all aspects of wild-type behaviour. The irt2-1 mutant, which carries an En insertion in the highly homologous IRT2 gene of Arabidopsis thaliana, was identified by reverse genetics and shows no symptoms of iron deficiency. This, together with the finding that irt1-1 can be complemented by 35S::IRT1 but not by 35S::IRT2, demonstrates that, although the products of the two genes are closely related, only AtIRT1 is required for iron homeostasis under physiological conditions.

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