Transposable element dynamics among asymbiotic and ectomycorrhizal amanita fungi

Abstract

Transposable elements (TEs) are ubiquitous inhabitants of eukaryotic genomes and their proliferation and dispersal shape genome architectures and diversity. Nevertheless, TE dynamics are often explored for one species at a time and are rarely considered in ecological contexts. Recent work with plant pathogens suggests a link between symbiosis and TE abundance. The genomes of pathogenic fungi appear to house an increased abundance of TEs, and TEs are frequently associated with the genes involved in symbiosis. To investigate whether this pattern is general, and relevant to mutualistic plant-fungal symbioses, we sequenced the genomes of related asymbiotic (AS) and ectomycorrhizal (ECM) Amanita fungi. Using methods developed to interrogate both assembled and unassembled sequences, we characterized and quantified TEs across three AS and three ECM species, including the AS outgroup Volvariella volvacea. The ECM genomes are characterized by abundant numbers of TEs, an especially prominent featureofunassembledsequencing libraries. IncreasedTEactivityinECMspecies is alsosupportedbyphylogeneticanalysisof thethree most abundant TE superfamilies; phylogenies revealed many radiations within contemporary ECMspecies. However, the AS species Amanita thiersii also houses extensive amplifications of elements, highlighting the influence of additional evolutionary parameters on TEabundance.Ouranalysesprovide further evidenceforalinkbetweensymbioticassociationsamongplantsandfungi,andincreased TE activity, while highlighting the importance individual species' natural historiesmay have in shaping genome architecture. © The Author(s) 2014.