Fungal Genomes Research Articles

To Study The Antifungal Susceptibility Pattern, Molecular Profiling And Its Sequencing Analysis Of Trichophyton Rubrum Isolated From Human Sample: A Cross Sectional Case Study From Uttar Pradesh, India

Introduction: There has been a sudden, unexplained surge in dermatophytoses in India since past 5 years. T. rubrum being the most common etiological agent isolated from clinically diagnosed lesions of cutaneus dermatophytosis. It has a significantly higher capacity of transmission than other anthropophilic dermatophytes. Aim and Objective: To study the Antifungal Susceptibility Pattern , Molecular Profiling and its Sequencing Analysis of Trichophyton rubrum isolated from human Sample. Material and Methods: This was a a prospective study carried out in the Department of Microbiology at Rama Medical College Hospital and Research Centre Mandhana, Kanpur for a period of 1 year i.e, March 2017 to March 2018. A total of 375 clinically suspected cases of superficial fungal infection were collected with proper informed consent. Dermatophytosis was confirmed in cases by direct microscopy and culture methods. Antifungal drug susceptibility profiles, MIC of isolates were 50 90 determined using the broth microdilution method according to the CLSI guidelines. The DNA isolation was done using the Qiagen DNA extraction kit followed by the PCR. The sequencing methods were used for the genetic analysis of virulence gene for the confirmation. Results: Out of the total of 375 clinically suspected cases of superficial fungal infection 31 isolates of Trichophyton rubrum were studied. The ratio of Male were more 27 (87%) as compared to the Female 4 (12.9% ). The maximum number of isolates was found in the Skin 28 (90.3%) followed by the Nail 3 (9.6%). The ITZ was most sensitive toward T. rubrum than KTZ, TBF, and FCZ. The molecular characterization for the detection of 18s gene was performed which was confirmed by the Sequencing Analysis. Conclusion: Antifungal resistance against T. rubrum is increasing over the last few decades due to genetic diversity in the fungal genome. The molecular identification is a gold standard technique for the identification of T. rubrum allowing important factor in providing fungal infection prevention and treatment approaches.

Do mitochondria use efflux pumps to protect their ribosomes from antibiotics?

Fungal environments are rich in natural and engineered antimicrobials, and this, combined with the fact that fungal genomes are rich in coding sequences for transporters, suggests that fungi are an intriguing group in which to search for evidence of antimicrobial efflux pumps in mitochondria. Herein, the range of protective mechanisms used by fungi against antimicrobials is introduced, and it is hypothesized, based on the susceptibility of mitochondrial and bacterial ribosomes to the same antibiotics, that mitochondria might also contain pumps that efflux antibiotics from these organelles. Preliminary evidence of ethidium bromide efflux is presented and several candidate efflux pumps are identified in fungal mitochondrial proteomes.

Genome mining for unknown-unknown natural products.

Genome mining of biosynthetic pathways with no identifiable core enzymes can lead to discovery of the so-called unknown (biosynthetic route)-unknown (molecular structure) natural products. Here we focused on a conserved fungal biosynthetic pathway that lacks a canonical core enzyme and used heterologous expression to identify the associated natural product, a highly modified cyclo-arginine-tyrosine dipeptide. Biochemical characterization of the pathway led to identification of a new arginine-containing cyclodipeptide synthase (RCDPS), which was previously annotated as a hypothetical protein and has no sequence homology to non-ribosomal peptide synthetase or bacterial cyclodipeptide synthase. RCDPS homologs are widely encoded in fungal genomes; other members of this family can synthesize diverse cyclo-arginine-Xaa dipeptides, and characterization of a cyclo-arginine-tryptophan RCDPS showed that the enzyme is aminoacyl-tRNA dependent. Further characterization of the biosynthetic pathway led to discovery of new compounds whose structures would not have been predicted without knowledge of RCDPS function.

CusProSe: a customizable protein annotation software with an application to the prediction of fungal secondary metabolism genes

We report here a new application, CustomProteinSearch (CusProSe), whose purpose is to help users to search for proteins of interest based on their domain composition. The application is customizable. It consists of two independent tools, IterHMMBuild and ProSeCDA. IterHMMBuild allows the iterative construction of Hidden Markov Model (HMM) profiles for conserved domains of selected protein sequences, while ProSeCDA scans a proteome of interest against an HMM profile database, and annotates identified proteins using user-defined rules. CusProSe was successfully used to identify, in fungal genomes, genes encoding key enzyme families involved in secondary metabolism, such as polyketide synthases (PKS), non-ribosomal peptide synthetases (NRPS), hybrid PKS-NRPS and dimethylallyl tryptophan synthases (DMATS), as well as to characterize distinct terpene synthases (TS) sub-families. The highly configurable characteristics of this application makes it a generic tool, which allows the user to refine the function of predicted proteins, to extend detection to new enzymes families, and may also be applied to biological systems other than fungi and to other proteins than those involved in secondary metabolism.

Fungal NRPS-PKS Hybrid Enzymes Biosynthesize New γ-Lactam Compounds, Taslactams A-D, Analogous to Actinomycete Proteasome Inhibitors.

Proteasome inhibitors with γ-lactam structure, such as lactacystin and salinosporamide A, have been isolated from actinomycetes and have attracted attention as lead compounds for anticancer drugs. Previously, we identified a unique enzyme TAS1, which is the first reported fungal NRPS-PKS hybrid enzyme, from the filamentous fungus Pyricularia oryzae for the biosynthesis of a mycotoxin tenuazonic acid, a tetramic acid compound without γ-lactam structure. Homologues of TAS1 have been identified in several fungal genomes and classified into four groups (A-D). Here, we show that the group D TAS1 homologues from two filamentous fungi can biosynthesize γ-lactam compounds, taslactams A-D, with high similarity to actinomycete proteasome inhibitors. One of the γ-lactam compounds, taslactam C, showed potent proteasome inhibitory activity. In contrast to actinomycete γ-lactam compounds which require multiple enzymes for biosynthesis, the TAS1 homologue alone was sufficient for the biosynthesis of the fungal γ-lactam compounds.

Fungal composition in saliva and plaque in children with caries: Differences and influencing factors

Caries is a dental disease that can affect oral and psychological health and has a high incidence in children. The role of fungal flora in childhood caries has not been fully described. In this study, we aimed to investigate the fungal composition differences and the influencing factors in unstimulated saliva (S) and supragingival plaque (P) samples in childhood caries. S and P samples were collected from 63 children with caries. The ITS2 region in the fungal genome was then amplified and sequenced. Subsequently, we quantified and analyzed the fungal compositions in the samples. Cryptococcus was the most abundant genus in the S and P subgroups. The relative abundances of Cryptococcus and Wickerhamomyces significantly differed between the S and P subgroups (p ​< ​0.05). Significant differences were also observed in alpha and beta diversities between the two subgroups (p ​< ​0.05). However, no significant differences were observed between the mycobiome of the SFe and SMa subgroups or the PFe and PMa subgroups (p ​> ​0.05). Conversely, species differences were detected between the SDD and SMD subgroups (p ​< ​0.05) but not in the PDD and PPD subgroups (p ​> ​0.05). Our findings revealed significant differences in the mycobiome of unstimulated saliva and supragingival plaque. Dentition period and oral hygiene behaviors may have affected these differences.

In silico Analysis and Characterization of a Putative Aspartic Proteinase Inhibitor, IA3 from Lachancea kluyveri

Aspartic proteinases play important role in various physiological and biological processes. Understanding catalytic mechanisms of these enzymes could lead to crucial medical and biological applications. Two types of aspartic proteinase inhibitors have been identified i.e. small molecule inhibitor and naturally occurring peptides. Most of aspartic proteinases are highly susceptible to inhibition by a series of small, non-proteinaceous natural products; pepstatin. However, only limited number of naturally-occurring polypeptide inhibitors of aspartic proteinases has so far been discovered. One among these inhibitors is Saccharomyces cerevisiae IA3. The S. cerevisiae Proteinase A (ScPrA) is solely and potently inhibited by this small polypeptide at sub-nanomolar level. It was proven that, not only IA3 has no detectable effect against a wide range of aspartic proteinases, but it was also shown to be cleaved as a substrate of these non-target enzymes. Bioinformatics analysis of the IA3 structure has been undertaken in this study. Database searching for sequence homology from available fungal genome data bank using the Basic Local Alignment Search Tool (BLAST) revealed that 4 structurally related, IA3-like proteins have successfully been identified. The amino acid sequence of IA3-like proteins from Lachancea kluyveri share highest degree of similarity toward wild-type IA3. The Lk-IA3-like gene was synthesized using a PCR-based gene synthesis method. Protein expression in E. coli, protein purification and characterization of Lk-IA3-like by enzyme kinetic assays were performed. The results indicated that Lk-IA3-like protein inhibits ScPrA at the Ki value of 190 ± 0.11 nM and possesses no inhibitory effect toward AfPrA (Aspergillus fumigatus proteinase A) or HuCatD (Human cathepsin D). HIGHLIGHTS Aspartic proteinases enzyme family is crucially involved in various physiological and biological processes including in the pathogenesis of numerous diseases which make them a possible target for drug design Inhibitors of aspartic proteinases are not only applied for human disease treatment but also extended to plant and other economically important animals Aspartic proteinase from cerevisiae (Proteinase A) is solely and potently inhibited by a small peptideinhibitor, IA3 Bioinformatics analysis of the naturally occurring aspartic proteinases inhibitor, IA3 structure has been undertaken in this research and putative IA3-like proteins have successfully been identified IA3-like proteins from Lachancea kluyveri were produced in coli and enzyme inhibition assays revealed that Lk-IA3-like protein inhibits ScPrA at the Ki value of 190 ± 0.11 nM GRAPHICAL ABSTRACT

MethylC-analyzer: a comprehensive downstream pipeline for the analysis of genome-wide DNA methylation

DNA methylation is a crucial epigenetic modification involved in multiple biological processes and diseases. Current approaches for measuring genome-wide DNA methylation via bisulfite sequencing (BS-seq) include whole-genome bisulfite sequencing (WGBS), reduced representation bisulfite sequencing (RRBS), and enzymatic methyl-seq (EM-seq). The computational analysis tools available for BS-seq data include customized aligners for mapping bisulfite-converted reads and computational pipelines for downstream data analysis. Current post-alignment methylation tools are specialized for the interpretation of CG methylation, which is known to dominate mammalian genomes, however, non-CG methylation (CHG and CHH, where H refers to A, C, or T) is commonly observed in plants and fungi and is closely associated with gene regulation, transposon silencing, and plant development. Thus, we have developed a MethylC-analyzer to analyze and visualize post-alignment WGBS, RRBS, and EM-seq data focusing on CG. The tool is able to also analyze non-CG sites to enhance deciphering genomes of plants and fungi. By processing aligned data and gene location files, MethylC-analyzer generates a genome-wide view of methylation levels and methylation in user-specified genomic regions. The meta-plot, for example, allows the investigation of DNA methylation within specific genomic elements. Moreover, our tool identifies differentially methylated regions (DMRs) and investigates the enrichment of genomic features associated with variable methylation. MethylC-analyzer functionality is not limited to specific genomes, and we demonstrated its performance on both plant and human BS-seq data. MethylC-analyzer is a Python- and R-based program designed to perform comprehensive downstream analyses of methylation data, providing an intuitive analysis platform for scientists unfamiliar with DNA methylation analysis. It is available as either a standalone version for command-line uses or a graphical user interface (GUI) and is publicly accessible at https://github.com/RitataLU/MethylC-analyzer.

The genome of Lyophyllum shimeji provides insight into the initial evolution of ectomycorrhizal fungal genomes

Mycorrhizae are one of the most fundamental symbioses between plants and fungi, with ectomycorrhizae being the most widespread in boreal forest ecosystems. Ectomycorrhizal fungi are hypothesized to have evolved convergently from saprotrophic ancestors in several fungal clades, especially members of the subdivision Agaricomycotina. Studies on fungal genomes have identified several typical characteristics of mycorrhizal fungi, such as genome size expansion and decreases in plant cell-wall degrading enzymes (PCWDEs). However, genomic changes concerning the evolutionary transition to the ectomycorrhizal lifestyle are largely unknown. In this study, we sequenced the genome of Lyophyllum shimeji, an ectomycorrhizal fungus that is phylogenetically related to saprotrophic species and retains some saprotroph-like traits. We found that the genome of Ly. shimeji strain AT787 lacks both incremental increases in genome size and reduced numbers of PCWDEs. Our findings suggest that the previously reported common genomic traits of mycorrhizal fungi are not essential for the ectomycorrhizal lifestyle, but are a result of abolishing saprotrophic activity. Since Ly. shimeji is commercially consumed as an edible mushroom, the newly available genomic information may also impact research designed to enhance the cultivation of this mushroom.

Copy Number Variation and Allele Ratio Analysis in Candida albicans Using Whole Genome Sequencing Data.

Whole genome sequencing of human fungal pathogens has revolutionized the speed and accuracy in which sequence variants that cause antifungal resistance can be identified. Genome rearrangements resulting in copy number variation (CNV) are a significant source of acquired antifungal drug resistance across diverse fungal species. Some CNVs are transient in nature, while other CNVs are stable and well tolerated even in the absence of antifungal drugs. By visualizing whole genome sequencing read depth as a function of genomic location, CNVs and CNV breakpoints (genomic positions where the copy number changes occur relative to the rest of the genome) are rapidly identified. A similar analysis can be used to visualize allele ratio changes that occur across the genomes of heterozygous fungal species, both in the presence and absence of CNVs. This protocol walks through the bioinformatic analysis of CNVs and allele ratios utilizing free, open-source visualization tools. We provide code to use with an example dataset (matched antifungal drug-sensitive and drug-resistant Candida albicans isolates) and notes on how to expand this protocol to other fungal genomes.

Identifying Fungal Secondary Metabolites and Their Role in Plant Pathogenesis.

Pathogenic fungi are the main infectious agents of plants. Secondary metabolites produced by these fungi, also recognized as natural products, are key mediators of plant-fungal interactions. Knowledge on the biosynthesis of these metabolites, the accessibility to fungal genome sequences, and the development of gene disruption techniques open up opportunities to identify many more of these metabolites both in vitro and in planta. This methodology chapter gives a detailed systematic approach aiming to discover new natural products from phytopathogenic fungi and characterize their role in triggering plant cell death and plant disease. This approach takes advantage of the global regulation of fungal secondary metabolite production by regulatory proteins reported in various fungal species.

Current status of secondary metabolite pathways linked to their related biosynthetic gene clusters in Aspergillus section Nigri.

Covering: up to the end of 2021Aspergilli are biosynthetically 'talented' micro-organisms and therefore the natural products community has continually been interested in the wealth of biosynthetic gene clusters (BGCs) encoding numerous secondary metabolites related to these fungi. With the rapid increase in sequenced fungal genomes combined with the continuous development of bioinformatics tools such as antiSMASH, linking new structures to unknown BGCs has become much easier when taking retro-biosynthetic considerations into account. On the other hand, in most cases it is not as straightforward to prove proposed biosynthetic pathways due to the lack of implemented genetic tools in a given fungal species. As a result, very few secondary metabolite biosynthetic pathways have been characterized even amongst some of the most well studied Aspergillus spp., section Nigri (black aspergilli). This review will cover all known biosynthetic compound families and their structural diversity known from black aspergilli. We have logically divided this into sub-sections describing major biosynthetic classes (polyketides, non-ribosomal peptides, terpenoids, meroterpenoids and hybrid biosynthesis). Importantly, we will focus the review on metabolites which have been firmly linked to their corresponding BGCs.

Chromosomal genome sequence assembly and mating-type (MAT) locus characterization of the leprose asexual lichenized fungus Lepraria neglecta (Nyl.) Erichsen

AbstractComplete chromosomal-level assemblies of fungal genomes are rare. The intimate ecological symbioses and complex reproduction strategies utilized by fungi make highly contiguous, gapless genome assemblies particularly difficult. Here, we use long-read sequencing on the Oxford Nanopore Technology MinION platform to sequence and assemble the genome of Lepraria neglecta (Ascomycota, Lecanorales). In addition to eight contigs ascribable to chromosomes, six of which are assembled telomere-to-telomere, we discovered the presence of a complete MAT locus with two conserved MAT1-2 genes and a putative MAT1-1 pseudogene. The full genome assembly of a widespread, common species presents an opportunity for new insights into lichen reproduction while the presence of the mating-type locus in the genome of an asexual lichen raises fundamental questions about reproductive biology in fungi generally.

High-throughput functional profiling of the human fungal pathogen Candida albicans genome

Candida albicans is a major fungal pathogen of humans. Although its genome has been sequenced more than two decades ago, there are still over 4300 uncharacterized C. albicans genes. We previously generated an ORFeome as well as a collection of destination vectors to facilitate overexpression of C. albicans ORFs. Here, we report the construction of ∼2500 overexpression mutants and their evaluation by in vitro spotting on rich medium and in a liquid pool experiment in rich medium, allowing the identification of genes whose overexpression has a fitness cost. The candidates were further validated at the individual strain level. This new resource allows large-scale screens in different growth conditions to be performed routinely. Altogether, based on the concept of identifying functionally related genes by cluster analysis, the availability of this overexpression mutant collection will facilitate the characterization of gene functions in C. albicans.

New insights into genome annotation in Podospora anserina through re-exploiting multiple RNA-seq data

BackgroundPublicly available RNA-seq datasets are often underused although being helpful to improve functional annotation of eukaryotic genomes. This is especially true for filamentous fungi genomes which structure differs from most well annotated yeast genomes. Podospora anserina is a filamentous fungal model, which genome has been sequenced and annotated in 2008. Still, the current annotation lacks information about cis-regulatory elements, including promoters, transcription starting sites and terminators, which are instrumental to integrate epigenomic features into global gene regulation strategies.ResultsHere we took advantage of 37 RNA-seq experiments that were obtained in contrasted developmental and physiological conditions, to complete the functional annotation of P. anserina genome. Out of the 10,800 previously annotated genes, 5’UTR and 3’UTR were defined for 7554, among which, 3328 showed differential transcriptional signal starts and/or transcriptional end sites. In addition, alternative splicing events were detected for 2350 genes, mostly due alternative 3’splice sites and 1732 novel transcriptionally active regions (nTARs) in unannotated regions were identified.ConclusionsOur study provides a comprehensive genome-wide functional annotation of P. anserina genome, including chromatin features, cis-acting elements such as UTRs, alternative splicing events and transcription of non-coding regions. These new findings will likely improve our understanding of gene regulation strategies in compact genomes, such as those of filamentous fungi. Characterization of alternative transcripts and nTARs paves the way to the discovery of putative new genes, alternative peptides or regulatory non-coding RNAs.

Reference-based read clustering improves the de novo genome assembly of microbial strains

Constructing accurate microbial genome assemblies is necessary to understand genetic diversity in microbial genomes and its functional consequences. However, it still remains as a challenging task especially when only short-read sequencing technologies are used. Here, we present a new read-clustering algorithm, called RBRC, for improving de novo microbial genome assembly, by accurately estimating read proximity using multiple reference genomes. The performance of RBRC was confirmed by simulation-based evaluation in terms of assembly contiguity and the number of misassemblies, and was successfully applied to existing fungal and bacterial genomes by improving the quality of the assemblies without using additional sequencing data. RBRC is a very useful read-clustering algorithm that can be used (i) for generating high-quality genome assemblies of microbial strains when genome assemblies of related strains are available, and (ii) for upgrading existing microbial genome assemblies when the generation of additional sequencing data, such as long reads, is difficult.

Multiplex Base-Editing Enables Combinatorial Epigenetic Regulation for Genome Mining of Fungal Natural Products.

Genome mining of cryptic natural products (NPs) remains challenging, especially in filamentous fungi, owing to their complex genetic regulation. Increasing evidence indicates that several epigenetic modifications often act cooperatively to control fungal gene transcription, yet the ability to predictably manipulate multiple genes simultaneously is still largely limited. Here, we developed a multiplex base-editing (MBE) platform that significantly improves the capability and throughput of fungal genome manipulation, leading to the simultaneous inactivation of up to eight genes using a single transformation. We then employed MBE to inactivate three negative epigenetic regulators combinatorially in Aspergillus nidulans, enabling the activation of eight cryptic gene clusters compared to the wild-type strains. A group of novel NPs harboring unique cichorine and polyamine hybrid chemical scaffolds were identified, which were not reported previously. We envision that our scalable and efficient MBE platform can be readily applied in other filamentous fungi for the genome mining of novel NPs, providing a powerful approach for the exploitation of fungal chemical diversity.

MycoCosm, the JGI's Fungal Genome Portal for Comparative Genomic and Multiomics Data Analyses.

MycoCosm ( https://mycocosm.jgi.doe.gov/ ) is an integrated fungal genomics portal that currently includes over 2000 fungal genomes. Efficiently exploring these genomes allows the scientific community to address challenges associated with energy and the environment. Here, we provide examples and guidelines for navigating around MycoCosm, and for using a variety of analysis tools to compare genomics and other "omics" data from the fungus Neocallimastix californiae with its relatives.

Horizontal transfer of tRNA genes to mitochondrial plasmids facilitates gene loss from fungal mitochondrial DNA

Fungal and plant mitochondria are known to exchange DNA with retroviral plasmids. Transfer of plasmid DNA to the organellar genome is best known and occurs through wholesale insertion of the plasmid. Less well known is the transfer of organellar DNA to plasmids, in particular tRNA genes. Presently, it is unknown whether fungal plasmids can adopt mitochondrial functions such as tRNA production through horizontal gene transfer. In this paper, we studied the exchange of DNA between fungal linear plasmids and fungal mtDNA, mainly focusing on the basidiomycete family Lyophyllaceae. We report at least six independent transfers of complete tRNA genes to fungal plasmids. Furthermore, we discovered two independent cases of loss of a tRNA gene from a fungal mitochondrial genome following transfer of such a gene to a linear mitochondrial plasmid. We propose that loss of a tRNA gene from mtDNA following its transfer to a plasmid creates a mutualistic dependency of the host mtDNA on the plasmid. We also find that tRNA genes transferred to plasmids encode codons that occur at the lowest frequency in the host mitochondrial genomes, possibly due to a higher number of unused transcripts. We discuss the potential consequences of mtDNA transfer to plasmids for both the host mtDNA and the plasmid.

Generating a construct harboring the rpb1 promoter for enhancing recombinant protein expression in the medicinal mushroom Cordyceps militaris

Cordyceps militaris is a valuable medicinal mushroom that contains numerous bioactive ingredients such as cordycepin, adenosine, pentostatin, polysaccharides, and carotenoids. However, the contents of these substances in wild-type strains of C. militaris are relatively low. Recently, the genome of C. militaris has been fully sequenced, and genes involved in the biosynthesis of beneficial constituents have been identified. Therefore, research on enhancing the biosynthesis of the bioactive compounds in this fungus by recombinant DNA technology has advantages. In the present study, the authors have successfully generated a binary vector with a T-DNA region carrying a construct regulated by the native rpb1 promoter that can enhance gene expression in C. militaris. The T-DNA structure from the binary vector was then transferred into the C. militaris genome by Agrobacterium tumefaciens-mediated transformation. Analysis of some fungal transformants by PCR using the specific primer pairs indicated that the T-DNA structure was successfully integrated into the fungal genome. Observation of the transformants under fluorescence microscopy confirmed the overexpression of the DsRed fluorescent protein under the regulation of the rpb1promoter. The binary vector carrying the rpb1 promoter constructed in this study can be employed to promote the expression of target genes in the medicinal mushroom C. militaris.