Hydrogen-rich water alleviates the toxicities of different stresses to mycelial growth in Hypsizygus marmoreus

Hydrogen gas: A new fresh keeping agent of perishable horticultural products

Hydrogen gas (H2), a gaseous signaling molecule, is involved in plant growth and development. This review collates emerging evidence to show that H2 regulates the postharvest senescence of horticultural products through critical biochemical processes, including the improvement of antioxidant systems, the activation of cell wall metabolism, the promotion of energy metabolism, the inhibition of ethylene biosynthesis and the regulation of bacterial communities. Additionally, the interactions between H2 and other signaling molecules are also discussed. This paper presents the current status of H2 research in terms of its biological effects and safety in postharvest products by combining the research results on the molecular mechanisms of biological effects and H2 signaling. The action mechanism of H2 for postharvest preservation is also proposed, and it reflects the complexity and diversity of the pathways involved. Furthermore, a growing body of evidence has found a large number of downstream pathways or targets for the medical effects of H2. Therefore, the scientific and practical aspects of H2 biology are proposed for the postharvest preservation of horticultural products.

Exogenous γ-Aminobutyric Acid (GABA) Enhanced Response to Abiotic Stress in Hypsizygus marmoreus by Improving Mycelial Growth and Antioxidant Capacity

γ-Aminobutyric (GABA) acid is a nutrient and signaling molecule existing in many plants, participating in the regulation of metabolism and various physiological activities. Two strains of Hypsizygus marmoreus (a white variety and a brown variety) were investigated to study the impact of exogenous GABA on mycelial growth and the response to stress. Mycelial growth, microscopic morphology, antioxidant profile, and gad2 expression in H. marmoreu were investigated under salt, dehydration, or cold stress. The results indicated that 5 mM GABA stimulated mycelial growth under standard cultivation conditions, whereas GABA addition over 10 mM hindered the growth. Under salt, dehydration, or cold stress, treatment with 5 mM GABA significantly enhanced the mycelial growth rate and density of both H. marmoreus strains by promoting front hyphae branching. Meanwhile, the activities of key antioxidant enzymes such as peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were enhanced by GABA, thereby augmenting the defensive network against abiotic stress. Additionally, gad2 expression and GABA concentration were increased under abiotic stresses as a resistance regulation response. The exogenous addition of GABA strengthened the upregulation of gad2 expression and GABA production. These findings indicated that exogenously adding low concentrations of GABA effectively enhanced the mycelial growth and antioxidant profile of H. marmoreus, thereby improving its resistance against stresses.

Improving the productivity of malic acid by alleviating oxidative stress during Aspergillus niger fermentation

BACKGROUND

As an attractive platform chemical, malic acid has been commonly used in the food, feed and pharmaceutical field. Microbial fermentation of biobased sources to produce malic acid has attracted great attention because it is sustainable and environment-friendly. However, most studies mainly focus on improving yield and ignore shortening fermentation time. A long fermentation period means high cost, and hinders the industrial applications of microbial fermentation. Stresses, especially oxidative stress generated during fermentation, inhibit microbial growth and production, and prolong fermentation period. Previous studies have shown that polypeptides could effectively relieve stresses, but the underlying mechanisms were poorly understood.

RESULTS

In this study, polypeptides (especially elastin peptide) addition improves the productivity of malic acid in A. niger, resulting in shortening of fermentation time from 120 to 108 h. Transcriptome and biochemical analyses demonstrated that both antioxidant enzyme-mediated oxidative stress defense system, such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), and nonenzymatic antioxidant system, such as glutathione, were enhanced in the presence of elastin peptide, suggesting elastin peptide relieving oxidative stresses is involved in many pathways. In order to further investigate the relationship between oxidative stress defense and malic acid productivity, we overexpressed three enzymes (Sod1, CAT, Tps1) related to oxidation resistance in A. niger, respectively, and these resulting strains display varying degree of improvement in malic acid productivity. Especially, the strain overexpressing the Sod1 gene achieved a malate titer of 91.85 ± 2.58 g/L in 96 h, corresponding to a productivity of 0.96 g/L/h, which performs better than elastin peptide addition.

CONCLUSIONS

Our investigation provides an excellent reference for alleviating the stress of the fungal fermentation process and improving fermentation efficiency.

Evaluation of the impact of hydrogen-rich water on the quality attribute notes of butter

The effects of washing raw butter with hydrogen-rich water (HRW), prepared with hydrogen (H₂) and/or magnesium (Mg), on butter quality were investigated in this research paper. During the washing process, titratable acidity (TA) decreased by 12% for all washed samples. During the storage period, TA increased by 28% and 93% (control), 14% and 58% (H₂), and 10% and 66% (Mg) for the 60^th and 90^th days, respectively. Peroxide value (mEq O₂/kg) increased to 2.76 and 8.83 (control), 1.92 and 7.25 (H₂), and 2.02 and 8.12 (Mg) for the 60^th and 90^th days. HRW samples showed the lowest acid degree value (ADV) and the highest color notes (L*, C*, and h). The HRW treatment of raw butter has shown improving effects on the product without any harmful residuals in the final product or the environment.

Roles of Hydrogen Gas in Plants under Abiotic Stress: Current Knowledge and Perspectives

Hydrogen gas (H₂) is a unique molecular messenger, which is known to be involved in diverse physiological processes in plants, from seed germination to seedling growth to regulation of environmental stresses. In this review, we focus on the role of H₂ in plant responses to abiotic stresses, such as temperature, osmotic stress, light, paraquat (PQ)-induced oxidative stresses, and metal stresses. In general, H₂ can alleviate environmental stresses by improving the antioxidant defense system, photosynthetic capacity, re-establishing ion homeostasis and glutathione homeostasis, maintaining nutrient element homeostasis, mediating glucose metabolism and flavonoid pathways, regulating heme oxygenase-1 (HO-1) signaling, and interaction between H₂ and nitric oxide (NO), carbonic oxide (CO), or plant hormones. In addition, some genes modulated by H₂ under abiotic stresses are also discussed. Detailed evidence of molecular mechanisms for H₂-mediated particular pathways under abiotic stress, however, is scarce. Further studies regarding the regulatory roles of H₂ in modulating abiotic stresses research should focus on the molecular details of the particular pathways that are activated in plants. More research work will improve knowledge concerning possible applications of hydrogen-rich water (HRW) to respond to abiotic stresses with the aim of enhancing crop quality and economic value.

Transcriptome and Differentially Expressed Gene Profiles in Mycelium, Primordium and Fruiting Body Development in Stropharia rugosoannulata

Stropharia rugosoannulata uses straw as a growth substrate during artificial cultivation and has been widely promoted in China. However, its fruiting body formation and development processes have not been elucidated. In this study, the developmental transcriptomes were analyzed at three stages: the mycelium (G-S), primordium (P-S) and fruiting body (M-F) stages. A total of 9690 differentially expressed genes (DEGs) were identified in the different developmental stages. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that these DEGs were involved mainly in hydrolase activity, structural molecule activity and oxidoreductase activity as well as xenobiotic biodegradation and metabolism and energy metabolism pathways. We further found that the higher expression of most carbohydrate enzyme (i.e., GH, CE, CBM, AA and PL) genes in the hyphal (i.e., G-S) stage was related mainly to substrate degradation, while the upregulation of glycosyltransferase (GT) gene expression in the P-S and M-F stages may be related to cell wall synthesis. In addition, we found that CO₂-sensing-related genes (i.e., CA-2, CA-3, PKA-1 and PKA-2) were upregulated in the P-S and M-F stages, heat shock protein genes (HSP60 and HSP90) were significantly downregulated in the P-S stage and upregulated in the M-F stage and the transcription factors (i.e., steA, MYB, nosA, HAP1, and GATA-4/5/6) involved in growth and development were significantly upregulated in the P-S stage. These results suggest that environmental factors (i.e., CO₂ and temperature) and transcription factors may play a key role in primordium formation. In short, this study provides new insights into the study of stimulating primordia formation affecting the development of fruiting bodies of S. rugosoannulata.

Transcriptomic analysis of Stropharia rugosoannulata reveals carbohydrate metabolism and cold resistance mechanisms under low-temperature stress

Low temperature is an important environmental factor that restricts the growth of Stropharia rugosoannulata; however, the molecular mechanisms underlying S. rugosoannulata responses to low-temperature stress are largely unknown. In this study, we performed a transcriptome analysis of a high-sensitivity strain (DQ-1) and low-sensitivity strain (DQ-3) under low-temperature stress. The liquid hyphae of S. rugosoannulata treated at 25 °C and 10 °C were analyzed by RNA-Seq, and a total of 9499 differentially expressed genes (DEGs) were identified. GO and KEGG enrichment analyses showed that these genes were enriched in "xenobiotic biodegradation and metabolism", "carbohydrate metabolism", "lipid metabolism" and "oxidoreductase activity". Further research found that carbohydrate enzyme (AA, GH, CE, and GT) genes were downregulated more significantly in DQ-1 than DQ-3 and several cellulase activities were also reduced to a greater extent. Moreover, the CAT1, CAT2, GR, and POD genes and more heat shock protein genes (HSP20, HSP78 and sHSP) were upregulated in the two strains after low-temperature stress, and the GPX gene and more heat shock protein genes were upregulated in DQ-3. In addition, the enzyme activity and qRT-PCR results showed trends similar to those of the RNA-Seq results. This result indicates that low-temperature stress reduces the expression of different AA, GH, CE, and GT enzyme genes and reduces the secretion of cellulase, thereby reducing the carbohydrate metabolism process and mycelial growth of S. rugosoannulata. Moreover, the expression levels of different types of antioxidant enzymes and heat shock proteins are also crucial for S. rugosoannulata to resist low-temperature stress. In short, this study will provide a basis for further research on important signaling pathways, gene functions and variety breeding of S. rugosoannulata related to low-temperature stress.

The Importance of Nitric Oxide as the Molecular Basis of the Hydrogen Gas Fumigation-Induced Alleviation of Cd Stress on Ganoderma lucidum

Whether or not hydrogen gas (H₂) can reduce cadmium (Cd) toxicity in Ganoderma lucidum has remained largely unknown. Here, we report that Cd-induced growth inhibition in G. lucidum was significantly alleviated by H₂ fumigation or hydrogen-rich water (HRW), evaluated by lower oxidative damage and Cd accumulation. Moreover, the amelioration effects of H₂ fumigation were better than of HRW in an optimum concentration of H₂ under our experimental conditions. Further results showed that H₂-alleviated growth inhibition in G. lucidum was accompanied by increased nitric oxide (NO) level and nitrate reductase (NR) activity under Cd stress. On the other hand, the mitigation effects were reversed after removing endogenous NO with its scavenger cPTIO or inhibiting H₂-induced NR activity with sodium tungstate. The role of NO in H₂-alleviated growth inhibition under Cd stress was proved to be achieved through a restoration of redox balance, an increase in cysteine and proline contents, and a reduction in Cd accumulation. In summary, these results clearly revealed that NR-dependent NO might be involved in the H₂-alleviated Cd toxicity in G. lucidum through rebuilding redox homeostasis, increasing cysteine and proline levels, and reducing Cd accumulation. These findings may open a new window for H₂ application in Cd-stressed economically important fungi.

Citric acid and AMF inoculation combination-assisted phytoextraction of vanadium (V) by Medicago sativa in V mining contaminated soil

The use of citric acid (CA) chelator to facilitate metal bioavailability is a promising approach for the phytoextraction of heavy metal contaminants. However, the role of the CA chelator associated with arbuscular mycorrhizal fungi (AMF) inoculation on phytoextraction of vanadium (V) has not been studied. Therefore, in this study, a greenhouse pot experiment was conducted to evaluate the combined effect of CA chelator and AMF inoculation on growth performance and V phytoextraction of plants in V-contaminated soil. The experiment was performed via CA (at 0, 5, and 10 mM kg^-1 soil levels) application alone or in combination with AMF inoculation by Medicago sativa Linn. (M. sativa). Plant biomass, root mycorrhizal colonization, P and V accumulation, antioxidant enzyme activity in plants, and soil chemical speciation of V were evaluated. Results depicted (1) a marked decline in plant biomass and root mycorrhizal colonization in 5- and 10-mM CA treatments which were accompanied by a significant increased V accumulation in plant tissues. The effects could be attributed to the enhanced acid-soluble V fraction transferring from the reducible fraction. (2) The presence of CA significantly enhanced P acquisition while the P/V concentration ratio in plant shoots and roots decreased, owing to the increased V translocation from soil to plant. (3) In both CA-treated soil, AMF-plant symbiosis significantly improved dry weight (31.4-73.3%) and P content (37.3-122.5%) in shoots and roots of M. sativa. The combined treatments also showed markedly contribution in reduction of malondialdehyde (MDA) content (12.8-16.2%) and higher antioxidants (SOD, POD, and CAT) activities in the leaves. This suggests their combination could promote growth performance and stimulate antioxidant response to alleviate V stress induced by CA chelator. (4) Taken together, 10 mM kg^-1 CA application and AMF inoculation combination exhibited a higher amount of extracted V both in plant shoots and roots. Thus, citric acid-AMF-plant symbiosis provides a novel remediation strategy for in situ V phytoextraction by M. sativa in V-contaminated soil.

The Applications of Molecular Hydrogen in Horticulture

Improvements in the growth, yield, and quality of horticultural crops require the development of simply integrated, cost-efficient, and eco-friendly solutions. Hydrogen gas (H2) has been observed to have fertilization effects on soils by influencing rhizospheric microorganisms, resulting in improvements in crop yield and quality. Ample studies have shown that H2 has positive effects on horticultural crops, such as promoting root development, enhancing tolerance against abiotic and biotic stress, prolonging storage life, and improving postharvest quality of fruits, vegetables and cut flowers. In this review, we aim to evaluate the feasibility of molecular hydrogen application in horticulture and the strategies for its application, including H2 delivery methods, treatment timing, and the concentration of H2 applied. The discussion will be accompanied by outlining the effects of H2 and the likely mechanisms of its efficacy. In short, the application of H2 may provide novel opportunities for simple and cost efficient improvements of horticultural production in terms of increased yield and product quality but with low carbon dioxide emissions.

Molecular Hydrogen: Is This a Viable New Treatment for Plants in the UK?

Despite being trialed in other regions of the world, the use of molecular hydrogen (H₂) for enhanced plant growth and the postharvest storage of crops has yet to be widely accepted in the UK. The evidence that the treatment of plants and plant products with H₂ alleviates plant stress and slows crop senescence continues to grow. Many of these effects appear to be mediated by the alteration of the antioxidant capacity of plant cells. Some effects seem to involve heme oxygenase, whilst the reduction in the prosthetic group Fe³⁺ is also suggested as a mechanism. Although it is difficult to use as a gaseous treatment in a field setting, the use of hydrogen-rich water (HRW) has the potential to be of significant benefit to agricultural practices. However, the use of H₂ in agriculture will only be adopted if the benefits outweigh the production and application costs. HRW is safe and relatively easy to use. If H₂ gas or HRW are utilized in other countries for agricultural purposes, it is tempting to suggest that they could also be widely used in the UK in the future, particularly for postharvest storage, thus reducing food waste.

Glutathione produced by γ-glutamyl cysteine synthetase acts downstream of hydrogen to positively influence lateral root branching

Hydrogen gas (H₂) mediation of lateral root (LR) branching was previously described. However, related signaling pathway is largely unexplored. In this study, we discovered that application with H₂ using hydrogen-rich water, mimicking the responses of exogenous glutathione (GSH), not only enhanced GSH synthesis, but also induced tomato LR development. The changes in the transcripts of auxin signaling-related genes and cell cycle regulatory genes were matched with above phenotypes. The addition of H₂ could trigger higher transcript levels of SlGSH1 and SlGSH2, encoding γ-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase (GS), confirming the stimulation of GSH synthesis. These responses were greatly abolished when the inhibitor of γ-ECS was applied. The inhibition in lateral root primordium development, especially in emergence stage, was also observed. Genetic evidence revealed that the defects in GSH production and lateral rooting in Arabidopsis cad2-1, a γ-ECS defective mutant, were obviously abolished in the presence of GSH compared to those in the presence of H₂. Further evidence revealed that mRNA levels of target genes elicited by H₂ in wild-type, were differentially impaired in mutant plants. Together, above data clearly demonstrated that γ-ECS-dependent GSH production might be closely associated with H₂ control of LR branching.

Hydrogen agronomy: research progress and prospects

Agriculture is the foundation of social development. Under the pressure of population growth, natural disasters, environmental pollution, climate change, and food safety, the interdisciplinary "new agriculture" is becoming an important trend of modern agriculture. In fact, new agriculture is not only the foundation of great health and new energy sources, but is also the cornerstone of national food security, energy security, and biosafety. Hydrogen agronomy focuses mainly on the mechanism of hydrogen gas (H₂) biology effects in agriculture, and provides a theoretical foundation for the practice of hydrogen agriculture, a component of the new agriculture. Previous research on the biological effects of H₂ focused chiefly on medicine. The mechanism of selective antioxidant is the main theoretical basis of hydrogen medicine. Subsequent experiments have demonstrated that H₂ can regulate the growth and development of plant crops, edible fungus, and livestock, and enhance the tolerance of these agriculturally important organisms against abiotic and biotic stresses. Even more importantly, H₂ can regulate the growth and development of crops by changing the soil microbial community composition and structure. Use of H₂ can also improve the nutritional value and postharvest quality of agricultural products. Researchers have also shown that the biological functions of molecular hydrogen are mediated by modulating reactive oxygen species (ROS), nitric oxide (NO), and carbon monoxide (CO) signaling cascades in plants and microbes. This review summarizes and clarifies the history of hydrogen agronomy and describes recent progress in the field. We also argue that emerging hydrogen agriculture will be an important direction in the new agriculture. Further, we discuss several scientific problems in hydrogen agronomy, and suggest that the future of hydrogen agronomy depends on contributions by multiple disciplines. Important future research directions of hydrogen agronomy include hydrogen agriculture in special environments, such as islands, reefs, aircraft, and outer space.

Hydrogen Commonly Applicable from Medicine to Agriculture: From Molecular Mechanisms to the Field

The emerging field of hydrogen biology has to date mainly been applied in medicine. However, hydrogen biology can also enable positive outcomes in agriculture. Agriculture faces significant challenges resulting from a growing population, climate change, natural disasters, environmental pollution, and food safety issues. In fact, hydrogen agriculture is a practical application of hydrogen biology, which may assist in addressing many of these challenges. It has been demonstrated that hydrogen gas (H₂) may enhance plant tolerance towards abiotic and biotic stresses, regulate plant growth and development, increase nutritional values, prolong the shelf life, and decrease the nitrite accumulation during the storage of vegetables, as well as increase the resilience of livestock to pathogens. Our field trials show that H₂ may have a promising potential to increase yield and improve the quality of agricultural products. This review aims to elucidate mechanisms for a novel agricultural application of H₂ in China. Future development of hydrogen agriculture is proposed as well. Obviously, hydrogen agriculture belongs to a low carbon economy, and has great potential to provide "safe, tasty, healthy, and high-yield" agricultural products so that it may improve the sustainability of agriculture.

Enhancement of carotenoid production and its regulation in edible mushroom Cordyceps militaris by abiotic stresses

Cordyceps militaris carotenoids are widely used as food additives, animal feed supplements, and so on. However, the biosynthetic pathway of carotenoids in C. militaris is still obscure. In this paper, changes of mycelial morphology and carotenoid accumulation of C. militaris were investigated under oxidative (KMnO₄) and osmotic stress (NaCl). Subsequently, qRT-PCR was employed to detect the expression levels of genes related to carotenogenesis to explore the mechanism of adaptation to abiotic stress. When the concentrations of KMnO₄ and NaCl were respectively 0.4 g/L and 2 g/L, carotenoid accumulation reached a maximum of 6616.82 ± 666.43 μg/g and 6416.77 ± 537.02 μg/g. Under the oxidative stress condition of KMnO₄, the expressions of psy and hsp70 increased significantly compared with control. Besides, the genes fus3 and hog1 were significantly enriched in the MAPK signal pathway. Compared with the control group, there was no significant difference in expression of psy in the NaCl group. Moreover, the accumulation of triacylglycerols may contribute significantly to the increase in carotenoid accumulation. The increased accumulation of antioxidant carotenoids induced under environmental stress is to resist oxidative conditions. Fus3 and Hog1 signaling in the MAPK pathway was activated and subsequently take effects on the resistance of oxidative condition by regulating related metabolic processes. C. militaris resist the stress of high oxygen by producing a large amount of glycerol and carotenoids when this fungus is cultured in a saline environment for a long time.

Direct Targets and Subsequent Pathways for Molecular Hydrogen to Exert Multiple Functions: Focusing on Interventions in Radical Reactions

Molecular hydrogen (H₂) was long regarded as non-functional in mammalian cells. We overturned the concept by demonstrating that H₂ exhibits antioxidant effects and protects cells against oxidative stress. Subsequently, it has been revealed that H₂ has multiple functions in addition to antioxidant effects, including antiinflammatory, anti-allergic functions, and as cell death and autophagy regulation. Additionally, H₂ stimulates energy metabolism. As H₂ does not readily react with most biomolecules without a catalyst, it is essential to identify the primary targets with which H₂ reacts or interacts directly. As a first event, H₂ may react directly with strong oxidants, such as hydroxyl radicals (•OH) in vivo. This review addresses the key issues related to this in vivo reaction. •OH may have a physiological role because it triggers a free radical chain reaction and may be involved in the regulation of Ca2+- or mitochondrial ATP-dependent K+-channeling. In the subsequent pathway, H₂ suppressed a free radical chain reaction, leading to decreases in lipid peroxide and its end products. Derived from the peroxides, 4-hydroxy-2-nonenal functions as a mediator that up-regulates multiple functional PGC-1α. As the other direct target in vitro and in vivo, H₂ intervenes in the free radical chain reaction to modify oxidized phospholipids, which may act as an antagonist of Ca2+-channels. The resulting suppression of Ca2+-signaling inactivates multiple functional NFAT and CREB transcription factors, which may explain H₂ multi-functionality. This review also addresses the involvement of NFAT in the beneficial role of H₂ in COVID-19, Alzheimer's disease and advanced cancer. We discuss some unsolved issues of H₂ action on lipopolysaccharide signaling, MAPK and NF-κB pathways and the Nrf2 paradox. Finally, as a novel idea for the direct targeting of H2, this review introduces the possibility that H₂ causes structural changes in proteins via hydrate water changes.

The functions of glutathione peroxidase in ROS homeostasis and fruiting body development in Hypsizygus marmoreus

Glutathione peroxidase (GPX) is one of the most important antioxidant enzymes for maintaining reactive oxygen species (ROS) homeostasis. Although studies on fungi have suggested many important physiological functions of GPX, few studies have examined the role of this enzyme in Basidiomycetes, particularly its functions in fruiting body developmental processes. In the present study, GPX-silenced (GPxi) strains were obtained by using RNA interference. The GPxi strains of Hypsizygus marmoreus showed defects in mycelial growth and fruiting body development. In addition, the results indicated essential roles of GPX in controlling ROS homeostasis by regulating intracellular H₂O₂ levels, maintaining GSH/GSSG balance, and promoting antioxidant enzyme activity. Furthermore, lignocellulose enzyme activity levels were reduced and the mitochondrial phenotype and mitochondrial complex activity levels were changed in the H. marmoreus GPxi strains, possibly in response to impediments to mycelial growth and fruiting body development. These findings indicate that ROS homeostasis has a complex influence on growth, fruiting body development, GSH/GSSG balance, and carbon metabolism in H. marmoreus.Key points• ROS balance, energy metabolism, fruiting development.

Exogenous l-ascorbic acid regulates the antioxidant system to increase the regeneration of damaged mycelia and induce the development of fruiting bodies in Hypsizygus marmoreus

Hypsizygus marmoreus is an important commercial edible fungus, but the lack of basic studies on this fungus has hindered further development of its commercial value. In this study, we found that the treatment of damaged vegetative mycelia with 1 mM l-ascorbic acid (ASA) significantly increased the antioxidant enzyme activities (GPX, GR, CAT and SOD) and antioxidant contents (GSH and ASA) and reduced the ROS levels (H₂O₂ and O₂^-) in mechanically damaged mycelia. Additionally, this treatment increased mycelial biomass. At the reproductive stage, our results demonstrated that the treatment of damaged H. marmoreus mycelia with 2.24 mM ASA significantly increased the antioxidant enzyme activities (GPX, GR, GST, TRXR and CAT), endogenous ASA contents and GSH/GSSG ratios in different developmental stages and significantly decreased the MDA and H₂O₂ contents. Furthermore, this study showed that the expression levels of the antioxidant enzyme genes were consistent with the enzyme activities. Damaged mycelia treated with ASA regenerated 2-3 d earlier than the control group and showed significantly enhanced fruiting body production. These results suggested that exogenous ASA regulated mycelia intracellular ASA content to increase mycelial antioxidant abilities, induce the regeneration of damaged mycelia and regulate the development of fruiting bodies in H. marmoreus.

Different Classes of Phytohormones Act Synergistically to Enhance the Growth, Lipid and DHA Biosynthetic Capacity of Aurantiochytrium sp. SW1

In the present study, the impact of eight phytohormones from six different classes on the growth, lipid and docosahexaenoic acid (DHA) biosynthetic capacity of Aurantiochytrium sp. SW1 (SW1) was evaluated. Kinetin (KIN), jasmonic acid (JA) and gibberellic acid (GA) significantly enhanced the growth and DHA production of SW1 by 16%-28% and 66%-84% in comparison to the control, respectively. The synergistic effect of these three phytohormones, evaluated by the response surface methodology (RSM), showed that a combination of 3.6 mg/L GA, 2.0 mg/L KIN and 20.0 mg/L JA further increased the growth and DHA production of SW1 by 16% to 28% and 22% to 36%, respectively, in comparison to the individual supplementation. The synergistic effect of these phytohormones was also shown to be time-dependent, where feeding at 24 h of cultivation led to 15%, 26% and 35% further increments in the biomass, lipid and DHA production in comparison to that of 0 h, respectively. The determination of stress markers, antioxidant enzymes and key enzymes involved in fatty acid biosynthesis aided to elucidate the potential mechanism underlying the improvement of growth and DHA production by SW1 at various times of feeding. Supplementation with the phytohormones at 24 h exhibited the maximum impact on reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as augmented the antioxidants (superoxide dismutase and catalase) and key metabolic enzymes involved in lipogenesis (malic, glucose-6-phosphate dehydrogenase and ATP-citrate lyase) in comparison to the control and other time points. This study signifies the potential application of phytohormones for improving the growth, lipid and DHA production in Aurantiochytrium spp.

Comparative transcriptome analysis reveals potential fruiting body formation mechanisms in Morchella importuna

Morchella importuna has been artificially cultivated, but stable production remains difficult because its mechanisms of fruiting body formation are unclear. To investigate the fruiting body formation mechanisms, we sequenced the transcriptomes of Morchella importuna at the mycelial and young fruiting body stages. Among the 12,561 differentially expressed genes (DEGs), 9215 were upregulated, and 3346 were downregulated. DEG enrichment analysis showed that these genes were enriched in the "generation of precursor metabolites and energy", "carbohydrate catabolic process", and "oxidoreductase activity" Gene Ontology (GO) functional categories. Enzyme activity assay results indicated that the activity levels of CAZymes (carbohydrate-active enzymes), oxidoreductases (SOD (superoxide dismutase), CAT (catalase)) and mitochondrial complex (complex I, II, III) proteins were significantly increased from the mycelial stage to the young fruiting body stage. In addition, the genes encoding CAZymes, mitochondrial proteins, oxidoreductases and heat shock proteins had higher expression levels in the young fruiting body stage than in the mycelial stage, and the qRT-PCR results showed similar trends to the RNA-Seq results. In summary, these results suggest that carbohydrate catabolism and energy metabolism are significantly enhanced in the young fruiting body stage and that growth environment temperature changes affect the formation of fruiting bodies.

Enhancing biomass and lipid accumulation in the microalgae Schizochytrium sp. by addition of fulvic acid and EDTA

Enhancing lipid productivity and reducing oxidative damage is essential for lipid overproduction in microalgae. In this study, addition of 20 mg/L fulvic acid (FA) resulted a 34.4% increase of lipid yield in Schizochytrium sp. Furthermore, the cooperative effect of FA and EDTA on cell growth and lipid production was investigated. The combined addition of 20 mg/L FA and 1.0 g/L EDTA yielded a maximal cell dry weight of 130.7 g/L and lipid productivity of 1.16 g/L/h, representing 36.4% and threefold increase over the non-supplemented group, respectively. Moreover, compared with the non-supplemented group, the combined addition strategy exhibited overall lower levels of reactive oxygen species and malondialdehyde, which accompanied with 66.7% and 81.9% higher superoxide dismutase and catalase activity, respectively. Furthermore, a 24.1–37.1% increase of malic enzyme and 19.4–25.2% decrease of phosphoenolpyruvate carboxylase activity was observed during the entire fermentation stage (0–108 h). Results suggested that the combined addition strategy not only enhanced lipid accumulation, but also prevented the lipid peroxidation.

Hydrogen-rich solution attenuates myocardial injury caused by cardiopulmonary bypass in rats via the Janus-activated kinase 2/signal transducer and activator of transcription 3 signaling pathway

The incidence of complications and mortality following open-heart surgery with cardiopulmonary bypass (CPB) is associated with the severity of the myocardial injury that occurs during surgery. Hydrogen-rich solution (HRS) may prevent antioxidant stress and inhibit apoptosis and inflammation. The present study was designed to investigate the effects of HRS on CPB-induced myocardial injury, and to investigate its potential regulation of the Janus-activated kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway. The HRS treatment resulted in the significant upregulation of malonyl dialdehyde (MDA) and myeloperoxidase (MPO), whilesuperoxide dismutase (SOD) levels were significantly downregulated, compared with the Sham group (P<0.05). Additionally, HRS treatment improved myocardial injury, and decreased the expression levels of cardiac troponins, heart-type fatty acid binding protein, interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, MDA and MPO, and increased SOD release in CPB rats (P<0.05). Additionally, in the CPB group without the HRS treatment, the expression levels of B-cell lymphoma (Bcl)-2, JAK2, phospho-JAK2 (p-JAK2), STAT3 and phospho-STAT3 (p-STAT3) were significantly decreased, and Bax was significantly increased, compared with the Sham group (P<0.05). By contrast, compared with the CPB group, the expression levels of B-cell lymphoma 2 (Bcl-2), JAK2, phosphorylated (p)-JAK2, STAT3 and p-STAT3 in the HRS group were significantly increased, and Bcl-2-associated X protein expression was significantly decreased (P<0.05). In JAK2 knockdown experiments using siRNA, HRS treatment following hypoxia/reoxygenation also significantly increased the viability of myocardial cells, decreased the rate of myocardial cell apoptosis, elevated the levels of SOD and suppressed the release of MDA and lactate dehydrogenase in the control siRNA and CPB groups (P<0.05). Furthermore, JAK2 siRNA attenuated these protective effects of HRS (P<0.05 vs. control siRNA, HRS and CPB groups). Additionally, the results demonstrated that the HRS treatment significantly increased the expression levels of p-JAK2, p-STAT3 and Bcl-2 in myocardial cells following hypoxia and decreased Bax expression in the control siRNA and CPB groups (P<0.05). In addition, JAK2 siRNA was determined to attenuate these effects of HRS (P<0.05 vs. control siRNA, HRS and CPB groups). Taken together, these results indicated that HRS may alleviate CPB-induced myocardial injury, inhibit myocardial cell apoptosis and protect myocardial cells through regulation of the JAK2/STAT3 signaling pathway.

Hydrogen-rich water mediates redox regulation of the antioxidant system, mycelial regeneration and fruiting body development in Hypsizygus marmoreus

Hypsizygus marmoreus is an important industrialized mushroom, yet the lack of basic research on this fungus has hindered further development of its economic value. In this study, mycelia injured by scratching were treated with hydrogen-rich water (HRW) to investigate the involvement of the redox system in fruiting body development. Compared to the control group, damaged mycelia treated with HRW regenerated earlier and showed significantly enhanced fruiting body production. Antioxidant capacity increased significantly in damaged mycelia after HRW treatment, as indicated by higher antioxidant enzyme activities and antioxidant contents; the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) were also reduced at the mycelial regeneration stage after treatment with HRW. Furthermore, genes involved in ROS, Ca²⁺, MAPK and oxylipin signaling pathways were up-regulated by HRW treatment. In addition, laccase and manganese peroxidase activities and mycelial biomass were higher after HRW treatment, suggesting that HRW might enhance the substrate-degradation rate to provide more carbon sources for fruiting body production.

Hydrogen-rich water increases postharvest quality by enhancing antioxidant capacity in Hypsizygus marmoreus

In the present study, we aimed to assess the effect of hydrogen-rich water (HRW) on the physicochemical characteristics and antioxidant capacity of Hypsizygus marmoreus during 12 days of postharvest storage at 4 °C. Different concentrations of HRW (25, 50 and 100%) were tested, and our data showed that 25% HRW treatment had the most significant effect on preservation of nutrients in H. marmoreus compared with the control group. In addition, 25% HRW treatment significantly reduced the relative electrolyte leakage rate and malonaldehyde (MDA) content (P < 0.05) and increased anti-superoxide-radical (O₂^-) activity compared with the control group. The activities of antioxidants, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were activated by 25% HRW treatment, and the expression levels of these genes were also induced. These results suggested that HRW treatment could delay rot incidence in mushrooms during storage by regulating antioxidant defense ability. This study supplies a new and simple method to maintain the quality and extend the shelf life of mushrooms.