Arabidopsis CUL3A and CUL3B genes are essential for normal embryogenesis

Authors

  • Alexis Thomann,

    1. Institut de Biologie Moléculaire des Plantes du CNRS, 12, rue du Général Zimmer, 67084 Strasbourg Cedex, France,
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    • These authors contributed equally to this work.

  • Vladimir Brukhin,

    1. Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland, and
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    • These authors contributed equally to this work.

  • Monika Dieterle,

    1. Institut de Biologie Moléculaire des Plantes du CNRS, 12, rue du Général Zimmer, 67084 Strasbourg Cedex, France,
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  • Jacqueline Gheyeselinck,

    1. Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland, and
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  • Marylin Vantard,

    1. Laboratoire de Physiologie Cellulaire Végétale, UMR5019 CNRS/CEA/INRA/Université Joseph Fourier, DRDC-CEA Grenoble, 17 rue des martyrs, F-38054 Grenoble Cedex 9, France
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  • Ueli Grossniklaus,

    1. Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland, and
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  • Pascal Genschik

    Corresponding author
    1. Institut de Biologie Moléculaire des Plantes du CNRS, 12, rue du Général Zimmer, 67084 Strasbourg Cedex, France,
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(fax +33 (0) 3 88 61 44 42; e-mail pascal.genschik@ibmp-ulp.u-strasbg.fr).

Summary

Cullin (CUL)-dependent ubiquitin ligases form a class of structurally related multisubunit enzymes that control the rapid and selective degradation of important regulatory proteins involved in cell cycle progression and development, among others. The CUL3-BTB ligases belong to this class of enzymes and despite recent findings on their molecular composition, our knowledge on their functions and substrates remains still very limited. In contrast to budding and fission yeast, CUL3 is an essential gene in metazoans. The model plant Arabidopsis thaliana encodes two related CUL3 genes, called CUL3A and CUL3B. We recently reported that cul3a loss-of-function mutants are viable but exhibit a mild flowering and light sensitivity phenotype. We investigated the spatial and temporal expression of the two CUL3 genes in reproductive tissues and found that their expression patterns are largely overlapping suggesting possible functional redundancy. Thus, we investigated the consequences on plant development of combined Arabidopsis cul3a cul3b loss-of-function mutations. Homozygous cul3b mutant plants developed normally and were fully fertile. However, the disruption of both the CUL3A and CUL3B genes reduced gametophytic transmission and caused embryo lethality. The observed embryo abortion was found to be under maternal control. Arrest of embryogenesis occurred at multiple stages of embryo development, but predominantly at the heart stage. At the cytological level, CUL3 loss-of-function mutations affected both embryo pattern formation and endosperm development.

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