SYMPA-PEP

Secreted plant peptide hormones orchestrate plant development and regulate interactions with microorganisms from the rhizosphere. In leguminous plants, beneficial nitrogen-fixing bacteria (NFB), arbuscular mycorrhizal fungi (AMF), and pathogenic gall nematodes (GN) all trigger transcriptional reprogramming of the fate of root cells to favor their interaction with host roots. While specific plant genes coding for different classes of peptide hormones are regulated by each of these three microorganisms, AMF and GN also produce molecules mimicking these peptides, called mimetic peptides. In the SYMPA-PEP project, we will analyze the role of new signaling peptides, which are either produced by AMF and / or GN, or induced in the plant during these symbiotic interactions. Based both on our recent analyzes that allowed the identification of microbial mimetic peptides, as well as on the knowledge progress on peptide hormone signaling pathways acting in plants, we will characterize the role of these peptides in the specification plant root cells during development and / or during the maintenance of these beneficial and parasitic interactions. We will use the leguminous plant Medicago truncatula as a model because it allows to study both symbiotic interactions with AMF (Rhizophagus irregularis) and NFB (Sinorhizobium meliloti), and a plant-pathogen interaction with GN (Meloidogyne incognita). Two main questions will be addressed within the framework of the SYMPA-PEP project: (i) which are the roles of novel plant peptide hormones of the IDA and CLE families that are induced during NFB and AMF and / or by GN, and that are anticipated to reprogram root cells to promote the establishment of these interactions; and (ii) what is the role of mimetic peptides of the CLE, CEP and IDA type recently identified in silico and encoded by AMF and / or GN. We will use a combination of genetic, transcriptomic and cell biology approaches, including mutants, overexpression strategies, high throughput RNA sequencing, reporter gene fusions analyzed by confocal microscopy, to characterize the function and regulation of these plant and microbial peptide hormones. The main objective of this project will be to define, for each peptide hormone selected, which molecular and cellular targets are specifically recruited, or alternatively shared, between mutualist and parasite interactions. This will allow identifying genetic determinants typical of the recruitment of each of these peptides in a given biotic interaction, and how they affect root growth and development in a similar / different way. By studying mimetic peptides secreted by these microorganisms, we will have the opportunity to discover conserved and potentially new roles compared to their closest plant counterparts. Finally, by describing regulatory and signaling pathways of these plant or microbial peptide hormones associated to the different interactions analyzed, this project could allow designing innovative strategies to improve the protection of cultures against parasitic nematodes without being detrimental for mutualist symbioses, as well as to stimulate mutual plant-microorganism beneficial interactions in the context of the development of a more sustainable agriculture.