Chitooligosaccharide receptors modulate root microbiota to enhance symbiosis and growth in Medicago

Plant roots interact with beneficial microbes, such as arbuscular mycorrhizal fungi (AMF), to aid in nutrient uptake. The interaction with AMF is initiated by plant Lysin motif (LysM) receptor-like kinases, CERK1 and LYR4 in Medicago truncatula, that detect AMF signals such as chitooligosaccharides (COs). However, the broader role of AMF-detecting receptors in shaping the root microbial community is largely unknown, and the impact of these receptor-mediated microbial communities on the AMF symbiosis is yet to be determined. This study examines the effects of CERK1 and LYR4 mutations on the root bacterial community, showing that these receptors have significant effects on shaping the bacterial community. Using bacteria isolated from wild-type roots, we created a synthetic bacterial community (SynCom), CO-SynCom. Plants inoculated with CO-SynCom exhibited significantly enhanced growth and AMF colonization in a manner dependent on the CO receptors LYR4 and CERK1, likely due to CERK1- and LYR4-mediated changes in hormone-related pathways and activation of symbiosis signaling. Our results highlight the essential role of plant symbiotic receptors in shaping root microbiota and offer valuable insights into optimizing plant-microbe interactions to enhance symbiosis and support sustainable agriculture.