Hydrogen sulfide, a novel small molecule signalling agent, participates in the regulation of ganoderic acids biosynthesis induced by heat stress in Ganoderma lucidum

Enhanced H2S biogenesis followed by its postharvest application retarded senescence development by promoting multiple antioxidant protection systems in button mushroom during cold storage

Rapid postharvest quality deterioration of button mushroom as fruit body surface browning brings about senescence development and limits its distribution potential and postharvest storage. In this investigation, 0.5 mM of NaHS as the optimum concentration for H2S fumigation was applied to retain the quality of Agaricus bisporus mushrooms concerning some qualitative and biochemical attributes evaluation throughout 15 storage-day at 4 °C and 80-90% relative humidity. In H2S fumigated mushrooms, pileus browning index, weight loss and softening decreased, concomitant with higher cell membrane stability as revealed by subsidiary electrolyte leakage, malondialdehyde (MDA) and H2O2 contents compared to the control during the cold storage period. H2S fumigation boosted total phenolics, as presented by the enhanced phenylalanine ammonia-lyase (PAL) activity and total antioxidant scavenging activity, while polyphenol oxidase (PPO) activity diminished. Moreover, in H2S fumigated mushrooms not only peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) activities but also ascorbic acid and glutathione (GSH) contents increased, even though glutathione (GSSG) content declined. The raised endogenous H2S level prompted by greater cystathionine ß-synthase (CBS), cystathionine ?-lyase (CSE), cysteine synthase (CS), L-cysteine desulfhydrases (LCD) and D-cysteine desulfhydrases (DCD) enzymes activities until 10d in fumigated mushrooms. In general, the increase in endogenous H2S biogenesis promoted by H2S fumigation in button mushrooms resulted in retarding senescence development, maintaining redox balance by boosting multiple enzymatic and non-enzymatic antioxidants defense parameters.

The CBS/H2S signalling pathway regulated by the carbon repressor CreA promotes cellulose utilization in Ganoderma lucidum

Cellulose is an important abundant renewable resource on Earth, and the microbial cellulose utilization mechanism has attracted extensive attention. Recently, some signalling molecules have been found to regulate cellulose utilization and the discovery of underlying signals has recently attracted extensive attention. In this paper, we found that the hydrogen sulfide (H2S) concentration under cellulose culture condition increased to approximately 2.3-fold compared with that under glucose culture condition in Ganoderma lucidum. Further evidence shown that cellulase activities of G. lucidum were improved by 18.2-27.6% through increasing H2S concentration. Then, we observed that the carbon repressor CreA inhibited H2S biosynthesis in G. lucidum by binding to the promoter of cbs, a key gene for H2S biosynthesis, at "CTGGGG". In our study, we reported for the first time that H2S increased the cellulose utilization in G. lucidum, and analyzed the mechanism of H2S biosynthesis induced by cellulose. This study not only enriches the understanding of the microbial cellulose utilization mechanism but also provides a reference for the analysis of the physiological function of H2S signals.

GlPRMT5 inhibits GlPP2C1 via symmetric dimethylation and regulates the biosynthesis of secondary metabolites in Ganoderma lucidum

PRMT5, a type II arginine methyltransferase, is involved in transcriptional regulation, RNA processing and other biological processes and signal transduction. Secondary metabolites are vital pharmacological compounds in Ganoderma lucidum, and their content is an important indicator for evaluating the quality of G. lucidum. Here, we found that GlPRMT5 negatively regulates the biosynthesis of secondary metabolites. In further in-depth research, GlPP2C1 (a type 2C protein phosphatase) was identified out as an interacting protein of GlPRMT5 by immunoprecipitation-mass spectrometry (IP-MS). Further mass spectrometry detection revealed that GlPRMT5 symmetrically dimethylates the arginine 99 (R99) and arginine 493 (R493) residues of GlPP2C1 to weaken its activity. The symmetrical dimethylation modification of the R99 residue is the key to affecting GlPP2C1 activity. Symmetrical demethylation-modified GlPP2C1 does not affect the interaction with GlPRMT5. In addition, silencing GlPP2C1 clearly reduced GA content, indicating that GlPP2C1 positively regulates the biosynthesis of secondary metabolites in G. lucidum. In summary, this study reveals the molecular mechanism by which GlPRMT5 regulates secondary metabolites, and these studies provide further insights into the target proteins of GlPRMT5 and symmetric dimethylation sites. Furthermore, these studies provide a basis for the mutual regulation between different epigenetic modifications.

PRMT5 regulates the polysaccharide content by controlling the splicing of thaumatin-like protein in Ganoderma lucidum

IMPORTANCE

PRMT5 contributes to secondary metabolite biosynthesis in Ganoderma lucidum. However, the mechanism through which PRMT5 regulates the biosynthesis of secondary metabolites remains unclear. In the current study, PRMT5 silencing led to a significant decrease in the biosynthesis of polysaccharides from G. lucidum through the action of the alternative splicing of TLP. A shorter TLP2 isoform can directly bind to PGI and regulated polysaccharide biosynthesis. These results suggest that PRMT5 enhances PGI activity by regulating TLP binding to PGI. The results of the current study reveal a novel target gene for PRMT5-mediated alternative splicing and provide a reference for the identification of PRMT5 regulatory target genes.

Comparative analysis of genome-wide transcriptional responses to continuous heat stress in Pleurotus tuoliensis

Temperature plays an impactful role in mushroom cultivation. To obtain insights of transcriptomic response in macrofungi against heat stress, we performed RNA-seq analysis using Pleurotus tuoliensis mycelium cells that were treated under 32 °C and 36 °C for consecutive 96 h. By comparing the growth rate data, we found mycelium cells could maintain normal growth rate almost the same as control under 32 °C, yet halted the growths under 36 °C. In total, 2724 differential expressed genes were identified from the three pair-wise comparisons, which were classified to four clusters based on their expression patterns. We also performed gene set enrichment analysis using both GO and KEGG databases, and revealed 48, 113 and 105 enriched GO terms, and 1, 5, and 6 enriched KEGG pathways for three pair-wise comparisons accordingly. In addition, we identified 9 overlapping GO terms and 1 overlapping KEGG pathway shared by the three comparisons. Differentially expressed genes (DEGs) involved in cell communication, amino acid metabolic process, intracellular signal transduction and small molecule biosynthesis were identified in two heat stress treatments despite of the stress intensity. However, the expression of two heat shock protein genes (HSP10 and HSP60) were induced by increasing temperature. Our findings also suggested the DEGs associated with cell cycle regulation had various expression patterns under two heat stress conditions possibly due to different functions. Furthermore, 11 DEGs related to ergosterol biosynthesis were identified with similar expression trends, indicating the ergosterol levels and cell membrane composition may have a tight connection to the acquisition of thermotolerance, which warrant further investigations for deeper understanding of molecular mechanisms in fungal stress responses.

Integrative analysis of genome and transcriptome reveal the genetic basis of high temperature tolerance in pleurotus giganteus (Berk. Karun & Hyde)

BACKGROUND

Pleurotus giganteus is a commonly cultivated mushroom with notable high temperature resistance, making it significant for the growth of the edible fungi industry in the tropics. Despite its practical importance,, the genetic mechanisms underlying its ability to withstand high temperature tolerance remain elusive.

RESULTS

In this study, we performed high-quality genome sequencing of a monokaryon isolated from a thermotolerant strain of P. giganteus. The genome size was found to be 40.11 Mb, comprising 17 contigs and 13,054 protein-coding genes. Notably, some genes related to abiotic stress were identified in genome, such as genes regulating heat shock protein, protein kinase activity and signal transduction. These findings provide valuable insights into the genetic basis of P. giganteus' high temperature resistance. Furthermore, the phylogenetic tree showed that P. giganteus was more closely related to P. citrinopileatus than other Pleurotus species. The divergence time between Pleurotus and Lentinus was estimated as 153.9 Mya, and they have a divergence time with Panus at 168.3 Mya, which proved the taxonomic status of P. giganteus at the genome level. Additionally, a comparative transcriptome analysis was conducted between mycelia treated with 40 °C heat shock for 18 h (HS) and an untreated control group (CK). Among the 2,614 differentially expressed genes (DEGs), 1,303 genes were up-regulated and 1,311 were down-regulated in the HS group. The enrichment analysis showed that several genes related to abiotic stress, including heat shock protein, DnaJ protein homologue, ubiquitin protease, transcription factors, DNA mismatch repair proteins, and zinc finger proteins, were significantly up-regulated in the HS group. These genes may play important roles in the high temperature adaptation of P. giganteus. Six DEGs were selected according to fourfold expression changes and were validated by qRT-PCR, laying a good foundation for further gene function analysis.

CONCLUSION

Our study successfully reported a high-quality genome of P. giganteus and identified genes associated with high-temperature tolerance through an integrative analysis of the genome and transcriptome. This study lays a crucial foundation for understanding the high-temperature tolerance mechanism of P. giganteus, providing valuable insights for genetic modification of P. giganteus strains and the development of high-temperature strains for the edible fungus industry, particularly in tropical regions.

Comparative proteomic analysis of two divergent strains provides insights into thermotolerance mechanisms of Ganoderma lingzhi

Heat stress (HS) is a major abiotic factor influencing fungal growth and metabolism. However, the genetic basis of thermotolerance in Ganoderma lingzhi (G. lingzhi) remains largely unknown. In this study, we investigated the thermotolerance capacities of 21 G. lingzhi strains and screened the thermo-tolerant (S566) and heat-sensitive (Z381) strains. The mycelia of S566 and Z381 were collected and subjected to a tandem mass tag (TMT)-based proteome assay. We identified 1493 differentially expressed proteins (DEPs), with 376 and 395 DEPs specific to the heat-tolerant and heat-susceptible genotypes, respectively. In the heat-tolerant genotype, upregulated proteins were linked to stimulus regulation and response. Proteins related to oxidative phosphorylation, glycosylphosphatidylinositol-anchor biosynthesis, and cell wall macromolecule metabolism were downregulated in susceptible genotypes. After HS, the mycelial growth of the heat-sensitive Z381 strain was inhibited, and mitochondrial cristae and cell wall integrity of this strain were severely impaired, suggesting that HS may inhibit mycelial growth of Z381 by damaging the cell wall and mitochondrial structure. Furthermore, thermotolerance-related regulatory pathways were explored by analyzing the protein-protein interaction network of DEPs considered to participate in the controlling the thermotolerance capacity. This study provides insights into G. lingzhi thermotolerance mechanisms and a basis for breeding a thermotolerant germplasm bank for G. lingzhi and other fungi.

Mitochondrial pyruvate carrier influences ganoderic acid biosynthesis in Ganoderma lucidum

Mitochondrial pyruvate carriers (MPCs), located in the inner membrane of mitochondria, are essential carriers for pyruvate to enter mitochondria. MPCs regulate a wide range of intracellular metabolic processes, such as glycolysis, the tricarboxylic acid cycle (TCA cycle), fatty acid metabolism, and amino acid metabolism. However, the metabolic regulation of MPCs in macrofungi is poorly studied. We studied the role of MPCs in Ganoderma lucidum (GlMPC) on ganoderic acid (GA) biosynthesis regulation in G. lucidum. In this study, we found that the mitochondrial/cytoplasmic ratio of pyruvate was downregulated about 75% in GlMPC1- and GlMPC2-silenced transformants compared with wild type (WT). In addition, the GA content was 17.72 mg/g and increased by approximately 50% in GlMPC1- and GlMPC2-silenced transformants compared with WT. By assaying the expression levels of three key enzymes and the enzyme activities of isocitrate dehydrogenase (IDH) and α-ketoglutarate dehydrogenase (α-KGDH) of the TCA cycle in GlMPC1- and GlMPC2-silenced transformants, it was found that the decrease in GlMPCs activity did not significantly downregulate the TCA cycle rate, and the enzyme activity of IDH increased by 44% compared with WT. We then verified that fatty acid β-oxidation (FAO) supplements the TCA cycle by detecting the expression levels of key enzymes involved in FAO. The results showed that compared with WT, the GA content was 1.14 mg/g and reduced by approximately 40% in co-silenced transformants. KEY POINTS: • GlMPCs affects the distribution of pyruvate between mitochondria and the cytoplasm. • Acetyl-CoA produced by FAO maintains the TCA cycle. • Acetyl-CoA produced by FAO promotes the accumulation of GA.

The associative induction of succinic acid and hydrogen sulfide for high-producing biomass, astaxanthin and lipids in Haematococcus pluvialis

To obtain higher yield of natural astaxanthin, the present study aims to develop a viable and economic induction strategy for astaxanthin production comprising succinic acid (SA) combined with sodium hydrosulfide (NaHS). The biomass (1.33 g L^-1), astaxanthin concentration (44.96 mg L^-1), astaxanthin content (163.55 pg cell^-1), and lipid content (55.34%) were achieved under 1.0 mM SA and 100 μM NaHS treatment. These results were concomitant with enhanced hydrogen sulfide (H₂S) but diminished reactive oxide species (ROS). Further study discovered that endogenous H₂S could improve astaxanthin and lipid coproduction under SA induction by mediating related gene transcript levels and ROS signalling. Additionally, the concentrations of biomass and astaxanthin increased to 2.14 g L^-1 and 66.25 mg L^-1, respectively, under the induction of SA and NaHS in a scaled-up bioreactor. Briefly, the work proposed a novel feasible strategy for high yields of biomass and astaxanthin by H. pluvialis.

GSNOR regulates ganoderic acid content in Ganoderma lucidum under heat stress through S-nitrosylation of catalase

As a master regulator of the balance between NO signaling and protein S-nitrosylation, S-nitrosoglutathione (GSNO) reductase (GSNOR) is involved in various developmental processes and stress responses. However, the proteins and specific sites that can be S-nitrosylated, especially in microorganisms, and the physiological functions of S-nitrosylated proteins remain unclear. Herein, we show that the ganoderic acid (GA) content in GSNOR-silenced (GSNORi) strains is significantly lower (by 25%) than in wild type (WT) under heat stress (HS). Additionally, silencing GSNOR results in an 80% increase in catalase (CAT) activity, which consequently decreases GA accumulation via inhibition of ROS signaling. The mechanism of GSNOR-mediated control of CAT activity may be via protein S-nitrosylation. In support of this possibility, we show that CAT is S-nitrosylated (as shown via recombinant protein in vitro and via GSNORi strains in vivo). Additionally, Cys (cysteine) 401, Cys642 and Cys653 in CAT are S-nitrosylation sites (assayed via mass spectrometry analysis), and Cys401 may play a pivotal role in CAT activity. These findings indicate a mechanism by which GSNOR responds to stress and regulates secondary metabolite content through protein S-nitrosylation. Our results also define a new S-nitrosylation site and the function of an S-nitrosylated protein regulated by GSNOR in microorganisms.

Liu et al. identify catalase as a target of S-nitrosylation by GSNOR and the specific sites of S-nitrosylation critical for its role in regulating secondary metabolite production in Ganoderma lucidum under heat stress. This study suggests that GSNOR regulates other metabolic pathways in microorganisms through S-nitrosylation of target proteins in response to environmental changes.

In silico analysis and characterization of medicinal mushroom cystathionine beta-synthase as an angiotensin converting enzyme (ACE) inhibitory protein

Angiotensin-converting enzyme (ACE) regulates blood pressure and has been implicated in several conditions including lung injury, fibrosis and Alzheimer's disease. Medicinal mushroom Ganordema lucidum (Reishi) cystathionine beta-synthase (GlCBS) was previously reported to possess ACE inhibitory activities. However, the inhibitory mechanism of CBS protein remains unreported. Therefore, this study integrates in silico sequencing, structural and functional based-analysis, protein modelling, molecular docking and binding affinity calculation to elucidate the inhibitory mechanism of GlCBS and Lignosus rhinocerus (Tiger milk mushroom) CBS protein (LrCBS) towards ACE. In silico analysis indicates that CBSs from both mushrooms share high similarities in terms of physical properties, structural properties and domain distribution. Protein-protein docking analysis revealed that both GlCBS and LrCBS potentially modulate the C-terminal domain of ACE (C-ACE) activity via regulation of chloride activation and/or prevention of substrate entry. GICBS and LrCBS were also shown to interact with ACE at the same region that presumably inhibits the function of ACE.

Heme oxygenase-1/carbon monoxide signaling participates in the accumulation of triterpenoids of Ganoderma lucidum

Ganoderic triterpenoids (GTs) are the primary bioactive constituents of the Basidiomycotina fungus, Ganoderma lucidum. These compounds exhibit antitumor, anti-hyperlipidemic, and immune-modulatory pharmacological activities. This study focused on GT accumulation in mycelia of G. lucidum mediated by the heme oxygenase-1 (HO-1)/carbon monoxide (CO) signaling. Compared with the control, hemin (10 μmol/L) induced an increase of 60.1% in GT content and 57.1% in HO-1 activity. Moreover, carbon monoxide-releasing molecule-2 (CORM-2), CO donor, increased GT content by 56.0% and HO-1 activity by 18.1%. Zn protoporphyrin IX (ZnPPIX), a specific HO-1 inhibitor, significantly reduced GT content by 26.0% and HO-1 activity by 15.8%, while hemin supplementation reversed these effects. Transcriptome sequencing showed that HO-1/CO could function directly as a regulator involved in promoting GT accumulation by regulating gene expression in the mevalonate pathway, and modulating the reactive oxygen species (ROS) and Ca²⁺ pathways. The results of this study may help enhance large-scale GT production and support further exploration of GT metabolic networks and relevant signaling cross-talk.

Heat stress in macrofungi: effects and response mechanisms

Temperature is one of the key factors that affects the growth and development of macrofungi. Heat stress not only negatively affects the morphology and growth rate of macrofungi, but also destroys cell structures and influences cell metabolism. Due to loosed structure of cell walls and increased membrane fluidity, which caused by heat stress, the outflow of intracellular nutrients makes macrofungi more vulnerable to invasion by pathogens. Macrofungi accumulate reactive oxygen species (ROS), Ca²⁺, and nitric oxide (NO) when heat-stressed, which transmit and amplify the heat stimulation signal through intracellular signal transduction pathways. Through regulation of some transcription factors including heat response factors (HSFs), POZCP26 and MYB, macrofungi respond to heat stress by different mechanisms. In this paper, we present mechanisms used by macrofungi to adapt and survive under heat stress conditions, including antioxidant defense systems that eliminate the excess ROS, increase in trehalose levels that prevent enzymes and proteins deformation, and stabilize cell structures and heat shock proteins (HSPs) that repair damaged proteins and synthesis of auxins, which increase the activity of antioxidant enzymes. All of these help macrofungi resist and adapt to heat stress. KEY POINTS: • The effects of heat stress on macrofungal growth and development were described. • The respond mechanisms to heat stress in macrofungi were summarized. • The further research directions of heat stress in macrofungi were discussed.

Hydrogen sulfide and calcium effects on cadmium removal and resistance in the white-rot fungus Phanerochaete chrysosporium

Hydrogen sulfide (H₂S), an emerging gas transmitter, has been shown to be involved in multiple intracellular physiological and biochemical processes. In this study, the effects of hydrogen sulfide coupled with calcium on cadmium removal and resistance in Phanerochaete chrysosporium were examined. The results revealed that H₂S enhanced the uptake of calcium by P. chrysosporium to resist cadmium stress. The removal and accumulation of cadmium by the mycelium was reduced by H₂S and Ca²⁺ pretreatment. Moreover, oxidative damage and membrane integrity were alleviated by H₂S and Ca²⁺. Corresponding antioxidative enzyme activities and glutathione were also found to positively respond to H₂S and Ca²⁺, which played an important role in the resistance to cadmium-induced oxidative stress. The effects of hydroxylamine (HA; a hydrogen sulfide inhibitor) and ethylene glycol-bis-(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA; a calcium chelator) toward H₂S and Ca²⁺ and their cross-interactions confirmed the positive roles and the potential crosstalk of H₂S and Ca²⁺ in cadmium stress resistance. These findings imply that the protective effects of H₂S in P. chrysosporium under cadmium stress may occur through a reduction in the accumulation of cadmium and promotion of the antioxidant system, and the H₂S-regulated pathway may be associated with the intracellular calcium signaling system.Key points• Altered monoterpenoid tolerance mainly related to altered activity of efflux pumps.• Increased tolerance to geranic acid surprisingly caused by decreased export activity.• Reduction of export activity can be beneficial for biotechnological conversions.

Interplay between hydrogen sulfide and other signaling molecules in the regulation of guard cell signaling and abiotic/biotic stress response

Stomatal aperture controls the balance between transpirational water loss and photosynthetic carbon dioxide (CO2) uptake. Stomata are surrounded by pairs of guard cells that sense and transduce environmental or stress signals to induce diverse endogenous responses for adaptation to environmental changes. In a recent decade, hydrogen sulfide (H2S) has been recognized as a signaling molecule that regulates stomatal movement. In this review, we summarize recent progress in research on the regulatory role of H2S in stomatal movement, including the dynamic regulation of phytohormones, ion homeostasis, and cell structural components. We focus especially on the cross talk among H2S, nitric oxide (NO), and hydrogen peroxide (H2O2) in guard cells, as well as on H2S-mediated post-translational protein modification (cysteine thiol persulfidation). Finally, we summarize the mechanisms by which H2S interacts with other signaling molecules in plants under abiotic or biotic stress. Based on evidence and clues from existing research, we propose some issues that need to be addressed in the future.

Putrescine regulates nitric oxide accumulation in Ganoderma lucidum partly by influencing cellular glutamine levels under heat stress

When fungi are subjected to abiotic stresses, the polyamines (PAs) level alter significantly. Here, we reveal that the polyamine putrescine (Put) could play an important role in alleviating heat stress(HS)-induced accumulation of nitric oxide (NO). Ornithine decarboxylase (ODC)-silenced mutants that were defective in Put biosynthesis exhibited significantly lower NO levels than the wild type (WT) when subjected to HS. With addition of 5 mM exogenous Put, the ODC-silenced mutant endogenous Put obviously increased under HS. At the same time, the contents of NO in the ODC-silenced mutants recovered to approximately WT levels after the administration of exogenous Put. However, the elevated NO content in the ODC-silenced mutants disappeared when exogenous Put and carboxy-PTIO (PTIO is a specific scavenger of NO) were added. Intriguingly, the content of glutamine (Gln) was significantly increased in the ODC-silenced strains. When exogenous Put was added to the WT, the Gln content was significantly decreased. The appearance of a high level of Gln was accompanied by nitrate reductase (NR) activity reduction. Further studies showed that Put influenced ganoderic acids (GAs) biosynthesis by regulating NO content, possibly through NR, under HS. Our work reported that Put regulates HS-induced NO accumulation by changing the cellular Gln level in filamentous fungi. IMPORTANCE: In our present work, it was HS as an ubiquitous environmental stress that affects the important pharmacological secondary metabolite (GAs) content in G. lucidum. Afterwards, we began to explore the network formed between multiple substances to jointly reduce the massive accumulation of GAs content caused by HS. We firstly focused on Put, a substance that enhances resistance to multiple stresses. Further, we discovered an influence on Put could changing the NO content, which has been shown to decrease the accumulation of GAs via HS. Then, we also found the change of NO content may be due to Put level that would affect intracellular Gln content. It has never been reported. And ultimately, it is Put related network that could reduce HS-inducing secondary metabolite mess in fungi.

Lactic acid accumulation under heat stress related to accelerated glycolysis and mitochondrial dysfunction inhibits the mycelial growth of Pleurotus ostreatus

High temperature is a major threat to Pleurotus ostreatus cultivation. In this study, a potential mechanism by which P. ostreatus mycelia growth is inhibited under heat stress was explored. Lactate, as a microbial fermentation product, was found unexpectedly in the mycelia of P. ostreatus under heat stress, and the time-dependent accumulation and corresponding inhibitory effect of lactate on mycelial growth was further confirmed. The addition of a glycolysis inhibitor, 2-deoxy-D-glucose (2DG), reduced the lactate content in mycelia and slightly restored mycelial growth under high-temperature conditions, which indicated the accumulation of lactate can be inhibited by glycolysis inhibition. Further data revealed mitochondrial dysfunction under high-temperature conditions, with evidence of decreased oxygen consumption and adenosine triphosphate (ATP) synthesis and increased reactive oxygen species (ROS). The removal of ROS with ascorbic acid decreased the lactate content, and mycelial growth recovered to a certain extent, indicating lactate accumulation could be affected by the mitochondrial ROS. Moreover, metabolic data showed that glycolysis and the tricarboxylic acid cycle were enhanced. This study reported the accumulation of lactate in P. ostreatus mycelia under heat stress and the inhibitory effect of lactate on the growth of mycelia, which might provide further insights into the stress response mechanism of edible fungi. Key Points • Lactate can accumulate in Pleurotus ostreatus mycelia under heat stress and inhibit its growth. • The accumulation of lactate may be due to the acceleration of glycolysis and the dysfunction of mitochondria of P. ostreatus mycelia under high-temperature stress. • The glycolysis and tricarboxylic acid cycle of P. ostreatus mycelia were accelerated under high-temperature stress.

Stress responsive gene regulation in relation to hydrogen sulfide in plants under abiotic stress

Plants often face a variety of abiotic stresses, which affects them negatively and lead to yield loss. The antioxidant system efficiently removes excessive reactive oxygen species and maintains redox homeostasis in plants. With better understanding of these protective mechanisms, recently the concept of hydrogen sulfide (H₂ S) and its role in cell signaling has become the center of attention. H₂ S has been recognized as a third gasotransmitter and a potent regulator of growth and development processes such as germination, maturation, senescence and defense mechanism in plants. Because of its gaseous nature, H₂ S can diffuse to different part of the cells and balance the antioxidant pools by supplying sulfur to cells. H₂ S showed tolerance against a plethora of adverse environmental conditions like drought, salt, high temperature, cold, heavy metals and flood via changing in level of osmolytes, malonaldialdehyde, Na⁺ /K⁺ uptake, activities of H₂ S biosynthesis and antioxidative enzymes. It also promotes cross adaptation through persulfidation. H₂ S along with calcium, methylglyoxal and nitric oxide, and their cross talk induces the expression of mitogen activated protein kinases as well as other genes in response to stress. Therefore, it is sensible to evaluate and explore the stress responsive genes involved in H₂ S regulated homeostasis and stress tolerance. The current article is aimed to summarize the recent updates on H₂ S-mediated gene regulation in special reference to abiotic stress tolerance mechanism, and cross adaptation in plants. Moreover, new insights into the H₂ S-associated signal transduction pathway have also been explored.

Glsnf1-mediated metabolic rearrangement participates in coping with heat stress and influencing secondary metabolism in Ganoderma lucidum

The AMP-activated protein kinase (AMPK)/Sucrose-nonfermenting serine-threonine protein kinase 1 (Snf1) plays an important role in metabolic remodelling in response to energy stress. However, the role of AMPK/Snf1 in responding to other environmental stresses and metabolic remodelling in microorganisms was unclear. Heat stress (HS), which is one important environmental factor, could induce the production of reactive oxygen species and the accumulation of ganoderic acids (GAs) in Ganoderma lucidum. Here, the functions of AMPK/Snf1 were analysed under HS condition in G. lucidum. We observed that Glsnf1 was rapidly and strongly activated when G. lucidum was exposed to HS. HS significantly increased intracellular H₂O₂ levels (by approximately 1.6-fold) and decreased the dry weight of G. lucidum (by approximately 45.6%). The exogenous addition of N-acetyl-l-cysteine (NAC) and ascorbic acid (VC), which function as ROS scavengers, partially inhibited the HS-mediated reduction in biomass. Adding the AMPK/Snf1 inhibitor compound C (20 μM) under HS conditions increased the H₂O₂ content (by approximately 2.3-fold of that found in the strain without HS treatment and 1.5-fold of that found in the strain under HS treatment without compound C) and decreased the dry weight of G. lucidum (an approximately 28.5% decrease compared with that of the strain under HS conditions without compound C). Similar results were obtained by silencing the Glsnf1 gene. Further study found that Glsnf1 meditated metabolite distribution from respiration to glycolysis, which is considered a protective mechanism against oxidative stress. In addition, Glsnf1 negatively regulated the biosynthesis of GA by removing ROS. In conclusion, our results suggest that Glsnf1-mediated metabolic remodelling is involved in heat stress adaptability and the biosynthesis of secondary metabolites in G. lucidum.

Metabolic Response of Pleurotus ostreatus to Continuous Heat Stress

Heat stress seriously threatens the growth of Pleurotus ostreatus. Various studies have been performed to study the resistance of P. ostreatus to heat stress. Here, the metabolome was evaluated to determine the response of P. ostreatus mycelia to heat stress at different times (6, 12, 24, 48 h). More than 70 differential metabolites were detected and enriched in their metabolic pathways. Dynamic metabolites changes in enrichment pathways under heat stress showed that heat stress enhanced the degradation of unsaturated fatty acids and nucleotides, increased the content of amino acids and vitamins, and accelerated glycolysis and the tricarboxylic acid cycle in P. ostreatus. The time course changes of P. ostreatus metabolites under continuous heat stress demonstrated that amino acids continuously changed with heat stress, nucleotides clearly changed with heat stress at 12 and 48 h, and lipids exhibited an increasing trend with prolonged heat stress, while few types saccharides and vitamins changed under heat stress. Additionally, heat-treated P. ostreatus produced salicylic acid and other stress-resistant substances that were reported in plants. This study first reported the metabolites changes in P. ostreatus mycelia during 48 h of heat stress. The metabolic pathways and substances that changed with heat stress in this research will aid future studies on the resistance of P. ostreatus and other edible fungi to heat stress.

Integrated Proteomics and Metabolomics Analysis Provides Insights into Ganoderic Acid Biosynthesis in Response to Methyl Jasmonate in Ganoderma Lucidum

Ganoderma lucidum is widely recognized as a medicinal basidiomycete. It was previously reported that the plant hormone methyl jasmonate (MeJA) could induce the biosynthesis of ganoderic acids (GAs), which are the main active ingredients of G. lucidum. However, the regulatory mechanism is still unclear. In this study, integrated proteomics and metabolomics were employed on G. lucidum to globally identify differences in proteins and metabolites under MeJA treatment for 15 min (M15) and 24 h (M24). Our study successfully identified 209 differential abundance proteins (DAPs) in M15 and 202 DAPs in M24. We also identified 154 metabolites by GC-MS and 70 metabolites by LC-MS in M24 that are involved in several metabolic pathways. With an in-depth analysis, we found some DAPs and metabolites that are involved in the oxidoreduction process, secondary metabolism, energy metabolism, transcriptional and translational regulation, and protein synthesis. In particular, our results reveal that MeJA treatment leads to metabolic rearrangement that inhibited the normal glucose metabolism, energy supply, and protein synthesis of cells but promoted secondary metabolites, including GAs. In conclusion, our proteomics and metabolomics data further confirm the promoting effect of MeJA on the biosynthesis of GAs in G. lucidum and will provide a valuable resource for further investigation of the molecular mechanisms of MeJA signal response and GA biosynthesis in G. lucidum and other related species.