P-397 - Characterization of the interactome of Lotus japonicus RAM1, a GRAS protein required for arbuscule development

More than 80% of land plants establish symbiotic interactions with arbuscular mycorrhiza fungi (AMF). During these interactions, AMF provide water and mineral nutrients to host plants and in return, plants support the fungi with fatty acids and carbohydrates. This nutrient exchange takes place through highly specialized AMF structures known as arbuscules. One of the central players in the development of arbuscules is the plant GRAS transcription factor REQUIRED FOR ARBUSCULAR MYCORRHIZATION 1 (RAM1). RAM1 is essential for cortex cell remodeling to allow fine branching of arbuscules. RAM1 targets downstream genes essential for nutrient exchange such as PT4 or STR. However, RAM1, as most of the GRAS proteins, does not directly bind to the DNA. Therefore, the interaction with other DNA-binding proteins appears essential for the gene regulation by RAM1. To date, the RAM1 interactome has been poorly described. Therefore, we have used proximity labelling to identify interaction partners of Lotus japonicus RAM1 and we expect that the characterization of these interactors will provide us with a deeper understanding of RAM1 function, regulation and more broadly, the regulation of arbuscule accommodation in root cortex cells.