A key question in biology is how a given phenotype is generated from a genotype. We now have a good understanding of the role of transcriptional control in generating a phenotype. However, there is a major observation that is still not understood: multiple phenotypes can derive from one genome in one environment. This variability between genetically identical individuals in the same environment has been overlooked for a long time. Transcriptional variability has been observed between cells but also between individuals in multicellular organisms. While this variability might be partly caused by the micro-environment, there is evidence that it is at least partly genetically controlled and is biologically relevant. One of the factors that has been shown to regulate gene expression variability between cells, is chromatin. However we still don’t have a proof of the role of chromatin in cell-to-cell variability in plants and its possible role in inter-individual gene expression variability has not been studied yet. I will use a combination of transcriptomic, imaging and targeted functional studies to define the role of chromatin in inter-individual and cell-to-cell transcriptional variability, and its phenotypic consequences using genes involved in nitrate nutrition in Arabidopsis. The response to nitrate is a good model for such study, as not only have I observed that some of the main factors of the response to nitrate show high variability, but nitrate availability in the soil is also spatially and temporally heterogeneous in the wild. The project will highlight the control of transcriptional variability and its role in the genotype to phenotype link.

Globally, dietary risks contribute significantly chronic diseases such as obesity, cardiovascular diseases, cancer, and diabetes. In high-income countries, lower socioeconomic status is associated with a higher prevalence of diet-related chronic diseases. Consequently, reducing diet-related health inequalities has become a major concern. It is now recognized that dietary behaviors are not solely a matter of individual choice but are also shaped by the environments in which people live. Yet, understanding the environmental influences on dietary behaviors and social inequalities in access to healthy food is still lacking. Better understanding these relationships requires apprehending the complex interrelations between individuals and the environments they are exposed to through ecological approaches, particularly in urban spaces. This entails analyzing how different dimensions of the food environment to which urban dwellers are exposed (such as availability, accessibility, and cost of food) influence food choices and behaviors according to socioeconomic characteristics. The Trip2food project aims to provide unique insights into the socio-economic inequalities in access and use of the food environment as well as in diet-related behaviors. The project will pursue three main research objectives: 1) Study the spatialization of household food supplies in relation to objective and perceived exposure to food environments, daily mobility, and socioeconomic characteristics. 2) Evaluate to what extent these patterns of food provisioning behaviors can shape diet quality and contribute to diet-related inequalities. 3) Examine the effect of urban transformations on daily mobility for food shopping and on dietary behaviors in a disadvantaged neighborhood. The study will be conducted within the Montpellier metropolitan area, which is experiencing sustained population growth combined with a strong urban renewal process. The significant interest of local policymakers regarding the sustainability of food systems and social justice makes the Metropole of Montpellier an ideal case study for assessing the relationships between the urban environment and dietary behaviors. This interdisciplinary project will apply mixed methods integrated into a community-based participatory research (CBPR) approach. Drawing on the expertise of an interdisciplinary team and strong partnerships with local stakeholders, the ambition of this project is to come up with an innovative perspective which can robustly support policymakers in designing food environment can that effectively address issues of social justice and nutrition.

Les insectes herbivores constituent plus d'un quart des organismes macroscopiques. Ces insectes sont engagés dans des interactions plus ou moins spécialisées avec les plantes dont ils se nourrissent, ils représentent aussi les hôtes d'une multitude de bactéries et de parasitoïdes. Les interactions interspécifiques dans lesquelles ces insectes sont engagés et les processus évolutifs qui en résultent jouent probablement un rôle majeur dans l'origine et le maintien de cette diversité biologique. Ce projet a deux objectifs principaux: 1) comprendre les processus de diversification dans des associations interspécifiques complexes, en s'intéressant à deux niveaux trophiques le niveau plante/phytophage et le niveau phytophage/endosymbionte, nous étudierons en particulier le poids des contraintes phylogénétiques par rapport aux processus d'adaptation dans l'évolution de ces interactions, 2) identifier les facteurs écologiques et traits d'histoire de vie qui influencent la richesse en espèces de parasitoïdes d'un insecte phytophage. Pour répondre à ces objectifs, cette étude sera focalisée sur un genre de la famille des Aphididae (pucerons), le genre Brachycaudus, leurs endobactéries (type Buchnera) et les parasitoïdes associés. Le genre Brachycaudus est particulièrement intéressant pour étudier l'évolution des associations plantes/phytophages car les espèces présentent des degrés de spécificité variable vis à vis de leurs plantes hôtes et des variations dans des traits d'histoire de vie tels que l'utilisation d'un hôte secondaire durant le cycle de vie (hétéroécie). A l'aide de phylogénies moléculaires, nous retracerons l'histoire de ces caractères. Nous utiliserons des analyses comparative afin d'identifier s'il existe chez les pucerons des caractères qui sont associés à des transitions évolutives importantes dans l'histoire des associations plantes/pucerons. A l'aide de ces analyses nous établirons des scénarii des modes de spéciation chez les Brachycaudus. La phylogénie moléculaire de bactéries du type Buchnera sera aussi retracée, nous testerons ainsi la spécificité de l'interaction ainsi que l'hypothèse selon laquelle il y a eu cospéciation entre ces bacteries et leurs pucerons hôtes. Quant aux associations pucerons/parasitoïdes, en prenant en compte la phylogénie des Brachycaudus nous chercherons à mettre en évidence les caractères des pucerons (e. g. taille, myrmécophilie, site de nutrition) qui influencent la diversité spécifique des parasitoïdes associés à chaque espèce. Ce projet alliera donc un travail de terrain important (récolte des échantillons et données biologiques), des reconstructions phylogénétiques et des analyses comparatives. L'approche comparative que nous proposons d'adopter a été jusque là très peu appliquée à l'étude des communautés de parasitoïdes et devrait permettre de tester l'importance des facteurs écologiques par rapport aux facteurs historiques dans l'établissement de ces assemblages.