I am interested in understanding how developmental processes evolve and generate such great animal and plant diversity. More generally, I have a strong interest in the relationship between ontogeny and phylogeny. My work therefore fits into the field of evolutionary developmental biology or evo-devo.
EVOLUTION OF STRUCTURAL COLOR IN BUTTERFLIES Structural color is responsible for the vivid blue and green colors of the wings of many butterflies. For example, the famous Morpho butterflies get their blue color from light interacting with the 'Christmas tree' like structure of its upper lamina. The nanostructures that underlie the structural color are very diverse in butterflies, from upper lamina ornamentations (ridges, cross-ribs) to lower lamina variable thickness. My goal is to reconstruct the evolutionary origin of these different types of nanostructures in butterflies. Moreover, I have been using cutting-edge technologies in ion microscopy to disentangle the contribution of the different nanostructures. Besides bringing new insights in the evolution of colors in butterflies, I aim at paving the way to the development of new bio-inspired materials.
MORPHOLOGICAL & ADAPTIVE EVOLUTION IN SEMI-AQUATIC INSECTS Semi-aquatic insects (Heteroptera, Gerromorpha) have the unique ability to walk on water. Water surface invasion from a common terrestrial ancestor is tightly associated with the ability of these insects to support their body weight on water surface by exploiting surface tension (Andersen, 1976). Water striders evolved particular hairs on their legs, whose density, morphology, and planar orientation, allow the trapping of air to form a cushion at the leg-water interface (Gao and Jiang, 2004). My goal is to understand the developmental genetic basis of these morphological novelties.
ORIENTATION OF CELL DIVISION IN DROSOPHILA EMBRYO Together with cell shape changes and cell rearrangements, oriented cell division is a key cell behaviour during the morphogenesis of animal tissues. The observation in many developing tissues that symmetric cell divisions tend to orientate in a stereotypical way has led to the proposal that oriented cell division participates in tissue morphogenesis (Wallingford, 2012). For example, cell divisions oriented along a given tissue axis could contribute to tissue elongation (da Silva and Vincent, 2007; Quesada-Hernandez et al., 2010). Alternatively, appropriate orientation of cell division in growing tissues could release stresses on the tissue and contribute to maintaining tissue homeostasis (Minc and Piel, 2012). Moreover, improper control of spindle orientation can lead to tumor initiation (Pease and Tirnauer, 2011), as well as developmental defects such as microcephaly (Megraw et al., 2011) and polycystic kidney disease (Fischer et al., 2006). My goal is to investigate the relative contribution of molecular signalling versus physical forces in oriented cell division, using an in vivo model, the Drosophila embryo.
PIGMENTATION AND EVOLUTION OF GENE NETWORKS IN DIPTERA Wing pigmentation arose several times independently during dipteran evolution. In particular, the wings of Drosophilidae flies have evolved a wide variety of pigmentation patterns, ranging from a single distal melanic spot (e.g., Drosophila suzukii) to more elaborate spotty and stripy patterns (e.g., Drosophila grimshawi). How are these pigmentation patterns generated? How do gene networks underlying pigmentation evolve? Drosophilid flies do not exhibit colorful wing patterns found in butterflies, but they nevertheless bring the opportunity to unravel the molecular mechanisms underlying the diversification of wing pigmentation. Thus, it has been recently shown that the origin of black spots on D. guttifera wing is linked to the co-option of the protein Wingless (Werner et al., 2010).
ORIGIN OF FLOWERING PLANTS The origin of the flower required three main steps: (i) the coming together of male and female reproductive organs of a single axis, (ii) the closure of a fertile bract to form the carpel, (iii) the development of sterile organs to form the perianth. During my PhD, I have identified some molecular events that could have played a role in the evolutionary appearance of carpel. The genes ARF3 and ARF4 are involved in carpel development in the model species Arabidopsis thaliana. The reconstruction of the evolutionary history of these two genes suggests they result from a preangiosperm gene duplication event. Moreover, these genes may have predominantly evolved by independent loss of functional regions in the ARF3 or ARF4 lineages (Finet et al., 2010). The evolutionary appearance of non-canonical ARF3 and ARF4 proteins lacking auxin-responsive domains could have played a role in the origin and the diversification of the carpel in angiosperms.
ORIGIN AND DIVERSIFICATION OF LAND PLANTS
Among the green algae, charophytes are the closest living relatives of land plants (Karol et al., 2001). However, which of these charophyte groups is the sister-group to land plants has long been debated. The recent release of transcriptomic data for several charophyte species has facilitated the retrieval of markers for phylogenomic studies. Thus, my collaborators and I have identified the clade (Coleochaetales + Zygnematales) as the closest relatives to extant land plants (Finet et al., 2010).
Land plants diverged from charophytes and rapidly diversified and gave rise to the major clades found today. To gain insights into this process, I have reconstructed the evolutionary history of the Auxin Response Factor (ARF) gene family in land plants. I have shown that gene duplication, domain rearrangement and post-transcriptional regulation have enabled a subtle control of auxin signaling through ARF proteins that may have contributed to the critical importance of these regulators in plant development and evolution (Finet et al., 2013). More generally, I am convinced that changes in auxin biology could have played a role in the diversification of land plants (Finet and Jaillais, 2012).