Fertilization-dependent auxin response in ovules triggers fruit development through the modulation of gibberellin metabolism in Arabidopsis

Authors

  • Eavan Dorcey,

    Search for more papers by this author
    • Present address: Department of Plant Molecular Biology, University of Lausanne, Biophore Building, CH–1015 Lausanne, Switzerland.

  • Cristina Urbez,

    1. Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia (CSIC-UPV), Avenida de los naranjos s/n, 46022 Valencia, Spain
    Search for more papers by this author
  • Miguel A. Blázquez,

    1. Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia (CSIC-UPV), Avenida de los naranjos s/n, 46022 Valencia, Spain
    Search for more papers by this author
  • Juan Carbonell,

    1. Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia (CSIC-UPV), Avenida de los naranjos s/n, 46022 Valencia, Spain
    Search for more papers by this author
  • Miguel A. Perez-Amador

    Corresponding author
      For correspondence (fax +34 963877859; e-mail mpereza@ibmcp.upv.es).
    Search for more papers by this author

For correspondence (fax +34 963877859; e-mail mpereza@ibmcp.upv.es).

Summary

Fruit development is usually triggered by ovule fertilization, and it requires coordination between seed development and the growth and differentiation of the ovary to host the seeds. Hormones are known to synchronize these two processes, but the role of each hormone, and the mechanism by which they interact, are still unknown. Here we show that auxin and gibberellins (GAs) act in a hierarchical scheme. The synthetic reporter construct DR5:GFP showed that fertilization triggered an increase in auxin response in the ovules, which could be mimicked by blocking polar auxin transport. As the application of GAs did not affect auxin response, the most likely sequence of events after fertilization involves auxin-mediated activation of GA synthesis. We have confirmed this, and have shown that GA biosynthesis upon fertilization is localized specifically in the fertilized ovules. Furthermore, auxin treatment caused changes in the expression of GA biosynthetic genes similar to those triggered by fertilization, and also restricted to the ovules. Finally, GA signaling was activated in ovules and valves, as shown by the rapid downregulation of the fusion protein RGA-GFP after pollination and auxin treatment. Taken together, this evidence suggests a model in which fertilization would trigger an auxin-mediated promotion of GA synthesis specifically in the ovule. The GAs synthesized in the ovules would be then transported to the valves to promote GA signaling and thus coordinate growth of the silique.

Ancillary