In varied animals (birds, bats, insects), wings provide both lift and propulsion. Flying is useful for many functions: to escape from ground predators, and predate other animals, to explore new ecological niches and find new food source inaccessible to terrestrial animals, to increase the size of the territory and the dispersion of a population, to migrate and find more favorable conditions. Among the 240 000 species of Diptera (insects with one pair of wings), many are important for their contribution on both ecological perspective (pollinization, parasitism) as well as human health (disease transmission). When they fly, flies have to face atmospheric turbulence and wind blow which heavely impact on the dispersion of molecular cues and vortex gradients of odorants, rendering it difficult to trace the emitting source. Apart flight orientation, fly wings may have other roles related to sensory communication like taste, tactile perception, proprioception, and sound production during courtship. Moreover, before or during courtship, flies often brush wings, head and superficial part of the cuticle with the frontal legs. This grooming behavior could serve for chemical self-sampling. If the role of chemosensory hairs present on the antennal, labial, tarsal, maxillary palps appendages and on the female ovipositor have been largely explored this is not the case for the chemosensory hairs carried by the anterior margin of the wing. There is no information for any fly, or insect, on the role that wing sensory organs could play on chemically-driven orientation behaviors. We recently detected the presence of gustatory receptors in wings of aphid, honey bee and in Drosophila. We also found that the partial or total uni- and bilateral wing ablation strongly altered the orientation of Drosophila melanogaster flies to chemosensory cues from a food source or from conspecifics (pheromones). These data taken with the presence of several odorant-binding proteins (OBPs) and some putative odorant receptors in the developing wing. strongly suggest that Drosophila flies use their wings for chemoperception. Our project will consist to show that Drosophila flies use their wing sensors to orient towards chemical cues. Three Drosophila species will be tested in the three dimensions of space to elucidate the role of wings in chemoperception. We have chosen two cosmopolitan phylogenetically distant species, D.melanogaster, D.virilis, together with D.sechellia, a species closely related to D.melanogaster but with a different chemosensory preference. We will combine behavioral, physiological, surgical, genetic and modelization approaches to reveal the role of wing chemosensors to simple food molecules and to pheromones. Individual flies will be placed either in a small constraining chamber (1-D; autoperception), or in a larger flat chamber (2-D; courtship and guidance in a planar environment), or in a real volume (3-D; orientation in a flight tunnel). Members of the two teams involved in the project do possess complementary skills and expertise to successfully carry out the different methodological aspects of this project (genetics, wing surgery, electrophysiology, tracking behavior): They have already published results obtained with these methods in international papers. If the two PIs involved in this project have never published together, they have regularly exchanged scientific information for the last 20 years. Moreover, all tools, species and strains required for this project already exist in our labs or are easily available. Therefore, we believe that we can show how the wing neurosensory system is crucial for insects to navigate and investigate their environment. If this will help to monitor insects population in agricultural and urban space, this should also provide new hints to promote alternative tools to neurotoxic pesticides in order to control insect dispersion and proliferation.

The root hair plays crucial roles in water and nutrient uptake, and thus in plant development. In Legumes, it also plays a central role in the establishment of the nitrogen-fixing symbiotic interaction with rhizobia, which has a crucial importance for sustainable agriculture as it largely contributes to limitation of nitrogen fertilizers. Furthermore, the root hair provides a model to investigate the biology of a single differentiated plant cell type, one of the present challenges for plant scientists, and is considered as a highly promising model for plant cell systems biology. A hallmark feature of the root hair, shared with very few cell types (pollen tube, fungal hyphae and animal axons), is its polarised cell growth, occurring only at the tip. This so-called tip growth is a highly complex process, in which ion channels and reactive oxygen species (ROS) are key actors. Furthermore, these actors play interacting roles: channel activity can be controlled by ROS involving signals and, reciprocally, signalling ROS production can depend on channel driven ion fluxes. Evidence is available that this ion channel-ROS mediated control of root hair tip growth, initially observed in the model plant Arabidopsis thaliana, is also active in Legumes. Moreover, in the latter case, re-orientation of the tip growth occurs during the initial physical interaction with the rhizobial microsymbiont, an early step in the establishment of the nitrogen-fixing symbiosis: bacterial infection is initiated by attachment of the bacteria to the root hairs that curl, due to this re-orientation. The aim of the CAROLS project is to obtain a holistic view of the involvement of root hair plasma membrane ion channels and of their regulation by ROS during the first steps of the symbiotic interaction between the model Legume Medicago truncatula and its microsymbiont Sinorhizobium meliloti. The work will be divided into six tasks: (i) in situ electrophysiological analyses, providing the functional repertoire of the ion conductances active in the plasma membrane of M. truncatula root hairs, (ii) molecular analyses and cloning, providing the molecular repertoire of the ion channel genes expressed in root hairs, (iii) verification that the channels selected during task (ii) are actually present in the root hair plasma membrane, (iv) functional characterisation of cloned channels in heterologous systems, (v) analyses of the role of ROS in the ion channel regulation and (vi) in planta analyses of selected mutant plants (affected in channel activities or ROS production) and phenotyping of their root hair growth and symbiotic abilities. By combining up-to-date electrophysiology techniques (laser dissection coupled to patch-clamping, a methodology that is already available in the consortium) with molecular, genetic and functional analyses, the project will provide the first systematic and integrated study of the root hair plasma membrane ion channels. In particular, through the use of the laser dissection technique, it will allow to study the ROS effects on channel activities at various stages of root hair growth, including root hair curling and infection thread initiation. These innovative methodology and device, which may be unique at the international level, give to the project an ideal situation in the framework of the international competition. Moreover, the project will benefit from the almost completed sequencing of the M. truncatula genome. It will lead to important breakthroughs in the analysis of the roles of ion channels and their regulation by ROS in root hair tip growth and interaction with symbiotic bacteria. Finally, at a still wider level of biological concerns, it will open new research lines in the analysis of the interplay between ROS and ion channels in plant signalling and adaptation to biotic and abiotic environmental conditions, root hair physiology and systems biology.