Fungal cytochrome p450 monooxygenases: their distribution, structure, functions, family expansion, and evolutionary origin

Phylogenomics Reveal the Dynamic Evolution of Fungal Nitric Oxide Reductases and Their Relationship to Secondary Metabolism

Fungi expressing P450nor, an unconventional nitric oxide (NO) reducing cytochrome P450, are considered significant contributors to environmental nitrous oxide (N₂O) emissions. Despite extensive efforts, fungal contributions to N₂O emissions remain uncertain. For example, the majority of N₂O emitted from antibiotic-amended soil microcosms is attributed to fungal activity, yet axenic fungal cultures do not couple N-oxyanion respiration to growth and these fungi produce only minor quantities of N₂O. To assist in reconciling these conflicting observations and produce a benchmark genomic analysis of fungal denitrifiers, genes underlying denitrification were examined in >700 fungal genomes. Of 167 p450nor—containing genomes identified, 0, 30, and 48 also harbored the denitrification genes narG, napA, or nirK, respectively. Compared with napA and nirK, p450nor was twice as abundant and exhibited 2–5-fold more gene duplications, losses, and transfers, indicating a disconnect between p450nor presence and denitrification potential. Furthermore, cooccurrence of p450nor with genes encoding NO-detoxifying flavohemoglobins (Spearman r = 0.87, p = 1.6e⁻¹⁰) confounds hypotheses regarding P450nor’s primary role in NO detoxification. Instead, ancestral state reconstruction united P450nor with actinobacterial cytochrome P450s (CYP105) involved in secondary metabolism (SM) and 19 (11%) p450nor-containing genomic regions were predicted to be SM clusters. Another 40 (24%) genomes harbored genes nearby p450nor predicted to encode hallmark SM functions, providing additional contextual evidence linking p450nor to SM. These findings underscore the potential physiological implications of widespread p450nor gene transfer, support the undiscovered affiliation of p450nor with fungal SM, and challenge the hypothesis of p450nor’s primary role in denitrification.

Bioremediation and microbial metabolism of benzo(a)pyrene

The growing release of organic contaminants into the environment due to industrial processes has inevitably increased the incidence of their exposure to humans which often results in negative health effects. Microorganisms are also increasingly exposed to the pollutants, yet their diverse metabolic capabilities enable them to survive toxic exposure making these degradation mechanisms important to understand. Fungi are the most abundant microorganisms in the environment, yet less has been studied to understand their ability to degrade contaminants than in bacteria. This includes specific enzyme production and the genetic regulation which guides metabolic networks. This review intends to compare what is known about bacterial and fungal degradation of toxic compounds using benzo(a)pyrene as a relevant example. Most research is done in the context of using fungi for bioremediation, however, we intend to also point out how fungal metabolism may impact human health in other ways including through their participation in microbial communities in the human gut and skin and through inhalation of fungal spores.

A Xenobiotic Detoxification Pathway through Transcriptional Regulation in Filamentous Fungi

Fungi are known to utilize transcriptional regulation of genes that encode efflux transporters to detoxify xenobiotics; however, to date it is unknown how fungi transcriptionally regulate and coordinate different phases of detoxification system (phase I, modification; phase II, conjugation; and phase III, secretion). Here we present evidence of an evolutionary convergence between the fungal and mammalian lineages, whereby xenobiotic detoxification genes (phase I coding for cytochrome P450 monooxygenases [CYP450s] and phase III coding for ATP-binding cassette [ABC] efflux transporters) are transcriptionally regulated by structurally unrelated proteins. Following next-generation RNA sequencing (RNA-seq) analyses of a filamentous fungus, Sclerotinia homoeocarpa, the causal agent of dollar spot on turfgrasses, a multidrug resistant (MDR) field strain was found to overexpress phase I and III genes, coding for CYP450s and ABC transporters for xenobiotic detoxification. Furthermore, there was confirmation of a gain-of-function mutation of the fungus-specific transcription factor S. homoeocarpa XDR1 (ShXDR1), which is responsible for constitutive and induced overexpression of the phase I and III genes, resulting in resistance to multiple classes of fungicidal chemicals. This fungal pathogen detoxifies xenobiotics through coordinated transcriptional control of CYP450s, biotransforming xenobiotics with different substrate specificities and ABC transporters, excreting a broad spectrum of xenobiotics or biotransformed metabolites. A Botrytis cinerea strain harboring the mutated ShXDR1 showed increased expression of phase I (BcCYP65) and III (BcatrD) genes, resulting in resistance to fungicides. This indicates the regulatory system is conserved in filamentous fungi. This molecular genetic mechanism for xenobiotic detoxification in fungi holds potential for facilitating discovery of new antifungal drugs and further studies of convergent and divergent evolution of xenobiotic detoxification in eukaryote lineages.IMPORTANCE Emerging multidrug resistance (MDR) in pathogenic filamentous fungi is a significant threat to human health and agricultural production. Understanding mechanisms of MDR is essential to combating fungal pathogens; however, there is still limited information on MDR mechanisms conferred by xenobiotic detoxification. Here, we report for the first time that overexpression of phase I drug-metabolizing monooxygenases (cytochrome P450s) and phase III ATP-binding cassette efflux transporters is regulated by a gain-of-function mutation in the fungus-specific transcription factor in the MDR strains of the filamentous plant-pathogenic fungus Sclerotinia homoeocarpa This study establishes a novel molecular mechanism of MDR through the xenobiotic detoxification pathway in filamentous fungi, which may facilitate the discovery of new antifungal drugs to control pathogenic fungi.

NYD-OP7/PLC regulatory signaling pathway regulates deltamethrin resistance in Culex pipiens pallens (Diptera: Culicidae)

BACKGROUND

Investigation of insecticide resistance mechanisms is considered a vital first step towards the creation of effective strategies to control resistant mosquitoes and manage mosquito-borne diseases. Our previous study revealed that NYD-OP7 may be associated with deltamethrin resistance in Culex pipiens pallen. However, the precise function of NYD-OP7 in deltamethrin resistance is still unclear. In this study, we investigated the role of NYD-OP7 in the molecular mechanisms underlying pyrethroid resistance.

RESULTS

Knockdown of NYD-OP7 not only increased the susceptibility of the mosquitoes to deltamethrin in vivo but also simultaneously repressed both expression and enzyme activity of its downstream effector molecule, phospholipase C (PLC) and expression of several insecticide resistance-related P450 genes. Knockdown of PLC also sensitized the mosquitoes to deltamethrin and reduced the expression of the P450 genes.

CONCLUSIONS

Our results revealed that NYD-OP7 and its downstream effector PLC contribute to deltamethrin resistance by regulating the expression of P450s in Cx. pipiens pallens.

Genome-wide analysis of cytochrome P450s of Trichoderma spp.: annotation and evolutionary relationships

Background

Cytochrome P450s form an important group of enzymes involved in xenobiotics degradation and metabolism, both primary and secondary. These enzymes are also useful in industry as biotechnological tools for bioconversion and a few are reported to be involved in pathogenicity. Trichoderma spp. are widely used in industry and agriculture and are known for their biosynthetic potential of a large number of secondary metabolites. For realising the full biosynthetic potential of an organism, it is important to do a genome-wide annotation and cataloguing of these enzymes.

Results

Here, we have studied the genomes of seven species (T. asperellum, T. atroviride, T. citrinoviride, T. longibrachiatum, T. reesei , T. harzianum and T. virens) and identified a total of 477 cytochrome P450s. We present here the classification, evolution and structure as well as predicted function of these proteins. This study would pave the way for functional characterization of these groups of enzymes and will also help in realization of their full economic potential.

Conclusion

Our CYPome annotation and evolutionary studies of the seven Trichoderma species now provides opportunities for exploration of research-driven strategies to select Trichoderma species for various applications especially in relation to secondary metabolism and degradation of environmental pollutants.

Characterization of Heterobasidion occidentale transcriptomes reveals candidate genes and DNA polymorphisms for virulence variations

Characterization of genes involved in differentiation of pathogen species and isolates with variations of virulence traits provides valuable information to control tree diseases for meeting the challenges of sustainable forest health and phytosanitary trade issues. Lack of genetic knowledge and genomic resources hinders novel gene discovery, molecular mechanism studies and development of diagnostic tools in the management of forest pathogens. Here, we report on transcriptome profiling of Heterobasidion occidentale isolates with contrasting virulence levels. Comparative transcriptomic analysis identified orthologous groups exclusive to H. occidentale and its isolates, revealing biological processes involved in the differentiation of isolates. Further bioinformatics analyses identified an H. occidentale secretome, CYPome and other candidate effectors, from which genes with species- and isolate-specific expression were characterized. A large proportion of differentially expressed genes were revealed to have putative activities as cell wall modification enzymes and transcription factors, suggesting their potential roles in virulence and fungal pathogenesis. Next, large numbers of simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) were detected, including more than 14 000 interisolate non-synonymous SNPs. These polymorphic loci and species/isolate-specific genes may contribute to virulence variations and provide ideal DNA markers for development of diagnostic tools and investigation of genetic diversity.

Pathogenic adaptations of Colletotrichum fungi revealed by genome wide gene family evolutionary analyses

The fungal genus Colletotrichum contains hemibiotrophic phytopathogens being highly variable in host and tissue specificities. We sequenced a C. fructicola genome (1104–7) derived from an isolate of apple in China and compared it with the reference genome (Nara_gc5) derived from an isolate of strawberry in Japan. Mauve alignment and BlastN search identified 0.62 Mb lineage-specific (LS) genomic regions in 1104–7 with a length criterion of 10 kb. Genes located within LS regions evolved more dynamically, and a strongly elevated proportion of genes were closely related to non-Colletotrichum sequences. Two LS regions, containing nine genes in total, showed features of fungus-to-fungus horizontal transfer supported by both gene order collinearity and gene phylogeny patterns. We further compared the gene content variations among 13 Colletotrichum and 11 non-Colletotrichum genomes by gene function annotation, OrthoMCL grouping and CAFE analysis. The results provided a global evolutionary picture of Colletotrichum gene families, and identified a number of strong duplication/loss events at key phylogenetic nodes, such as the contraction of the detoxification-related RTA1 family in the monocot-specializing graminicola complex and the expansions of several ammonia production-related families in the fruit-infecting gloeosporioides complex. We have also identified the acquirement of a RbsD/FucU fucose transporter from bacterium by the Colletotrichum ancestor. In sum, this study summarized the pathogenic evolutionary features of Colletotrichum fungi at multiple taxonomic levels and highlights the concept that the pathogenic successes of Colletotrichum fungi require shared as well as lineage-specific virulence factors.

Fungal Genomes and Insights into the Evolution of the Kingdom

The kingdom Fungi comprises species that inhabit nearly all ecosystems. Fungi exist as both free-living and symbiotic unicellular and multicellular organisms with diverse morphologies. The genomes of fungi encode genes that enable them to thrive in diverse environments, invade plant and animal cells, and participate in nutrient cycling in terrestrial and aquatic ecosystems. The continuously expanding databases of fungal genome sequences have been generated by individual and large-scale efforts such as Génolevures, Broad Institute's Fungal Genome Initiative, and the 1000 Fungal Genomes Project (http://1000.fungalgenomes.org). These efforts have produced a catalog of fungal genes and genomic organization. The genomic datasets can be utilized to better understand how fungi have adapted to their lifestyles and ecological niches. Large datasets of fungal genomic and transcriptomic data have enabled the use of novel methodologies and improved the study of fungal evolution from a molecular sequence perspective. Combined with microscopes, petri dishes, and woodland forays, genome sequencing supports bioinformatics and comparative genomics approaches as important tools in the study of the biology and evolution of fungi.

Intraspecific comparative genomics of isolates of the Norway spruce pathogen (Heterobasidion parviporum) and identification of its potential virulence factors

BACKGROUND

Heterobasidion parviporum is an economically most important fungal forest pathogen in northern Europe, causing root and butt rot disease of Norway spruce (Picea abies (L.) Karst.). The mechanisms underlying the pathogenesis and virulence of this species remain elusive. No reference genome to facilitate functional analysis is available for this species.

RESULTS

To better understand the virulence factor at both phenotypic and genomic level, we characterized 15 H. parviporum isolates originating from different locations across Finland for virulence, vegetative growth, sporulation and saprotrophic wood decay. Wood decay capability and latitude of fungal origins exerted interactive effects on their virulence and appeared important for H. parviporum virulence. We sequenced the most virulent isolate, the first full genome sequences of H. parviporum as a reference genome, and re-sequenced the remaining 14 H. parviporum isolates. Genome-wide alignments and intrinsic polymorphism analysis showed that these isolates exhibited overall high genomic similarity with an average of at least 96% nucleotide identity when compared to the reference, yet had remarkable intra-specific level of polymorphism with a bias for CpG to TpG mutations. Reads mapping coverage analysis enabled the classification of all predicted genes into five groups and uncovered two genomic regions exclusively present in the reference with putative contribution to its higher virulence. Genes enriched for copy number variations (deletions and duplications) and nucleotide polymorphism were involved in oxidation-reduction processes and encoding domains relevant to transcription factors. Some secreted protein coding genes based on the genome-wide selection pressure, or the presence of variants were proposed as potential virulence candidates.

CONCLUSION

Our study reported on the first reference genome sequence for this Norway spruce pathogen (H. parviporum). Comparative genomics analysis gave insight into the overall genomic variation among this fungal species and also facilitated the identification of several secreted protein coding genes as putative virulence factors for the further functional analysis. We also analyzed and identified phenotypic traits potentially linked to its virulence.

Synthesis, Molecular Docking, and Antimycotic Evaluation of Some 3-Acyl Imidazo[1,2-a]pyrimidines

A series of 3-benzoyl imidazo[1,2-a]pyrimidines, obtained from N-heteroarylformamidines in good yields, was tested in silico and in vitro for binding and inhibition of seven Candida species (Candida albicans (ATCC 10231), Candida dubliniensis (CD36), Candida glabrata (CBS138), Candida guilliermondii (ATCC 6260), Candida kefyr, Candida krusei (ATCC 6358) and Candida tropicalis (MYA-3404)). To predict binding mode and energy, each compound was docked in the active site of the lanosterol 14α-demethylase enzyme (CYP51), essential for fungal growth of Candida species. Antimycotic activity was evaluated as the 50% minimum inhibitory concentration (MIC50) for the test compounds and two reference drugs, ketoconazole and fluconazole. All test compounds had a better binding energy (range: -6.11 to -9.43 kcal/mol) than that found for the reference drugs (range: 48.93 to -6.16 kcal/mol). In general, the test compounds showed greater inhibitory activity of yeast growth than the reference drugs. Compounds 4j and 4f were the most active, indicating an important role in biological activity for the benzene ring with electron-withdrawing substituents. These compounds show the best MIC50 against C. guilliermondii and C. glabrata, respectively. The current findings suggest that the 3-benzoyl imidazo[1,2-a]pyrimidine derivatives, herein synthesized by an accessible methodology, are potential antifungal drugs.

Fungal Cytochrome P450s and the P450 Complement (CYPome) of Fusarium graminearum

Cytochrome P450s (CYPs), heme-containing monooxygenases, play important roles in a wide variety of metabolic processes important for development as well as biotic/trophic interactions in most living organisms. Functions of some CYP enzymes are similar across organisms, but some are organism-specific; they are involved in the biosynthesis of structural components, signaling networks, secondary metabolisms, and xenobiotic/drug detoxification. Fungi possess more diverse CYP families than plants, animals, or bacteria. Various fungal CYPs are involved in not only ergosterol synthesis and virulence but also in the production of a wide array of secondary metabolites, which exert toxic effects on humans and other animals. Although few studies have investigated the functions of fungal CYPs, a recent systematic functional analysis of CYP genes in the plant pathogen Fusarium graminearum identified several novel CYPs specifically involved in virulence, asexual and sexual development, and degradation of xenobiotics. This review provides fundamental information on fungal CYPs and a new platform for further metabolomic and biochemical studies of CYPs in toxigenic fungi.

Genomic Understanding of an Infectious Brain Disease from the Desert

Rhinocladiella mackenziei accounts for the majority of fungal brain infections in the Middle East, and is restricted to the arid climate zone between Saudi Arabia and Pakistan. Neurotropic dissemination caused by this fungus has been reported in immunocompromised, but also immunocompetent individuals. If untreated, the infection is fatal. Outside of humans, the environmental niche of R. mackenziei is unknown, and the fungus has been only cultured from brain biopsies. In this paper, we describe the whole-genome resequencing of two R. mackenziei strains from patients in Saudi Arabia and Qatar. We assessed intraspecies variation and genetic signatures to uncover the genomic basis of the pathogenesis, and potential niche adaptations. We found that the duplicated genes (paralogs) are more susceptible to accumulating significant mutations. Comparative genomics with other filamentous ascomycetes revealed a diverse arsenal of genes likely engaged in pathogenicity, such as the degradation of aromatic compounds and iron acquisition. In addition, intracellular accumulation of trehalose and choline suggests possible adaptations to the conditions of an arid climate region. Specifically, protein family contractions were found, including short-chain dehydrogenase/reductase SDR, the cytochrome P450 (CYP) (E-class), and the G-protein β WD-40 repeat. Gene composition and metabolic potential indicate extremotolerance and hydrocarbon assimilation, suggesting a possible environmental habitat of oil-polluted desert soil.

Heterologous pathway assembly reveals molecular steps of fungal terreic acid biosynthesis

Terreic acid is a potential anticancer drug as it inhibits Bruton's tyrosine kinase; however, its biosynthetic molecular steps remain unclear. In this work, the individual reactions of terreic acid biosynthesis were determined by stepwise pathway assembly in a heterologous host, Pichia pastoris, on the basis of previous knockout studies in a native host, Aspergillus terreus. Polyketide synthase AtX was found to catalyze the formation of partially reduced polyketide 6-methylsalicylic acid, followed by 3-methylcatechol synthesis by salicylate 1-monooxygenase AtA-mediated decarboxylative hydroxylation of 6-methylsalicylic acid. Our results show that cytochrome P450 monooxygenase AtE hydroxylates 3-methylcatechol, thus producing the next product, 3-methyl-1,2,4-benzenetriol. A smaller putative cytochrome P450 monooxygenase, AtG, assists with this step. Then, AtD causes epoxidation and hydroxyl oxidation of 3-methyl-1,2,4-benzenetriol and produces a compound terremutin, via which the previously unknown function of AtD was identified as cyclooxygenation. The final step involves an oxidation reaction of a hydroxyl group by a glucose-methanol-choline oxidoreductase, AtC, which leads to the final product: terreic acid. Functions of AtD and AtG were determined for the first time. All the genes were reanalyzed and all intermediates and final products were isolated and identified. Our model fully defines the molecular steps and corrects previous results from the literature.

The binding mechanism between azoles and FgCYP51B, sterol 14α-demethylase of Fusarium graminearum

BACKGROUND

Fusarium graminearum is the main pathogen of Fusarium head blight (FHB), a worldwide plant disease and a major disease of wheat in China. Control of FHB is mainly dependent on the application of demethylase inhibitor (DMI) fungicides. Fungal sterol 14α-demethylase enzymes (CYP51) are the main target for DMI fungicides. A molecular modeling study and biological evaluation were performed to investigate the binding mechanism between azoles and CYP51B in F. graminearum.

RESULTS

A homology model based on the crystal structure of Aspergillus fumigatus was built. Molecular docking and molecular dynamics (MD) simulations were then used to identify the optimum binding mode of propiconazole (PRP), diniconazole (DIN), triadimenol (TRL), tebuconazole (TEC) and triadimefon (TRN) with FgCYP51B. Furthermore, the binding free energy of the five protein-inhibitor complexes was calculated using molecular mechanics generalized Born surface area and Poisson-Boltzmann surface area (MM-GB/PBSA) methods. Key residues in the selective binding of azoles to FgCYP51B were recognized by per-residue free energy decomposition analysis. The five ligands have a similar binding mode in the active pocket. The binding free energy to the enzyme for inhibitors PRP and TEC is more favorable than that of TRN, TRL and DIN. Furthermore, the amino acid residues Phe511, Val136, Ile374, Ala308, Ser312 and Try137 of FgCYP51B are key residues interacting with azoles fungicides. From the experimental evaluation, the 50% effective concentration (EC₅₀ ) values for PRP, TEC, DIN, TRL and TRN are 0.024, 0.047, 0.148, 0.154 and 0.474 mg L^-1 , respectively. These five molecules exhibit potential inhibitory activity against CYP51B protein from F. graminearum.

CONCLUSION

Azole fungicides for FgCYP51B should possess more hydrophobic groups interacting with residues Phe511, Val136, Ile374, Ala308, Ser312 and Tyr137. PRP and TEC are preferable for the control of FHB than DIN, TRL and TRN. © 2017 Society of Chemical Industry.

Condition-dependent co-regulation of genomic clusters of virulence factors in the grapevine trunk pathogen Neofusicoccum parvum

The ascomycete Neofusicoccum parvum, one of the causal agents of Botryosphaeria dieback, is a destructive wood-infecting fungus and a serious threat to grape production worldwide. The capability to colonize woody tissue, combined with the secretion of phytotoxic compounds, is thought to underlie its pathogenicity and virulence. Here, we describe the repertoire of virulence factors and their transcriptional dynamics as the fungus feeds on different substrates and colonizes the woody stem. We assembled and annotated a highly contiguous genome using single-molecule real-time DNA sequencing. Transcriptome profiling by RNA sequencing determined the genome-wide patterns of expression of virulence factors both in vitro (potato dextrose agar or medium amended with grape wood as substrate) and in planta. Pairwise statistical testing of differential expression, followed by co-expression network analysis, revealed that physically clustered genes coding for putative virulence functions were induced depending on the substrate or stage of plant infection. Co-expressed gene clusters were significantly enriched not only in genes associated with secondary metabolism, but also in those associated with cell wall degradation, suggesting that dynamic co-regulation of transcriptional networks contributes to multiple aspects of N. parvum virulence. In most of the co-expressed clusters, all genes shared at least a common motif in their promoter region, indicative of co-regulation by the same transcription factor. Co-expression analysis also identified chromatin regulators with correlated expression with inducible clusters of virulence factors, suggesting a complex, multi-layered regulation of the virulence repertoire of N. parvum.

Deciphering lignocellulose deconstruction by the white rot fungus Irpex lacteus based on genomic and transcriptomic analyses

BACKGROUND

Irpex lacteus is one of the most potent white rot fungi for biological pretreatment of lignocellulose for second biofuel production. To elucidate the underlying molecular mechanism involved in lignocellulose deconstruction, genomic and transcriptomic analyses were carried out for I. lacteus CD2 grown in submerged fermentation using ball-milled corn stover as the carbon source.

RESULTS

Irpex lacteus CD2 efficiently decomposed 74.9% lignin, 86.3% cellulose, and 83.5% hemicellulose in corn stover within 9 days. Manganese peroxidases were rapidly induced, followed by accumulation of cellulase and hemicellulase. Genomic analysis revealed that I. lacteus CD2 possessed a complete set of lignocellulose-degrading enzyme system composed mainly of class II peroxidases, dye-decolorizing peroxidases, auxiliary enzymes, and 182 glycoside hydrolases. Comparative transcriptomic analysis substantiated the notion of a selection mode of degradation. These analyses also suggested that free radicals, derived either from MnP-organic acid interplay or from Fenton reaction involving Fe²⁺ and H₂O₂, could play an important role in lignocellulose degradation.

CONCLUSIONS

The selective strategy employed by I. lacteus CD2, in combination with low extracellular glycosidases cleaving plant cell wall polysaccharides into fermentable sugars, may account for high pretreatment efficiency of I. lacteus. Our study also hints the importance of free radicals for future designing of novel, robust lignocellulose-degrading enzyme cocktails.

Sterol metabolism in the filasterean Capsaspora owczarzaki has features that resemble both fungi and animals

Sterols are essential for several physiological processes in most eukaryotes. Sterols regulate membrane homeostasis and participate in different signalling pathways not only as precursors of steroid hormones and vitamins, but also through its role in the formation of lipid rafts. Two major types of sterols, cholesterol and ergosterol, have been described so far in the opisthokonts, the clade that comprise animals, fungi and their unicellular relatives. Cholesterol predominates in derived bilaterians, whereas ergosterol is what generally defines fungi. We here characterize, by a combination of bioinformatic and biochemical analyses, the sterol metabolism in the filasterean Capsaspora owczarzaki, a close unicellular relative of animals that is becoming a model organism. We found that C. owczarzaki sterol metabolism combines enzymatic activities that are usually considered either characteristic of fungi or exclusive to metazoans. Moreover, we observe a differential transcriptional regulation of this metabolism across its life cycle. Thus, C. owczarzaki alternates between synthesizing 7-dehydrocholesterol de novo, which happens at the cystic stage, and the partial conversion—via a novel pathway—of incorporated cholesterol into ergosterol, the characteristic fungal sterol, in the filopodial and aggregative stages.

Genetic redundancy in the catabolism of methylated amines in the yeast Scheffersomyces stipitis

The catabolism of choline as a source of nitrogen in budding yeasts is thought to proceed via the intermediates trimethylamine, dimethylamine and methylamine before the release of ammonia. The present study investigated the utilisation of choline and its downstream intermediates as nitrogen sources in the yeast Scheffersomyces stipitis using a reverse genetics approach. Six genes (AMO1, AMO2, SFA1, FGH1, PICST_49761, PICST_63000) that have previously been predicted to be directly or indirectly involved in the catabolism of methylated amines were individually deleted. The growth of each deletion mutant was assayed on minimal media with methylamine, dimethylamine, trimethylamine or choline as the sole nitrogen source. The two amine oxidase-encoding genes AMO1 and AMO2 appeared to be functionally redundant for growth on methylated amines as both deletion mutants displayed growth on all nitrogen sources tested. However, deletion of AMO1 resulted in a pronounced growth lag on all four methylated amines while deletion of AMO2 only caused a growth lag when methylamine was the sole nitrogen source. The glutathione-dependent formaldehyde dehydrogenase-encoding gene SFA1 was found to be absolutely essential for growth on all methylated amines tested while deletion of the S-formylglutathione hydrolase gene FGH1 caused a pronounced growth lag on dimethylamine, trimethylamine and choline. The putative cytochrome P450 monooxygenase-encoding genes PICST_49761 and PICST_63000 were considered likely candidates for demethylation of di- and trimethylamine but produced no discernable phenotype on any of the tested nitrogen sources when deleted. This study revealed notable instances of genetic redundancies in the choline catabolic pathway, which are discussed.

In silico analysis of cytochrome P450 monooxygenases in chronic granulomatous infectious fungus Sporothrix schenckii: Special focus on CYP51

Sporotrichosis is an emerging chronic, granulomatous, subcutaneous, mycotic infection caused by Sporothrix species. Sporotrichosis is treated with the azole drug itraconazole as ketoconazole is ineffective. It is a well-known fact that azole drugs act by inhibiting cytochrome P450 monooxygenases (P450s), heme-thiolate proteins. To date, nothing is known about P450s in Sporothrix schenckii and the molecular basis of its resistance to ketoconazole. Here we present genome-wide identification, annotation, phylogenetic analysis and comprehensive P450 family-level comparative analysis of S. schenckii P450s with pathogenic fungi P450s, along with a rationale for ketoconazole resistance by S. schenckii based on in silico structural analysis of CYP51. Genome data-mining of S. schenckii revealed 40 P450s in its genome that can be grouped into 32 P450 families and 39 P450 subfamilies. Comprehensive comparative analysis of P450s revealed that S. schenckii shares 11 P450 families with plant pathogenic fungi and has three unique P450 families: CYP5077, CYP5386 and CYP5696 (novel family). Among P450s, CYP51, the main target of azole drugs was also found in S. schenckii. 3D modeling of S. schenckii CYP51 revealed the presence of characteristic P450 motifs with exceptionally large reductase interaction site 2. In silico analysis revealed number of mutations that can be associated with ketoconazole resistance, especially at the channel entrance to the active site. One of possible reason for better stabilization of itraconazole, compared to ketoconazole, is that the more extended molecule of itraconazole may form a hydrogen bond with ASN-230. This in turn may explain its effectiveness against S. schenckii vis-a-vis resistant to ketoconazole. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone.

Overview on the Biochemical Potential of Filamentous Fungi to Degrade Pharmaceutical Compounds

Pharmaceuticals represent an immense business with increased demand due to intensive livestock raising and an aging human population, which guarantee the quality of human life and well-being. However, the development of removal technologies for these compounds is not keeping pace with the swift increase in their use. Pharmaceuticals constitute a potential risk group of multiclass chemicals of increasing concern since they are extremely frequent in all environments and have started to exhibit negative effects on micro- and macro-fauna as well as on human health. In this context, fungi are known to be extremely diverse and poorly studied microorganisms despite being well suited for bioremediation processes, taking into account their metabolic and physiological characteristics for the transformation of even highly toxic xenobiotic compounds. Increasing studies indicate that fungi can transform many structures of pharmaceutical compounds, including anti-inflammatories, β-blockers, and antibiotics. This is possible due to different mechanisms in combination with the extracellular and intracellular enzymes, which have broad of biotechnological applications. Thus, fungi and their enzymes could represent a promising tool to deal with this environmental problem. Here, we review the studies performed on pharmaceutical compounds biodegradation by the great diversity of these eukaryotes. We examine the state of the art of the current application of the Basidiomycota division, best known in this field, as well as the assembly of novel biodegradation pathways within the Ascomycota division and the Mucoromycotina subdivision from the standpoint of shared enzymatic systems, particularly for the cytochrome P450 superfamily of enzymes, which appear to be the key enzymes in these catabolic processes. Finally, we discuss the latest advances in the field of genetic engineering for their further application.

Novel gene-sequence markers for isolate tracking within Monilinia fructicola lesions

BACKGROUND

Monilinia fructicola is a diverse pathogen of pome and stone fruits that causes severe economic losses each year. However, little is known about inoculum flow within or between orchards and pathogen establishment in an orchard, because few methods exist for detecting diversity or tracking isolates over time. SSR loci are an effective option, but may be confounded by a high degree of mutability and potential sensitivity to abiotic stress.

RESULTS

Through transcriptome analysis, we identified novel markers mrr1, DHFR and MfCYP01 and validated stability of these markers under fungicide stress in natural infection sites. Nucleotide variation within mrr1, DHFR and MfCYP01 sequences differentiated isolates at all spatial scales: within the same infection site, between trees and between two farms. Sequenced regions were also effective for matching isolates collected from blossoms at the beginning of the season to progeny in cankers obtained at the end of the season.

CONCLUSIONS

Collectively, results show that mrr1, DHFR and MfCYP01 are able to accurately differentiate M. fructicola isolates at the population level, can be used to track isolates over time, and are more stable than SSRs under external stresses. Either by themselves or combined with SSR markers, these gene-encoding regions are a much-needed tool for better understanding M. fructicola population dynamics. © 2017 Society of Chemical Industry.

Cytochromes P450 for natural product biosynthesis in Streptomyces: sequence, structure, and function

Covering: up to January 2017Cytochrome P450 enzymes (P450s) are some of the most exquisite and versatile biocatalysts found in nature. In addition to their well-known roles in steroid biosynthesis and drug metabolism in humans, P450s are key players in natural product biosynthetic pathways. Natural products, the most chemically and structurally diverse small molecules known, require an extensive collection of P450s to accept and functionalize their unique scaffolds. In this review, we survey the current catalytic landscape of P450s within the Streptomyces genus, one of the most prolific producers of natural products, and comprehensively summarize the functionally characterized P450s from Streptomyces. A sequence similarity network of >8500 P450s revealed insights into the sequence-function relationships of these oxygen-dependent metalloenzymes. Although only ∼2.4% and <0.4% of streptomycete P450s have been functionally and structurally characterized, respectively, the study of streptomycete P450s involved in the biosynthesis of natural products has revealed their diverse roles in nature, expanded their catalytic repertoire, created structural and mechanistic paradigms, and exposed their potential for biomedical and biotechnological applications. Continued study of these remarkable enzymes will undoubtedly expose their true complement of chemical and biological capabilities.

Proteomic Insights on the Metabolism of Penicillium janczewskii during the Biotransformation of the Plant Terpenoid Labdanolic Acid

Plant terpenoids compose a natural source of chemodiversity of exceptional value. Many of these compounds own biological/pharmacological activity, others are regarded as unique chemical skeletons for the synthesis of derivatives with improved properties. Functional chemical modification of terpenoids through biotransformation frequently relies on the use of Ascomycota strains, but information on major cellular responses is still largely lacking. Penicillium janczewskii mediates a stereo-selective hydroxylation of labdanolic acid (LA)-terpenoid found abundantly in Cistus ladanifer-producing 3β-hydroxy-labdanolic acid with yields >90%. Herein, combined analyses of mycelial and extracellular differential proteomes demonstrated that the plant terpenoid increased stress responses, especially against oxidative stress (e.g., accumulation of superoxide dismutase) and apparently altered mitochondria functioning. One putative cytochrome P450 monooxygenase differentially accumulated in the secretome and the terpenoid bioconversion was inhibited in vivo in the presence of a P450 inhibitor. The stereo-selective hydroxylation of the plant terpenoid is likely mediated by P450 enzymes, yet its unequivocal identity remains unclear. To the best of our knowledge, this is the first time that proteomics was used to investigate how a plant terpenoid impacts the metabolism of a filamentous fungus during its efficiently biotransformation. Our findings may encourage the development of new strategies for the valorization of plant natural resources through biotechnology.

Characterization of the cytochrome P450 monooxygenase genes (P450ome) from the carotenogenic yeast Xanthophyllomyces dendrorhous

BACKGROUND

The cytochromes P450 (P450s) are a large superfamily of heme-containing monooxygenases involved in the oxidative metabolism of an enormous diversity of substrates. These enzymes require electrons for their activity, and the electrons are supplied by NAD(P)H through a P450 electron donor system, which is generally a cytochrome P450 reductase (CPR). The yeast Xanthophyllomyces dendrorhous has evolved an exclusive P450-CPR system that specializes in the synthesis of astaxanthin, a carotenoid with commercial potential. For this reason, the aim of this work was to identify and characterize other potential P450 genes in the genome of this yeast using a bioinformatic approach.

RESULTS

Thirteen potential P450-encoding genes were identified, and the analysis of their deduced proteins allowed them to be classified in ten different families: CYP51, CYP61, CYP5139 (with three members), CYP549A, CYP5491, CYP5492 (with two members), CYP5493, CYP53, CYP5494 and CYP5495. Structural analyses of the X. dendrorhous P450 proteins showed that all of them have a predicted transmembrane region at their N-terminus and have the conserved domains characteristic of the P450s, including the heme-binding region (FxxGxRxCxG); the PER domain, with the characteristic signature for fungi (PxRW); the ExxR motif in the K-helix region and the oxygen-binding domain (OBD) (AGxDTT); also, the characteristic secondary structure elements of all the P450 proteins were identified. The possible functions of these P450s include primary, secondary and xenobiotic metabolism reactions such as sterol biosynthesis, carotenoid synthesis and aromatic compound degradation.

CONCLUSIONS

The carotenogenic yeast X. dendrorhous has thirteen P450-encoding genes having potential functions in primary, secondary and xenobiotic metabolism reactions, including some genes of great interest for fatty acid hydroxylation and aromatic compound degradation. These findings established a basis for future studies about the role of P450s in the carotenogenic yeast X. dendrorhous and their potential biotechnological applications.

Transcriptomic analysis of basidiocarp development in Ustilago maydis (DC) Cda

Previously, we demonstrated that when Ustilago maydis (DC) Cda., a phytopathogenic basidiomycete and the causal agent of corn smut, is grown in the vicinity of maize embryogenic calli in a medium supplemented with the herbicide Dicamba, it developed gastroid-like basidiocarps. To elucidate the molecular mechanisms involved in the basidiocarp development by the fungus, we proceeded to analyze the transcriptome of the process, identifying a total of 2002 and 1064 differentially expressed genes at two developmental stages, young and mature basidiocarps, respectively. Function of these genes was analyzed with the use of different databases. MIPS analysis revealed that in the stage of young basidiocarp, among the ca. two thousand differentially expressed genes, there were some previously described for basidiocarp development in other fungal species. Additional elements that operated at this stage included, among others, genes encoding the transcription factors FOXO3, MIG3, PRO1, TEC1, copper and MFS transporters, and cytochromes P450. During mature basidiocarp development, important up-regulated genes included those encoding hydrophobins, laccases, and ferric reductase (FRE/NOX). The demonstration that a mapkk mutant was unable to form basidiocarps, indicated the importance of the MAPK signaling pathway in this developmental process.

A novel cytochrome P450, CYP3201B1, is involved in (R)-mandelonitrile biosynthesis in a cyanogenic millipede

Specialized arthropods and more than 2500 plant species biosynthesize hydroxynitriles and release hydrogen cyanide as a defensive mechanism. The millipede Chamberlinius hualienensis accumulates (R)-mandelonitrile as a cyanide precursor. Although biosynthesis of hydroxynitriles in cyanogenic plants and in an insect are extensively studied, (R)-mandelonitrile biosynthesis in cyanogenic millipedes has remained unclear. In this study, we identified the biosynthetic precursors of (R)-mandelonitrile and an enzyme involved in (R)-mandelonitrile biosynthesis. Using deuterium-labelled compounds, we revealed that (E/Z)-phenylacetaldoxime and phenylacetonitrile are the biosynthetic precursors of (R)-mandelonitrile in the millipede as well as other cyanogenic organisms. To identify the enzymes involved in (R)-mandelonitrile biosynthesis, 50 cDNAs encoding cytochrome P450s were cloned and coexpressed with yeast cytochrome P450 reductase in yeast, as cytochrome P450s are involved in the biosynthesis of hydroxynitriles in other cyanogenic organisms. Among the 50 cytochrome P450s from the millipede, CYP3201B1 produced (R)-mandelonitrile from phenylacetonitrile but not from (E/Z)-phenylacetaldoxime, whereas plant and insect cytochrome P450s catalysed the dehydration of aldoximes and hydroxylation of nitriles. CYP3201B1 is not phylogenetically related to cytochrome P450s from other cyanogenic organisms, indicating that hydroxynitrile biosynthetic cytochrome P450s have independently evolved in distant species. Our study will shed light on the evolution of cyanogenesis among plants, insects and millipedes.

DATABASE

Nucleotide sequence data are available in the DDBJ/EMBL/GenBank databases under the accession numbers LC125356-LC125405.

De novo Transcriptome Assembly of Phomopsis liquidambari Provides Insights into Genes Associated with Different Lifestyles in Rice (Oryza sativa L.)

The mechanisms that trigger the switch from endophytic fungi to saprophytic fungi are largely unexplored. Broad host range Phomopsis liquidambari is established in endophytic and saprophytic systems with rice (Oryza sativa L.). Endophytic P. liquidambari promotes rice growth, increasing rice yield and improving the efficiency of nitrogen fertilizer. This species's saprophytic counterpart can decompose rice litterfall, promoting litter organic matter cycling and the release of nutrients and improving the soil microbial environment. Fluorescence microscopy, confocal laser scanning microscopy and quantitative PCR investigated the colonization dynamics and biomass of P. liquidambari in rice in vivo. P. liquidambari formed infection structures similar to phytopathogens with infected vascular tissues that systematically spread to acrial parts. However, different from pathogenic infection, P. liquidambari colonization exhibits space restriction and quantity restriction. Direct comparison of a fungal transcriptome under three different habitats provided a better understanding of lifestyle conversion during plant-fungi interactions. The isolated total RNA of Ck (pure culture), EP (endophytic culture) and FP (saprophytic culture) was subjected to Illumina transcriptome sequencing. To the best of our knowledge, this study is the first to investigate Phomopsis sp. using RNA-seq technology to obtain whole transcriptome information. A total of 27,401,258 raw reads were generated and 22,700 unigenes were annotated. Functional annotation indicated that carbohydrate metabolism and biosynthesis of secondary metabolites played important roles. There were 2522 differentially expressed genes (DEGs) between the saprophytic and endophytic lifestyles. Quantitative PCR analysis validated the DEGs of RNA-seq. Analysis of DEGs between saprophytic and endophytic lifestyles revealed that most genes from amino acids metabolism, carbohydrate metabolism, fatty acid biosynthesis, secondary metabolism and terpenoid and steroid biosynthesis were up-regulated in EP. Secondary metabolites of these pathways may affect fungal growth and development and contribute to signaling communication with the host. Most pathways of xenobiotic biodegradation and metabolism were upregulated in FP. Cytochrome P450s play diverse vital roles in endophytism and saprophytism, as their highly specialized functions are evolutionarily adapted to various ecological niches. These results help to characterize the relationship between fungi and plants, the diversity of fungi for ecological adaptations and the application prospects for fungi in sustainable agriculture.

CYPome of the conifer pathogen Heterobasidion irregulare: Inventory, phylogeny, and transcriptional analysis of the response to biocontrol

The molecular mechanisms underlying the interaction of the pathogen, Heterobasidion annosum s.l., the conifer tree and the biocontrol fungus, Phlebiopsis gigantea have not been fully elucidated. Members of the cytochrome P450 (CYP) protein family may contribute to the detoxification of components of chemical defence of conifer trees by H. annosum during infection. Additionally, they may also be involved in the interaction between H. annosum and P. gigantea. A genome-wide analysis of CYPs in Heterobasidion irregulare was carried out alongside gene expression studies. According to the Standardized CYP Nomenclature criteria, the H. irregulare genome has 121 CYP genes and 17 CYP pseudogenes classified into 11 clans, 35 families, and 64 subfamilies. Tandem CYP arrays originating from gene duplications and belonging to the same family and subfamily were found. Phylogenetic analysis showed that all the families of H. irregulare CYPs were monophyletic groups except for the family CYP5144. Microarray analysis revealed the transcriptional pattern for 130 transcripts of CYP-encoding genes during growth on culture filtrate produced by P. gigantea. The high level of P450 gene diversity identified in this study could result from extensive gene duplications presumably caused by the high metabolic demands of H. irregulare in its ecological niches.

Discovery of the molecular mechanisms of the novel chalcone-based Magnaporthe oryzae inhibitor C1 using transcriptomic profiling and co-expression network analysis

Background

In our previous studies, we discovered a series of chalcone-based phytopathogenic fungus inhibitors. However, knowledge of their effects, detailed targets and molecular mechanisms in Magnaporthe oryzae (M. oryzae) remained limited.

Methods

To explore the expression and function of differentially expressed genes in M. oryzae after treatment with compound C1, we analyzed the expression profile of mRNAs using a microarray analysis and GO, KEGG and WGCNA analysis, followed by qRT-PCR and Western blots to validate our findings.

Results

A total of 1013 up-regulated and 995 down-regulated mRNAs were differentially expressed after M. oryzae was treated with C1 compared to those of the control samples. Among these, cytochrome P450, glycylpeptide N-myristoyltransferase (NMT) and peroxisomal membrane protein 4 were identified as the most significant DEGs and were validated by experiments.

Conclusion

In conclusion, our study suggests that the combination of transcriptomic microarray, bioinformatics analysis and weighted gene co-expression networks can be used to predict potential therapeutic targets and to map the pathways regulated by small molecular natural product-like drugs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-3385-9) contains supplementary material, which is available to authorized users.

Molecular evolutionary dynamics of cytochrome P450 monooxygenases across kingdoms: Special focus on mycobacterial P450s

Since the initial identification of cytochrome P450 monooxygenases (CYPs/P450s), great progress has been made in understanding their structure-function relationship, diversity and application in producing compounds beneficial to humans. However, the molecular evolution of P450s in terms of their dynamics both at protein and DNA levels and functional conservation across kingdoms still needs investigation. In this study, we analyzed 17 598 P450s belonging to 113 P450 families (bacteria -42; fungi -19; plant -28; animal -22; plant and animal -1 and common P450 family -1) and found highly conserved and rapidly evolving P450 families. Results suggested that bacterial P450s, particularly P450s belonging to mycobacteria, are highly conserved both at protein and DNA levels. Mycobacteria possess the highest P450 diversity percentage compared to other microbes and have a high coverage of P450s (≥1%) in their genomes, as found in fungi and plants. Phylogenetic and functional analyses revealed the functional conservation of P450s despite belonging to different biological kingdoms, suggesting the adherence of P450s to their innate function such as their involvement in either generation or oxidation of steroids and structurally related molecules, fatty acids and terpenoids. This study's results offer new understanding of the dynamic structural nature of P450s.

Versatile biocatalysis of fungal cytochrome P450 monooxygenases

Cytochrome P450 (CYP) monooxygenases, the nature’s most versatile biological catalysts have unique ability to catalyse regio-, chemo-, and stereospecific oxidation of a wide range of substrates under mild reaction conditions, thereby addressing a significant challenge in chemocatalysis. Though CYP enzymes are ubiquitous in all biological kingdoms, the divergence of CYPs in fungal kingdom is manifold. The CYP enzymes play pivotal roles in various fungal metabolisms starting from housekeeping biochemical reactions, detoxification of chemicals, and adaptation to hostile surroundings. Considering the versatile catalytic potentials, fungal CYPs has gained wide range of attraction among researchers and various remarkable strategies have been accomplished to enhance their biocatalytic properties. Numerous fungal CYPs with multispecialty features have been identified and the number of characterized fungal CYPs is constantly increasing. Literature reveals ample reviews on mammalian, plant and bacterial CYPs, however, modest reports on fungal CYPs urges a comprehensive review highlighting their novel catalytic potentials and functional significances. In this review, we focus on the diversification and functional diversity of fungal CYPs and recapitulate their unique and versatile biocatalytic properties. As such, this review emphasizes the crucial issues of fungal CYP systems, and the factors influencing efficient biocatalysis.

Identification and characterization of a pathogenicity-related gene VdCYP1 from Verticillium dahliae

Verticillium dahliae is a phytopathogenic fungus that causes vascular wilt disease in a wide variety of crop plants, thereby causing extensive economic loss. In present study, one V. dahliae T-DNA mutant M01C06 showed the pathogenicity loss on cotton, and the expression of a flanking gene encoding cytochrome P450 monooxygenase (P450, VdCYP1) was strongly repressed. P450s of fungi could affect the fungal pathogenicity by involving in the synthesis of secondary metabolites. However, there was no report about the pathogenic function of P450s in V. dahliae. VdCYP1 gene deletion and complementation experiments confirmed that VdCYP1 was the pathogenicity-related gene in V. dahliae. A comparison of culture supernatants of the VdCYP1 deletion mutants and wild-type strains indicates that at least 14 kinds of secondary metabolites syntheses were affected due to VdCYP1 gene deletion. One of these compounds, sulfacetamide, had the ability to induce the necrosis and wilting symptoms in cotton. Above results indicate that VdCYP1 could participate in pathogenesis by involving the secondary metabolism in V. dahliae, such as the compound sulfacetamide. In conclusion, VdCYP1 acts as an important pathogenicity-related factor to involve in secondary metabolism that likely contributes to the pathogenic process in V. dahliae.

Cytochrome P450 complement (CYPome) of Candida oregonensis, a gut-associated yeast of bark beetle, Dendroctonus rhizophagus

Bark beetles (Curculionidae: Scolytinae) and associated microorganisms must overcome a complex tree's defence system, which includes toxic monoterpenes, to successfully complete their life cycle. A number of studies have suggested these microorganisms could have ecological roles related with the nutrition, detoxification, and semiochemical production. In particular, in filamentous fungi symbionts, cytochrome P450 (CYP) have been involved with terpenoid detoxification and biotransformation processes. Candida oregonensis has been isolated from the gut, ovaries, and frass of different bark beetle species, and it is a dominant species in the Dendroctonus rhizophagus gut. In this study, we identify, characterise, and infer the phylogenetic relationships of C. oregonensis CYP genes. The results indicate that the cytochrome P450 complement (CYPome) is composed of nine genes (CYP51F1, CYP61A1, CYP56D1, CYP52A59, CYP52A60, CYP52A61, CYP52A62, CYP5217A8, and CYP5217B1), which might participate in primary metabolic reactions such as sterol biosynthesis, biodegradation of xenobiotic, and resistance to environmental stress. The prediction of the cellular location suggests that these CYPs to be anchored to the plasma membrane, membranes of the endoplasmic reticulum, mitochondria, and peroxisomes. These findings lay the foundation for future studies about the functional role of P450s, not only for yeasts, but also for the insects with which they interact.

Tricking Arthrinium malaysianum into Producing Industrially Important Enzymes Under 2-Deoxy D-Glucose Treatment

This study catalogs production of industrially important enzymes and changes in transcript expression caused by 2-deoxy D-glucose (2-DG) treatment in Arthrinium malaysianum cultures. Carbon Catabolite Repression (CCR) induced by 2-DG in this species is cAMP independent unlike many other organisms. Higher levels of secreted endoglucanase (EG), β-glucosidase (BGL), β-xylosidase (BXL), and filter paper activity assay (FPase) enzymes under 2-DG treatment can be exploited for commercial purposes. An integrated RNA sequencing and quantitative proteomic analysis was performed to investigate the cellular response to 2-DG in A. malaysianum. Analysis of RNASeq data under 2-DG treated and control condition reveals that 56% of the unigenes do not have any known similarity to proteins in non-redundant database. Gene Ontology IDs were assigned to 36% of the transcripts (13260) and about 5207 (14%) were mapped to Kyoto Encyclopedia of Genes and Genomes pathway (KEGG). About 1711 genes encoding 2691 transcripts were differentially expressed in treated vs. control samples. Out of the 2691 differentially expressed transcripts, only 582 have any known function. The most up regulated genes belonged to Pentose Phosphate Pathways and carbohydrate degradation class as expected. In addition, genes involved in protein folding, binding, catalytic activity, DNA repair, and secondary metabolites were up-regulated under 2-DG treatment. Whereas genes encoding glycosylation pathways, growth, nutrient reservoir activity was repressed. Gene ontology analysis of the differentially expressed genes indicates metabolic process (35%) is the pre-dominant class followed by carbohydrate degradation (11%), protein folding, and trafficking (6.2%) and transport (5.3%) classes. Unlike other organisms, conventional unfolded protein response (UPR) was not activated in either control or treated conditions. Major enzymes secreted by A. malaysianum are those degrading plant polysaccharides, the most dominant ones being β-glucosidase, as demonstrated by the 2D gel analysis. A set of 7 differentially expressed mRNAs were validated by qPCR. Transmission electron microscopy analyses demonstrated that the 2-DG treated cell walls of hyphae showed significant differences in the cell-wall thickness. Overall 2-DG treatment in A. malaysianum induced secretion of large amount of commercially viable enzymes compared to other known species.

Functional roles and substrate specificities of twelve cytochromes P450 belonging to CYP52 family in n-alkane assimilating yeast Yarrowia lipolytica

Yarrowia lipolytica possesses twelve ALK genes, which encode cytochromes P450 in the CYP52 family. In this study, using a Y. lipolytica strain from which all twelve ALK genes had been deleted, strains individually expressing each of the ALK genes were constructed and their roles and substrate specificities were determined by observing their growth on n-alkanes and analyzing fatty acid metabolism. The results suggested that the twelve Alk proteins can be categorized into four groups based on their substrate specificity: Alk1p, Alk2p, Alk9p, and Alk10p, which have significant activities to hydroxylate n-alkanes; Alk4p, Alk5p, and Alk7p, which have significant activities to hydroxylate the ω-terminal end of dodecanoic acid; Alk3p and Alk6p, which have significant activities to hydroxylate both n-alkanes and dodecanoic acid; and Alk8p, Alk11p, and Alk12p, which showed faint or no activities to oxidize these substrates. The involvement of Alk proteins in the oxidation of fatty alcohols and fatty aldehydes was also analyzed by measuring viability of the mutant deleted for twelve ALK genes in medium containing dodecanol and by observing growth on dodecanal of a mutant strain, in which twelve ALK genes were deleted along with four fatty aldehyde dehydrogenase genes. It was suggested that ALK gene(s) is/are involved in the detoxification of dodecanol and the assimilation of dodecanal. These results imply that genes encoding CYP52-family P450s have undergone multiplication and diversification in Y. lipolytica for assimilation of various hydrophobic compounds.

Genomic Analysis of Detoxification Supergene Families in the Mosquito Anopheles sinensis

Anopheles sinensis is an important malaria vector in China and other Southeast Asian countries, and the emergence of insecticide resistance in this mosquito poses a serious threat to the efficacy of malaria control programs. The recently published An. sinensis genome and transcriptome provide an opportunity to understand the molecular mechanisms of insecticide resistance. Analysis of the An. sinensis genome revealed 174 detoxification genes, including 93 cytochrome P450s (P450s), 31 glutathione-S-transferases (GSTs), and 50 choline/carboxylesterases (CCEs). The gene number was similar to that in An. gambiae, but represented a decrease of 29% and 42% compared with Aedes aegypti and Culex quinquefasciatus, respectively. The considerable contraction in gene number in Anopheles mosquitoes mainly occurred in two detoxification supergene families, P450s and CCEs. The available An. sinensis transcriptome was also re-analyzed to further identify key resistance-associated detoxification genes. Among 174 detoxification genes, 124 (71%) were detected. Several candidate genes overexpressed in a deltamethrin-resistant strain (DR-strain) were identified as belonging to the CYP4 or CYP6 family of P450s and the Delta GST class. These generated data provide a basis for identifying the resistance-associated genes of An. sinensis at the molecular level.

Genome-Wide Annotation and Comparative Analysis of Cytochrome P450 Monooxygenases in Basidiomycete Biotrophic Plant Pathogens

Fungi are an exceptional source of diverse and novel cytochrome P450 monooxygenases (P450s), heme-thiolate proteins, with catalytic versatility. Agaricomycotina saprophytes have yielded most of the available information on basidiomycete P450s. This resulted in observing similar P450 family types in basidiomycetes with few differences in P450 families among Agaricomycotina saprophytes. The present study demonstrated the presence of unique P450 family patterns in basidiomycete biotrophic plant pathogens that could possibly have originated from the adaptation of these species to different ecological niches (host influence). Systematic analysis of P450s in basidiomycete biotrophic plant pathogens belonging to three different orders, Agaricomycotina (Armillaria mellea), Pucciniomycotina (Melampsora laricis-populina, M. lini, Mixia osmundae and Puccinia graminis) and Ustilaginomycotina (Ustilago maydis, Sporisorium reilianum and Tilletiaria anomala), revealed the presence of numerous putative P450s ranging from 267 (A. mellea) to 14 (M. osmundae). Analysis of P450 families revealed the presence of 41 new P450 families and 27 new P450 subfamilies in these biotrophic plant pathogens. Order-level comparison of P450 families between biotrophic plant pathogens revealed the presence of unique P450 family patterns in these organisms, possibly reflecting the characteristics of their order. Further comparison of P450 families with basidiomycete non-pathogens confirmed that biotrophic plant pathogens harbour the unique P450 families in their genomes. The CYP63, CYP5037, CYP5136, CYP5137 and CYP5341 P450 families were expanded in A. mellea when compared to other Agaricomycotina saprophytes and the CYP5221 and CYP5233 P450 families in P. graminis and M. laricis-populina. The present study revealed that expansion of these P450 families is due to paralogous evolution of member P450s. The presence of unique P450 families in these organisms serves as evidence of how a host/ecological niche can influence shaping the P450 content of an organism. The present study initiates our understanding of P450 family patterns in basidiomycete biotrophic plant pathogens.

Analysis of cytochrome b(5) reductase-mediated metabolism in the phytopathogenic fungus Zymoseptoria tritici reveals novel functionalities implicated in virulence

Septoria tritici blotch (STB) caused by the Ascomycete fungus Zymoseptoria tritici is one of the most economically damaging diseases of wheat worldwide. Z. tritici is currently a major target for agricultural fungicides, especially in temperate regions where it is most prevalent. Many fungicides target electron transfer enzymes because these are often important for cell function. Therefore characterisation of genes encoding such enzymes may be important for the development of novel disease intervention strategies. Microsomal cytochrome b5 reductases (CBRs) are an important family of electron transfer proteins which in eukaryotes are involved in the biosynthesis of fatty acids and complex lipids including sphingolipids and sterols. Unlike the model yeast Saccharomyces cerevisiae which possesses only one microsomal CBR, the fully sequenced genome of Z. tritici bears three possible microsomal CBRs. RNA sequencing analysis revealed that ZtCBR1 is the most highly expressed of these genes under all in vitro and in planta conditions tested, therefore ΔZtCBR1 mutant strains were generated through targeted gene disruption. These strains exhibited delayed disease symptoms on wheat leaves and severely limited asexual sporulation. ΔZtCBR1 strains also exhibited aberrant spore morphology and hyphal growth in vitro. These defects coincided with alterations in fatty acid, sphingolipid and sterol biosynthesis observed through GC-MS and HPLC analyses. Data is presented which suggests that Z. tritici may use ZtCBR1 as an additional electron donor for key steps in ergosterol biosynthesis, one of which is targeted by azole fungicides. Our study reports the first functional characterisation of CBR gene family members in a plant pathogenic filamentous fungus. This also represents the first direct observation of CBR functional ablation impacting upon fungal sterol biosynthesis.

Diversity and evolution of cytochrome P450 monooxygenases in Oomycetes

Cytochrome P450 monooxygenases (P450s) are heme-thiolate proteins whose role as drug targets against pathogens, as well as in valuable chemical production and bioremediation, has been explored. In this study we performed comprehensive comparative analysis of P450s in 13 newly explored oomycete pathogens. Three hundred and fifty-six P450s were found in oomycetes. These P450s were grouped into 15 P450 families and 84 P450 subfamilies. Among these, nine P450 families and 31 P450 subfamilies were newly found in oomycetes. Research revealed that oomycetes belonging to different orders contain distinct P450 families and subfamilies in their genomes. Evolutionary analysis and sequence homology data revealed P450 family blooms in oomycetes. Tandem arrangement of a large number of P450s belonging to the same family indicated that P450 family blooming is possibly due to its members’ duplications. A unique combination of amino acid patterns was observed at EXXR and CXG motifs for the P450 families CYP5014, CYP5015 and CYP5017. A novel P450 fusion protein (CYP5619 family) with an N-terminal P450 domain fused to a heme peroxidase/dioxygenase domain was discovered in Saprolegnia declina. Oomycete P450 patterns suggested host influence in shaping their P450 content. This manuscript serves as reference for future P450 annotations in newly explored oomycetes.

Distinctive expansion of gene families associated with plant cell wall degradation, secondary metabolism, and nutrient uptake in the genomes of grapevine trunk pathogens

BACKGROUND

Trunk diseases threaten the longevity and productivity of grapevines in all viticulture production systems. They are caused by distantly-related fungi that form chronic wood infections. Variation in wood-decay abilities and production of phytotoxic compounds are thought to contribute to their unique disease symptoms. We recently released the draft sequences of Eutypa lata, Neofusicoccum parvum and Togninia minima, causal agents of Eutypa dieback, Botryosphaeria dieback and Esca, respectively. In this work, we first expanded genomic resources to three important trunk pathogens, Diaporthe ampelina, Diplodia seriata, and Phaeomoniella chlamydospora, causal agents of Phomopsis dieback, Botryosphaeria dieback, and Esca, respectively. Then we integrated all currently-available information into a genome-wide comparative study to identify gene families potentially associated with host colonization and disease development.

RESULTS

The integration of RNA-seq, comparative and ab initio approaches improved the protein-coding gene prediction in T. minima, whereas shotgun sequencing yielded nearly complete genome drafts of Dia. ampelina, Dip. seriata, and P. chlamydospora. The predicted proteomes of all sequenced trunk pathogens were annotated with a focus on functions likely associated with pathogenesis and virulence, namely (i) wood degradation, (ii) nutrient uptake, and (iii) toxin production. Specific patterns of gene family expansion were described using Computational Analysis of gene Family Evolution, which revealed lineage-specific evolution of distinct mechanisms of virulence, such as specific cell wall oxidative functions and secondary metabolic pathways in N. parvum, Dia. ampelina, and E. lata. Phylogenetically-informed principal component analysis revealed more similar repertoires of expanded functions among species that cause similar symptoms, which in some cases did not reflect phylogenetic relationships, thereby suggesting patterns of convergent evolution.

CONCLUSIONS

This study describes the repertoires of putative virulence functions in the genomes of ubiquitous grapevine trunk pathogens. Gene families with significantly faster rates of gene gain can now provide a basis for further studies of in planta gene expression, diversity by genome re-sequencing, and targeted reverse genetic approaches. The functional validation of potential virulence factors will lead to a more comprehensive understanding of the mechanisms of pathogenesis and virulence, which ultimately will enable the development of accurate diagnostic tools and effective disease management.

Fungal cytochrome P450 monooxygenases of Fusarium oxysporum for the synthesis of ω-hydroxy fatty acids in engineered Saccharomyces cerevisiae

Background

Omega hydroxy fatty acids (ω-OHFAs) are multifunctional compounds that act as the basis for the production of various industrial products with broad commercial and pharmaceutical implications. However, the terminal oxygenation of saturated or unsaturated fatty acids for the synthesis of ω-OHFAs is intricate to accomplish through chemocatalysis, due to the selectivity and controlled reactivity in C-H oxygenation reactions. Cytochrome P450, the ubiquitous enzyme is capable of catalyzing the selective terminal omega hydroxylation naturally in biological kingdom.

Results

To gain a deep insight on the biochemical role of fungal P450s towards the production of omega hydroxy fatty acids, two cytochrome P450 monooxygenases from Fusarium oxysporum (FoCYP), FoCYP539A7 and FoCYP655C2; were identified, cloned, and heterologously expressed in Saccharomyces cerevisiae. For the efficient production of ω-OHFAs, the S. cerevisiae was engineered to disrupt the acyl-CoA oxidase enzyme and the β-oxidation pathway inactivated (ΔPox1) S. cerevisiae mutant was generated. To elucidate the significance of the interaction of redox mechanism, FoCYPs were reconstituted with the heterologous and homologous reductase systems - S. cerevisiae CPR (ScCPR) and F. oxysporum CPR (FoCPR). To further improve the yield, the effect of pH was analyzed and the homologous FoCYP-FoCPR system efficiently hydroxylated caprylic acid, capric acid and lauric acid into their respective ω-hydroxy fatty acids with 56%, 79% and 67% conversion. Furthermore, based on computational simulations, we identified the key residues (Asn106 of FoCYP539A7 and Arg235 of FoCYP655C2) responsible for the recognition of fatty acids and demonstrated the structural insights of the active site of FoCYPs.

Conclusion

Fungal CYP monooxygenases, FoCYP539A7 and FoCYP655C2 with its homologous redox partner, FoCPR constitutes a promising catalyst due to its high regio- and stereo-selectivity in the hydroxylation of fatty acids and in the substantial production of industrially valuable ω-hydroxy fatty acids.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0228-2) contains supplementary material, which is available to authorized users.

Oleic acid metabolism via a conserved cytochrome P450 system-mediated ω-hydroxylation in the bark beetle-associated fungus Grosmannia clavigera

The bark beetle-associated fungus Grosmannia clavigera participates in the large-scale destruction of pine forests. In the tree, it must tolerate saturating levels of toxic conifer defense chemicals (e.g. monoterpenes). The fungus can metabolize some of these compounds through the ß-oxidation pathway and use them as a source of carbon. It also uses carbon from pine triglycerides, where oleic acid is the most common fatty acid. High levels of free fatty acids, however, are toxic and can cause additional stress during host colonization. Fatty acids induce expression of neighboring genes encoding a cytochrome P450 (CYP630B18) and its redox partner, cytochrome P450 reductase (CPR2). The aim of this work was to study the function of this novel P450 system. Using LC/MS, we biochemically characterized CYP630 as a highly specific oleic acid ω-hydroxylase. We explain oleic acid specificity using protein interaction modeling. Our results underscore the importance of ω-oxidation when the main ß-oxidation pathway may be overwhelmed by other substrates such as host terpenoid compounds. Because this CYP-CPR gene cluster is evolutionarily conserved, our work has implications for metabolism studies in other fungi.

Aromatic metabolism of filamentous fungi in relation to the presence of aromatic compounds in plant biomass

The biological conversion of plant lignocellulose plays an essential role not only in carbon cycling in terrestrial ecosystems but also is an important part of the production of second generation biofuels and biochemicals. The presence of the recalcitrant aromatic polymer lignin is one of the major obstacles in the biofuel/biochemical production process and therefore microbial degradation of lignin is receiving a great deal of attention. Fungi are the main degraders of plant biomass, and in particular the basidiomycete white rot fungi are of major importance in converting plant aromatics due to their ability to degrade lignin. However, the aromatic monomers that are released from lignin and other aromatic compounds of plant biomass are toxic for most fungi already at low levels, and therefore conversion of these compounds to less toxic metabolites is essential for fungi. Although the release of aromatic compounds from plant biomass by fungi has been studied extensively, relatively little attention has been given to the metabolic pathways that convert the resulting aromatic monomers. In this review we provide an overview of the aromatic components of plant biomass, and their release and conversion by fungi. Finally, we will summarize the applications of fungal systems related to plant aromatics.

The molecular mechanism of azole resistance in Aspergillus fumigatus: from bedside to bench and back

The growing use of immunosuppressive therapies has resulted in a dramatic increased incidence of invasive fungal infections (IFIs) caused by Aspergillus fumigatus, a common pathogen, and is also associated with a high mortality rate. Azoles are the primary guideline-recommended therapy agents for first-line treatment and prevention of IFIs. However, increased azole usage in medicinal and agricultural settings has caused azole-resistant isolates to repeatedly emerge in the environment, resulting in a significant threat to human health. In this review, we present and summarize current research on the resistance mechanisms of azoles in A. fumigatus as well as efficient susceptibility testing methods. Moreover, we analyze and discuss the putative clinical (bedside) indication of these findings from bench work.