ADDORE

Certain plants have the remarkable ability of establishing beneficial root symbioses with soil bacteria to acquire nitrogen, an essential nutrient for their growth. The bacteria provide nitrogen to their host within new specialized root organs, called nodules, formed through integrated multicellular re-differentiation of plant cells. Bacterial entry is a crucial step in this process, and often occurs through the creation of new transcellular apoplastic compartments called infection threads (IT), which guide the symbiotic bacteria towards the developing nodule. These processes must be tightly coordinated, and partner’s exciting new findings suggest that cross-kingdom cell polarisation processes may regulate them. Indeed, through expression and functional studies, they discovered that genes encoding novel DIX-domain plant polarity proteins are linked to nodule formation in various nitrogen-fixing symbioses. DIX-domains are key for plasma membrane association, enabling these proteins to orchestrate PM signal relay via protein-protein interactions. These findings raise the exciting question of whether plants use ancestral DIX-mediated polarization process for nodule ontogeny and bacterial accommodation. Using complementary model legumes (Medicago, Lotus and Mimosa) and non-legume (Parasponia) this project will combine original multi-species functional genomics, phylogenetic foot printing, live microscopy and protein biochemistry strategies to study their roles in the unexplored context of root nodule symbioses. The project should provide innovative results on their ancestral cellular roles, evolutionary recruitment and molecular interactors, and thus shed light on how they organize the infection machinery and nodule formation across different species.