Rapid divergence of genome architectures following the origin of an ectomycorrhizal symbiosis in the genus Amanita

Fungi are evolutionary shape shifters and adapt quickly to new environments. Ectomycorrhizal (EM) symbioses are mutualistic associations between fungi and plants and have evolved repeatedly and independently across the fungal tree of life, suggesting lineages frequently reconfigure genome content to take advantage of open ecological niches. To date analyses of genomic mechanisms facilitating EM symbioses have involved comparisons of distantly related species, but here, we use the genomes of three EM and two asymbiotic (AS) fungi from the genus Amanita as well as an AS outgroup to study genome evolution following a single origin of symbiosis. Our aim was to identify the defining features of EM genomes, but our analyses suggest no clear differentiation of genome size, gene repertoire size or transposable element content between EM and AS species. Phylogenetic inference of gene gains and losses suggests the transition to symbiosis was dominated by the loss of plant cell wall decomposition ...真菌在演化过程中具备形态可塑性，可快速适应各类新环境。外生菌根（Ectomycorrhizal, EM）共生是真菌与植物间的互利共生关系，该共生模式在真菌生命树中多次独立演化，这提示真菌类群常通过重构基因组内容以开拓开放生态位。迄今为止，有关介导EM共生的基因组机制的研究多采用远缘物种比较分析策略。本研究则选取鹅膏属（Amanita）的3株EM真菌、2株非共生（asymbiotic, AS）真菌，以及1株AS外类群的基因组，探究单次共生起源事件后的基因组演化历程。本研究最初旨在明确EM基因组的典型特征，但分析结果显示，EM与AS物种在基因组大小、基因库大小以及转座因子（transposable element）含量上均无显著差异。基于基因得失事件的系统发育推断表明，向共生生活方式的转变主要伴随植物细胞壁分解相关基因的丢失……