Recherche - Nouveaux entrants - 2025

Plants have evolved complex structures, like hydathodes and stomata, that regulate water balance and gas exchange, essential for survival and growth. Hydathodes, specialised structures located at leaf edges, allow guttation, where excess water is expelled as droplets, especially in high humidity and low transpiration. In contrast, stomata on the leaf's abaxial surface regulate gas exchange, allowing CO₂ in for photosynthesis and releasing O₂ and water vapor. Hydathode pores (HPs) are formed by pairs of guard cells, like stomata. However, unlike stomata, HPs remain predominantly open and thus help prevent excess turgor pressure but on the other hand can allow pathogen entry, especially for moisture-loving bacteria. Examining the differing roles of hydathodes and stomata in pathogen susceptibility is key to understanding plant resilience to environmental stress and diseases. Although HPs and stomata are crucial in plant physiology, their comparative roles are still under-explored. While initial studies identified cell clusters in Arabidopsis leaves encompassing guard cells and hydathodes, the scarcity of hydathode cells has limited their in-depth characterisation. Transcriptomics at the single cell level is revolutionising plant studies and is particularly suited for the characterisation of rare cell populations and hence could help reveal unique gene expression profiles in HPs versus stomata. My project aims to use single cell transcriptomics to deeply characterise HPs versus stomata and to analyse the impact of HPs on host-pathogen interaction.

In the three domains of life, there is a great diversity of metabolisms. This diversity is the consequence of multiple evolutionary events, linked to changes in the ecological niches and constrained by the ancestral metabolic network topology. Methanogenesis, one of the most ancient pathways in Archaea, represents a particularly suitable model pathway for the analysis of dynamics of metabolism. Although being very ancient and central in metabolism, it has been lost several times during the diversification of Archaea. Due to the place occupied by the methanogenesis, it is thought that its loss has induced a drastic reshuffle of the central metabolism, such as losses of ancient metabolic blocks associated to methanogenesis (MBAM), acquisitions of alternative enzymes to methanogenesis and MBAM, and substantial modifications of related enzymes.

The aim of my research is to identify the key events of MBAM losses that have profoundly influenced the evolution of Archaea, using comparative genomics and phylogenomics. This work also holds potential for biotechnological advancements, particularly through the discovery of novel enzymes. Furthermore, it will provide critical insights into the dynamics of metabolism at the scale of an entire domain of life and reveal the evolutionary constraints tied to the structure of metabolic networks. This enhanced understanding will shed light on the physiology of the earliest living organisms.