Format: ORAL

La Rambaud-Lavigne1, Marie Morel2, Bastien Boussau2, Raquel Tavares3, Eva Alvarez Medrano4, Jos Manuel Franco Zorrilla4, Richard Bateman5, Paula Rudall5, Niels Jacobsen6, Pierre Chambrier1, Charlie Scutt1

1 Ecole Normale Supérieure de Lyon, France 2 Université Claude-Bernard, Lyon, France 3 BIOPOLIS/CIBIO-InBIO, Vairão Portugal 4 Centro Nacional de Biotecnología, Madrid, Spain 5 Royal Botanic Gardens-Kew, London, UK 6 University of Copenhagen, Denmark Contact: charlie.scutt@ens-lyon.fr

The angiosperms, also known as flowering plants, contain numerous traits that are absent from their molecular-phylogenetically identified sister group, the living gymnosperms. Such angiosperm-specific traits include the outer integument of the ovule, the carpel, the perianth, and the bisexual reproductive axis. The extinct gymnosperm orders Caytoniales and Bennettitales have been suggested as strong candidates for ancestors or close stem relatives of angiosperms, but these possess contrasting sets of angiosperm-like features. In Caytoniales, the ovules are enclosed within a cupule, which might (or might not) represent a precursor to either the carpel or the outer integument of angiosperms. In Bennettitales, by contrast, there is no cupule, but a perianth-like structure and a bisexual axis (in some taxa) are present. We are analyzing the evolution of gene lineages that control the development of, or are specifically expressed in, the above-listed angiosperm-specific features. Our aim is to deduce the order of potential neo-functionalization events in these lineages and hence the likely order-of-origin of the traits/organs with which they are associated. In particular, the epsilon whole genome duplication, which preceded the radiation of living angiosperms, provides a useful genome-wide time-point to separate earlier and later evolutionary events along the angiosperm stem lineage. The proposition that the outer integument of the angiosperm ovule arose from a Caytoniales-type cupule has been particularly prominent in recent literature, which emphasizes the curved symmetry found in both the cupule and the anatropous angiosperm ovule. A part of our project accordingly focusses on the molecular mechanism of ovule curvature and its degree of conservation between model and early diverging angiosperms.