Despite the ubiquity and importance of ectomycorrhizal fungi to ecosystem function, our
understanding of their functional ecology remains poor. The highly melanized and common ectomycorrhizal fungus, Cenococcum geophilum, is drought tolerant and abundant inwater-stressed habitats, yet the responsible functional traits have not been identified. The production of melanin, a class of complex dark ... [Show full abstract] polymers found in fungal cell walls, may be a key functional trait to water stress tolerance. To test this hypothesis, we devised a series
of experiments determining the effect of the melanin biosynthesis inhibitor, tricyclazole,
on response to osmotic and desiccation stresses. Melanin inhibition only had negative
effects on growth when C. geophilum isolates were subjected to osmotic and desiccation
stress (-1.7 MPa and desiccated) but not under control conditions (-0.01 MPa and nondesiccated).This suggests that melanin production is an important functional trait that
contributes to water stress tolerance of this cosmopolitan ectomycorrhizal fungus.