Hallmarks of basidiomycete soft- and white-rot in wood-decay -omics data ofArmillaria

Abstract

AbstractThe genusArmillariaspp. (Fungi, Basidiomycota) includes devastating pathogens of temperate forests and saprotrophs that decay wood. Pathogenic and saprotrophicArmillariaspecies 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-specialistsArmillaria ostoyaeandA. cepistipesusing transcriptomic and proteomic data. Transcript and protein levels were altered more extensively in the saprotrophicA. cepistipesthan in the pathogenicA. ostoyaeand 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 byArmillariadiffers from that of typical white-rot fungi and shows features resembling soft rot. We propose thatArmillariaspecies have modified the ancestral white-rot machinery so that it allows for selective ligninolysis based on environmental conditions and/or host types.