• We sequenced and compared the genomes of seven species of milk-cap fungi (Lactarius, Russulales) with contrasted host-specificity. We also compared these genomes with those of symbiotic and saprotrophic Russulales species aiming to identify genes involved in their ecology and host-specificity.
• The size of Lactarius genomes is significantly larger than other Russulales species, owing to a massive accumulation of transposable elements and duplication of dispensable genes. As expected, their repertoire of genes coding for plant cell wall degrading enzymes is restricted, but they retained a substantial set of genes involved in microbial cell wall degradation. Notably, Lactarius species showed a striking expansion of genes encoding proteases, such as secreted ectomycorrhiza-induced sedolisins. A high copy number of genes coding for small secreted LysM proteins and Lactarius-specific lectins were detected, which may be linked to host-specificity.
• This study revealed a large diversity in the genome landscapes and gene repertoires within Russulaceae. The known host-specificity of Lactarius symbionts may be related to mycorrhiza-induced species-specific genes, including secreted sedolisins.
- Comparative genomics
- Ectomycorrhizal fungi
- Trait evolution