Grouping of multicopper oxidases in Lentinula edodes by sequence similarities and expression patterns

Expression profiling of laccase and β-glucan synthase genes in Pleurotus ostreatus during different developmental stages

BACKGROUND

Pleurotus ostreatus, commonly known as the oyster mushroom, is a saprophytic fungus with many applications in biotechnology and medicine. This mushroom is a rich source of proteins, polysaccharides, and bioactive compounds that have been shown to possess anticancer, antioxidant, and immunomodulatory properties. In this study, we investigated the expression profile of laccase (POXA3) and β-glucan synthase (FKS) genes during different developmental stages in two strains of P. ostreatus.

METHODS AND RESULTS

Cultural and morphological studies of the two strains were studied. DMR P115 strain recorded faster mycelial growth compared to the HUC strain. However, both strains produced white, thick fluffy mycelial growth with radiating margin. Morphological characteristics of the mushroom fruiting body were also higher in the DMR P115 strain. The expression of these genes was analyzed using quantitative real-time PCR (qPCR) and the results were compared to those of the reference gene β-actin. The expression of laccase (POXA3) was higher in the mycelial stage of DMR P115 and HUC strains indicating its role in the fruiting body development and substrate degradation. The expression of β-glucan synthase (FKS) was upregulated in the mycelium and mature fruiting body of the DMR P115 strain. In contrast, there was only significant upregulation in the mycelial stage of the HUC strain, which indicates its role in cell wall formation and the immunostimulatory properties of that strain.

CONCLUSION

The results deepen the understanding of the molecular mechanism of the fruiting body development in P. ostreatus and can be used as a foundation for future lines of research related to strain improvement of P. ostreatus.

Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes

Fruiting bodies (sporocarps, sporophores or basidiomata) of mushroom-forming fungi (Agaricomycetes) are among the most complex structures produced by fungi. Unlike vegetative hyphae, fruiting bodies grow determinately and follow a genetically encoded developmental program that orchestrates their growth, tissue differentiation and sexual sporulation. In spite of more than a century of research, our understanding of the molecular details of fruiting body morphogenesis is still limited and a general synthesis on the genetics of this complex process is lacking. In this paper, we aim at a comprehensive identification of conserved genes related to fruiting body morphogenesis and distil novel functional hypotheses for functionally poorly characterised ones. As a result of this analysis, we report 921 conserved developmentally expressed gene families, only a few dozens of which have previously been reported to be involved in fruiting body development. Based on literature data, conserved expression patterns and functional annotations, we provide hypotheses on the potential role of these gene families in fruiting body development, yielding the most complete description of molecular processes in fruiting body morphogenesis to date. We discuss genes related to the initiation of fruiting, differentiation, growth, cell surface and cell wall, defence, transcriptional regulation as well as signal transduction. Based on these data we derive a general model of fruiting body development, which includes an early, proliferative phase that is mostly concerned with laying out the mushroom body plan (via cell division and differentiation), and a second phase of growth via cell expansion as well as meiotic events and sporulation. Altogether, our discussions cover 1 480 genes of Coprinopsis cinerea, and their orthologs in Agaricus bisporus, Cyclocybe aegerita, Armillaria ostoyae, Auriculariopsis ampla, Laccaria bicolor, Lentinula edodes, Lentinus tigrinus, Mycena kentingensis, Phanerochaete chrysosporium, Pleurotus ostreatus, and Schizophyllum commune, providing functional hypotheses for ~10 % of genes in the genomes of these species. Although experimental evidence for the role of these genes will need to be established in the future, our data provide a roadmap for guiding functional analyses of fruiting related genes in the Agaricomycetes. We anticipate that the gene compendium presented here, combined with developments in functional genomics approaches will contribute to uncovering the genetic bases of one of the most spectacular multicellular developmental processes in fungi. Citation: Nagy LG, Vonk PJ, Künzler M, Földi C, Virágh M, Ohm RA, Hennicke F, Bálint B, Csernetics Á, Hegedüs B, Hou Z, Liu XB, Nan S, M. Pareek M, Sahu N, Szathmári B, Varga T, Wu W, Yang X, Merényi Z (2023). Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes. Studies in Mycology 104: 1-85. doi: 10.3114/sim.2022.104.01.

Extracellular enzymes secreted in the mycelial block of Lentinula edodes during hyphal growth

Lentinula edodes (shiitake mushroom) is one of the most widely cultivated edible mushrooms and is primarily cultivated using sawdust medium. While there have been improvements in the cultivation technology, the mechanism of mycelial block cultivation, such as mycelial growth and enzymatic sawdust degradation, has not been clarified. In this study, the mycelium was elongated longitudinally in the bottle sawdust culture for 27 days, and the cultivated sawdust medium was divided into three sections (top, middle, and bottom parts). To determine spatial heterogeneity in the enzyme secretion, the enzymatic activities of each part were analyzed. Lignocellulose degradation enzymes, such as endoglucanase, xylanase, and manganese peroxidase were highly secreted in the top part of the medium. On the other hand, amylase, pectinase, fungal cell wall degradation enzyme (β-1,3-glucanase, β-1,6-glucanase, and chitinase), and laccase activities were higher in the bottom part. The results indicate that the principal sawdust degradation occurs after mycelial colonization. Proteins with the laccase activity were purified from the bottom part of the medium, and three laccases, Lcc5, Lcc6 and Lcc13, were identified. In particular, the expression of Lcc13 gene was higher in the bottom part compared with the level in the top part, suggesting Lcc13 is mainly produced from the tip region and have important roles for mycelial spread and nutrient uptake during early stage of cultivation.

Laccase mediated delignification of wasted and non-food agricultural biomass: Recent developments and challenges

Utilization of microbial laccases is considered as the cleaner and target specific biocatalytic mechanism for the recovery of cellulose and hemicelluloses from nonfood and wasted agricultural, lignocellulosic biomass (LCB). The extent of lignin removal by laccase depends on the biochemical composition of biomass and the redox potential (E⁰) of the biocatalyst. Intensive research efforts are going on all over the world for the recognition of appropriate and easily available agricultural lignocellulosic feedstocks to exploit maximally for the production of value-added bioproducts and biofuels. In such circumstances, laccase can play a major role as a leading biocatalyst and potent substitute for chemical based deconstruction of the lignocellulosic materials. The limited commercialization of laccase at an industrial scale has been feasible due to its full working efficiency mostly expressed in the presence of cost intensive redox mediators only. Although, recently there are some reports that came on the mediator free biocatalysis of enzyme but still not considerably explored and neither understood in depth. The present review will address the various research gaps and shortcomings that acted as the big hurdles before the complete exploitation of laccases at an industrial scale. Further, this article also reveals insights on different microbial laccases and their diverse functional environmental conditions that affect the deconstruction process of LCB.

The study of early screening technique for fruiting ability of <i>Lentinula edodes</i> hybrid progenies

Crossbreeding is the most commonly used method in breeding of Lentinula edodes, however low fruiting rate of the hybrids has always caused troubles and barriers for breeders. An early screening method of the fruiting ability could make the breeding work more efficient. In this paper, a rapid and high-throughput laccase activity detection method based on agar diffusion principle was developed. In this way, we investigated the constitutive and inducible extracellular laccase activity of 36 strains in a breeding population of L. edodes on different media and performed a correlation analysis with fruiting ability of these strains. The results showed the laccase activity of mycelium cultured in non-induced medium for 8 d could be used as an early screening index to judge whether it had fruiting ability at the later stage. Early rapid and simple screening method for hybrid populations was established based on laccase activity characteristics of mycelia. 127 strains from another 5 different hybrid populations were used to verify the early screening method. From the validation results, the early screening method was effective, but the appropriate screening threshold was needed to select according to the cross population, which would greatly to improve the breeding efficiency of L. edodes.

Genome-wide characterization of laccase gene family in Schizophyllum commune 20R-7-F01, isolated from deep sediment 2 km below the seafloor

Laccases are ligninolytic enzymes that play a crucial role in various biological processes of filamentous fungi, including fruiting-body formation and lignin degradation. Lignin degradation is a complex process and its degradation in Schizophyllum commune is greatly affected by the availability of oxygen. Here, a total of six putative laccase genes (ScLAC) were identified from the S. commune 20R-7-F01 genome. These genes, which include three typical Cu-oxidase domains, can be classified into three groups based on phylogenetic analysis. ScLAC showed distinct intron-exon structures and conserved motifs, suggesting the conservation and diversity of ScLAC in gene structures. Additionally, the number and type of cis-acting elements, such as substrate utilization-, stress-, cell division- and transcription activation-related cis-elements, varied between ScLAC genes, suggesting that the transcription of laccase genes in S. commune 20R-7-F01 could be induced by different substrates, stresses, or other factors. The SNP analysis of resequencing data demonstrated that the ScLAC of S. commune inhabiting deep subseafloor sediments were significantly different from those of S. commune inhabiting terrestrial environments. Similarly, the large variation of conserved motifs number and arrangement of laccase between subseafloor and terrestrial strains indicated that ScLAC had a diverse structure. The expression of ScLAC5 and ScLAC6 genes was significantly up-regulated in lignin/lignite medium, suggesting that these two laccase genes might be involved in fungal utilization and degradation of lignite and lignin under anaerobic conditions. These findings might help in understanding the function of laccase in white-rot fungi and could provide a scientific basis for further exploring the relationship between the LAC family and anaerobic degradation of lignin by S. commune.

Optimization of culture medium for Sanghuangporus vaninii and a study on its therapeutic effects on gout

The increasing incidence of gout poses a very challenging management problem. However, the currently available drugs often have various toxic side effects. As a traditional edible and medicinal macrofungus, Sanghuangporus vaninii presents high medical research value. Therefore, to improve fermentation efficiency and identify novel anti-gout drugs, we optimized the culture medium of S. vaninii with lignin and further investigated its anti-gout effects. The results indicated that 0.06 g/L of lignin was most favorable for S. vaninii growth. In the hyperuricemia cell model, we found that S. vaninii could significantly induce the downregulation of xanthine oxidoreductase and the upregulation of hypoxanthine-guanine phosphoribosyltransferase. Furthermore, following oral administration of the extracts, the serum uric acid levels of mice with hyperuricemia were effectively reduced. In a gouty arthritis rat model, S. vaninii also achieved strong suppression of synovial swelling, indicating its anti-inflammatory activity. In addition, the antioxidant assays suggested that S. vaninii shows a strong free radical scavenging capacity and can effectively alleviate cellular oxidative stress. This activity further enhances its anti-inflammatory activity and reduces the incidence of comorbidities. In summary, our results provide the basis for the utilization of S. vaninii to develop anti-gout drugs.

Expression Profile of Laccase Gene Family in White-Rot Basidiomycete Lentinula edodes under Different Environmental Stresses

Laccases belong to ligninolytic enzymes and play important roles in various biological processes of filamentous fungi, including fruiting-body formation and lignin degradation. The process of fruiting-body development in Lentinula edodes is complex and is greatly affected by environmental conditions. In this paper, 14 multicopper oxidase-encoding (laccase) genes were analyzed in the draft genome sequence of L. edodes strain W1-26, followed by a search of multiple stress-related Cis-elements in the promoter region of these laccase genes, and then a transcription profile analysis of 14 laccase genes (Lelcc) under the conditions of different carbon sources, temperatures, and photoperiods. All laccase genes were significantly regulated by varying carbon source materials. The expression of only two laccase genes (Lelcc5 and Lelcc6) was induced by sodium-lignosulphonate and the expression of most laccase genes was specifically upregulated in glucose medium. Under different temperature conditions, the expression levels of most laccase genes decreased at 39 °C and transcription was significantly increased for Lelcc1, Lelcc4, Lelcc5, Lelcc9, Lelcc12, Lelcc13, and Lelcc14 after induction for 24 h at 10 °C, indicating their involvement in primordium differentiation. Tyrosinase, which is involved in melanin synthesis, was clustered with the same group as Lelcc4 and Lelcc7 in all the different photoperiod treatments. Meanwhile, five laccase genes (Lelcc8, Lelcc9, Lelcc12, Lelcc13, and Lelcc14) showed similar expression profiles to that of two blue light receptor genes (LephrA and LephrB) in the 12 h light/12 h dark treatment, suggesting the involvement of laccase genes in the adaptation process of L. edodes to the changing environment and fruiting-body formation. This study contributes to our understanding of the function of the different Lelcc genes and facilitates the screening of key genes from the laccase gene family for further functional research.

Selection and Validation of Reference Genes for qRT-PCR in Lentinula edodes under Different Experimental Conditions

Lentinula edodes is the most consumed mushroom in Asia due to its nutritional and medicinal values, and the optimal reference gene is crucial for normalization of its gene expression analysis. Here, the expression stability of 18 candidate reference genes (CRGs) in L. edodes was analyzed by three statistical algorithms (geNorm, NormFinder and BestKeeper) under different stresses (heat, cadmium excess and Trichoderma atroviride infection), different substrates (straw, sawdust and corn stalk) and different development stages (mycelia, primordia and fruit bodies). Among the 18 CRGs, 28S, Actin and α-tub exhibited the highest expression stability in L. edodes under all conditions, while GPD, SPRYP and MSF showed the least stable expression. The best reference gene in different conditions was different. The pairwise variation values showed that two genes would be sufficient for accurate normalization under different conditions of L. edodes. This study will contribute to more accurate estimation of the gene relative expression levels under different conditions using the optimal reference gene in qRT-PCR (quantitative reverse transcription polymerase chain reaction) analysis.

Production of polyextremotolerant laccase by Achromobacter xylosoxidans HWN16 and Citrobacter freundii LLJ16

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The biochemical properties of two proteobacteria laccases were assessed.

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Polyextremotolerant qualities of the laccases were identified.

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Multiple laccase-encoding genes were observed in laccase-producing strains.

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Their implication in biotechnological applications was deliberated.

Given the upwelling of a variety of potential applications laccases could participate in, it would be fitting to equally make available laccases that are well suited for the aforementioned. Therefore historian understanding of the catalytic and physicochemical properties is desirable. Owing to this, the biochemical properties of the crude laccases from Achromobacter xylosoxidans HWN16 (Hb9c) and Citrobacter freundii LLJ 16 (Ie1c) were assessed. Furthermore, a hint of the molecular basis for their production from respective organisms was presented. Results showed that both laccases were tolerant, and sometimes had their activities improved by the set of parameters tested. They were active at broad range of temperature (0–90 °C), pH (3–11), and were equally thermo- and pH-stable. Their activities were either improved, or left unabated by cations, detergents, and chloride (5–40%), however, the highlight of the study was their augmented activity, when they were incubated with certain concentrations of fluoride (2–20%), a potent inhibitor. They were depicted to have multiple homologous laccase encoding genes, on molecular evaluation, which may be responsible the conferral of these remarkable qualities they possess. Therefore, the laccases might be beneficial, if employed in formulations for a wide range of environmental and biotechnological applications. Moreover, the molecular machinery of their production be exploited for economical benefits in the immediate future.

Laccases: Production, Expression Regulation, and Applications in Pharmaceutical Biodegradation

Laccases are a family of copper-containing oxidases with important applications in bioremediation and other various industrial and biotechnological areas. There have been over two dozen reviews on laccases since 2010 covering various aspects of this group of versatile enzymes, from their occurrence, biochemical properties, and expression to immobilization and applications. This review is not intended to be all-encompassing; instead, we highlighted some of the latest developments in basic and applied laccase research with an emphasis on laccase-mediated bioremediation of pharmaceuticals, especially antibiotics. Pharmaceuticals are a broad class of emerging organic contaminants that are recalcitrant and prevalent. The recent surge in the relevant literature justifies a short review on the topic. Since low laccase yields in natural and genetically modified hosts constitute a bottleneck to industrial-scale applications, we also accentuated a genus of laccase-producing white-rot fungi, Cerrena, and included a discussion with regards to regulation of laccase expression.

Comparative secretomic analysis of lignocellulose degradation by Lentinula edodes grown on microcrystalline cellulose, lignosulfonate and glucose

Lentinula edodes has the potential to degrade woody and nonwoody lignocellulosic biomass. However, the mechanism of lignocellulose degradation by L. edodes is unclear. The aim of this work is to explore the profiling of soluble secreted proteins involved in lignocellulose degradation in L. edodes. For that, we compared the secretomes of L. edodes grown on microcrystalline cellulose, cellulose with lignosulfonate and glucose. Based on nanoliquid chromatography coupled with tandem mass spectrometry of whole-protein hydrolysate, 230 proteins were identified. Label-free proteomic analysis showed that the most abundant carbohydrate-active enzymes involved in polysaccharide hydrolysis were endo-β-1,4-glucanase, α-galactosidase, polygalacturonase and glucoamylase in both cellulosic secretomes. In contrast, enzymes involved in lignin degradation were most abundant in glucose culture, with laccase 1 being the predominant protein (13.13%). When the cellulose and cellulose with lignosulfonate secretomes were compared, the abundance of cellulases and hemicellulases was higher in cellulose with lignosulfonate cultures, which was confirmed by enzyme activity assays. In addition, qRT-PCR analysis demonstrated that the expression levels of genes encoding cellulases and hemicellulases were significantly increased (by 32.2- to 1166.7-fold) when L. edodes was grown in cellulose with lignosulfonate medium.

BIOLOGICAL SIGNIFICANCE

In this article, the secretomes of L. edodes grown on three different carbon sources were compared. The presented results revealed the profiling of extracellular enzymes involved in lignocellulose degradation, which is helpful to further explore the mechanism of biomass bioconversion by L. edodes.

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.

Genome Sequence of the Edible Cultivated Mushroom Lentinula edodes (Shiitake) Reveals Insights into Lignocellulose Degradation

Lentinula edodes, one of the most popular, edible mushroom species with a high content of proteins and polysaccharides as well as unique aroma, is widely cultivated in many Asian countries, especially in China, Japan and Korea. As a white rot fungus with lignocellulose degradation ability, L. edodes has the potential for application in the utilization of agriculture straw resources. Here, we report its 41.8-Mb genome, encoding 14,889 predicted genes. Through a phylogenetic analysis with model species of fungi, the evolutionary divergence time of L. edodes and Gymnopus luxurians was estimated to be 39 MYA. The carbohydrate-active enzyme genes in L. edodes were compared with those of the other 25 fungal species, and 101 lignocellulolytic enzymes were identified in L. edodes, similar to other white rot fungi. Transcriptome analysis showed that the expression of genes encoding two cellulases and 16 transcription factor was up-regulated when mycelia were cultivated for 120 minutes in cellulose medium versus glucose medium. Our results will foster a better understanding of the molecular mechanism of lignocellulose degradation and provide the basis for partial replacement of wood sawdust with agricultural wastes in L. edodes cultivation.

Laccase Gene Family in Cerrena sp. HYB07: Sequences, Heterologous Expression and Transcriptional Analysis

Laccases are a class of multi-copper oxidases with industrial potential. In this study, eight laccases (Lac1-8) from Cerrena sp. strain HYB07, a white-rot fungus with high laccase yields, were analyzed. The laccases showed moderate identities to each other as well as with other fungal laccases and were predicted to have high redox potentials except for Lac6. Selected laccase isozymes were heterologously expressed in the yeast Pichia pastoris, and different enzymatic properties were observed. Transcription of the eight laccase genes was differentially regulated during submerged and solid state fermentation, as shown by quantitative real-time polymerase chain reaction and validated reference genes. During 6-day submerged fermentation, Lac7 and 2 were successively the predominantly expressed laccase gene, accounting for over 95% of all laccase transcripts. Interestingly, accompanying Lac7 downregulation, Lac2 transcription was drastically upregulated on days 3 and 5 to 9958-fold of the level on day 1. Consistent with high mRNA abundance, Lac2 and 7, but not other laccases, were identified in the fermentation broth by LC-MS/MS. In solid state fermentation, less dramatic differences in transcript abundance were observed, and Lac3, 7 and 8 were more highly expressed than other laccase genes. Elucidating the properties and expression profiles of the laccase gene family will facilitate understanding, production and commercialization of the fungal strain and its laccases.