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Asset Tag: Fungus

July 7, 2019

Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists.

To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a ‘symbiosis toolkit’, with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.

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July 7, 2019

Dissecting the fungal biology of Bipolaris papendorfii: from phylogenetic to comparative genomic analysis.

Bipolaris papendorfii has been reported as a fungal plant pathogen that rarely causes opportunistic infection in humans. Secondary metabolites isolated from this fungus possess medicinal and anticancer properties. However, its genetic fundamental and basic biology are largely unknown. In this study, we report the first draft genome sequence of B. papendorfii UM 226 isolated from the skin scraping of a patient. The assembled 33.4 Mb genome encodes 11,015 putative coding DNA sequences, of which, 2.49% are predicted transposable elements. Multilocus phylogenetic and phylogenomic analyses showed B. papendorfii UM 226 clustering with Curvularia species, apart from other plant pathogenic Bipolaris species. Its genomic features suggest that it is a heterothallic fungus with a putative unique gene encoding the LysM-containing protein which might be involved in fungal virulence on host plants, as well as a wide array of enzymes involved in carbohydrate metabolism, degradation of polysaccharides and lignin in the plant cell wall, secondary metabolite biosynthesis (including dimethylallyl tryptophan synthase, non-ribosomal peptide synthetase, polyketide synthase), the terpenoid pathway and the caffeine metabolism. This first genomic characterization of B. papendorfii provides the basis for further studies on its biology, pathogenicity and medicinal potential. © The Author 2015. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.

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July 7, 2019

Genome sequence of Penicillium capsulatum strain ATCC 48735, a rare Penicillium species used in paper manufactories but that recently caused invasive infection.

The genus Penicillium phylogenetically belongs to Trichocomaceae, with approximately 300 reported species. The majority of these species are saprobic and commonly occur in soil. This paper reports the genome sequence of Penicillium capsulatum strain ATCC 48735, a rare Penicillium species used in paper manufactories and that was recently reported as a human-invasive opportunist. Copyright © 2015 Yang et al.

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July 7, 2019

Comparative analyses of clinical and environmental populations of Cryptococcus neoformans in Botswana.

Cryptococcus neoformans var. grubii (Cng) is the most common cause of fungal meningitis, and its prevalence is highest in sub-Saharan Africa. Patients become infected by inhaling airborne spores or desiccated yeast cells from the environment, where the fungus thrives in avian droppings, trees and soil. To investigate the prevalence and population structure of Cng in southern Africa, we analysed isolates from 77 environmental samples and 64 patients. We detected significant genetic diversity among isolates and strong evidence of geographic structure at the local level. High proportions of isolates with the rare MATa allele were observed in both clinical and environmental isolates; however, the mating-type alleles were unevenly distributed among different subpopulations. Nearly equal proportions of the MATa and MATa mating types were observed among all clinical isolates and in one environmental subpopulation from the eastern part of Botswana. As previously reported, there was evidence of both clonality and recombination in different geographic areas. These results provide a foundation for subsequent genomewide association studies to identify genes and genotypes linked to pathogenicity in humans. © 2015 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.

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July 7, 2019

The genome of the Saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives.

Vascular wilts caused by Verticillium spp. are destructive plant diseases affecting hundreds of hosts. Only a few Verticillium spp. are causal agents of vascular wilt diseases, of which V. dahliae is the most notorious pathogen, and several V. dahliae genomes are available. In contrast, V. tricorpus is mainly known as a saprophyte and causal agent of opportunistic infections. Based on a hybrid approach that combines second and third generation sequencing, a near-gapless V. tricorpus genome assembly was obtained. With comparative genomics, we sought to identify genomic features in V. dahliae that confer the ability to cause vascular wilt disease. Unexpectedly, both species encode similar effector repertoires and share a genomic structure with genes encoding secreted proteins clustered in genomic islands. Intriguingly, V. tricorpus contains significantly fewer repetitive elements and an extended spectrum of secreted carbohydrate- active enzymes when compared with V. dahliae. In conclusion, we highlight the technical advances of a hybrid sequencing and assembly approach and show that the saprophyte V. tricorpus shares many hallmark features with the pathogen V. dahliae.

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July 7, 2019

Complete mitochondrial genome of the medicinal fungus Ophiocordyceps sinensis.

As part of a genome sequencing project for Ophiocordyceps sinensis, strain 1229, a complete mitochondrial (mt) genome was assembled as a single circular dsDNA of 157,510?bp, one of the largest reported for fungi. Conserved genes including the large and small rRNA subunits, 27 tRNA and 15 protein-coding genes, were identified. In addition, 58 non-conserved open reading frames (ncORFs) in the intergenic and intronic regions were also identified. Transcription analyses using RNA-Seq validated the expression of most conserved genes and ncORFs. Fifty-two introns (groups I and II) were found within conserved genes, accounting for 68.5% of the genome. Thirty-two homing endonucleases (HEs) with motif patterns LAGLIDADG (21) and GIY-YIG (11) were identified in group I introns. The ncORFs found in group II introns mostly encoded reverse transcriptases (RTs). As in other hypocrealean fungi, gene contents and order were found to be conserved in the mt genome of O. sinensis, but the genome size was enlarged by longer intergenic regions and numerous introns. Intergenic and intronic regions were composed of abundant repetitive sequences usually associated with mobile elements. It is likely that intronic ncORFs, which encode RTs and HEs, may have contributed to the enlarged mt genome of O. sinensis.

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July 7, 2019

GMcloser: closing gaps in assemblies accurately with a likelihood-based selection of contig or long-read alignments.

Genome assemblies generated with next-generation sequencing (NGS) reads usually contain a number of gaps. Several tools have recently been developed to close the gaps in these assemblies with NGS reads. Although these gap-closing tools efficiently close the gaps, they entail a high rate of misassembly at gap-closing sites.We have found that the assembly error rates caused by these tools are 20-500-fold higher than the rate of errors introduced into contigs by de novo assemblers. We here describe GMcloser, a tool that accurately closes these gaps with a preassembled contig set or a long read set (i.e. error-corrected PacBio reads). GMcloser uses likelihood-based classifiers calculated from the alignment statistics between scaffolds, contigs and paired-end reads to correctly assign contigs or long reads to gap regions of scaffolds, thereby achieving accurate and efficient gap closure. We demonstrate with sequencing data from various organisms that the gap-closing accuracy of GMcloser is 3-100-fold higher than those of other available tools, with similar efficiency.GMcloser and an accompanying tool (GMvalue) for evaluating the assembly and correcting misassemblies except SNPs and short indels in the assembly are available at https://sourceforge.net/projects/gmcloser/.shunichi.kosugi@riken.jpSupplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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July 7, 2019

A novel type pathway-specific regulator and dynamic genome environments of solanapyrone biosynthesis gene cluster in the fungus Ascochyta rabiei.

Secondary metabolite genes are often clustered together and situated in particular genomic regions, like the subtelomere, that can facilitate niche adaptation in fungi. Solanapyrones are toxic secondary metabolites produced by fungi occupying different ecological niches. Full-genome sequencing of the ascomycete Ascochyta rabiei revealed a solanapyrone biosynthesis gene cluster embedded in an AT-rich region proximal to a telomere end and surrounded by Tc1/Mariner-type transposable elements. The highly AT-rich environment of the solanapyrone cluster is likely the product of repeat-induced point mutations. Several secondary metabolism-related genes were found in the flanking regions of the solanapyrone cluster. Although the solanapyrone cluster appears to be resistant to repeat-induced point mutations, a P450 monooxygenase gene adjacent to the cluster has been degraded by such mutations. Among the six solanapyrone cluster genes (sol1 to sol6), sol4 encodes a novel type of Zn(II)2Cys6 zinc cluster transcription factor. Deletion of sol4 resulted in the complete loss of solanapyrone production but did not compromise growth, sporulation, or virulence. Gene expression studies with the sol4 deletion and sol4-overexpressing mutants delimited the boundaries of the solanapyrone gene cluster and revealed that sol4 is likely a specific regulator of solanapyrone biosynthesis and appears to be necessary and sufficient for induction of the solanapyrone cluster genes. Despite the dynamic surrounding genomic regions, the solanapyrone gene cluster has maintained its integrity, suggesting important roles of solanapyrones in fungal biology. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

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July 7, 2019

Genome sequence of Stachybotrys chartarum strain 51-11.

The Stachybotrys chartarum strain 51-11 genome was sequenced by shotgun sequencing utilizing Illumina HiSeq 2000 and PacBio technologies. Since S. chartarum has been implicated as having health impacts within water-damaged buildings, any information extracted from the genomic sequence data relating to toxins or the metabolism of the fungus might be useful. Copyright © 2015 Betancourt et al.

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July 7, 2019

Comparative genomics and metabolic profiling of the genus Lysobacter.

Lysobacter species are Gram-negative bacteria widely distributed in soil, plant and freshwater habitats. Lysobacter owes its name to the lytic effects on other microorganisms. To better understand their ecology and interactions with other (micro)organisms, five Lysobacter strains representing the four species L. enzymogenes, L. capsici, L. gummosus and L. antibioticus were subjected to genomics and metabolomics analyses.Comparative genomics revealed a diverse genome content among the Lysobacter species with a core genome of 2,891 and a pangenome of 10,028 coding sequences. Genes encoding type I, II, III, IV, V secretion systems and type IV pili were highly conserved in all five genomes, whereas type VI secretion systems were only found in L. enzymogenes and L. gummosus. Genes encoding components of the flagellar apparatus were absent in the two sequenced L. antibioticus strains. The genomes contained a large number of genes encoding extracellular enzymes including chitinases, glucanases and peptidases. Various nonribosomal peptide synthase (NRPS) and polyketide synthase (PKS) gene clusters encoding putative bioactive metabolites were identified but only few of these clusters were shared between the different species. Metabolic profiling by imaging mass spectrometry complemented, in part, the in silico genome analyses and allowed visualisation of the spatial distribution patterns of several secondary metabolites produced by or induced in Lysobacter species during interactions with the soil-borne fungus Rhizoctonia solani.Our work shows that mining the genomes of Lysobacter species in combination with metabolic profiling provides novel insights into the genomic and metabolic potential of this widely distributed but understudied and versatile bacterial genus.

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July 7, 2019

De novo assembly of Dekkera bruxellensis: a multi technology approach using short and long-read sequencing and optical mapping.

It remains a challenge to perform de novo assembly using next-generation sequencing (NGS). Despite the availability of multiple sequencing technologies and tools (e.g., assemblers) it is still difficult to assemble new genomes at chromosome resolution (i.e., one sequence per chromosome). Obtaining high quality draft assemblies is extremely important in the case of yeast genomes to better characterise major events in their evolutionary history. The aim of this work is two-fold: on the one hand we want to show how combining different and somewhat complementary technologies is key to improving assembly quality and correctness, and on the other hand we present a de novo assembly pipeline we believe to be beneficial to core facility bioinformaticians. To demonstrate both the effectiveness of combining technologies and the simplicity of the pipeline, here we present the results obtained using the Dekkera bruxellensis genome.In this work we used short-read Illumina data and long-read PacBio data combined with the extreme long-range information from OpGen optical maps in the task of de novo genome assembly and finishing. Moreover, we developed NouGAT, a semi-automated pipeline for read-preprocessing, de novo assembly and assembly evaluation, which was instrumental for this work.We obtained a high quality draft assembly of a yeast genome, resolved on a chromosomal level. Furthermore, this assembly was corrected for mis-assembly errors as demonstrated by resolving a large collapsed repeat and by receiving higher scores by assembly evaluation tools. With the inclusion of PacBio data we were able to fill about 5 % of the optical mapped genome not covered by the Illumina data.

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July 7, 2019

Evaluation and validation of assembling corrected PacBio long reads for microbial genome completion via hybrid approaches.

Despite the ever-increasing output of next-generation sequencing data along with developing assemblers, dozens to hundreds of gaps still exist in de novo microbial assemblies due to uneven coverage and large genomic repeats. Third-generation single-molecule, real-time (SMRT) sequencing technology avoids amplification artifacts and generates kilobase-long reads with the potential to complete microbial genome assembly. However, due to the low accuracy (~85%) of third-generation sequences, a considerable amount of long reads (>50X) are required for self-correction and for subsequent de novo assembly. Recently-developed hybrid approaches, using next-generation sequencing data and as few as 5X long reads, have been proposed to improve the completeness of microbial assembly. In this study we have evaluated the contemporary hybrid approaches and demonstrated that assembling corrected long reads (by runCA) produced the best assembly compared to long-read scaffolding (e.g., AHA, Cerulean and SSPACE-LongRead) and gap-filling (SPAdes). For generating corrected long reads, we further examined long-read correction tools, such as ECTools, LSC, LoRDEC, PBcR pipeline and proovread. We have demonstrated that three microbial genomes including Escherichia coli K12 MG1655, Meiothermus ruber DSM1279 and Pdeobacter heparinus DSM2366 were successfully hybrid assembled by runCA into near-perfect assemblies using ECTools-corrected long reads. In addition, we developed a tool, Patch, which implements corrected long reads and pre-assembled contigs as inputs, to enhance microbial genome assemblies. With the additional 20X long reads, short reads of S. cerevisiae W303 were hybrid assembled into 115 contigs using the verified strategy, ECTools + runCA. Patch was subsequently applied to upgrade the assembly to a 35-contig draft genome. Our evaluation of the hybrid approaches shows that assembling the ECTools-corrected long reads via runCA generates near complete microbial genomes, suggesting that genome assembly could benefit from re-analyzing the available hybrid datasets that were not assembled in an optimal fashion.

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