Conserved vs. Divergent strategies for fungal accommodation in endomycorrhizas

Endomycorrhizas are symbiotic associations between plant roots and fungi that play a crucial role in plant nutrition and ecosystem functioning. This review explores conserved and divergent strategies underlying fungal accommodation in arbuscular (AM), ericoid (ERM), and orchid (ORM) mycorrhizas. One feature common to all three symbioses is the formation of an interface compartment that mediates nutrient exchange, a trait first observed in AM and later confirmed in ERM and ORM. In this process, the host cell organization undergoes significant modifications, including vacuolar fragmentation, nuclear repositioning and cytoskeletal rearrangement. While transcriptomic and genomic analyses confirm the conservation of several features, such as the upregulation of plant and fungal membrane transporters, substantial differences emerge in fungal hydrolytic enzyme activity and nutrient acquisition strategies. The evolutionary history of these associations suggests that AM fungi were the ancestral symbionts of land plants, with ERM and ORM fungi replacing them in specific ecological niches. Advances in single-nucleus transcriptomics and nuclear dynamics studies are providing new insights into the mechanisms governing these complex symbioses. Understanding the balance between conservation and divergence in endomycorrhizal interactions is critical for unravelling their functional significance in plant-fungal co-evolution.