Characterization, molecular cloning, and differential expression analysis of laccase genes from the edible mushroom Lentinula edodes

Uranium mining effluents: What about the re-use of mining wastes to improve the bioproduction of industrially relevant bioactive compounds?

The shift towards a circular economy, where waste generation is minimized through waste re-use and the development of valorization strategies, is crucial for the establishment of a low carbon, sustainable, and resource-efficient economy. However, there is a lack of strategies for re-using and valorizing specific types of waste, particularly those containing naturally occurring radioactive materials (NORM), despite the prevalence of industrial activities that produce such waste due to their chemical and radiological hazards. Living organisms, including fungi, are valuable sources of bioactive compounds with various industrial applications. In this study, we assessed the growth and metabolic profile changes of three white rot fungi species in response to low concentrations of a uranium mine effluent containing NORM and metals to explore their potential for producing biotechnologically relevant bioactive compounds. The growth rate was assessed in three different culture media, with and without the uranium mine effluent (1% V/V)), and the metabolic profile was analyzed using FTIR-ATR spectroscopy. Results suggested an improvement in growth rates in media containing the uranium mine effluent, although not statistically significant. T. versicolor showed promise in terms of bioactive compound production. The production of droplets during growth experiments and significant metabolic changes, associated with the production of bioactive compounds like laccase, melanin, and oxalic acid, were observed in T. versicolor grown in mYEPDA with the uranium mine effluent. These findings present new research opportunities for utilizing waste to enhance the biotechnological production of industrially relevant bioactive compounds and promote the development of circular economy strategies for re-using and valorizing NORM-containing waste.

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.

Applications and immobilization strategies of the copper-centred laccase enzyme; a review

Laccase is a multi-copper enzyme widely expressed in fungi, higher plants, and bacteria which facilitates the direct reduction of molecular oxygen to water (without hydrogen peroxide production) accompanied by the oxidation of an electron donor. Laccase has attracted attention in biotechnological applications due to its non-specificity and use of molecular oxygen as secondary substrate. This review discusses different applications of laccase in various sectors of food, paper and pulp, waste water treatment, pharmaceuticals, sensors, and fuel cells. Despite the many advantages of laccase, challenges such as high cost due to its non-reusability, instability in harsh environmental conditions, and proteolysis are often encountered in its application. One of the approaches used to minimize these challenges is immobilization. The various methods used to immobilize laccase and the different supports used are further extensively discussed in this review.

Brassinosteroids is involved in methane-induced adventitious root formation via inducing cell wall relaxation in marigold

BACKGROUND

Methane (CH₄) and brassinosteroids (BRs) are important signaling molecules involved in a variety of biological processes in plants.

RESULTS

Here, marigold (Tagetes erecta L. 'Marvel') was used to investigate the role and relationship between CH₄ and BRs during adventitious root (AR) formation. The results showed a dose-dependent effect of CH₄ and BRs on rooting, with the greatest biological effects of methane-rich water (MRW, CH₄ donor) and 2,4-epibrassinolide (EBL) at 20% and 1 μmol L^- 1, respectively. The positive effect of MRW on AR formation was blocked by brassinoazole (Brz, a synthetic inhibitor of EBL), indicating that BRs might be involved in MRW-regulated AR formation. MRW promoted EBL accumulation during rooting by up-regulating the content of campestanol (CN), cathasterone (CT), and castasterone (CS) and the activity of Steroid 5α-reductase (DET2), 22α-hydroxylase (DWF4), and BR-6-oxidase (BR6ox), indicating that CH₄ could induce endogenous brassinolide (BR) production during rooting. Further results showed that MRW and EBL significantly down-regulated the content of cellulose, hemicellulose and lignin during rooting and significantly up-regulated the hydrolase activity, i.e. cmcase, xylanase and laccase. In addition, MRW and EBL also significantly promoted the activity of two major cell wall relaxing factors, xyloglucan endotransglucosylase/hydrolase (XTH) and peroxidase, which in turn promoted AR formation. While, Brz inhibited the role of MRW on these substances.

CONCLUSIONS

BR might be involved in CH₄-promoted AR formation by increasing cell wall relaxation.

Functional Characterization of Laccase Isozyme (PoLcc1) from the Edible Mushroom Pleurotus ostreatus Involved in Lignin Degradation in Cotton Straw

Fungal laccases play important roles in the degradation of lignocellulose. In this study, the laccase producing cotton straw medium for Pleurotus ostreatus was optimized by single-factor and orthogonal experiments, and to investigate the role of Lacc1 gene, one of the laccase-encoding genes, in the degradation of cotton straw lignin, an overexpression strain of Lacc1 gene was constructed, which was analyzed for the characteristics of lignin degradation. The results demonstrated that the culture conditions with the highest lignin degradation efficiency of the P. ostreatus were the cotton straw particle size of 0.75 mm, a solid-liquid ratio of 1:3 and containing 0.25 g/L of Tween in the medium, as well as an incubation temperature of 26 °C. Two overexpression strains (OE L1-1 and OE L1-4) of Lacc1 gene were obtained, and the gene expression increased 12.08- and 33.04-fold, respectively. The results of 1H-NMR and FTIR analyses of significant changes in lignin structure revealed that Lacc1 gene accelerated the degradation of lignin G-units and involved in the cleavage of β-O-4 linkages and the demethylation of lignin units. These findings will help to improve the efficiency of biodelignification and expand our understanding of its mechanism.

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.

Expression and in vitro anticancer activity of Lp16-PSP, a member of the YjgF/YER057c/UK114 protein family from the mushroom Lentinula edodes C91-3

Latcripin-16 (Lp16-PSP) is a gene that was extracted as a result of de novo characterization of the Lentinula edodes strain C_91-3 transcriptome. The aim of the present study was to clone, express, and investigate the selective in vitro anticancer potential of Lp16-PSP in human cell lines. Lp16-PSP was analyzed using bioinformatics tools, cloned in a prokaryotic expression vector pET32a (+) and transformed into E. coli Rosetta gami. It was expressed and solubilized under optimized conditions. The differential scanning fluorometry (DSF)-guided refolding method was used with modifications to identify the proper refolding conditions for the Lp16-PSP protein. To determine the selective anticancer potential of Lp16-PSP, a panel of human cancerous and non-cancerous cell lines was used. Lp16-PSP protein was identified as endoribonuclease L-PSP protein and a member of the highly conserved YjgF/YER057c/UK114 protein superfamily. Lp16-PSP was expressed under optimized conditions (37 °C for 4 h following induction with 0.5 mM isopropyl β-D-1-thiogalactopyranoside). Solubilization was achieved with mild solubilization buffer containing 2 M urea using the freeze-thaw method. The DSF guided refolding method identified the proper refolding conditions (50 mM Tris-HCl, 100 mM NaCl, 1 mM EDTA, 400 mM Arginine, 0.2 mM GSH and 2 mM GSSG; pH 8.0) for Lp16-PSP, with a melting transition of ~ 58 °C. A final yield of ~ 16 mg of purified Lp16-PSP from 1 L of culture was obtained following dialysis and concentration by PEG 20,000. A Cell Counting Kit-8 assay revealed the selective cytotoxic effect of Lp16-PSP. The HL-60 cell line was demonstrated to be most sensitive to Lp16-PSP, with an IC₅₀ value of 74.4 ± 1.07 µg/ml. The results of the present study suggest that Lp16-PSP may serve as a potential anticancer agent; however, further investigation is required to characterize this anticancer effect and to elucidate the molecular mechanism underlying the action of Lp16-PSP.

RNA-Seq-based high-resolution linkage map reveals the genetic architecture of fruiting body development in shiitake mushroom, Lentinula edodes

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We constructed a reference genetic map of Lentinula edodes.

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We re-assembled a chromosome-level genome of L. edodes.

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We disclosed three hotspots regions for fruiting body-related traits in shiitake.

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We scanned candidate genes for fruiting body-related traits.

Fruiting body development (FBD) of mushroom-forming fungi has attracted tremendous interest. However, the genetic and molecular basis of FBD is poorly known. Here, using Lentinula edodes (shiitake) as a model, we deciphered the genetic architecture underlying fruiting body-related traits (FBRTs) by combined genomic, genetic and phenotypic data. Using RNA-Seq of fruiting bodies from 110 dikaryons in a bi-parental mapping population, we constructed an ultra-high-density genetic map of L. edodes (Lemap2.0) with a total length of 810.14 cM, which covered 81.7% of the shiitake genome. A total of 94 scaffolds of the shiitake genome were aligned to Lemap2.0 and re-anchored into nine pseudo-chromosomes. Then via quantitative trait locus (QTL) analysis, we disclosed an outline of the genetic architecture of FBD in shiitake. Twenty-nine QTLs and three main genomic regions associated with FBD of shiitake were identified. Using meta-QTL analysis, seven pleiotropic QTLs for multiple traits were detected, which contributed to the correlations of FBRTs. In the mapped QTLs, the expression of 246 genes were found to significantly correlate with the phenotypic traits. Thirty-three of them were involved in FBD and could represent candidate genes controlling the shape and size of fruiting bodies. Collectively, our findings have advanced our understanding of the genetic regulation of FBD in shiitake and mushroom-forming fungi at large.

Purification and characterisation of new laccase from Trametes polyzona WRF03

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Trametes polyzona WRF03 produced high yield of true laccase.

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Trametes polyzona WRF03 laccase was relatively pH and temperature stable.

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Fe²⁺, sodium azide and sodium cyanide greatly inhibited laccase activity.

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Trametes polyzona WRF03 laccase decolorised many classes of synthetic dyes.

The molecular screening for laccase specific gene sequences in Trametes polyzona WRF03 (TpWRF03) using designed oligonucleotide primers analogous to the conserved sequences on the copper-binding regions of known laccases showed positive amplification with an amplicon size corresponding to 1500 bp. The purified TpWRF03 laccase (TpL) is a monomer with a molecular weight corresponding to 66 kDa. The enzyme had an optimal pH of 4.5 and temperature of 55 °C. TpL was most stable within pH of 5.5–6.5 and at a temperature range of 40–50 °C. Sodium azide, sodium cyanide and Fe²⁺ greatly inhibited the enzyme activity. TpL showed more than 50 % decolourisation efficiency on coomassie brilliant blue (72.35 %) and malachite green (57.84 %) but displayed low decolourisation efficiency towards Azure B (1.78 %) and methylene blue (0.38 %). The results showed that TpWRF03 produces high-yield of true laccase with robust properties for biotechnological applications.

Oxidation of the Oak Ellagitannin, Vescalagin

Vescalagin (1) is a major ellagitannin from young spring leaves of Quercus glauca; however, the amount of 1 decreases as the leaves mature with a concomitant rise in the levels of catechin (3) and procyanidins. In this report, the chemical mechanism responsible for the degradation of 1 was investigated. In vitro model experiments indicated that initially a polyphenol oxidase oxidizes the catechin B-ring, and the resulting catechin o-quinone oxidizes one of the pyrogallol rings of 1 to give a cyclopenten-1,2-dione-type product 4. The presence of 4 in young oak leaves was confirmed by the detection of 4 and its quinoxaline derivative 4a. Furthermore, it was demonstrated that the cyclopenten-1,2-dione moiety of 4 nonenzymatically reacted with the catechin A-ring to yield the conjugate 5. Similar conjugations probably occur with procyanidins; thus, these reactions are possibly responsible for the decrease in the levels of 1 in leaves. The same cyclopenten-1,2-dione product 4 was also generated by treatment of 1 with a wood-rotting mushroom, Lentinula edodes, and further oxidative cleavage of a second pyrogallol ring of 4 was also observed. The results indicate the presence of a common degradation mechanism of 1 by plants and microbes.

Validation of reference genes for quantitative gene expression analysis in Auricularia cornea

Auricularia cornea Ehrenb., previously named A. polytricha (Mont.) Sacc, has become one of the most widely cultivated mushrooms in China. Considerable research has been conducted on its cultivation, pathogen identification, proteomics, and more. However, to the best of our knowledge, no studies have been performed on reference-gene validation in this species. Formerly, reference genes were selected for their expression levels only relied upon from others species, owing to the fact that the gene stability in this species is unknown. In this study, nine candidate genes, including tubulin alpha-1A chain (TUBA1A), β-tubulin (Btu), phosphoglucomutase (Pgm), actin 1 (Act1), protein phosphatase 2A regulatory subunit (PP2A), polyubiquitin (UBQ), glyceraldehyde-3-phosphate dehydrogenase (Gapdh), 18S ribosomal protein (18S) and 28S ribosomal protein (28S), were evaluated among different strains and developmental stages. Four algorithms (i.e., geNorm, NormFinder, BestKeeper and RefFinder) were used to analyze candidate genes. The results revealed that UBQ was the most stable reference gene, while 18S was the least stable. Despite these results, the candidate genes were largely inadequate and only two were considered suitable. Based on candidate gene stability, PP2A and UBQ were identified as a set of usable interior control genes for future analyses in this species. This is the first systematic study conducted for selecting reference genes in A. cornea, and lays the foundation for identifying genes and quantifying gene expression in this species.

Laccase-Mediated Treatment of Pharmaceutical Wastes

Laccases are versatile multi-copper enzymes belonging to the superfamily of oxidase enzymes, which have been known since the nineteenth century. Recent discoveries have refined investigators' views of the potential of laccase as a magic tool for remarkable biotechnological purposes. A literature review of the capabilities of laccases, their assorted substrates, and their molecular mechanism of action now indicates the emergence of a new direction for laccase application as part of an arsenal in the fight against the contamination of water supplies by a number of frequently prescribed medications. This chapter provides a critical review of the literature and reveals the pivotal role of laccases in the elimination and detoxification of pharmaceutical contaminants in aquatic environments and wastewaters.

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.

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

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

Stone-Eating Fungi: Mechanisms in Bioweathering and the Potential Role of Laccases in Black Slate Degradation With the Basidiomycete Schizophyllum commune

Many enzymes, such as laccases, are involved in the saprotrophic lifestyle of fungi and the effects of those may be linked to enhanced bioweathering on stone surfaces. To test this hypothesis, we studied the decomposition of kerogen-enriched lithologies, especially with black slate containing up to 20% of C_org. Indeed, a formation of ditches with attached hyphal material could be observed. To address enzymes involved, proteomics was performed and one group of enzymes, the multicopper oxidase family members of laccases, was specifically investigated. A role in bioweathering of rocks containing high contents of organic carbon in the form of kerogen could be shown using the basidiomycete Schizophyllum commune, a white rot fungus that has been used as a model organism to study the role of filamentous basidiomycete fungi in bioweathering of black slate.

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

The edible white rot fungus Lentinula edodes possesses a variety of lignin degrading enzymes such as manganese peroxidases and laccases. Laccases belong to the multicopper oxidases, which have a wide range of catalytic activities including polyphenol degradation and synthesis, lignin degradation, and melanin formation. The exact number of laccases in L. edodes is unknown, as are their complete properties and biological functions. We analyzed the draft genome sequence of L. edodes D703PP-9 and identified 13 multicopper oxidase-encoding genes; 11 laccases in sensu stricto, of which three are new, and two ferroxidases. lcc8, a laccase previously reported in L. edodes, was not identified in D703PP-9 genome. Phylogenetic analysis showed that the 13 multicopper oxidases can be classified into laccase sensu stricto subfamily 1, laccase sensu stricto subfamily 2 and ferroxidases. From sequence similarities and expression patterns, laccase sensu stricto subfamily 1 can be divided into two subgroups. Laccase sensu stricto subfamily 1 group A members are mainly secreted from mycelia, while laccase sensu stricto subfamily 1 group B members are expressed mainly in fruiting bodies during growth or after harvesting but are lowly expressed in mycelia. Laccase sensu stricto subfamily 2 members are mainly expressed in mycelia, and two ferroxidases are mainly expressed in the fruiting body during growth or after harvesting, and are expressed at very low levels in mycelium. Our data suggests that L. edodes laccases in same group share expression patterns and would have common biological functions.

A novel Lentinula edodes laccase and its comparative enzymology suggest guaiacol-based laccase engineering for bioremediation

Laccases are versatile biocatalysts for the bioremediation of various xenobiotics, including dyes and polyaromatic hydrocarbons. However, current sources of new enzymes, simple heterologous expression hosts and enzymatic information (such as the appropriateness of common screening substrates on laccase engineering) remain scarce to support efficient engineering of laccase for better "green" applications. To address the issue, this study began with cloning the laccase family of Lentinula edodes. Three laccases perfectio sensu stricto (Lcc4A, Lcc5, and Lcc7) were then expressed from Pichia pastoris, characterized and compared with the previously reported Lcc1A and Lcc1B in terms of kinetics, stability, and degradation of dyes and polyaromatic hydrocarbons. Lcc7 represented a novel laccase, and it exhibited both the highest catalytic efficiency (assayed with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS]) and thermostability. However, its performance on "green" applications surprisingly did not match the activity on the common screening substrates, namely, ABTS and 2,6-dimethoxyphenol. On the other hand, correlation analyses revealed that guaiacol is much better associated with the decolorization of multiple structurally different dyes than are the two common screening substrates. Comparison of the oxidation chemistry of guaiacol and phenolic dyes, such as azo dyes, further showed that they both involve generation of phenoxyl radicals in laccase-catalyzed oxidation. In summary, this study concluded a robust expression platform of L. edodes laccases, novel laccases, and an indicative screening substrate, guaiacol, which are all essential fundamentals for appropriately driving the engineering of laccases towards more efficient "green" applications.

Lcc1 and Lcc5 are the main laccases secreted in liquid cultures of Coprinopsis cinerea strains

The litter-degrading dung fungus Coprinopsis cinerea has the high number of seventeen different laccase genes. In this work, ten different monokaryons were compared in their ability to produce laccases in two different complete media at different temperatures. Few strains showed laccase activity at the optimal growth temperature of 37 °C. Nine of the strains gave laccase activities between 0.2 and 5.9 U mL(-1) at the suboptimal temperature of 25 °C in mKjalke medium. Laccase activities in YMG/T medium were detected for only three strains (0.5-4.5 U mL(-1)). Zymograms of supernatants from mKjalke medium resulted in total in 10 different laccase bands but strains differed in distribution. LC-MS/MS analysis with Mascot searches of the annotated C. cinerea genome identified isoenzymes from five different genes (Lcc1, Lcc2, Lcc5, Lcc9 and Lcc10) and of Lcc1 three and of Lcc5 two distinct electrophoretical forms. Lcc1 and Lcc5 were expressed in all laccase positive strains, but not all forms were found in all of the strains. Lcc2, Lcc9 and Lcc10 occurred only in three strains as minor laccases, indicating that Lcc1 and Lcc5 are the main laccases of C. cinerea secreted in liquid mKjalke medium.

The relationship between lignin peroxidase and manganese peroxidase production capacities and cultivation periods of mushrooms

Mushrooms are able to secrete lignin peroxidase (LiP) and manganese peroxidase (MnP), and able to use the cellulose as sources of carbon. This article focuses on the relation between peroxidase-secreting capacity and cultivation period of mushrooms with non-laccase activity. Methylene blue and methyl catechol qualitative assay and spectrophotometry quantitative assay show LiP secreting unvaryingly accompanies the MnP secreting in mushroom strains. The growth rates of hyphae are detected by detecting the dry hyphal mass. We link the peroxidase activities to growth rate of mushrooms and then probe into the relationship between them. The results show that there are close relationships between LiP- and/or MnP-secretory capacities and the cultivation periods of mushrooms. The strains with high LiP and MnP activities have short cultivation periods. However, those strains have long cultivation periods because of the low levels of secreted LiP and/or MnP, even no detectable LiP and/or MnP activity. This study provides the first evidence on the imitate relation between the level of secreted LiP and MnP activities and cultivation periods of mushrooms with non-laccase activity. Our study has significantly increased the understanding of the role of LiP and MnP in the growth and development of mushrooms with non-laccase activity.

Expression of the laccase gene from a white rot fungus in Pichia pastoris can enhance the resistance of this yeast to H2O2-mediated oxidative stress by stimulating the glutathione-based antioxidative system

Laccase is a copper-containing polyphenol oxidase that has great potential in industrial and biotechnological applications. Previous research has suggested that fungal laccase may be involved in the defense against oxidative stress, but there is little direct evidence supporting this hypothesis, and the mechanism by which laccase protects cells from oxidative stress also remains unclear. Here, we report that the expression of the laccase gene from white rot fungus in Pichia pastoris can significantly enhance the resistance of yeast to H(2)O(2)-mediated oxidative stress. The expression of laccase in yeast was found to confer a strong ability to scavenge intracellular H(2)O(2) and to protect cells from lipid oxidative damage. The mechanism by which laccase gene expression increases resistance to oxidative stress was then investigated further. We found that laccase gene expression in Pichia pastoris could increase the level of glutathione-based antioxidative activity, including the intracellular glutathione levels and the enzymatic activity of glutathione peroxidase, glutathione reductase, and γ-glutamylcysteine synthetase. The transcription of the laccase gene in Pichia pastoris was found to be enhanced by the oxidative stress caused by exogenous H(2)O(2). The stimulation of laccase gene expression in response to exogenous H(2)O(2) stress further contributed to the transcriptional induction of the genes involved in the glutathione-dependent antioxidative system, including PpYAP1, PpGPX1, PpPMP20, PpGLR1, and PpGSH1. Taken together, these results suggest that the expression of the laccase gene in Pichia pastoris can enhance the resistance of yeast to H(2)O(2)-mediated oxidative stress by stimulating the glutathione-based antioxidative system to protect the cell from oxidative damage.

Controlling the simultaneous production of laccase and lignin peroxidase from Streptomyces cinnamomensis by medium formulation

BACKGROUND

Use of crude ligninase of bacterial origin is one of the most promising ways to improve the practical biodegradation of lignocellulosic biomass. However, lignin is composed of diverse monolignols with different abundance levels in different plant biomass and requires different proportions of ligninase to realize efficient degradation. To improve activity and reduce cost, the simultaneous submerged fermentation of laccase and lignin peroxidase (LiP) from a new bacterial strain, Streptomyces cinnamomensis, was studied by adopting formulation design, principal component analysis, regression analysis and unconstrained mathematical programming.

RESULTS

The activities of laccase and LiP from S. cinnamomensis cultured with the optimal medium formulations were improved to be five to eight folders of their initial activities, and the measured laccase:LiP activity ratios reached 0.1, 0.4 and 1.7 when cultured on medium with formulations designed to produce laccase:LiP complexes with theoretical laccase:LiP activity ratios of 0.05 to 0.1, 0.5 to 1 and 1.1 to 2.

CONCLUSION

Both the laccase and LiP activities and also the activity ratio of laccase to LiP could be controlled by the medium formulation as designed. Using a crude laccase-LiP complex with a specially designed laccase:LiP activity ratio has the potential to improve the degradation of various plant lignins composed of diverse monolignols with different abundance levels.

Biodegradation of dyes and polyaromatic hydrocarbons by two allelic forms of Lentinula edodes laccase expressed from Pichia pastoris

Laccases from basidiomycetes are efficient enzymes in the degradation of xenobiotics. In this study we aimed to provide an industrially relevant expression system for Lentinula edodes laccases, to characterize their enzymatic properties, and to evaluate their potential in bioremediation. Two 1573-bp allelic laccase genes from L. edodes L54 were cloned based on gene models in the genome sequence. A novel upstream consensus (GCTCCGA/CCGGAG) was proposed as an alternative signature sequence for laccases. Both alleles were overexpressed in Pichia pastoris, purified, and verified by zymograms. Kinetic analyses suggested an order of catalytic efficiency of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)>2,6-dimethoxyphenol>guaiacol>l-3,4-dihydroxyphenylalanine>catechol, and a stable range of working temperature below 40 °C. With the appropriate mediators, 1-hydroxybenzotriazole and 2,2,6,6-tetramethylpiperidine-1-oxyl, the recombinant enzymes could catalyze a 70-100% decolorization of selected dyes and a complete degradation of anthracene. These results laid a solid foundation for the use of L. edodes laccases in bioremediations and for improvement with protein engineering.

Decolorization of different dyes by a newly isolated white-rot fungi strain Ganoderma sp.En3 and cloning and functional analysis of its laccase gene

A laccase-producing white-rot fungi strain Ganoderma sp.En3 was newly isolated from the forest of Tzu-chin Mountain in China. Ganoderma sp.En3 had a strong ability of decolorizing four synthetic dyes, two simulated dye bath effluents and the real textile dye effluent. Induction in the activity of laccase during the decolorization process indicated that laccase played an important role in the efficient decolorization of different dyes by this fungus. Phytotoxicity study with respect to Triticum aestivum and Oryza sativa demonstrated that Ganoderma sp.En3 was able to detoxify four synthetic dyes, two simulated dye effluents and the real textile dye effluent. The laccase gene lac-En3-1 and its corresponding full-length cDNA were then cloned and characterized from Ganoderma sp.En3. The deduced protein sequence of LAC-En3-1 contained four copper-binding conserved domains of typical laccase protein. The functionality of lac-En3-1 gene encoding active laccase was verified by expressing this gene in the yeast Pichia pastoris successfully. The recombinant laccase produced by the yeast transformant could decolorize the synthetic dyes, simulated dye effluents and the real textile dye effluent. The ability of decolorizing different dyes was positively related to the laccase activity. In addition, the 5'-flanking sequence upstream of the start codon ATG in lac-En3-1 gene was obtained. Many putative cis-acting responsive elements were predicted in the promoter region of lac-En3-1.

Multiple multi-copper oxidase gene families in basidiomycetes - what for?

Genome analyses revealed in various basidiomycetes the existence of multiple genes for blue multi-copper oxidases (MCOs). Whole genomes are now available from saprotrophs, white rot and brown rot species, plant and animal pathogens and ectomycorrhizal species. Total numbers (from 1 to 17) and types of mco genes differ between analyzed species with no easy to recognize connection of gene distribution to fungal life styles. Types of mco genes might be present in one and absent in another fungus. Distinct types of genes have been multiplied at speciation in different organisms. Phylogenetic analysis defined different subfamilies of laccases sensu stricto (specific to Agaricomycetes), classical Fe2+-oxidizing Fet3-like ferroxidases, potential ferroxidases/laccases exhibiting either one or both of these enzymatic functions, enzymes clustering with pigment MCOs and putative ascorbate oxidases. Biochemically best described are laccases sensu stricto due to their proposed roles in degradation of wood, straw and plant litter and due to the large interest in these enzymes in biotechnology. However, biological functions of laccases and other MCOs are generally little addressed. Functions in substrate degradation, symbiontic and pathogenic intercations, development, pigmentation and copper homeostasis have been put forward. Evidences for biological functions are in most instances rather circumstantial by correlations of expression. Multiple factors impede research on biological functions such as difficulties of defining suitable biological systems for molecular research, the broad and overlapping substrate spectrum multi-copper oxidases usually possess, the low existent knowledge on their natural substrates, difficulties imposed by low expression or expression of multiple enzymes, and difficulties in expressing enzymes heterologously.

Cataloging and profiling genes expressed in Lentinula edodes fruiting body by massive cDNA pyrosequencing and LongSAGE

This study investigated the molecular mechanism of the fruiting body development and sporulation in the cap of the Shiitake mushroom, Lentinula edodes. Although there has been much research into L. edodes, there remain significant gaps in our knowledge of how the species reproduces. In order to provide molecular resources and to understand the molecular mechanism of the fruiting body development in basidiomycete comprehensively, we searched for the genes which are important for fruiting body development and sporulation in the cap of mature fruiting body of L. edodes by using the whole-genome approach. Massive cDNA pyrosequencing was used to generate >7000 sequence contigs from mature fruiting bodies. We used Gene Ontology to categorize the contigs to form the catalog of genes expressed at the stage of the mature fruiting body. We also assigned the contigs into the KEGG pathways. The catalog of expressed genes indicates that the mature fruiting bodies (1) sense the external environment, (2) transmit signals to express genes through regulatory systems, (3) produce many proteins, (4) degrade unwanted proteins, (5) perform extensive biosynthesis, (6) generate energy, (7) regulate the internal environment, (8) transport molecules, (9) carry out cell division, and (10) differentiate and develop. After establishing the catalog of expressed genes in L. edodes, we used the LongSAGE approach to analyze the expression levels of genes found in mature fruiting bodies before (FB) and after (FBS) spores appeared. Gene-expression patterns according to GO categories were similar in these two stages. We have also successfully identified genes differentially expressed in FB and FBS. Fold-changes in expression levels of selected genes based on LongSAGE tag counts were similar to those obtained by real-time RT-PCR. The consistency between real-time RT-PCR and LongSAGE results indicates reliability of the LongSAGE results. Overall, this study provides valuable information on the fruiting processes of L. edodes through a combination of massive cDNA pyrosequencing and LongSAGE sequencing, and the knowledge thereby obtained may provide insight into the improvement of the yield of commercially grown Shiitake mushrooms.

The level of secreted laccase activity in the edible fungi and their growing cycles are closely related

This article focuses on the relation between laccase-secreting ability and growing cycle in the edible fungi. First, laccase activities of fifteen different edible fungi were detected and determined by plate assay and spectrophotometric method using 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) as the substrate. The results showed the laccase-secreting ability in the edible fungi and their growing cycles are closely related. The edible fungi strains with short growing cycles originate from their high levels of secreted laccase activity. However, those strains require long growing cycles due to the low levels of secreted laccase, even no detectable laccase activity. The research provides the first evidence on the corresponding relation between the level of secreted laccase activity and growth cycles of edible fungi. Our study has significantly increased the understanding of the role of laccase in the growth and development of edible fungi.

A chimeric laccase with hybrid properties of the parental Lentinula edodes laccases

We created a chimeric laccase from two different laccases, Lcc1 and Lcc4, from Lentinula edodes. Lcc1 is a secretory lignin-degrading enzyme produced in liquid cultures of L. edodes. Lcc4 is a tissue-accumulating-type enzyme, which is thought to be involved in melanin synthesis in fruiting body after harvesting. Lcc1 and Lcc4 differ in their Km values for some substrates, especially beta-(3,4-dihydroxyphenyl) alanine (L-DOPA) and catechol. The novel chimeric laccase, Lcc4/1, has properties that are a hybrid of those of Lcc1 and Lcc4. Lcc4/1 acts upon both Lcc1 and Lcc4 substrates and most of its Km values are lower than those of Lcc1 and Lcc4. Homology modeling indicates that the deduced shape of the substrate-binding pocket of the chimeric laccase is larger than that of Lcc1 and similar to that of Lcc4. The other biochemical properties, such as temperature and pH dependency, are intermediate between those of Lcc1 and Lcc4.

Expression of phenol oxidase and heat-shock genes during the development of Agaricus bisporus fruiting bodies, healthy and infected by Lecanicillium fungicola

The fungal pathogen Lecanicillium fungicola (formerly Verticillium fungicola) is responsible for severe losses worldwide in the mushroom (Agaricus bisporus) industry. Infected crops are characterised by masses of undifferentiated tissue (bubbles) growing in place of sporophores. The expression of three laccase genes (lcc1, lcc2 and lcc3), two tyrosinase genes (AbPPO1 and AbPPO2) and the hspA gene encoding a heat-shock protein known to be potentially associated with host-pathogen interaction was investigated in mycelial aggregates and during the development of healthy sporophores and bubbles of a susceptible cultivar. The lcc3, AbPPO2 and hspA genes were each expressed at different levels at the different stages of sporophore morphogenesis, whilst they showed a stable expression throughout bubble development. The transcript levels were similar in bubbles and at the first developmental stage of healthy fruiting bodies, both showing no tissue differentiation. These observations suggest that lcc3, AbPPO2 and hspA are associated with A. bisporus morphogenesis. Comparing the expression of the hspA gene in three susceptible and three tolerant strains showed that the latter displayed a higher level of transcript in the primordium, which is the stage receptive to the pathogen. The six strains exhibited a comparable expression in the vegetative mycelium, non-receptive to L. fungicola.

A newly isolated Paecilomyces sp. WSH-L07 for laccase production: isolation, identification, and production enhancement by complex inducement

Laccase can catalyze the oxidation of a wide range of organic and inorganic substrates. In this study, an easily detectable method was employed for screening laccase-producing microorganisms by using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as laccase-secretion indicator. A novel laccase-producing strain was isolated and identified as Paecilomyces sp. WSH-L07 according to the morphological characteristics and the comparison of internal transcribed spacer (ITS) ribosomal DNA (rDNA) gene sequences. In further investigation, the production of laccase by Paecilomyces sp. WSH-L07 was greatly enhanced by the nontoxic inducers of copper sulphate and methylene blue. Under the induction of 50 microM copper sulphate and 20 microM methylene blue, the maximum laccase production was obtained. When these inducers were added into cultivation medium at 24 h and 12 h, respectively, an increment of about 100 times of laccase activity compared with that of in inducer-free medium and about two times of that of in single copper-supplemented medium was observed. Compared with other Paecilomyces species, Paecilomyces sp. WSH-L07 exhibit the better laccase-producing characteristics with an activity of 1,650 U/l on the eighth day, suggesting its potential ability for industrial application.

Heterologous expression of lcc1 from Lentinula edodes in tobacco BY-2 cells results in the production an active, secreted form of fungal laccase

Laccase (Lcc) is a lignin-degrading enzyme produced by white-rot fungi and has been the subject of much interest in the field of bioremediation due to its ability to oxidize phenolic compounds. In this report, we describe the isolation and characterization of lcc1, a novel gene of Lentinula edodes that encodes Lcc1, and demonstrate that recombinant Lcc1 is expressed in an active, secreted form in tobacco BY-2 cells in culture. The open reading frame of lcc1 was 1,557 base pairs in length and encoded a putative protein of 518 amino acids. We introduced a chimeric form of lcc1 (CaMV35Sp:clcc1) into tobacco BY-2 cells and obtained several stable clcc1 transformants that expressed active Lcc1. Lcc1 activity in BY-2 culture media was higher than in cellular extracts, which indicated that recombinant Lcc1 was produced in a secreted form. Recombinant Lcc1 had a smaller apparent molecular weight and exhibited a different pattern of posttranslational modification than Lcc1 purified from L. edodes. The substrate specificity of purified recombinant Lcc1 was similar to L. edodes Lcc1, and both enzymes were able to decolorize the same set of dyes. These results suggest that heterologous expression of fungal Lcc1 in BY-2 cells will be a valuable tool for the production of sufficient quantities of active laccase for bioremediation.

Enhancement of Rooibos (Aspalathus linearis) aqueous extract and antioxidant yield with fungal enzymes

The leaves and stems of the Rooibos plant ( Aspalathus linearis) are used for the production of an herbal tea known for its health promoting properties, which have been linked to its flavonoid content but which is substantially reduced by the traditional processing method employed. Selected food-grade fungi were screened for their potential to improve the yield of soluble matter extracted from rooibos plant material. Fungal cocktails of hydrolyzing enzymes enhanced either the yield of soluble solids ( Lentinula edodes and Rhizopus oryzae cultured in yeast peptone-wheat straw medium) or the yield in antioxidants from fermented rooibos ( R. oryzae cultured in potato dextrose or yeast peptone-wheat straw medium). When applied to green rooibos, L. edodes (cultured in yeast peptone-wheat straw medium) enhanced the release of soluble solids as well as color formation, leading to semifermented rooibos with a relatively high aspalathin content, compared to fermented rooibos.

Gene expression studies of the dikaryotic mycelium and primordium of Lentinula edodes by serial analysis of gene expression

Lentinula edodes (Shiitake mushroom) is a common edible mushroom that has high nutritional and medical value. Although a number of genes involved in the fruit of the species have been identified, little is known about the process of differentiation from dikaryotic mycelium to primordium. In this study, serial analysis of gene expression (SAGE) was applied to determine the gene expression profiles of the dikaryotic mycelium and primordium of L. edodes in an effort to advance our understanding of the molecular basis of fruit body development. A total of 6363 tags were extracted (3278 from the dikaryotic mycelium and 3085 from the primordium), 164 unique tags matched the in-house expressed sequence tag (EST) database. The difference between the expression profiles of the dikaryotic mycelium and primordium suggests that a specific set of genes is required for fruit body development. In the transition from the mycelium to the primordium, different hydrophobins were expressed abundantly, fewer structural genes were expressed, transcription and translation became active, different genes became involved in intracellular trafficking, and stress responses were expressed. These findings advance our understanding of fruit body development. We used cDNA microarray hybridization and Northern blotting to verify the SAGE results, and found SAGE to be highly efficient in the performance of transcriptome analysis. To our knowledge, this is the first SAGE study of a mushroom.

Isolation and transcript analysis of two-component histidine kinase gene Le.nik1 in Shiitake mushroom, Lentinula edodes

Le.nik1, a two-component histidine kinase gene of Lentinula edodes, the Shiitake mushroom, was identified. The relationship between this two-component signal transduction system and mushroom development was studied. We used a modified RNA arbitrarily-primed PCR (RAP-PCR) method to isolate Le.nik1 as a differentially expressed gene during L. edodes development. We determined the 6.29kb full-length cDNA sequence of Le.nik1. It had high sequence homology to Neurospora crassa nik1, which encoded a histidine kinase essential for development and osmotic response. In L. edodes, the expression level of Le.nik1 was highest during primordium formation and fruiting body maturation. The transcripts were localized predominantly in the developing hymenophores, or mushroom gills, which may indicate the role of a two-component signal transduction system in cell differentiation during mushroom development. Mannitol stress influenced transcript expression of Le.nik1, suggesting that it may be involved in osmo-sensing and regulation. To our knowledge, this is the first report on the two-component system in mushrooms and the first analysis on the distribution of Le.nik1 transcript in the course of fruiting body formation and in parts of fruiting bodies.

Diversity of laccase-like multicopper oxidase genes in Morchellaceae: identification of genes potentially involved in extracellular activities related to plant litter decay

Despite the important role played by soil-inhabiting ascomycetes in plant litter decay processes, studies on the diversity and function of their laccase-like multicopper oxidase (LMCO) genes are scarce. In the present work, the LMCO gene diversity in 15 strains representing nine Morchellaceae and one Discinaceae species was evaluated by PCR. One to six different genes were found within the species, representing 26 different sequence types. Cluster analysis revealed LMCO genes belonging to four main gene families encoding different protein classes (Class I-IV). To identify the genes related to extracellular activities and potentially involved in litter decay processes, liquid cultures were induced by different aromatic compounds. Morchella conica and Verpa conica showed the strongest LMCO activity enhancement in the presence of the naturally occurring phenolic compound guaiacol, and their expressed LMCO genes were identified by sequencing. Only genes belonging to the gene families encoding the Class II and III proteins were expressed. Both genes (Class II and III) of the mycorrhizal-like strain M. conica were exclusively expressed in the presence of guaiacol. In contrast to the saprotrophic strain V. conica, the gene encoding the Class III protein was constitutively expressed as it was also found in control cultures without guaiacol.

Le.MAPK and its interacting partner, Le.DRMIP, in fruiting body development in Lentinula edodes

Development in shiitake mushroom, Lentinula edodes, is a unique process and studies of the molecular basis of this process may lead to improvement in mushroom cultivation. Previous studies have identified a number of signal transduction genes related to mushroom development, but those genes have not been well characterized. The present work characterized a developmentally regulated MAP kinase, Le.MAPK, and its interaction with a novel gene, Le.DRMIP in the signal transduction pathway. The expression profiles of these two genes reveal their importance in fruiting body initiation and development; the Le.DRMIP transcript is localized predominantly in the developing young fruiting body and gills, which further signifies its role in cell differentiation during mushroom development.

Determination of laccase gene expression during degradation of 2,4,6-trinitrotoluene and its catabolic intermediates in Trametes versicolor

We have cloned a laccase gene fragment isolated from a Trametes versicolor strain in Korea. It showed high similarity in nucleotide sequences when compared with other fungal laccases. TNT (2,4,6-trinitrotoluene), a widely used explosive, was transformed rapidly by T. versicolor. When TNT and its catabolic intermediates were added to the fungal culture, they were transformed during the first few hours and the expression level of the laccase gene was increased during the early stage of cultivation.

Molecular cloning of developmentally specific genes by representational difference analysis during the fruiting body formation in the basidiomycete Lentinula edodes

To understand molecular mechanisms of the fruiting body development in basidiomycetes, we attempted to isolate developmentally regulated genes expressed specifically during the fruiting body formation of Lentinula edodes (Shiitake-mushroom). cDNA representational difference analysis (cDNA-RDA) between vegetatively growing mycelium and two developmental substages, primordium and mature fruiting body, resulted in an isolation of 105 individual genes (51 in primordium and 54 in mature fruiting body, respectively). A search of homology with the protein databases and two basidiomycetous genomes in Phanerochaete chrysosporium and Coprinopsis cinerea revealed that the obtained genes encoded various proteins similar to those involved in general metabolism, cell structure, signal transduction, and responses to stress; in addition, there were apparently several metabolic pathways and signal transduction cascades that could be involved in the fruiting body development. The expression products of several genes revealed no significant homologies to those in the databases, implying that those genes are unique in L. edodes and the encoding products may possess possible functions in the course of fruiting body development. RT-PCR analyses revealed that 20 candidates of the obtained genes were specifically or abundantly transcribed in the course of the fruiting body formation, suggesting that the obtained genes in this work play roles in fruiting body development in L. edodes.