Huayong Wang, Annegret Kohler, Francis Michel Martin

The ascomycete Cenococcum geophilum is a cosmopolitan and ecologically significant ectomycorrhizal (ECM) fungus that forms symbiotic associations with diverse host plants globally across various ecosystems. As the only known ECM member of Dothideomycetes, C. geophilum exhibits several distinctive characteristics that distinguish it from other ECM fungi. Its high genetic diversity is particularly noteworthy considering its asexual reproduction mode. This genetic variability may contribute to its adaptability and extensive distribution across habitats. As an early colonizer of primary forest succession, C. geophilum significantly contributes to ecosystem stability and development. Its ability to establish quickly in disturbed or newly formed habitats helps create conditions favorable for the establishment of other plant species, thereby playing a crucial role in ecological succession and ecosystem recovery. C. geophilum plays several key roles in forest and other terrestrial ecosystems. It is particularly important in nutrient cycling as it facilitates the transfer of nutrients, especially nitrogen and phosphorus, from the soil to its host plants. Additionally, C. geophilum has been demonstrated to enhance the drought resistance of its host plants, a trait that is becoming increasingly important in the context of climate change and frequent drought events. Recent advances in molecular biology and genomics have revealed that C. geophilum is not a single species but rather a species complex comprising multiple cryptic lineages. These lineages exhibit potential host preferences, suggesting a degree of specialization within the complex. The genome of C. geophilum has been sequenced and analyzed, providing valuable insights into its molecular biology and symbiotic capabilities. Notably, this genome encodes a reduced repertoire of carbohydrate-active enzymes and a large set of effector-like, small secreted proteins. These molecular traits likely facilitate host colonization across diverse plant taxa by enabling the fungus to interact with and modify plant cell walls, as well as to communicate with its host plants through various signaling pathways. Therefore, C. geophilum is a compelling model system for research on fungal ecology, evolution, and mycorrhizal symbiosis.