Mucoromycotina 'Fine Root Endophytes' - a new window into the evolution of mycorrhizal symbioses

Symbiosis between arbuscular mycorrhizal fungi (AMF) and plants have driven land plant evolution and contribute significantly to plant nutrition. However, recent reports indicate that the diversity of mycorrhizal fungi is largely underestimated. Notably, fine root endophytes belonging to the Mucoromycotina clade (MFREs), a direct sister lineage to AMF, are gaining interest due to their nutritional role in terrestrial ecosystems. In this study, we harness the unprecedented opportunity to apply genomic and molecular genetic approaches to the first isolated MFRE, exploring symbiotic strategies in this direct mycorrhizal sister lineage to AMF. We have assembled its genome using complementary short- (Illumina) and long-read (Nanopore) sequencing technologies, providing the first ever MFRE genome. Genomic analyses revealed shared genomic signatures between MFRE and AMF as well as striking differences, indicating that MFREs incorporate saprotrophic traits into a mycorrhizal lifestyle. Since many Mucoromycotina fungi are axenically cultivable and genetically tractable, we are establishing a molecular genetic toolkit in MFRE to study the role of conserved mycorrhizal genes in nutritional mutualism and host accommodation.