Melanin biosynthesis pathway in Agaricus bisporus mushrooms

Mushroom Tyrosinase: Six Isoenzymes Catalyzing Distinct Reactions

"Mushroom tyrosinase" from the common button mushroom is the most frequently used source of tyrosinase activity, both for basic and applied research. Here, the complete tyrosinase family from Agaricus bisporus var. bisporus (abPPO1-6) was cloned from mRNA and expressed heterologously using a single protocol. All six isoenzymes accept a wide range of phenolic and catecholic substrates, but display pronounced differences in their specificity and enzymatic reaction rate. AbPPO3 ignores γ-l-glutaminyl-4-hydroxybenzene (GHB), a natural phenol present in mM concentrations in A. bisporus, while AbPPO4 processes 100 μM GHB at 4-times the rate of the catechol l-DOPA. All six AbPPOs are biochemically distinct enzymes fit for different roles in the fungal life cycle, which challenges the traditional concept of isoenzymes as catalyzing the same physiological reaction and varying only in secondary properties. Transferring this approach to other enzymes and organisms will greatly stimulate both the study of the in vivo function(s) of enzymes and the application of these highly efficient catalysts.

Elucidating the role of monoacetylphlorogulcinol in the pathogenicity of Pseudomonas 'gingeri' against Agaricus bisporus

BACKGROUND

Agaricus bisporus is a globally important edible fungus. The occurrence of ginger blotch caused by Pseudomonas 'gingeri' during A. bisporus growth and post-harvest stages results in significant economic losses. The biotoxin monoacetylphloroglucinol (MAPG) produced by P. 'gingeri' is responsible for inducing ginger blotch on A. bisporus. However, the understanding of the toxic mechanisms of MAPG on A. bisporus remains limited, which hinders the precise control of ginger blotch disease in A. bisporus and the breeding of disease-resistant varieties.

RESULTS

Integrating transcriptomic, metabolomic, and physiological data revealed that MAPG led to an increase in intracellular superoxide anion (O2 -) levels and lipid peroxidation in A. bisporus. MAPG changed the cellular membrane composition of A. bisporus, causing to damage membrane permeability. MAPG inhibited the expression of genes associated with the 19s subunit of the proteasome, thereby impeding cellular waste degradation in A. bisporus. Unlike melanin, MAPG stimulated the synthesis of flavonoids in A. bisporus, which might explain the manifestation of ginger-colored symptoms rather than browning. Meanwhile, the glutathione metabolism pathway in A. bisporus played a pivotal role in counteracting the cytotoxic effects of MAPG. Additionally, enhanced catalase activity and up-regulation of defense-related genes, including cytochrome P450s, Major Facilitator Superfamily (MFS), and ABC transporters, were observed.

CONCLUSION

This study provides comprehensive insights into MAPG toxicity in A. bisporus and uncovers the detoxification strategies of A. bisporus against MAPG. The findings offer valuable evidence for precise control and breeding of resistant varieties against ginger blotch in A. bisporus. © 2024 Society of Chemical Industry.

Population genetics provides insights into the important agronomic traits of Ganoderma cultivation varieties in China

This study aimed to investigate the species diversity and genetic differentiation of the genome of the main cultivated strains of Ganoderma in China. Population genomics analysis was conducted based on 150 cultivated strains of Ganoderma collected nationwide. The results indicated that the main species currently cultivated in China were Ganoderma sichuanense and Ganoderma lucidum, with a minor proportion of Ganoderma sessile, Ganoderma weberianum, Ganoderma sinense, Ganoderma gibbosum and Ganoderma australe. A total of 336,506 high-quality single nucleotide polymorphism (SNP) loci were obtained through population evolution analysis. The Fst values were calculated using a 5-kb sliding window, which ranged from 0.11 to 0.74. This suggests varying degrees of genetic differentiation between populations and genetic exchange among varieties. On this basis, the genes related to the stipe length, cap color and branch phenotypes of Ganoderma were excavated, and the region with the top 1% ZFst value region was used as a candidate region. A total of 137, 270 and 222 candidate genes were identified in the aforementioned 3 phenotypes, respectively. Gene annotation revealed that genes associated with stipe length were mainly related to cell division and differentiation, including proteins such as Nse4 protein and DIM1 protein. The genes related to Ganoderma red color were mainly related to the metabolism of tryptophan and flavonoids. The genes related to the branch were mainly related to cytokinin synthesis, ABC transporter and cytochrome P450. This study provided 150 valuable genome resequencing data in assessing the diversity and genetic differentiation of Ganoderma and laid a foundation for agronomic trait analysis and the development of new varieties of Ganoderma.

New colours for old in the blue-cheese fungus Penicillium roqueforti

Penicillium roqueforti is used worldwide in the production of blue-veined cheese. The blue-green colour derives from pigmented spores formed by fungal growth. Using a combination of bioinformatics, targeted gene deletions, and heterologous gene expression we discovered that pigment formation was due to a DHN-melanin biosynthesis pathway. Systematic deletion of pathway genes altered the arising spore colour, yielding white to yellow-green to red-pink-brown phenotypes, demonstrating the potential to generate new coloured strains. There was no consistent impact on mycophenolic acid production as a result of pathway interruption although levels of roquefortine C were altered in some deletants. Importantly, levels of methyl-ketones associated with blue-cheese flavour were not impacted. UV-induced colour mutants, allowed in food production, were then generated. A range of colours were obtained and certain phenotypes were successfully mapped to pathway gene mutations. Selected colour mutants were subsequently used in cheese production and generated expected new colourations with no elevated mycotoxins, offering the exciting prospect of use in future cheese manufacture.

Effects of antimicrobial nanocomposite films packaging on the postharvest quality and spoilage bacterial communities of mushrooms (Chanterelles)

Poly (lactic acid) (PLA) composite films with the addition of mesoporous silica nanoparticles MSN (0, 2, 4 and 6 wt%) loaded with 10 wt% citral (CIT) were prepared for application in Chanterelles packaging. Composite films with added MSN/CIT showed good mechanical properties, especially 4MSN/CIT/PLA. Changes in physicochemical properties and bacterial flora of Chanterelles during packaging and storage were tested. Compared with CIT/PLA, Chanterelles packed with 4MSN/CIT/PLA showed about 1.62-times lower browning value, 1.53-times lower electrolyte permeability, and 1.83- and 1.78-times lower PPO and POD, respectively, at 12 day. Better physicochemical properties of Chanterelles can be maintained. For bacterial flora changes, Chanterelles packaged with 4MSN/CIT/PLA had more stable flora (p < 0.05) and lower species diversity during storage (p < 0.05), effectively controlling the growth and reproduction of their dominant spoilage bacteria (Enterobacteriaceae spp). In conclusion, the composite membranes obtained by the addition of MSN/CIT to PLA have great potential in the storage of Chanterelles.

Comparative genomic analysis of pleurotus species reveals insights into the evolution and coniferous utilization of Pleurotus placentodes

Pleurotus placentodes (PPL) and Pleurotus cystidiosus (PCY) are economically valuable species. PPL grows on conifers, while PCY grows on broad-leaved trees. To reveal the genetic mechanism behind PPL's adaptability to conifers, we performed de novo genome sequencing and comparative analysis of PPL and PCY. We determined the size of the genomes for PPL and PCY to be 36.12 and 42.74 Mb, respectively, and found that they contain 10,851 and 15,673 protein-coding genes, accounting for 59.34% and 53.70% of their respective genome sizes. Evolution analysis showed PPL was closely related to P. ostreatus with the divergence time of 62.7 MYA, while PCY was distantly related to other Pleurotus species with the divergence time of 111.7 MYA. Comparative analysis of carbohydrate-active enzymes (CAZYmes) in PPL and PCY showed that the increase number of CAZYmes related to pectin and cellulose degradation (e.g., AA9, PL1) in PPL may be important for the degradation and colonization of conifers. In addition, geraniol degradation and peroxisome pathways identified by comparative genomes should be another factors for PPL's tolerance to conifer substrate. Our research provides valuable genomes for Pleurotus species and sheds light on the genetic mechanism of PPL's conifer adaptability, which could aid in breeding new Pleurotus varieties for coniferous utilization.

Transcription factors: switches for regulating growth and development in macrofungi

Macrofungi (or mushrooms) act as an extraordinarily important part to human health due to their nutritional and/or medicinal value, but the detailed researches in growth and development mechanisms have yet to be explored further. Transcription factors (TFs) play indispensable roles in signal transduction and affect growth, development, and metabolism of macrofungi. In recent years, increasing research effort has been employed to probe the relationship between the development of macrofungi and TFs. Herein, the present review comprehensively summarized the functional TFs researched in macrofungi, including modulating mycelial growth, fructification, sclerotial formation, sexual reproduction, spore formation, and secondary metabolism. Meanwhile, the possible effect mechanisms of TFs on the growth and development of some macrofungi were also revealed. Specific examples of functional characterizations of TFs in macrofungi (such as Schizophyllum commune and Coprinopsis cinerea) were described to a better comprehension of regulatory effect. Future research prospects in the field of TFs of macrofungi are discussed. We illustrated the functional versatility of the TFs in macrofungi based on specific examples. A systematical realization of the interaction and possible mechanisms between TFs and macrofungi can supply possible solutions to regulate genetic characteristics, which supply novel insights into the regulation of growth, development and metabolism of macrofungi. KEY POINTS: • The functional TFs researched in macrofungi were summarized. • The possible effect mechanisms of TFs in macrofungal were described. • The multiple physiological functions of TFs in macrofungi were discussed.

Transcriptome Analysis Revealed That Hydrogen Peroxide-Regulated Oxidative Phosphorylation Plays an Important Role in the Formation of Pleurotus ostreatus Cap Color

Pleurotus ostreatus is widely cultivated in China. H2O2, as a signaling molecule, can regulate the formation of cap color, but its regulatory pathway is still unclear, severely inhibiting the breeding of dark-colored strains. In this study, 614 DEGs specifically regulated by H2O2 were identified by RNA-seq analysis. GO-enrichment analysis shows that DEGs can be significantly enriched in multiple pathways related to ATP synthesis, mainly including proton-transporting ATP synthesis complex, coupling factor F(o), ATP biosynthetic process, nucleoside triphosphate metabolic processes, ATP metabolic process, purine nucleoside triphosphate biosynthetic and metabolic processes, and purine ribonuclease triphosphate biosynthetic metabolic processes. Further KEGG analysis revealed that 23 DEGs were involved in cap color formation through the oxidative phosphorylation pathway. They were enriched in Complexes I, III, IV, and V in the respiratory chain. Further addition of exogenous uncoupling agents and ATP synthase inhibitors clarifies the important role of ATP synthesis in color formation. In summary, H2O2 may upregulate the expression of complex-encoding genes in the respiratory chain and promote ATP synthesis, thereby affecting the formation of cap color. The results of this study lay the foundation for the breeding of dark-colored strains of P. ostreatus and provide a basis for the color-formation mechanism of edible fungi.

High-quality genome assembly and multi-omics analysis of pigment synthesis pathway in Auricularia cornea

Owing to its great market potential for food and health care, white Auricularia cornea, a rare edible fungus, has received increased attention in recent years. This study presents a high-quality genome assembly of A. cornea and multi-omics analysis of its pigment synthesis pathway. Continuous Long Reads libraries, combined with Hi-C-assisted assembly were used to assemble of white A. cornea. Based on this data, we analyzed the transcriptome and metabolome of purple and white strains during the mycelium, primordium, and fruiting body stages. Finally, we obtained the genome of A.cornea assembled from 13 clusters. Comparative and evolutionary analysis suggests that A.cornea is more closely related to Auricularia subglabra than to Auricularia heimuer. The divergence of white/purple A.cornea occurred approximately 40,000 years ago, and there were numerous inversions and translocations between homologous regions of the two genomes. Purple strain synthesized pigment via the shikimate pathway. The pigment in the fruiting body of A. cornea was γ-glutaminyl-3,4-dihydroxy-benzoate. During pigment synthesis, α-D-glucose-1P, citrate, 2-Oxoglutarate, and glutamate were four important intermediate metabolites, whereas polyphenol oxidase and other 20 enzyme genes were the key enzymes. This study sheds light on the genetic blueprint and evolutionary history of the white A.cornea genome, revealing the mechanism of pigment synthesis in A.cornea. It has important theoretical and practical implications for understanding the evolution of basidiomycetes, molecular breeding of white A.cornea, and deciphering the genetic regulations of edible fungi. Additionally, it provides valuable insights for the study of phenotypic traits in other edible fungi.

Emerging technologies for preservation and quality evaluation of postharvest edible mushrooms: A review

Edible mushrooms are the highly demanded foods of which production and consumption have been steadily increasing globally. Owing to the quality loss and short shelf-life in harvested mushrooms, it is necessary for the implementation of effective preservation and intelligent evaluation technologies to alleviate this issue. The aim of this review was to analyze the development and innovation thematic lines, topics, and trends by bibliometric analysis and review of the literature methods. The challenges faced in researching these topics were proposed and the mechanisms of quality loss in mushrooms during storage were updated. This review summarized the effects of chemical processing (antioxidants, ozone, and coatings), physical treatments (non-thermal plasma, packaging and latent thermal storage) and other emerging application on the quality of fresh mushrooms while discussing the efficiency in extending the shelf-life. It also discussed the emerging evaluation techniques based on the various chemometric methods and computer vision system in monitoring the freshness and predicting the shelf-life of mushrooms which have been developed. Preservation technology optimization and dynamic quality evaluation are vital for achieving mushroom quality control. This review can provide a comprehensive research reference for reducing mushroom quality loss and extending shelf-life, along with optimizing efficiency of storage and transportation operations.

Pseudo-Chromosomal Genome Assembly in Combination with Comprehensive Transcriptome Analysis in Agaricus bisporus Strain KMCC00540 Reveals Mechanical Stimulus Responsive Genes Associated with Browning Effect

Agaricus bisporus is one of the world’s most popular edible mushrooms, including in South Korea. We performed de novo genome assembly with a South Korean white-colored cultivar of A. bisporus, KMCC00540. After generating a scaffold-level genomic sequence, we inferred chromosome-level assembly by genomic synteny analysis with the representative A. bisporus strains H97 and H39. The KMCC00540 genome had 13 pseudochromosomes comprising 33,030,236 bp mostly covering both strains. A comparative genomic analysis with cultivar H97 indicated that most genomic regions and annotated proteins were shared (over 90%), ensuring that our cultivar could be used as a representative genome. However, A. bisporus suffers from browning even from only a slight mechanical stimulus during transportation, which significantly lowers its commercial value. To identify which genes respond to a mechanical stimulus that induces browning, we performed a time-course transcriptome analysis based on the de novo assembled genome. Mechanical stimulus induces up-regulation in long fatty acid ligase activity-related genes, as well as melanin biosynthesis genes, especially at early time points. In summary, we assembled the chromosome-level genomic information on a Korean strain of A. bisporus and identified which genes respond to a mechanical stimulus, which provided key hints for improving the post-harvest biological control of A. bisporus.

Azole inhibitors of mushroom and human tyrosinases: Current advances and prospects of drug development for melanogenic dermatological disorders

Azoles are a famous and promising class of drugs for treatment of a range of ailments especially fungal infections. A wide variety of azole derivatives are also known to exhibit tyrosinase inhibition, some of which possess promising activity with potential for treatment of dermatological disorders such as post-inflammatory hyperpigmentation, nevus, flecks, melasma, and melanoma. Recently, thiazolyl-resorcinol derivatives have demonstrated potent human tyrosinase inhibition with a safe and effective therapeutic profile for treatment of skin hyperpigmentation in humans, which are currently under clinical trials. If approved these derivatives would be the first azole drugs to be used for treatment of skin hyperpigmentation. Although the scientific literature has been witnessing general reviews on tyrosinase inhibitors to date, there is none that specifically and comprehensively discusses azole inhibitors of tyrosinase. Appreciating such potential of azoles, this focused review highlights a wide range of their derivatives with promising mushroom and human tyrosinase inhibitory activities and clinical potential for treatment of melanogenic dermatological disorders. Presently, these disorders have been treated with kojic acid, hydroquinone and other drugs, the design and development of which are based on their ability to inhibit mushroom tyrosinase. The active sites of mushroom and human tyrosinases carry structural differences which affect substrate or inhibitor binding. For this reason, kojic acid and other drugs pose efficacy and safety issues since they were originally developed using mushroom tyrosinase and have been clinically used on human tyrosinase. Design and development of tyrosinase inhibitors should be based on human tyrosinase, however, there are challenges in obtaining the human enzyme and understanding its structure and function. The review discusses these challenges that encompass structural and functional differences between mushroom and human tyrosinases and the manner in which they are inhibited. The review also gauges promising azole derivatives with potential for development of drugs against skin hyperpigmentation by analyzing and comparing their tyrosinase inhibitory activities against mushroom and human tyrosinases, computational data, and clinical profile where available. It aims to lay groundwork for development of new azole drugs for treatment of skin hyperpigmentation, melanoma, and related dermatological disorders.

Fine Mapping and Functional Analysis of the Gene PcTYR, Involved in Control of Cap Color of Pleurotus cornucopiae

Oyster mushrooms have a high biological efficiency and are easy to cultivate, which is why they are produced all over the world. Cap color is an important commercial trait for oyster mushrooms. Little is known about the genetic mechanism of the cap color trait in oyster mushrooms, which limits molecular breeding for the improvement of cap color-type cultivars. In this study, a 0.8-Mb major quantitative trait locus (QTL) region controlling cap color in the oyster mushroom Pleurotus cornucopiae was mapped on chromosome 7 through bulked-segregant analysis sequencing (BSA-seq) and extreme-phenotype genome-wide association studies (XP-GWAS). Candidate genes were further selected by comparative transcriptome analysis, and a tyrosinase gene (PcTYR) was identified as the highest-confidence candidate gene. Overexpression of PcTYR resulted in a significantly darker cap color, while the cap color of RNA interference (RNAi) strains for this gene was significantly lighter than that of the wild-type (WT) strains, suggesting that PcTYR plays an essential role in cap color formation. This is the first report about fine mapping and functional verification of a gene controlling cap color in oyster mushrooms. This will enhance our understanding of the genetic basis for cap color formation in oyster mushrooms and will facilitate molecular breeding for cap color. IMPORTANCE Oyster mushrooms are widely cultivated and consumed over the world for their easy cultivation and high biological efficiency (mushroom fresh weight/substrate dry weight × 100%). Fruiting bodies with dark caps are more and more popular according to consumer preferences, but dark varieties are rarely seen on the market. Little is known about the genetic mechanism of the cap color trait in oyster mushrooms, which limits molecular breeding for the improvement of cap color-type cultivars. A major QTL of cap color in oyster mushroom P. cornucopiae was fine mapped by using bulked-segregant analysis (BSA) and extreme-phenotype genome-wide association study (XP-GWAS) analysis. A candidate gene PcTYR coding tyrosinase was further identified with the help of comparative transcriptome analysis. qPCR analysis and genetic transformation tests proved that PcTYR played an essential role in cap color formation. This study will contribute to revealing the genetic mechanism of cap color formation in mushrooms, thereby facilitating molecular breeding for cap color trait.

Isolation and identification of pigments from oyster mushrooms with black, yellow and pink caps

The genus Pleurotus, namely oyster mushroom, is widely cultivated and consumed worldwide. Cap color is an important commercial trait for oyster mushroom. Diverse color is determined by various pigment constituents. However, the pigments of oyster mushrooms are still ambiguous. In this study, we extracted and identified pigments of oyster mushroom species with black, yellow and pink cap color. The extracted pigments appearing the three color types correspondingly to the cap color, which were all identified as melanin using a panel of spectroscopic and physical/imaging techniques. Nevertheless, HPLC and elemental analysis indicated that the melanin in oyster mushrooms was actually a mixture of eumelanin and phaeomelanin. Differences in the quantities and relative proportions of eumelanin and phaeomelanin resulted in the color variation in oyster mushroom caps. Electron microscopy studies showed that the melanin units are likely located in the cell wall, as reported in other fungi. The pigments in oyster mushrooms with three different cap color were extracted and identified for the first time in this study, which provided fundamental knowledge for future studies on the mechanism of color formation in mushrooms.

Preparation and characterization of chitosan/zein film loaded with lemon essential oil: Effects on postharvest quality of mushroom (Agaricus bisporus)

In this study, different concentrations of lemon essential oils (LEO) were incorporated into chitosan/zein complex film (C/Z/L films) to improve its antioxidant and antimicrobial capacity, and the effects of C/Z/L films on mushroom quality were evaluated at 4 °C for 12 d. The antioxidant and antimicrobial activity of C/Z films were effectively improved by addition of LEO in a concentration-dependent manner. What's more, EAB value and gas permeability increased while TS value and water vapor permeability decreased upon the gradual increase of LEO content. During the entire storage, C/Z/L films were effective in suppressing PPO and POD activity of mushrooms as well as inhibiting the growth of microorganism. Mushrooms packaged with the film containing 6% LEO showed the lowest browning index and respiration rate. In addition, the C/Z/L film-treated mushrooms exhibited higher antioxidant capacity and more satisfactory texture properties. The results of our study presented that C/Z active film loaded with LEO could be used to maintain the postharvest quality of mushrooms.

Genetic Linkage and Physical Mapping for an Oyster Mushroom (Pleurotus cornucopiae) and Quantitative Trait Locus Analysis for Cap Color

Oyster mushrooms are grown commercially worldwide, especially in many developing countries, for their easy cultivation and high biological efficiency. Pleurotus cornucopiae is one of the main oyster mushroom species because of its gastronomic value and nutraceutical properties. Cap color is an important trait, since consumers prefer dark mushrooms, which are now represented by only a small portion of the commercial varieties. Breeding efforts are required to improve quality-related traits to satisfy various demands of consumers. Here, we present a saturated genetic linkage map of P. cornucopiae constructed by using a segregating population of 122 monokaryons and 3,449 single nucleotide polymorphism (SNP) markers generated by the 2b-RAD approach. The map contains 11 linkage groups covering 961.6 centimorgans (cM), with an average marker spacing of 0.27 cM. The genome of P. cornucopiae was de novo sequenced, resulting in 425 scaffolds (>1,000 bp) with a total genome size of 35.1 Mb. The scaffolds were assembled to the pseudochromosome level with the assistance of the genetic linkage map. A total of 97% SNP markers (3,357) were physically localized on 140 scaffolds that were assigned to 11 pseudochromosomes, with a total of 32.5 Mb, representing 92.5% of the whole genome. Six quantitative trait loci (QTL) controlling cap color of P. cornucopiae were detected, accounting for a total phenotypic variation of 65.6%, with the highest value for the QTL on pseudochromosome 5 (18%). The results of our study provide a solid base for marker-assisted breeding for agronomic traits and especially for studies on biological mechanisms controlling cap color in oyster mushrooms. IMPORTANCE Oyster mushrooms are produced and consumed all over the world. Pleurotus cornucopiae is one of the main oyster mushroom species. Dark-cap oyster mushrooms are becoming more and more popular with consumers, but dark varieties are rare on the market. Prerequisites for efficient breeding programs are the availability of high-quality whole genomes and genetic linkage maps. Genetic studies to fulfill some of these prerequisites have hardly been done for P. cornucopiae. In this study, we de novo sequenced the genome and constructed a saturated genetic linkage map for P. cornucopiae. The genetic linkage map was effectively used to assist the genome assembly and identify QTL that genetically control the trait cap color. As well, the genome characteristics of P. cornucopiae were compared to the closely related species Pleurotus ostreatus. The results provided a basis for understanding the genetic background and marker-assisted breeding of this economically important mushroom species.

Fungal Melanins and Applications in Healthcare, Bioremediation and Industry

Melanin is a complex multifunctional pigment found in all kingdoms of life, including fungi. The complex chemical structure of fungal melanins, yet to be fully elucidated, lends them multiple unique functions ranging from radioprotection and antioxidant activity to heavy metal chelation and organic compound absorption. Given their many biological functions, fungal melanins present many possibilities as natural compounds that could be exploited for human use. This review summarizes the current discourse and attempts to apply fungal melanin to enhance human health, remove pollutants from ecosystems, and streamline industrial processes. While the potential applications of fungal melanins are often discussed in the scientific community, they are successfully executed less often. Some of the challenges in the applications of fungal melanin to technology include the knowledge gap about their detailed structure, difficulties in isolating melanotic fungi, challenges in extracting melanin from isolated species, and the pathogenicity concerns that accompany working with live melanotic fungi. With proper acknowledgment of these challenges, fungal melanin holds great potential for societal benefit in the coming years.

Prediction of the Mannose-Binding Site in the Agaricus bisporus Mannose-Binding Protein

Agaricus bisporus mannose-binding protein (Abmb) was discovered as part of mushroom tyrosinase (PPO3) complex. Apart from its presence, nothing is known about its function or activity in the mushroom. The protein is evolutionarily related to lectins with β-trefoil fold, which are glucose or galactose (and their derivatives) binding proteins. Abmb is also recently showed to display the typical agglutination activity of lectin when in complex with PPO3; this further supports Abmb similarity to its structural homologs from lectin with β-trefoil fold. However, Abmb has no affinity towards glucose or galactose but for mannose, thus its binding to the sugar may be different from its homologs. To date, the natural ligand of Abmb is unknown and the structure of Abmb in the presence of a ligand is not available. Therefore, the mannose-binding site of Abmb was predicted using molecular docking, which was consulted with the information from its structural homologs. This conservative approach would prevent over-speculation. The mannose-binding site of Abmb is likely located in the same region to that of Abmb structural homologs but with a shift in position due to the presence of additional surface loop. In addition, benefiting from the information from an in vitro study on Abmb sugar specificity, the mannose poses suggested that the sugar might interact with the side chains of Arg15, Thr45, Gln48, Asp49, Asp51 and Arg51. Most of these residues were equally present in Abmb structural homologs despite variation of their positions in the amino acid sequence. The variation probably originates from alteration of its amino acid sequence during evolution.

An Unconventional Melanin Biosynthesis Pathway in Ustilago maydis

Ustilago maydis is a phytopathogenic fungus responsible for corn smut disease. Although it is a very well-established model organism for the study of plant-microbe interactions, its potential to produce specialized metabolites, which might contribute to this interaction, has not been studied in detail. By analyzing the U. maydis genome, we identified a biosynthetic gene cluster whose activation led to the production of a black melanin pigment. Single deletion mutants of the cluster genes revealed that five encoded enzymes are required for the accumulation of the black pigment, including three polyketide synthases (pks3, pks4, and pks5), a cytochrome P450 monooxygenase (cyp4), and a protein with similarity to versicolorin B synthase (vbs1). Metabolic profiles of deletion mutants in this gene cluster suggested that Pks3 and Pks4 act in concert as heterodimers to generate orsellinic acid (OA), which is reduced to the corresponding aldehyde by Pks5. The OA-aldehyde can then react with triacetic acid lactone (TAL), also derived from Pks3/Pks4 heterodimers to form larger molecules, including novel coumarin derivatives. Our findings suggest that U. maydis synthesizes a novel type of melanin based on coumarin and pyran-2-one intermediates, while most fungal melanins are derived from 1,8-dihydroxynaphthalene (DHN) or l-3,4-dihydroxyphenylalanine (l-DOPA). Along with these observations, this work also provides insight into the mechanisms of polyketide synthases in this filamentous fungus.IMPORTANCE The fungus Ustilago maydis represents one of the major threats to maize plants since it is responsible for corn smut disease, which generates considerable economical losses around the world. Therefore, contributing to a better understanding of the biochemistry of defense mechanisms used by U. maydis to protect itself against harsh environments, such as the synthesis of melanin, could provide improved biological tools for tackling the problem and protect the crops. In addition, the fact that this fungus synthesizes melanin in an unconventional way, requiring more than one polyketide synthase for producing melanin precursors, gives a different perspective on the complexity of these multidomain enzymes and their evolution in the fungal kingdom.

Comparative phosphoproteome analysis to identify candidate phosphoproteins involved in blue light-induced brown film formation in Lentinula edodes

Light plays an important role in the growth and differentiation of Lentinula edodes mycelia, and mycelial morphology is influenced by light wavelengths. The blue light-induced formation of brown film on the vegetative mycelial tissues of L. edodes is an important process. However, the mechanisms of L. edodes' brown film formation, as induced by blue light, are still unclear. Using a high-resolution liquid chromatography-tandem mass spectrometry integrated with a highly sensitive immune-affinity antibody method, phosphoproteomes of L. edodes mycelia under red- and blue-light conditions were analyzed. A total of 11,224 phosphorylation sites were identified on 2,786 proteins, of which 9,243 sites on 2,579 proteins contained quantitative information. In total, 475 sites were up-regulated and 349 sites were down-regulated in the blue vs red group. To characterize the differentially phosphorylated proteins, systematic bioinformatics analyses, including gene ontology annotations, domain annotations, subcellular localizations, and Kyoto Encyclopedia of Genes and Genomes pathway annotations, were performed. These differentially phosphorylated proteins were correlated with light signal transduction, cell wall degradation, and melanogenesis, suggesting that these processes are involved in the formation of the brown film. Our study provides new insights into the molecular mechanisms of the blue light-induced brown film formation at the post-translational modification level.

Agaricus bisporus Crude Extract: Characterization and Analytical Application

In the present work crude Agaricus bisporus extract (ABE) has been prepared and characterized by its tyrosinase activity, protein composition and substrate specificity. The presence of mushroom tyrosinase (PPO3) in ABE has been confirmed using two-dimensional electrophoresis, followed by MALDI TOF/TOF MS-based analysis. GH27 alpha-glucosidases, GH47 alpha-mannosidases, GH20 hexosaminidases, and alkaline phosphatases have been also detected in ABE. ABE substrate specificity has been studied using 19 phenolic compounds: polyphenols (catechol, gallic, caffeic, chlorogenic, and ferulic acids, quercetin, rutin, dihydroquercetin, l-dihydroxyphenylalanine, resorcinol, propyl gallate) and monophenols (l-tyrosine, phenol, p-nitrophenol, o-nitrophenol, guaiacol, o-cresol, m-cresol, p-cresol). The comparison of ABE substrate specificity and affinity to the corresponding parameters of purified A. bisporus tyrosinase has revealed no major differences. The conditions for spectrophotometric determination have been chosen and the analytical procedures for determination of 1.4 × 10^-4-1.0 × 10^-3 M l-tyrosine, 3.1 × 10^-6-1.0 × 10^-4 M phenol, 5.4 × 10^-5-1.0 × 10^-3 M catechol, 8.5 × 10^-5-1.0 × 10^-3 M caffeic acid, 1.5 × 10^-4-7.5 × 10^-4 M chlorogenic acid, 6.8 × 10^-5-1.0 × 10^-3 M l-DOPA have been proposed. The procedures have been applied for the determination of l-tyrosine in food supplements, l-DOPA in synthetic serum, and phenol in waste water from the food manufacturing plant. Thus, we have demonstrated the possibility of using ABE as a substitute for tyrosinase in such analytical applications, as food supplements, medical and environmental analysis.

Advances in the Design of Genuine Human Tyrosinase Inhibitors for Targeting Melanogenesis and Related Pigmentations

Human tyrosinase (hsTYR) is the key enzyme ensuring the conversion of l-tyrosine to dopaquinone, thereby initiating melanin synthesis, i.e., melanogenesis. Although the protein has long been familiar, knowledge about its three-dimensional structure and efficient overexpression protocols emerged only recently. Consequently, for decades medicinal chemistry studies aiming at developing skin depigmenting agents relied almost exclusively on biological assays performed using mushroom tyrosinase (abTYR), producing a plethoric literature, often of little useful purpose. Indeed, several recent reports have pointed out spectacular differences in terms of interaction patterns and inhibition values between hsTYR and abTYR, including for widely used standard tyrosinase inhibitors. In this review, we summarize the last developments regarding the potential role of hsTYR in human pathologies, the advances in recombinant expression systems and structural data retrieving, and the pioneer generation of true hsTYR inhibitors. Finally, we present suggestions for the design of future inhibitors of this highly attractive target in pharmacology and dermocosmetics.

Chicken Egg White-Advancing from Food to Skin Health Therapy: Optimization of Hydrolysis Condition and Identification of Tyrosinase Inhibitor Peptides

Active fragments (bioactive peptides) from the chicken egg white proteins were expected to exert tyrosinase inhibitory activities in which skin hyperpigmentation could be prevented. Egg white was hydrolyzed by trypsin, chymotrypsin and the combination of both enzymes. The enzyme treatments achieved >50% degree of hydrolysis (DH) at substrate-to-enzyme (S/E) ratio of 10–30 (w/w) and hydrolysis time of 2–5 h. A crossed D-optimal experimental design was then used to determine the optimal enzyme composition, S/E ratio and hydrolysis time in order to yield hydrolysates with strong monophenolase and diphenolase inhibitory activities. The optimized conditions 55% trypsin, 45% chymotrypsin, S/E 10:1 w/w and 2 h achieved 45.9% monophenolase activity inhibition whereas 100% trypsin, S/E 22.13:1 w/w and 3.18 h achieved 48.1% diphenolase activity inhibition. LC/MS and MS/MS analyses identified the peptide sequences and the subsequent screening had identified 7 peptides (ILELPFASGDLLML, GYSLGNWVCAAK, YFGYTGALRCLV, HIATNAVLFFGR, FMMFESQNKDLLFK, SGALHCLK and YFGYTGALR) as the potential inhibitor peptides. These peptides were able to bind to H85, H94, H259, H263, and H296 (hotspots for active residues) as well as F92, M280 and F292 (stabilizing residues) of tyrosinase based on structure-activity relationship analysis. These findings demonstrated the potential of egg white-derived bioactive peptides as skin health therapy.

Lectins from the Edible Mushroom Agaricus bisporus and Their Therapeutic Potentials

The mushroom Agaricus bisporus secretes biologically active compounds and proteins with benefits for human health. Most reported proteins from A. bisporus are tyrosinases and lectins. Lectins are of therapeutic or pharmaceutical interest. To date, only limited information is available on A. bisporus lectins and lectin-like proteins. No therapeutic products derived from A. bisporus lectin (ABL) are available on the market despite its extensive exploration. Recently, A. bisporus mannose-binding protein (Abmb) was discovered. Its discovery enriches the information and increases the interest in proteins with therapeutic potential from this mushroom. Furthermore, the A. bisporus genome reveals the possible occurrence of other lectins in this mushroom that may also have therapeutic potential. Most of these putative lectins belong to the same lectin groups as ABL and Abmb. Their relationship is discussed. Particular attention is addressed to ABL and Abmb, which have been explored for their potential in medicinal or pharmaceutical applications. ABL and Abmb have anti-proliferative activities toward cancer cells and a stimulatory effect on the immune system. Possible scenarios for their use in therapy and modification are also presented.

Relationship of Agaricus bisporus mannose-binding protein to lectins with β-trefoil fold

Agaricus bisporus mannose-binding protein (Abmb) was discovered as part of the mushroom tyrosinase (PPO3) complex, but its function in the mushroom has remained obscure. The protein has a β-trefoil structure that is common for Ricin-B-like lectins. Indeed, its closest structural homologs are the hemagglutinin components of botulinum toxin (HA-33) and the Ricin-B-like lectin from Clitocybe nebularis (CNL), both of which bind galactose, and actinohivin, a recently discovered mannose-binding lectin from actinomycetes. Here we show that Abmb is evolutionarily related to them, which are lectins with a β-trefoil fold. We also show for the first time that Abmb can exhibit typical lectin agglutination activity but only when in the complex with mushroom tyrosinase. This is unexpected and unique because the two proteins are not evolutionarily related and have different activities. Lectin and tyrosinase major role in defense mechanism as well as Abmb and PPO3 gene regulation during the early stages of the development of mushroom fruiting bodies suggested that Abmb has likely a function in defense against bacterial infection and/or insect-induced damage.

Unravelling the Role of Melanin in Cd and Zn Tolerance and Accumulation of Three Dark Septate Endophytic Species

Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To test this hypothesis, we established a series of experiments using albino strains and melanin inhibitors and examined the responses to Cd and Zn. Six DSEs belonging to genera Cadophora sp., Leptodontidium sp. and Phialophora mustea, were evaluated. The strains mainly produced 1,8-dihydroxynaphthalene (DHN) melanin whereas 3,4-dihydroxyphenylalanin melanin was also synthetized. Cd and Zn decreased melanin synthesis in most of the strains. A reduction in melanin concentration in hyphae through the use of tricyclazole, an inhibitor of DHN-melanin synthesis, did not reduce the tolerance of the strains to Cd and Zn. Similarly, albino mutants of Leptodontidium sp. were not more sensitive to Cd and Zn than the WT strain. Moreover, tricyclazole-treated colonies accumulated less Cd but more Zn compared to untreated colonies. The Cd and Zn contents of Leptodontidium albino strains were variable and similar to that of the WT. The results suggest that melanin production is not an important functional trait that contributes to Cd and Zn tolerance, but might contribute to Cd accumulation.

Transcriptional Changes on Blight Fruiting Body of Flammulina velutipes Caused by Two New Bacterial Pathogens

A blight disease of Flammulina velutipes was identified with symptoms of growth cessation of young fruiting bodies, short stipe, and brown spots on the pileus. The pathogenic bacteria were identified as Arthrobacter arilaitensis and Pseudomonas yamanorum by Koch's postulate, gram staining, morphological and 16S ribosomal RNA gene sequence analyses. Either of the pathogenic bacteria or both of them can cause the same symptoms. Transcriptome changes in blighted F. velutipes were investigated between diseased and normal samples. Compared to the control group, 1,099 differentially expressed genes (DEGs) were overlapping in the bacteria-infected groups. The DEGs were significantly enriched in pathways such as xenobiotic metabolism by cytochrome P450 and tyrosine metabolism. Based on weighted correlation network analysis (WGCNA), the module most correlated to the pathogen-treated F. velutipes samples and candidate hub genes in the co-regulatory network were identified. Furthermore, a potential diseased mechanism involved in cell wall non-extension, phenolic substrate oxidation, and stress defense response was proposed based on the up-regulation of differentially expressed genes encoding chitin deacetylase, tyrosinase, cytochrome P450, MFS transporter, and clavaminate synthase-like protein. This study provides insights into the underlying reactions of young fruiting body of F. velutipes suffering from blight disease and facilitates the understanding of the pathogenic procedure of bacteriosis in edible mushrooms.

100 Years Since Tolaas: Bacterial Blotch of Mushrooms in the 21st Century

Among the biotic constraints of common mushroom (Agaricus bisporus) production, bacterial blotch is considered the most important mushroom disease in terms of global prevalence and economic impact. Etiology and management of bacterial blotch has been a major concern since its original description in 1915. Although Pseudomonas tolaasii is thought to be the main causal agent, various Pseudomonas species, as well as organisms from other genera have been reported to cause blotch symptoms on mushroom caps. In this review, we provide an updated overview on the etiology, epidemiology, and management strategies of bacterial blotch disease. First, diversity of the causal agent(s) and utility of high throughput sequencing-based approaches in the precise characterization and identification of blotch pathogen(s) is explained. Further, due to the limited options for use of conventional pesticides in mushroom farms against blotch pathogen(s), we highlight the role of balanced threshold of relative humidity and temperature in mushroom farms to combat the disease in organic and conventional production. Additionally, we discuss the possibility of the use of biological control agents (either antagonistic mushroom-associated bacterial strains or bacteriophages) for blotch management as one of the sustainable approaches for 21^st century agriculture. Finally, we aim to elucidate the association of mushroom microbiome in cap development and productivity on one hand, and blotch incidence/outbreaks on the other hand.

Map-based cloning of genes encoding key enzymes for pigment synthesis in Auricularia cornea

Color is an important quality attribute of fungi, and a useful marker for classification, genetic, and molecular research. However, there is much debate over which enzymes play key regulatory roles in pigment synthesis pathways among different fungi and even within the same species. Auricularia cornea is the most widely cultivated mushroom in the genus Auricularia; 1.834 million tons of this mushroom were produced in 2016 in China. Thus, systematic studies on its color inheritance and the genes encoding key enzymes for pigment synthesis have high scientific and economic value. In this study, the white strain ACW001 and the purple strain ACP004 of A. cornea were used as dikaryotic parents. Selfing populations of ACW001 and ACP004 were constructed with their monokaryotic strains. The fruiting body color of the two populations was consistent with that of their parents, confirming that the two parents were color homozygotes. All strains in the hybrid population of the two parents produced purple fruiting bodies. A robust hybrid strain (ACW001-33×ACP004-33) was selected from the hybrid population, and 87 monokaryotic strains of ACW001-33×ACP004-33 were obtained as a mapping population. Finally, a testcross population was constructed by crossing the mapping population with the test strain ACW001-9. The color genotype of each monokaryotic strain in the mapping population was identified by a fruiting test. The genomes of the two monokaryotic strains ACW001-33 and ACP004-33 were sequenced, and then simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) molecular marker primers were developed. Then, 88 pairs of primers that could distinguish the genotypes of the mapping population were used to construct a genetic linkage map. The genetic linkage map consisted of 12 linkage groups (LGs) spanning 1315.2 cM. The color control locus was preliminarily located at 24.5 cM of the 11th LG. Fine-mapping primers were designed based on sequence differences between ACW001-33 and ACP004-33 in the primary location region. Four color control candidate genes were located in an 8.2-kb region of ACW001-33_contig733 and a 9.2-kb region of ACP004-33_contig802. Homologous alignment and prediction of conserved domain analyses indicated that two of the color control candidate genes encoded proteins with unknown function, and the other two, ACP004_g11815 and ACP004_g11816, encoded glutamyl aminotransferases. These two genes were consecutively arranged on ACP004-33_contig802, and were likely to encode key enzymes in the γ-glutamine-4-hydroxy-benzoate (GHB) pigment synthesis pathway. Primers were designed from the flanking sequences of the two genes and used to analyze the testcross population. Products were amplified only from the 30 testcross strains with purple fruiting bodies, confirming the accuracy of the localization results. We discuss the deficiencies and advantages of map-based cloning in fungi vs. plants, and summarize the steps and requirements of the map-based cloning method for fungi. This study has provided novel ideas and methods for locating functional genes in fungi.

Orf239342 from the mushroom Agaricus bisporus is a mannose binding protein

A recently discovered lectin-like protein from mushroom tyrosinase designated as orf239342 inhibits proliferation of the MCF-7 breast cancer cells. This characteristic is likely derived from its ability to recognize sugar entity on the cell surface. Thereby, the binding specificity of orf239342 to sugars was studied. Orf239342 was found to bind specifically to mannose upon analysis with the surface plasmon resonance technique. Finally, our in vitro study showed that mannose impeded orf239342 ability to inhibit proliferation of the MCF-7 breast cancer cells, providing further evidence for the mannose binding onto the protein. Our finding is a breakthrough to characterise orf239342 i.e. to define its functioning in the mushroom, association to the tyrosinase, or even possible application in breast cancer therapy. In addition, the finding allows the more appropriate designation of the protein as Agaricus bisporus mannose binding-protein (AbMb).

Population genomics demystifies the defoliation phenotype in the plant pathogen Verticillium dahliae

Verticillium dahliae is a broad host-range pathogen that causes vascular wilts in plants. Interactions between three hosts and specific V. dahliae genotypes result in severe defoliation. The underlying mechanisms of defoliation are unresolved. Genome resequencing, gene deletion and complementation, gene expression analysis, sequence divergence, defoliating phenotype identification, virulence analysis, and quantification of V. dahliae secondary metabolites were performed. Population genomics previously revealed that G-LSR2 was horizontally transferred from the fungus Fusarium oxysporum f. sp. vasinfectum to V. dahliae and is exclusively found in the genomes of defoliating (D) strains. Deletion of seven genes within G-LSR2, designated as VdDf genes, produced the nondefoliation phenotype on cotton, olive, and okra but complementation of two genes restored the defoliation phenotype. Genes VdDf5 and VdDf6 associated with defoliation shared homology with polyketide synthases involved in secondary metabolism, whereas VdDf7 shared homology with proteins involved in the biosynthesis of N-lauroylethanolamine (N-acylethanolamine (NAE) 12:0), a compound that induces defoliation. NAE overbiosynthesis by D strains also appears to disrupt NAE metabolism in cotton by inducing overexpression of fatty acid amide hydrolase. The VdDfs modulate the synthesis and overproduction of secondary metabolites, such as NAE 12:0, that cause defoliation either by altering abscisic acid sensitivity, hormone disruption, or sensitivity to the pathogen.

Synergistic deletion of RGS1 and COS1 may reduce the pathogenicity of Magnaporthe oryzae

Rice blast, caused by Magnaporthe oryzae, is a serious threat to global rice production. In recent years, many pathogenicity genes of M. oryzae have been identified, although most of their functions remain unknown. In this study, we report the synergistic deletion of RGS1 and COS1 that may reduce the pathogenicity of M. oryzae. The investigation involved comparing ΔMorgs1, ΔMocos1, and ΔMorgs1/ΔMocos1 mutants. The ΔMorgs1/ΔMocos1 mutant showed a weak reduction in vegetative growth, and the colonies displayed fewer and smoother aerial hyphae. The ΔMorgs1/ΔMocos1 mutant exhibited delayed appressorium-like structure formation and 'low pathogenicity' on detached rice seedling leaves when compared with ΔMocos1. Moreover, the melanin content of the single and double mutants was remarkably lower than that of the WT type. Thus, our results indicate that the synergy between RGS1 and COS1 may be crucial in the pathogenicity of M. oryzae.

Comparative transcriptome analysis identified candidate genes involved in mycelium browning in Lentinula edodes

Background

Lentinula edodes is one of the most popular edible mushroom species in the world and contains useful medicinal components, such as lentinan. The light-induced formation of brown film on the vegetative mycelial tissues of L. edodes is an important process for ensuring the quantity and quality of this edible mushroom. To understand the molecular mechanisms underlying this critical developmental process in L. edodes, we characterized the morphological phenotypic changes in a strain, Chamaram, associated with abnormal brown film formation and compared its genome-wide transcriptional features.

Results

In the present study, we performed genome-wide transcriptome analyses of different vegetative mycelium growth phenotypes, namely, early white, normal brown, and defective dark yellow partial brown films phenotypes which were exposed to different light conditions. The analysis revealed the identification of clusters of genes specific to the light-induced brown film phenotypes. These genes were significantly associated with light sensing via photoreceptors such as FMN- and FAD-bindings, signal transduction by kinases and GPCRs, melanogenesis via activation of tyrosinases, and cell wall degradation by glucanases, chitinases, and laccases, which suggests these processes are involved in the formation of mycelial browning in L. edodes. Interestingly, hydrophobin genes such as SC1 and SC3 exhibited divergent expression levels in the normal and abnormal brown mycelial films, indicating the ability of these genes to act in fruiting body initiation and formation of dikaryotic mycelia. Furthermore, we identified the up-regulation of glycoside hydrolase domain-containing genes in the normal brown film but not in the abnormal film phenotype, suggesting that cell wall degradation in the normal brown film phenotype is crucial in the developmental processes related to the initiation and formation of fruiting bodies.

Conclusions

This study systematically analysed the expression patterns of light-induced browning-related genes in L. edodes. Our findings provide information for further investigations of browning formation mechanisms in L. edodes and a foundation for future L. edodes breeding.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5509-4) contains supplementary material, which is available to authorized users.

Bioconjugation of Captopril-Light Subunit of Agaricus bisporus Mushroom Tyrosinase: Characterization and Potential Use as a Drug Carrier for Oral Delivery

We show that a lectin like protein from the mushroom Agaricus bisporus (LSMT) is capable to permeate the epithelial monolayer barrier of the intestine ex vivo. The protein is not toxic or immunogenic upon prolonged administration and elevated dose in mice. Thus, it could be a candidate as a drug carrier for oral administration. However, its permeability should be tested after the protein has been modified, mimicking the condition in which it is used as a drug carrier. The protein was conjugated to captopril, the selected model of a Biopharmaceutical Classification System (BCS) class III drug, with high solubility but poor permeability. The drug was conjugated to LSMT that had been modified with 4-succinimidyloxycarbonyl-alpha-methyl-2-pyridyldithiotoluene (SMPT) as a linker. The success of LSMT modification was confirmed with TLC and MS; the latter also indicated the amount of captopril molecule linked. The modified LSMT could permeate through the intestinal monolayer barrier, and thus could be absorbed in the intestine after modification. The modified protein appears to remain stable after incubation in simulated gastrointestinal fluids. This pioneering work provides an essential basis for further development of the protein as a drug carrier for oral administration.

Purification and characterisation of a sulphur rich melanin from edible mushroom Termitomyces albuminosus Heim

Production, purification and characterisation of a black pigment from Termitomyces albuminosus as melanin is reported, for the first time, from shaken submerged culture condition using scanning electron microscopy (SEM), elemental analysis, ultraviolet-visible (UV-VIS), and Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) and 13C (CP/MAS) NMR spectra. SEM results on T. albuminosus revealed nanogranular nature of melanin nanoparticles within size range of 400-100 nm with fractal dimension D = 1.195-1.73. Elemental analysis of melanin indicated 54.6% C, 3.5% H, 2.4% N, 26.9% O, and 12% S. UV-VIS and FTIR spectra confirmed to the characteristic of melanin and were identical to the reference commercial sepia melanin. Further validation of the identity of pigment as melanin was achieved by EPR analysis. Termitomyces albuminosus melanin is postulated to be DOPA-type melanin confirmed by 13C (CP/MAS) NMR spectral analysis showing chemical shift at 200-170 ppm carbonyl, 160-110 ppm aromatic region, and with high 40-30 ppm open chain aliphatic region. Chemical modification through oxidation and cysteinylation (Pheomelanin) is implied as indicated by relatively high sulphur content (12%).

Efficient purification of a highly active H-subunit of tyrosinase from Agaricus bisporus

A highly-active tyrosinase (H subunit) isoform has been purified from a commercial crude extract of Agaricus bisporus by a specific, two step-hydrophobic chromatography cascade process based on the differential adsorption of the proteins from the extract to hydrophobic-functionalized supports. At first, commercial, crude tyrosinase from Agaricus bisporus (AbTyr) dissolved in aqueous media was added to octadecyl-Sepabeads matrix at 25 °C. Under these conditions, the support specifically adsorbed a protein with a molecular weight of 47 kDa which showed no tyrosinase activity. The known H subunit of tyrosinase from Agaricus bisporus (45 kDa, H-AbTyr) and another protein of 50 kDa were present in the supernatant. Sodium phosphate buffer was added to adjust the ionic strength of the solution up to 100 mM and Triton X-100 was added (final concentration of 0.07% v/v) to control the hydrophobicity effect for both proteins. This solution was offered again to fresh octadecyl-Sepabeads support, immobilizing selectively the H-AbTyr and leaving exclusively the 50 kDa protein as a pure sample in the supernatant. This tyrosinase isoform of 50 kDa was almost 4-fold more active than the known H-TyrAb, with a specific tyrosinase activity of more than 38,000 U/mg.

Heterologous expression and characterization of functional mushroom tyrosinase (AbPPO4)

Tyrosinases are an ubiquitous group of copper containing metalloenzymes that hydroxylate and oxidize phenolic molecules. In an application context the term 'tyrosinase' usually refers to 'mushroom tyrosinase' consisting of a mixture of isoenzymes and containing a number of enzymatic side-activities. We describe a protocol for the efficient heterologous production of tyrosinase 4 from Agaricus bisporus in Escherichia coli. Applying this procedure a pure preparation of a single isoform of latent tyrosinase can be achieved at a yield of 140 mg per liter of autoinducing culture medium. This recombinant protein possesses the same fold as the enzyme purified from the natural source as evidenced by single crystal X-ray diffraction. The latent enzyme can be activated by limited proteolysis with proteinase K which cleaves the polypeptide chain after K382, only one The latent enzyme can amino acid before the main in-vivo activation site. Latent tyrosinase can be used as obtained and enzymatic activity may be induced in the reaction mixture by the addition of an ionic detergent (e.g. 2 mM SDS). The proteolytically activated mushroom tyrosinase shows >50% of its maximal activity in the range of pH 5 to 10 and accepts a wide range of substrates including mono- and diphenols, flavonols and chalcones.

Lentinula edodes Genome Survey and Postharvest Transcriptome Analysis

Lentinula edodes is a popular, cultivated edible and medicinal mushroom. Lentinula edodes is susceptible to postharvest problems, such as gill browning, fruiting body softening, and lentinan degradation. We constructed a de novo assembly draft genome sequence and performed gene prediction for Lentinula edodesDe novo assembly was carried out using short reads from paired-end and mate-paired libraries and by using long reads by PacBio, resulting in a contig number of 1,951 and an N₅₀ of 1 Mb. Furthermore, we predicted genes by Augustus using transcriptome sequencing (RNA-seq) data from the whole life cycle of Lentinula edodes, resulting in 12,959 predicted genes. This analysis revealed that Lentinula edodes lacks lignin peroxidase. To reveal genes involved in the loss of quality of Lentinula edodes postharvest fruiting bodies, transcriptome analysis was carried out using serial analysis of gene expression (SuperSAGE). This analysis revealed that many cell wall-related enzymes are upregulated after harvest, such as β-1,3-1,6-glucan-degrading enzymes in glycoside hydrolase (GH) families GH5, GH16, GH30, GH55, and GH128, and thaumatin-like proteins. In addition, we found that several chitin-related genes are upregulated, such as putative chitinases in GH family 18, exochitinases in GH20, and a putative chitosanase in GH family 75. The results suggest that cell wall-degrading enzymes synergistically cooperate for rapid fruiting body autolysis. Many putative transcription factor genes were upregulated postharvest, such as genes containing high-mobility-group (HMG) domains and zinc finger domains. Several cell death-related proteins were also upregulated postharvest.IMPORTANCE Our data collectively suggest that there is a rapid fruiting body autolysis system in Lentinula edodes The genes for the loss of postharvest quality newly found in this research will be targets for the future breeding of strains that keep fresh longer than present strains. De novoLentinula edodes genome assembly data will be used for the construction of a complete Lentinula edodes chromosome map for future breeding.

Use of mushroom tyrosinase to introduce michaelis-menten enzyme kinetics to biochemistry students

An inexpensive enzyme kinetics laboratory exercise for undergraduate biochemistry students is described utilizing tyrosinase from white button mushrooms. The exercise can be completed in one or two three-hour lab sessions. The optimal amounts of enzyme, substrate (catechol), and inhibitor (kojic acid) are first determined, and then kinetic data is collected in the absence and presence of the inhibitor. A Microsoft Excel template is used to plot the data and to fit the Michaelis-Menten equation to the data to determine the kinetic parameters V_max and K_m . The exercise is designed to clarify and reinforce concepts covered in an accompanying biochemistry lecture course. It has been used with positive results in an upper-level biochemistry laboratory course for junior/senior students majoring in chemistry or biology. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(3):270-276, 2017.

Functions of fungal melanin beyond virulence

Melanins are ancient biological pigments found in all kingdoms of life. In fungi, their role in microbial pathogenesis is well established; however, these complex biomolecules also confer upon fungal microorganisms the faculty to tolerate extreme environments such as the Earth's poles, the International Space Station and places contaminated by toxic metals and ionizing radiation. A remarkable property of melanin is its capacity to interact with a wide range of electromagnetic radiation frequencies, functioning as a protecting and energy harvesting pigment. Other roles of fungal melanin include scavenging of free radical, thermo-tolerance, metal ion sequestration, cell development, and mechanical-chemical cellular strength. In this review, we explore the various functions ascribed to this biological pigment in fungi and its remarkable physicochemical properties.

A novel immune-tolerable and permeable lectin-like protein from mushroom Agaricus bisporus

A lectin like protein designated as LSMT is recently discovered in Agaricus bisporus. The protein adopts very similar structure to Ricin-B like lectin from Clitocybe nebularis (CNL) and HA-33 from Clostridium botulinum (HA-33), which both recognize sugar molecules that decorate the surface of the epithelial cells of the intestine. A preliminary study in silico pointed out potential capability of LSMT to perform such biological activity. Following that hypothesis, we demonstrated that LSMT is indeed capable of penetrating out from a dialysis tube of the mice intestine origin. Furthermore, the protein appeared not to evoke the immune response upon introduction into mice, unlike its structural homologs. This is the first report on the biological implication of LSMT that might lead to its application.

Crystal structure of recombinant tyrosinase-binding protein MtaL at 1.35 Å resolution

Mushroom tyrosinase-associated lectin-like protein (MtaL) binds to mature Agaricus bisporus tyrosinase in vivo, but the exact physiological function of MtaL is unknown. In this study, the crystal structure of recombinant MtaL is reported at 1.35 Å resolution. Comparison of its structure with that of the truncated and cleaved MtaL present in the complex with tyrosinase directly isolated from mushroom shows that the general β-trefoil fold is conserved. However, differences are detected in the loop regions, particularly in the β2-β3 loop, which is intact and not cleaved in the recombinant MtaL. Furthermore, the N-terminal tail is rotated inwards, covering the tyrosinase-binding interface. Thus, MtaL must undergo conformational changes in order to bind mature mushroom tyrosinase. Very interestingly, the β-trefoil fold has been identified to be essential for carbohydrate interaction in other lectin-like proteins. Comparison of the structures of MtaL and a ricin-B-like lectin with a bound disaccharide shows that MtaL may have a similar carbohydrate-binding site that might be involved in glycoreceptor activity.