FUSCA3encodes a protein with a conserved VP1/ABI3-like B3 domain which is of functional importance for the regulation of seed maturation inArabidopsis thaliana

Authors

  • Hartmut Luerßen,

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    • Present address: Institut für Angewandte Genetik der Freien Universität, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany.

  • Viktor Kirik,

    1. Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), Corrensstraße 3, D-06466 Gatersleben, Germany
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  • Petra Herrmann,

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    • Present address: Botanisches Institut der Ludwig-Maximilians-Universität, Menzinger Straße 67, D-80638 München, Germany.

  • Simon Miséra

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    • Present address: Institut für Angewandte Genetik der Freien Universität, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany.

    • Present address: Botanisches Institut der Ludwig-Maximilians-Universität, Menzinger Straße 67, D-80638 München, Germany.


*For correspondence (fax +49 89 1782274;
e-mail miserasi@botanik.biologie.uni-muenchen.de).

Summary

Conditionally lethal mutant alleles of theFUSCA3(FUS3) gene ofArabidopsis thalianaare specifically defective in the gene expression program responsible for seed maturation.FUS3was isolated by map-based cloning and expression of theFUS3cDNA resulted in complementation of the Fus3 phenotype. In the predicted FUS3 gene product, a continuous stretch of more than 100 amino acids shows significant sequence similarity to the B3 domains of the polypeptides encoded byABI3(Arabidopsis) andVP1(maize).FUS3transcription was detected mainly in siliques and was found to be developmentally regulated during embryogenesis. Transcripts of abnormal sizes were observed infus3mutants due to aberrant splicing caused by point mutations at intron termini. Sequence analysis of mutant and wild-typeFUS3alleles, as well as sequencing offus3cDNAs, revealed small in-frame deletions at two different sites of the coding region. While a deletion between B3 and the C-terminus of the predicted polypeptide was found in conjunction with normal FUS3 function, another deletion located within the conserved B3 domain (as well as truncations therein) were associated with the Fus3 phenotype. It is apparent, therefore, that an intact B3 domain is essential for the regulation of seed maturation by FUS3.

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