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Lichen-forming fungi are a diverse and ecologically important group of obligate mutualistic symbionts. Due to difficulties with maintaining them in culture and their extremely slow growth, lichenologists are increasingly opting for metagenomic sequencing followed by symbiont genome separation using bioinformatic pipelines. However, without knowing the true genome size of the lichen-forming fungus, we cannot quantify the completeness of the genome assembly and the efficacy of the bioinformatic filtering. To address this issue, we report here the first whole-genome assembly for the lichen-forming fungus Ramalina farinacea (L.) Ach. sequenced with Oxford Nanopore long-read technology alongside direct measurements of its genome size using flow cytometry. The assembly showed high contiguity (N50 = 1.55 Mb) and gene set completeness (BUSCO = 95.8%). The highly robust genome size of 33.61 Mb/1C (coefficients of variation = 2.98) that was obtained showed our assembly covered 97% of the entire genome. Our results demonstrate that accurate genome size measurements can be obtained directly from lichen thalli and used to provide a benchmark for assessing true cytometric completeness of metagenome-derived assemblies. [ABSTRACT FROM AUTHOR]

The Ascomycota form the largest phylum in the fungal kingdom and show a wide diversity of lifestyles, some involving associations with plants. Genomic data are available for many ascomycetes that are pathogenic to plants, but endophytes, which are asymptomatic inhabitants of plants, are relatively understudied. Here, using short- and long-read technologies, we have sequenced and assembled genomes for 15 endophytic ascomycete strains from CABI's culture collections. We used phylogenetic analysis to refine the classification of taxa, which revealed that 7 of our 15 genome assemblies are the first for the genus and/or species. We also demonstrated that cytometric genome size estimates can act as a valuable metric for assessing assembly "completeness", which can easily be overestimated when using BUSCOs alone and has broader implications for genome assembly initiatives. In producing these new genome resources, we emphasise the value of mining existing culture collections to produce data that can help to address major research questions relating to plant–fungal interactions. [ABSTRACT FROM AUTHOR]

Fungi produce a vast number of secondary metabolites that shape their interactions with other organisms and the environment. Characterizing the genes underpinning metabolite synthesis is therefore key to understanding fungal evolution and adaptation. Lichenized fungi represent almost one-third of Ascomycota diversity and boast impressive secondary metabolites repertoires. However, most lichen biosynthetic genes have not been linked to their metabolite products. Here we used metagenomic sequencing to survey gene families associated with production of anthraquinones, UV-protectant secondary metabolites present in various fungi, but especially abundant in a diverse order of lichens, the Teloschistales (class Lecanoromycetes , phylum Ascomycota). We successfully assembled 24 new, high-quality lichenized-fungal genomes de novo and combined them with publicly available Lecanoromycetes genomes from taxa with diverse secondary chemistry to produce a whole-genome tree. Secondary metabolite biosynthetic gene cluster (BGC) analysis showed that whilst lichen BGCs are numerous and highly dissimilar, core enzyme genes are generally conserved across taxa. This suggests metabolite diversification occurs via re-shuffling existing enzyme genes with novel accessory genes rather than BGC gains/losses or de novo gene evolution. We identified putative anthraquinone BGCs in our lichen dataset that appear homologous to anthraquinone clusters from non-lichenized fungi, suggesting these genes were present in the common ancestor of the subphylum Pezizomycotina. Finally, we identified unique transporter genes in Teloschistales anthraquinone BGCs that may explain why these metabolites are so abundant and ubiquitous in these lichens. Our results support the importance of metagenomics for understanding the secondary metabolism of non-model fungi such as lichens. [ABSTRACT FROM AUTHOR]

The fungal genus Fusarium (Ascomycota) includes well-known plant pathogens that are implicated in diseases worldwide, and many of which have been genome sequenced. The genus also encompasses other diverse lifestyles, including species found ubiquitously as asymptomatic-plant inhabitants (endophytes). Here, we produced structurally annotated genome assemblies for five endophytic Fusarium strains, including the first whole-genome data for Fusarium chuoi. Phylogenomic reconstruction of Fusarium and closely related genera revealed multiple and frequent lifestyle transitions, the major exception being a monophyletic clade of mutualist insect symbionts. Differential codon usage bias and increased codon optimisation separated Fusarium sensu stricto from allied genera. We performed computational prediction of candidate secreted effector proteins (CSEPs) and carbohydrate-active enzymes (CAZymes)—both likely to be involved in the host–fungal interaction—and sought evidence that their frequencies could predict lifestyle. However, phylogenetic distance described gene variance better than lifestyle did. There was no significant difference in CSEP, CAZyme, or gene repertoires between phytopathogenic and endophytic strains, although we did find some evidence that gene copy number variation may be contributing to pathogenicity. Large numbers of accessory CSEPs (i.e. present in more than one taxon but not all) and a comparatively low number of strain-specific CSEPs suggested there is a limited specialisation among plant associated Fusarium species. We also found half of the core genes to be under positive selection and identified specific CSEPs and CAZymes predicted to be positively selected on certain lineages. Our results depict fusarioid fungi as prolific generalists and highlight the difficulty in predicting pathogenic potential in the group. [ABSTRACT FROM AUTHOR]

The enormity of the breadth and depth of specimens held within the world's biological collections offers unparalleled opportunities to capture genomic data from across the entire range of known biological diversity. Such a task would take many lifetimes to complete if we could rely only on fresh samples. High-throughput sequencing provides a technical solution to the long-term problems of recalcitrant and degraded DNA typical of museum specimens, suggesting that we may be on the verge of a major collections-based revolution. Although the potential is great, the feasibility of using preserved collections for large-scale, taxonomically comprehensive phylogenomic studies remains unknown. In the present study, we demonstrate the continued relevance of fungarium collections in the genomic era by analyzing a genomic dataset composed of 39 genomes representing 26 family-level clades, including 14 newly generated draft genomes derived from short-read shotgun sequencing of preserved specimens, frozen and freeze-dried material, representing most of the known families of Agaricales. We predicted homologues of 210 putative single copy genes in the newly generated draft genome assemblies, of which 208 were used for phylogenetic reconstruction. Our analyses resulted in a robust and, for the first time, fully supported phylogeny of the Agaricales, enabling the recognition of seven suborders and providing a resource for testing hypotheses of the evolution of mushrooms. Our analysis of optimal combinations of ranked genes using an information theory-based method provides guidance on gene selection for future studies, enabling efficient application of high-throughput sequencing techniques toward unlocking the potential of collections-based research in the genomic era. [ABSTRACT FROM AUTHOR]