Effects of cadmium stress on physiological indexes and fruiting body nutritions of Agaricus brasiliensis.

In this study, 0, 0.5, 1, 1.5, 2, 4, 6 and 8 mg·kg-1 of cadmium were added to the cultivation materials. In order to study the effects of different concentrations of Cd stress on J1 and J77, the contents of antioxidant enzymes, proline and malondialdehyde, Cd content, agronomic traits and yield of fruiting bodies of Agaricus brasiliensis were determined, and the nutritional components such as polysaccharide, triterpene, protein, total sugar and total amino acid were determined. The results showed that the physiological indexes of strain J1 and J77 changed regularly under different concentrations of Cd stress. J1 was a high absorption and low tolerance variety, while J77 was a low absorption and high tolerance variety. Low concentration of Cd promoted the growth of strain J1, and higher concentration of Cd promoted the growth of strain J77. The contents of protein and total amino acids in the two strains changed greatly, followed by polysaccharides, which indicated that Cd stress had the greatest impact on the three nutrients, and other nutrients were not sensitive to Cd stress.

Melatonin retards senescence via regulation of the electron leakage of postharvest white mushroom (Agaricus bisporus).

Currently, melatonin (N-acetyl-5-methoxytrytamine) is recognized as a potential scavenger of free radicals. In this study, the effect of exogenous melatonin at various concentrations (0.05, 0.1, and 0.2 mM) on the texture, sensory qualities, and electron leakage in white mushrooms was evaluated at 3 ± 1 °C. It was observed that mushrooms treated with 0.1 mM melatonin were of good quality and their electron leakage was dramatically dampened. The results showed that 0.1 mM melatonin retained a higher adenosine triphosphate level and also prevented the release of cytochrome c into the cytoplasm. More significantly, it prominently inhibited electron leakage by increasing the activities of complexes I and III by the upregulation of AbNdufB9 and AbRIP1. It also regulated respiratory states in mushrooms; delayed the decline of respiratory state 3; enhanced respiratory state 4; boosted the oxidative phosphorylation and efficiency of mitochondria; and ultimately retarded the senescence of the white mushrooms.

Onion juice and extracts for the inhibition of enzymatic browning mechanisms in frozen Agaricus bisporus mushrooms.

BACKGROUND: The potential of onion juice, as well as extracts of waste (tunic) (5%) and fleshy scale leaves (25%), to inhibit enzymatic browning of frozen Agaricus bisporus was investigated. The onion materials were used for blanching and their effectiveness in conserving integrity and appearance of mushroom fruiting bodies was compared with the currently accepted method of blanching in a sodium metabisulfite (SM) solution. RESULTS: It was observed that l-phenylalanine content may be a useful indicator of the changes in enzymatic activity during frozen storage, and l-tyrosine may be an indicator of a loss of lightness in color (parameter L*). The enzymes responsible for color changes were mainly monophenolase (MON) and, to a lesser degree, diphenolase (DIP). After being stored frozen for 8 months, these enzymes were detected at a 29:1 (DIP:MON) ratio in untreated mushrooms and a 2:1 (DIP:MON) ratio in mushrooms treated with onion juice. CONCLUSION: Onion products may be a good alternative to an SM solution. The most effective method to conserve the light color of fruiting bodies was blanching in juice or in an extract of the fleshy scale leaves. The least effective inhibitor of MON was tunic extract, which did, however, cause a favourable increase in the reducing capacity (total polyphenols) and flavonoids. Although the onion waste (tunic) extract changed the color of mushrooms from white to creamy orange, the color of these products was attractive and positively evaluated by panellists. © 2020 Society of Chemical Industry.

Comparative transcriptome analysis reveals candidate genes related to cadmium accumulation and tolerance in two almond mushroom (Agaricus brasiliensis) strains with contrasting cadmium tolerance.

Cadmium (Cd) is a toxic metal occurring in the environment naturally. Almond mushroom (Agaricus brasiliensis) is a well-known cultivated edible and medicinal mushroom. In the past few decades, Cd accumulation in A.brasiliensis has received increasing attention. However, the molecular mechanisms of Cd-accumulation in A. brasiliensis are still unclear. In this paper, a comparative transcriptome of two A.brasiliensis strains with contrasting Cd accumulation and tolerance was performed to identify Cd-responsive genes possibly responsible for low Cd-accumulation and high Cd-tolerance. Using low Cd-accumulating and Cd-tolerant (J77) and high Cd-accumulating and Cd-sensitive (J1) A.brasiliensis strains, we investigated 0, 2 and 5 mg L-1 Cd-effects on mycelium growth, Cd-accumulation and transcriptome revealed by RNA-Seq. A total of 57,884 unigenes were obtained. Far less Cd-responsive genes were identified in J77 mycelia than those in J1 mycelia (e.g., ABC transporters, ZIP Zn transporter, Glutathione S-transferase and Cation efflux (CE) family). The higher Cd-accumulation in J1 mycelia might be due to Cd-induced upregulation of ZIP Zn transporter. Cd impaired cell wall, cell cycle, DNA replication and repair, thus decreasing J1 mycelium growth. Cd-stimulated production of sulfur-containing compounds, polysaccharides, organic acids, trehalose, ATP and NADPH, and sequestration of Cd might be adaptive responses of J1 mycelia to the increased Cd-accumulation. DNA replication and repair had better stability under 2 mg L-1 Cd, but greater positive modifications under 5 mg L-1 Cd. Better stability of DNA replication and repair, better cell wall and cell cycle stability might account for the higher Cd-tolerance of J77 mycelia. Our findings provide a comprehensive set of DEGs influenced by Cd stress; and shed light on molecular mechanism of A.brasiliensis Cd accumulation and Cd tolerance.

Ultrahigh-Pressure Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry-Based Metabolomics Reveal the Mechanism of Methyl Jasmonate in Delaying the Deterioration of Agaricus bisporus.

Conquering rapid postripeness and deterioration of Agaricus bisporus is quite challenging. We previously observed that methyl jasmonate (MeJA) pretreatment postponed the deterioration of A. bisporus, but the mechanism is unknown. Here, a nontargeted metabolomics analysis by ultrahigh-pressure liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) revealed that MeJA increased the synthesis of malate by inhibiting the decomposition of fumarate and cis-aconitate. MeJA maintained energy supply by enhancing ATP content and energy charge level and improving hexokinase and glucose-6-phosphate dehydrogenase activities as well. These results promoted ATP supply by maintaining glycolysis, the TCA cycle, and the pentose phosphate pathway. In addition, we revealed that the delayed deterioration was attributed to MeJA treatment which stimulated the energy status of A. bisporus by reducing the respiration rate and nutrient decomposition, thus maintaining energy production. Our results provide a new insight into the role of MeJA treatment in delaying deterioration of A. bisporus through ATP production and supply.

Exogenous adenosine triphosphate application retards cap browning in Agaricus bisporus during low temperature storage.

Exogenous adenosine triphosphate (ATP) treatment at 0, 250, 500, 750, and 1000 µM retarded cap browning in mushrooms by 0, 34, 26, 51 and 32 %, respectively, during storage at 4 °C for 18 days. Triggering signaling H2O2 accumulation arising from elevating NADPH oxidase enzyme activity during 6 days of storage at 4 °C may be pivotal for promoting shikimate dehydrogenase enzyme activity in mushrooms treated with ATP during 18 days of storage at 4 °C. Promoting melatonin accumulation (390 µg kg-1 FW vs. 160 µg kg-1 FW) in mushrooms treated with ATP during cold storage may attribute to signaling H2O2 accumulation. Higher DPPH scavenging capacity (72 % vs. 65 %) in mushrooms treated with ATP may attribute to higher phenols accumulation arising from higher phenylalanine ammonialyase/polyphenol oxidase enzymes activity concomitant with higher alternative oxidase gene expression during 18 days of storage at 4 °C.

Ornithine decarboxylase is involved in methyl jasmonate-regulated postharvest quality retention in button mushrooms (Agaricus bisporus).

BACKGROUND: In the present study, we investigated the role of ornithine decarboxylase (ODC) in the methyl jasmonate (MeJA)-regulated postharvest quality maintenance of Agaricus bisporus (J. E. Kange) Imbach button mushrooms by pretreating mushrooms with a specific irreversible inhibitor called α-difluoromethylornithine (DFMO) before exposure to MeJA vapor. RESULTS: Mushrooms were treated with 0 or 100 µmol L-1 MeJA or a combination of 120 µmol L-1 DFMO and 100 µmol L-1 MeJA, respectively, before storage at 4 °C for 21 days. Treatment with MeJA alone induced the increase in ODC activity whereas this effect was greatly suppressed by pretreatment with DFMO. α-Difluoromethylornithine strongly attenuated the effect of MeJA on decreasing cap opening, slowing the decline rate of soluble protein and total sugar, and accumulating total phenolics and flavonoids. α-Difluoromethylornithine pretreatment also counteracted the ability of MeJA to inhibit polyphenol oxidase and lipoxygenase activities, and malondialdehyde production, and to stimulate superoxide dismutase and catalase activities. It also largely downregulated MeJA-induced accumulation of free putrescine (Put). CONCLUSION: These results reveal that ODC is involved in MeJA-regulated postharvest quality retention of button mushrooms, and this involvement is likely to be associated with Put levels. © 2018 Society of Chemical Industry.

Chitosan nanoparticles-loaded Citrus aurantium essential oil: a novel delivery system for preserving the postharvest quality of Agaricus bisporus.

BACKGROUND: One of the main problems in the button mushroom industry is the rapid deterioration of fruit bodies after harvest. Today, nanotechnology has become a more reliable technique to improve the quality of products in food packaging. In the present study, the effectiveness of chitosan nanoparticles containing Citrus aurantium essential oil on postharvest quality of white button mushroom was examined and compared to essential oil fumigation and control treatments. RESULTS: Based on high-resolution transmission electron microscopy and dynamic light scattering, nanoparticles exhibited a spherical shape of 20-60 nm diameter. The results revealed that the application of chitosan nanoparticles loaded with C. aurantium oil significantly decelerated the rate of color change, weight loss and firmness compared to fumigation with essential oil and control treatments. Treatment of fruit bodies with chitosan nanoparticles loaded with C. aurantium oil promoted the accumulation of phenolic compounds and ascorbic acid, and resulted in increases in catalase and superoxide dismutase and a decrease in polyphenol oxidase activities, as the highest antioxidant capacity was observed after 15 days of cold storage. CONCLUSION: This present research demonstrates that gradual release of C. aurantium essential oil from chitosan nanoparticles could be an effective and practical method for extending the shelf life of white button mushroom up to 15 days without significant decrease in antioxidant capacity. © 2018 Society of Chemical Industry.

Effects of a high O2 dynamic-controlled atmosphere technology on the browning of postharvest white mushroom ( Agaricus bisporus) in relation to energy metabolism.

Browning is one of the main problems in senescence of mushrooms, and it is also one of the most important attributes accounting for the loss of the quality and reduction in market value. In order to study the relationship between the energy metabolism and the browning of white mushroom under high O2 dynamic-controlled atmosphere (HO-DCA), mushrooms were stored in 100% O2 (SCA1), 80% O2 + 20% CO2 (SCA2), 100% O2 for three days and then transferred into the treatment of 80% O2 + 20% CO2 (HO-DCA) at 2 ± 1 ℃ and air as control. In this study, adenosine triphosphate (ATP) content, energy charge level, sensory evaluation, browning of surface and flesh, cell membrane integrity, exogenous ATP, polyphenol oxidase (PPO) and peroxidase (POD) activity and genes encoding PPO of the white mushroom were investigated. These were all closely related to the browning of products. The optimal storage condition of the HO-DCA treatment could delay the browning of pericarp and flesh tissues of the mushrooms, inhibit PPO activity and reduce the relative expression levels of the three genes encoding PPO. Meanwhile, it maintained moderate POD activity, good sensory properties and cell membrane integrity in a certain extent and thus slowed down the senescence of mushrooms. Results indicated that there was a positive correlation between the ATP content and whitening index ( r = 0.901). In addition, HO-DCA maintained a higher ATP level, prolonged the storage time to 28 days and it might be an ideal strategy for preserving the quality of mushroom during storage.

Effect of different compounds on the induction of laccase production by Agaricus blazei.

Laccases are polyphenol oxidases produced by many fungi and have many applications in textile, food and beverage, and pulp and paper industries. Laccase production can be induced using aromatic or phenolic compounds that mostly affect the transcription of laccase-encoding genes. In this study, we analyzed laccase and biomass production by Agaricus blazei in the presence of different concentrations of nitrogen, copper, and inducers such as pyrogallol, veratryl alcohol, xylidine, vanillin, guaiacol, and ethanol. Laccase production by A. blazei U2-4 reached 43.8 U/mL in the presence of 2.8 g/L nitrogen and 150 µM copper. However, addition of copper to the cultivation medium decreased biomass production. Different compounds differentially induced laccase production by A. blazei. Moreover, different concentrations of these inducers exerted different effects on laccase activity. Ethanol (1.0 mM), guaiacol (0.5 mM), and vanillin (0.5 mM) were the best inducers and increased laccase activity by 120% (A. blazei U2-2), 30% (A. blazei U2-3), and 9% (A. blazei U2-4), respectively. In contrast, pyrogallol and xylidine decreased laccase activity but increased biomass production.

Browning inhibition and quality preservation of button mushroom (Agaricus bisporus) by essential oils fumigation treatment.

The effect of essential oil fumigation treatment on browning and postharvest quality of button mushrooms (Agaricus bisporus) was evaluated upon 16 days cold storage. Button mushrooms were fumigated with essential oils, including clove, cinnamaldehyde, and thyme. Changes in the browning index (BI), weight loss, firmness, percentage of open caps, total phenolics, ascorbic acid, microbial activity and activities of polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and peroxidase (POD) were measured. The results indicated that all essential oils could inhibit the senescence of mushrooms, and the most effective compound was cinnamaldehyde. Fumigation treatment with 5 µl l⁻¹ cinnamaldehyde decreased BI, delayed cap opening, reduced microorganism counts, promoted the accumulation of phenolics and ascorbic acid. In addition, 5 µl l⁻¹ cinnamaldehyde fumigation treatment inhibited the activities of PPO and POD, and increased PAL activity during the storage period. Thus, postharvest essential oil fumigation treatment has positive effects on improving the quality of button mushrooms.

The antibrowning agent sulfite inactivates Agaricus bisporus tyrosinase through covalent modification of the copper-B site.

Sulfite salts are widely used as antibrowning agents in food processing. Nevertheless, the exact mechanism by which sulfite prevents enzymatic browning has remained unknown. Here, we show that sodium hydrogen sulfite (NaHSO3) irreversibly blocks the active site of tyrosinase from the edible mushroom Agaricus bisporus, and that the competitive inhibitors tropolone and kojic acid protect the enzyme from NaHSO3 inactivation. LC-MS analysis of pepsin digests of NaHSO3 -treated tyrosinase revealed two peptides showing a neutral loss corresponding to the mass of SO3 upon MS(2) fragmentation. These peptides were found to be homologous peptides containing two of the three histidine residues that form the copper-B-binding site of mushroom tyrosinase isoform PPO3 and mushroom tyrosinase isoform PPO4, which were both present in the tyrosinase preparation used. Peptides showing this neutral loss behavior were not found in the untreated control. Comparison of the effects of NaHSO3 on apo-tyrosinase and holo-tyrosinase indicated that inactivation is facilitated by the active site copper ions. These data provide compelling evidence that inactivation of mushroom tyrosinase by NaHSO3 occurs through covalent modification of a single amino-acid residue, probably via addition of HSO3(-) to one of the copper-coordinating histidines in the copper-B site of the enzyme.

Brefeldin A is an estrogenic, Erk1/2-activating component in the extract of Agaricus blazei mycelia.

We purified an Erk1/2-activating component in Agaricus blazei and identified it as brefeldin A (BFA). The extract of A. blazei mycelia (ABE) previously showed an estrogenic gene-expression profile and positive effects in patients with cardiovascular symptoms. Here, we demonstrate that BFA has estrogenic activity in reporter gene assays and stimulates an estrogen-receptor pathway revealed by activation of Erk1/2, although BFA had no growth-stimulating activity in breast cancer MCF-7 cells. The presence of estrogenic activity without any explicit growth-stimulating effect is unique to BFA, and such components are termed here "silent estrogens". To test this hypothesis, we examined the target-gene transcription and signaling pathways induced by BFA. Furthermore, BFA was found in the mycelium but not fruiting body of A. blazei, suggesting the potential use of ABE for therapeutics and its supplementary use in traditional medicines and functional foods.

Postharvest application of methyl jasmonate for improving quality retention of Agaricus bisporus fruit bodies.

The influence of methyl jasmonate (MeJA) on postharvest quality and enzyme activities, gene expression level, and the functional component content linked to postharvest deterioration in Agaricus bisporus (J.E. Lange) Imbach fruit bodies was investigated. Freshly harvested fruit bodies were treated with 0 (control), 10 and 100 µM MeJA vapor at 20 °C for 12 h and then stored at 10 °C for up to 7 days. The results indicated that treatments with 100 µM MeJA vapor maintained a high level of soluble protein and total sugar, delayed browning, promoted the accumulation of phenolics and flavonoids, and inhibited the increase of respiratory rate and membrane leakage. Furthermore, 100 µM MeJA inhibited the activities of polyphenoloxidase, increased the antioxidant enzymes activities of catalase and superoxide dismutase, and lowered relative expression levels of three genes encoding polyphenol oxidase (AbPPO1, AbPPO2, and AbPPO3) throughout the storage period. Comparatively, 10 µM MeJA also had a clear beneficial effect on postharvest mushroom quality maintenance but was not as effective as 100 µM MeJA treatment. These findings suggest that application of MeJA could have potential in maintaining the quality of harvested A. bisporus fruit bodies.

Effect of natamycin in combination with pure oxygen treatment on postharvest quality and selected enzyme activities of button mushroom (Agaricus bisporus).

The combined effects of natamycin (NA) and pure oxygen (PO) treatment on microbial and physicochemical characteristics of button mushroom ( Agaricus bisporus ) stored at 4 ± 1 °C for 16 days was investigated. Mushroom respiration rate, weight loss, firmness, color, percent open caps, total soluble solids, microbial and activities of polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and peroxidase (POD) were measured. The results indicate that treatment with natamycin + pure oxygen (NAPO) maintained tissue firmness, inhibited increase of respiration rate, delayed browning and cap opening, and reduced microorganism counts of yeasts and molds compared to control treatment. The efficiency was better than that of NA or PO treatment. Furthermore, NAPO inhibited the activities of PPO, PAL, and POD throughout the storage period. Our study suggests that NAPO treatment has the potential to improve the quality of button mushroom and extend the shelf life.

Antithetical effects of hemicellulase-treated Agaricus blazei on the maturation of murine bone-marrow-derived dendritic cells.

We report the effects of hemicellulase-treated Agaricus blazei (ABH) on the maturation of bone-marrow-derived dendritic cells (BMDCs). ABH activated immature BMDCs, inducing up-regulation of surface molecules, such as CD40, CD80 and major histocompatibility complex class I antigens, as well as inducing allogeneic T-cell proliferation and T helper type 1 cell development. However, unlike lipopolysaccharide (LPS), ABH did not stimulate the BMDCs to produce proinflammatory cytokines, such as interleukin-12 (IL-12) p40, tumour necrosis factor-alpha, or IL-1beta. In addition, ABH suppressed LPS-induced DC responses. Pretreatment of DCs with ABH markedly reduced the levels of LPS-induced cytokine secretion, while only slightly decreasing up-regulation of the surface molecules involved in maturation. ABH also had a significant impact on peptidoglycan-induced or CpG oligodeoxynucleotide-induced IL-12p40 production in DCs. The inhibition of LPS-induced responses was not associated with a cytotoxic effect of ABH nor with an anti-inflammatory effect of IL-10. However, ABH decreased NF-kappaB-induced reporter gene expression in LPS-stimulated J774.1 cells. Interestingly, DCs preincubated with ABH and then stimulated with LPS augmented T helper type 1 responses in culture with allogeneic T cells as compared to LPS-stimulated but non-ABH-pretreated DCs. These observations suggest that ABH regulates DC-mediated responses.

Evaluation of a new biosensor-based mushroom (Agaricus bisporus) tissue homogenate: investigation of certain phenolic compounds and some inhibitor effects.

A biosensor based on mushroom tissue homogenate for detecting some phenolic compounds (PCs) and usage of the biosensor for quantifying certain substances that inhibit the polyphenol oxidase activity in mushroom (Agaricus bisporus) tissue homogenate is described. The mushroom tissue homogenate was immobilized to the top of a Clark-type oxygen electrode with gelatin and glutaraldehyde. Optimization of the experimental parameters was done by buffer system, pH, buffer concentration, and temperature. Besides, the detection range of eight phenolic compounds were obtained with the help of the calibration graphs. Thermal stability, storage stability, and repeatability of the biosensor were also investigated. A linear response was observed from 20 x 10(-3) to 200 x 10(-3) mM phenol. The biosensor retained approximately 74% of its original activity after 25 days of storage at 4 degrees C. In repeatability studies, variation coefficient (C.V.) and standard deviation (S.D.) were calculated as 2.44% and +/-0.002, respectively. Inhibition studies revealed that the proposed biosensor was applicable for monitoring benzoic acid and thiourea in soft drinks and fruit juices.

Biochemical and physiological aspects of brown blotch disease of Agaricus bisporus.

Pseudomonas tolaasii is a bacterium endemic to the compost beds where common mushroom (Agaricus bisporus) is cultivated. Under some environmental conditions still not well-determined, but influenced by temperature and relative humidity, the bacterium can become pathogenic and provoke the brown blotch disease. This review describes the interaction between P. tolaasii and A. bisporus that results in the appearance of brown spots on the mushroom caps, typical symptoms of the disease. Firstly, P. tolaasii is studied, the changes in pathogenicity are explained, the compounds that provoke the damage are enumerated as well as various experimental methods to identify the pathogenic form of the bacteria. Secondly, mechanisms involved in the formation of the brown colour on the A. bisporus caps upon infection are briefly mentioned, taking into account the enzymes that catalyse the reaction, their mechanism, substrates and reaction products. Afterwards, a detailed description of the infection process is presented step by step, starting by the chemotactical attraction, fixation, secretion of the toxins, membrane breakdown, effect of the toxin on mushroom polyphenol oxidases and on the discolouration reaction. A possible mechanism of infection is hypothesised at the molecular level. Finally, the strategies tested until now to control the disease are discussed.