Hallmarks of basidiomycete soft- and white-rot in wood-decay -omics data of Armillaria [AROC18]

The genus Armillaria spp. (Fungi, Basidiomycota) includes devastating pathogens of temperate forests and saprotrophs that decay wood. Pathogenic and saprotrophic Armillaria species can efficiently colonize and decay woody substrates, however, mechanisms of wood penetration and colonization are poorly known. We assayed the colonization and decay of autoclaved spruce roots using the conifer-specialists Armillaria ostoyae and A. cepistipes using transcriptomic and proteomic data. Transcript and protein levels were altered more extensively in the saprotrophic A. cepistipes than in the pathogenic A. ostoyae and in invasive mycelia of both species compared to their rhizomorphs. Diverse suites of carbohydrate-active enzyme genes (CAZymes), in particular pectinolytic ones and expansins, were upregulated in both species, whereas ligninolytic genes were mostly downregulated. Our gene expression data, together with previous comparative genomic and decay-chemistry analyses suggest that wood decay by Armillaria differs from that of typical white rot fungi and shows features resembling soft rot. We propose that Armillaria species have modified the ancestral white rot machinery so that it allows for selective ligninolysis based on environmental conditions and/or host types. Overall design: Tissue samples from pathogenic and saprotropic Armillaria species colonizing spurce root were collected and profiled. Each group has 2-3 replicates.

蜜环菌属（Armillaria spp.，隶属于真菌界、担子菌门）包含温带森林中的毁灭性病原菌以及分解木材的腐生真菌。致病性与腐生型蜜环菌均能高效定殖并分解木质基质，但目前人们对其木材穿透与定殖的分子机制仍知之甚少。本研究采用转录组与蛋白质组学技术，针对针叶树专化型的奥氏蜜环菌（Armillaria ostoyae）与cepistipes蜜环菌（A. cepistipes），分析其在高压灭菌云杉根上的定殖与分解过程。结果显示，相较于致病性菌株A. ostoyae，腐生型菌株A. cepistipes的转录本与蛋白质水平发生了更为广泛的变化；而相较于各自的菌索（rhizomorphs），两个物种的入侵菌丝体的分子变化也更为显著。两个物种中均上调表达了多类碳水化合物活性酶基因（CAZymes），其中尤以果胶酶类与扩张蛋白（expansins）的上调最为显著，而木质素降解基因则大多被下调。本研究的基因表达数据结合此前的比较基因组学与分解化学分析结果显示，蜜环菌的木材分解过程不同于典型的白腐真菌，其降解特征更接近软腐真菌。我们推测，蜜环菌已对其祖先型白腐降解机制进行了修饰，使其能够根据环境条件或宿主类型实现选择性木质素分解。实验整体设计：收集并分析了致病性与腐生型蜜环菌定殖云杉根的组织样本，每组设置2-3个生物学重复。