Diverse diseases are typically associated with perturbed microbiome homeostasis, across ecosystems such as the gut and root habitats. Clubroot, which is caused by the devastating soil-borne pathogen Plasmodiophora brassicae, is a broad-spectrum disease that infects almost all cruciferous vegetables. However, the microbial ecological and metabolic cues underlying pathogen-driven deleterious disruptions of the microbiome remain enigmatic. In this study, changes in the microbiome and metabolome of the rhizosphere and roots in susceptible (diseased and nondiseased) and resistant pakchoi plants infected with P. brassicae were investigated. Diverse potential beneficial and disease-suppressive microbial families, including Rhizobiaceae and Sphingomonadaceae, were enriched in the healthy group compared with the diseased group. Rhizobiaceae was further characterized as a core driver family between the healthy and diseased groups. Reductionist-based strain validation studies further confirmed that Rhizobium sp. 25F3 showed drastic disease-suppressing activity in soil. The integrated metabolome‒microbiome correlation analysis revealed that phenolic acids were negatively correlated with the relative abundance of Rhizobiaceae. We further confirmed that genes related to phenolic acids were upregulated in diseased roots and that two phenolic acids suppressed beneficial Rhizobiaceae growth and accelerated P. brassicae infection in pakchoi. Upon P. brassicae infection, significant differences in the microbiome and metabolome were observed between diseased and healthy plants, as well as between resistant and susceptible varieties. Rhizobiaceae is dominant in the root microbiome and acts as a keystone family affected by P. brassicae infection. P. brassicae-induced phenolic acid metabolites selectively inhibit the growth of beneficial Rhizobium sp. 25F3 while promoting P. brassicae bursts in pakchoi. Our work provides ecological and metabolic explanations for how pathogenesis ultimately triggers a decrease in the relative abundance of beneficial microbes, which can guide future genetic and microbiome-based approaches to control clubroot disease.

Agaricus bisporus is among the most widely cultivated edible mushrooms worldwide. Nutrient accumulation during composting affects yield and quality. In this study, we conducted an integrated analysis of the transcriptome and physiological and biochemical indicators during the growth and development stages. We analyzed lignocellulose degradation efficiency, carbon metabolism gene expression patterns, and dynamic changes in amino acid biosynthesis pathways in the A. bisporus cultivar ‘Shen K6’. The results indicated that ‘Shen K6’ substantially degraded hemicellulose, with a degradation efficiency of 51%. GO and KEGG enrichment analyses revealed that the differentially expressed genes (DEGs) were primarily involved in nitrogen compound metabolic process; carbohydrate derivative binding; starch and sucrose metabolism; glycolysis/gluconeogenesis; alanine, aspartate, and glutamate metabolism; and lysine degradation. Analysis of genes encoding key enzymes involved in carbon and nitrogen metabolism revealed significantly upregulated expression levels of Exo2, Endo2, Endo10, Xylo3, AXE1, VP1, GDH2, and ASNS1. In terms of glycolysis and the tricarboxylic acid (TCA) cycle, the upregulated expression of AK, AS, KGDH, and KGsyn promoted the biosynthesis of aspartate (Asp) and glutamate (Glu), driving the significant accumulation of these two flavor-related amino acids and ultimately improving the quality of A. bisporus. Therefore, this study elucidated the main pathways and key genes underlying carbon metabolism-regulated amino acid biosynthesis during the growth and development of ‘Shen K6’. These findings provide important molecular targets for improving the quality of A. bisporus and lay a foundation for understanding how nutrient transport regulates quality formation in edible fungi.

Morchella is an edible and medicinal fungus valued for its distinctive flavor and nutritional properties. However, unstable yield and quality remain major constraints on its commercial cultivation. Although soybean meal is used as an organic nutrient supplement in edible mushroom production, its effects on protein accumulation and transcriptional regulation in Morchella remain unclear. This study combined fruiting-body protein measurements with transcriptome analysis to compare soybean meal supplied through soil application or exogenous nutrient bags and to characterize tissue-specific responses in the cap and stipe. Soybean meal increased protein content in an application method-, concentration-, and tissue-dependent manner. Soil application was more effective than nutrient-bag supplementation, while stipes exhibited a stronger transcriptional response than caps. RNA sequencing detected 11,982 expressed genes and revealed both shared and tissue-specific responses to the two supplementation methods. Gene Ontology analysis showed broadly similar functional categories among comparison groups, whereas KEGG enrichment analysis revealed distinct metabolic responses. In caps, soil application was associated with glutathione metabolism and amino sugar and nucleotide sugar metabolism, while nutrient-bag supplementation was associated with the pentose phosphate pathway, glyoxylate and dicarboxylate metabolism, and pentose and glucuronate interconversions. In stipes, the genes involved in ribosome and aminoacyl-tRNA biosynthesis were downregulated under soil application and nutrient-bag supplementation, respectively. Weighted gene co-expression network analysis identified three modules associated with protein content and highlighted ribosome, aminoacyl-tRNA biosynthesis, glycerophospholipid metabolism, and arginine biosynthesis as candidate pathways. The most highly connected genes in each key module were identified as hub genes, and selected expression patterns were supported by qRT-PCR. These findings provide a transcriptomic framework for understanding how soybean meal supplementation is associated with protein accumulation and tissue-specific physiological responses in Morchella.

The artificially cultivated edible mushroom Stropharia rugosoannulata is widely promoted and cultivated in China because of its ability to efficiently decompose agricultural and forestry waste. However, methods for CRISPR/Cas9 genome editing have not yet been established for S. rugosoannulata. In this study, we identified three SrU6 promoters in S. rugosoannulata and constructed the CRISPR/Cas9 expression vector GPiE-SrU6. Moreover, we found that mutant strains were obtained only when the expression of the single guide RNA (sgRNA) was driven by the SrU6-3 promoter. We subsequently employed a tandemly repeated SrU6-tRNA-sgRNA module to knock out two sites within the ura3 gene. The expression vector was introduced into the mycelium via Agrobacterium-mediated transformation (ATMT). Following dual selection with 60 μg/mL hygromycin (Hyg) and 0.2 mg/mL 5-fluoroorotic acid (5-FOA), stable transformants were obtained and subcultured. The mutation efficiency at the targeted ura3 locus was subsequently assessed. The CRISPR/Cas9 system successfully disrupted the target marker gene (ura3), achieving an editing efficiency of 14.9%. In summary, this study reports the first successful establishment of a CRISPR/Cas9 genome editing system in S. rugosoannulata. This study not only meets a future need for genetic manipulation tools for S. rugosoannulata but also provides a robust platform for engineering superior strains for eco-circular agriculture.

Spent mushroom substrate (SMS) return is a vital strategy for agricultural waste recycling and soil fertility improvement, yet its ecological impacts of duration remain poorly understood. This study employed metagenomic sequencing to explore soil fertility, microbial dynamics, and nitrogen cycling across different SMS return durations (0, 1, and 3 years) within rice-mushroom crop rotation systems. Soil nutrients (organic matter, total nitrogen, total phosphorus) initially decreased and then increased throughout the rice growth cycle. The one-year return (y1) induced early nutrient depletion, whereas the three-year return (y3) significantly enhanced late-stage nutrient accumulation. With increasing duration, bacterial and archaeal assembly shifted from stochastic toward deterministic processes, while fungal diversity and stochasticity decreased continuously. Co-occurrence network analysis demonstrated that SMS return increased network complexity and intercommunity competition. This transition was accompanied by a functional shift in keystone taxa from those responsive to exogenous organic matter in y1 to those mediating nitrogen fixation, anammox, and sulfur metabolism in y3. Nitrogen cycling in y1 increased potential N2O emission risks through nirS upregulation and nosZ downregulation, whereas y3 mitigated inorganic nitrogen loss by upregulating gene abundances of ammonia assimilation, nitrification, and DNRA genes. Notably, the structure of nitrogen-cycling genes fluctuated in y1 but was resilient to y0 levels in y3. These findings demonstrated that while initial SMS return triggered ecological fluctuations and environmental risks, continuous return (y3) achieved functional stability by reshaping microbial niches. This study highlights the importance of SMS return duration in balancing soil fertility enhancement with environmental risk mitigation in sustainable paddy ecosystems.

Glutathione reductase (GR) is essential for maintaining cellular redox homeostasis by sustaining reduced glutathione (GSH) levels. In Hypsizygus marmoreus, GR silencing led to impaired mycelial growth, elevated reactive oxygen species (ROS) accumulation, and disrupted antioxidant enzyme activity, ultimately hindering fruiting body development. Mitochondrial size was markedly reduced in GR-silenced strains, indicating compromised cellular metabolism. Supplementation with the reducing agent vitamin C (Vc) partially restored redox balance and enzyme activity in a developmental stage–dependent manner, alleviating the defects caused by GR suppression. Moreover, GR was found to influence lignocellulose-degrading enzyme activity, further linking redox regulation to substrate utilization. Overall, these findings demonstrate that GR plays a central role in coordinating redox balance, energy metabolism, and enzyme function in H. marmoreus, providing new insights for enhancing industrial mushroom production through antioxidant regulation.

Ulcerative colitis is a common inflammatory bowel disease. This study evaluated the protective effect and potential mechanism of Stropharia rugosoannulata polysaccharide (SP-1a) and its carboxymethylated and phosphorylated derivatives (CSP-1a and PSP-1a) against dextran sulfate sodium (DSS)-induced ulcerative colitis. The results showed that treatment with SP-1a and its derivatives alleviated the symptoms of weight loss, colon shortening, and blood in the stool induced by . SP-1a and its derivatives restore the integrity of the intestinal barrier by controlling the expression of tight junction proteins. Furthermore, they play an anti-inflammatory role by reducing oxidative stress and inhibiting the expression of pro-inflammatory factors, pro-inflammatory proteins, and nuclear factor kappa-B (NF-κB) signaling pathways. The anti-inflammatory effects of CSP-1a and PSP-1a were greater than those of SP-1a. These results indicate that SP-1a could be a potential natural medicine to protect against DSS-induced colitis.

This study explored the use of ionic liquid-ultrasound (ILU)-assisted extraction to enhance the extraction rate of Platycodon grandiflorum saponins (PGSs), and the content, extraction mechanism, antioxidant activity, whitening, and antiaging activity of PGSs prepared using ILU, ultrasound-water, thermal reflux-ethanol, and cellulase hydrolysis were compared. The ILU method particularly disrupted the cell wall, improved PGS extraction efficiency, and yielded a high total saponin content of 1.45 +/- 0.02 mg/g. Five monomeric saponins were identified, with platycodin D being the most abundant at 1.357 mg/g. PGSs displayed excellent in vitro antioxidant activity and exhibited inhibitory effects on tyrosinase, elastase, and hyaluronidase. The results suggest that PGSs may have broad antioxidant, skin-whitening, and antiaging potential to a large extent. Overall, this study provided valuable insights into the extraction, identification, and bioactivities of PGSs, which could serve as a reference for future development and application of these compounds in the functional foods industry.

IntroductionThe artificial cultivation of morels has been a global research focus owing to production variability. Understanding the microbial ecology in cultivated soil is essential to increase morel yield and alleviate pathogen harm.MethodsA total of nine Morchella cultivation experiments in four soil field types, forest, paddy, greenhouse, and orchard in Shanghai city were performed to determine the potential ecological relationship between Morchella growth and soil microbial ecology.ResultsGenerally, significant variation was observed in the soil microbial diversity and composition between the different experimental field types. The niche width analysis indicated that the bacterial habitat niche breadth was significantly greater than the fungal community width, which was further confirmed by a null model that revealed that homogeneous selection could explain 46.26 and 53.64% of the variance in the bacterial and fungal assemblies, respectively. Moreover, the neutral community model revealed that stochastic processes dominate the bacterial community in forests and paddies and both the bacterial and fungal communities in orchard crops, whereas deterministic processes mostly govern the fungal community in forests and paddies and both the bacterial and the fungal communities in greenhouses. Furthermore, co-occurrence patterns were constructed, and the results demonstrated that the dynamics of the soil microbial community are related to fluctuations in soil physicochemical characteristics, especially soil potassium. Importantly, structural equation modeling further demonstrated that the experimental soil type significantly affects the potassium content of the soil, which can directly or indirectly promote Morchella yield by inhibiting soil fungal richness.DiscussionThis was the first study to predict morel yield through soil potassium fertilizer and soil fungal community richness, which provides new insights into deciphering the importance of microbial ecology in morel agroecosystems.

Temperature and moisture belong to the most important environmental factors affecting the growth and development of fungi. However, the effect of temperature on the mycelia of the edible Morchella mushrooms has not been determined. Here, a comprehensive analysis was performed to determine the influence of culture temperature on 13 strains of mycelia of three Morchella species (Morchella sextelata, Morchella septimelata, and Morchella importuna) at 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C. The mycelial branching and growth rate data showed that 15–20 °C was a suitable temperature range for the mycelial growth of the 13 Morchella strains. RNA sequences revealed that a total of 2843, 2404, 1973, 1572, and 1866 differentially expressed genes (DEGs) were identified at 5 °C, 10 °C, 15 °C, 25 °C, and 30 °C compared with 20 °C. A Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis further indicated that the purine nucleotide and tyrosine metabolism pathways were crucial for mycelium development. Moreover, the enrichment of autophagy of mitochondria, regulation of cell morphogenesis, and piecemeal microautophagy of the nuclei at 25 °C (vs. 20 °C) indicated the damage caused by heat stress in Morchella mycelia. Notably, a total of four unique module eigengenes (MEs) were identified through a weighted gene coexpression network analysis (WGCNA). Among them, 2293 genes in the turquoise module were significantly positively correlated with temperature (r = 0.946, p < 0.001), whereas 739 genes in the blue module were significantly negatively correlated with temperature (r = −0.896, p < 0.001), suggesting that the effect of high temperatures on mycelial genes was significantly greater than that of low temperatures. Moreover, the coexpression network indicated that high culture temperatures accelerated the oxidative stress response and energy metabolism in mycelia, while upregulation of purine nucleotide catabolism and ribosomal protein-related genes were improved by low-temperature tolerance. In addition, the upregulated expression of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and heat shock protein (HSP) genes in mycelia was associated with reactive oxygen species (ROS)-mediated damage at high temperatures. Overall, this study provides an important theoretical basis and application value for optimizing Morchella cultivation techniques.

IntroductionCurrently, straw biodegradation and soil improvement in rice-mushroom rotation systems have attracted much attention. However, there is still a lack of studies on the effects of rice-mushroom rotation on yield, soil properties and microbial succession.MethodsIn this study, no treatment (CK), green manure return (GM) and rice straw return (RS) were used as controls to fully evaluate the effect of Stropharia rugosoannulata cultivation substrate return (SRS) on soil properties and microorganisms.ResultsThe results indicated that rice yield, soil nutrient (organic matter, organic carbon, total nitrogen, available nitrogen and available potassium) and soil enzyme (urease, saccharase, lignin peroxidase and laccase) activities had positive responses to the rice-mushroom rotation. At the interannual level, microbial diversity varied significantly among treatments, with the rice-mushroom rotation significantly increasing the relative alpha diversity index of soil bacteria and enriching beneficial microbial communities such as Rhizobium, Bacillus and Trichoderma for rice growth. Soil nutrients and enzymatic activities were significantly correlated with microbial communities during rice-mushroom rotation. The fungal-bacterial co-occurrence networks were modular, and Latescibacterota, Chloroflexi, Gemmatimonadota and Patescibacteria were closely related to the accumulation of nutrients in the soil. The structural equation model (SEM) showed that fungal diversity responded more to changes in soil nutrients than did bacterial diversity.DiscussionOverall, the rice-mushroom rotation model improved soil nutrients and rice yields, enriched beneficial microorganisms and maintained microbial diversity. This study provides new insights into the use of S. rugosoannulata cultivation substrates in the sustainable development of agroecosystems.

Cultivation of Stropharia rugosoannulata with straw in forestland is effective for straw biodegradation and can prevent the waste of straw resources and environmental pollution and generate economic benefits. However, there is a lack of systematic evaluation of spent mushroom substrate (SMS) input into forestland, such as soil properties and microbial succession. In this experiment, 0 (CK), 10 (SA), 20 (SB), 30 (SC), 40 (SD), and 50 (SE) kg/m2 straw were used to cultivate S. rugosoannulata, and two soil layers (0-10 cm, 10-20 cm) of the cultivated forestland were analyzed. The results indicated that SMS significantly promoted nutrient accumulation in forestland. The bacterial alpha diversity in the SC treatment group was greater than that in the control and gradually decreased to the control level with interannual changes, while the trend of fungal alpha diversity was opposite to that of bacterial alpha diversity. Furthermore, the SC treatment group positively affected soil nitrogen metabolism -related microorganisms for two consecutive years and significantly promoted tree growth. Habitat niche breadth and null model analysis revealed that bacterial communities were more sensitive than fungal communities after SMS input. Linear mixed model (LMM) analysis revealed that SMS supplementation significantly positively affected bacteria (Gammaproteobacteria and Bacteroidota) and significantly negatively affected fungi (Coniochaetales). The constructed fungal -bacterial co -occurrence networks exhibited modularity, and the five types of bacteria were significantly correlated with soil organic matter (SOM), soil organic carbon (SOC), available potassium (AK), available phosphorus (AAP) and available nitrogen (AN) levels. The structural equation model (SEM) showed that bacterial diversity responded more to changes in soil nutrients than did fungal diversity. Overall, 30 kg/m2 of straw decomposition and 2 years of continuous cultivation were beneficial to soil health. This study provides new insights into the rational decomposition of straw and maintenance of forestland ecological balance by S. rugosoannulata.

Stropharia rugosoannulata has been used in environmental engineering to degrade straw in China. The nitrogen and carbon metabolisms are the most important factors affecting mushroom growth, and the aim of this study was to understand the effects of different nitrogen levels on carbon metabolism in S. rugosoannulata using transcriptome analysis. The mycelia were highly branched and elongated rapidly in A3 (1.37% nitrogen). GO and KEGG enrichment analyses revealed that the differentially expressed genes (DEGs) were mainly involved in starch and sucrose metabolism; nitrogen metabolism; glycine, serine and threonine metabolism; the MAPK signaling pathway; hydrolase activity on glycosyl bonds; and hemicellulose metabolic processes. The activities of nitrogen metabolic enzymes were highest in A1 (0.39% nitrogen) during the three nitrogen levels (A1, A2 and A3). However, the activities of cellulose enzymes were highest in A3, while the hemicellulase xylanase activity was highest in A1. The DEGs associated with CAZymes, starch and sucrose metabolism and the MAPK signaling pathway were also most highly expressed in A3. These results suggested that increased nitrogen levels can upregulate carbon metabolism in S. rugosoannulata. This study could increase knowledge of the lignocellulose bioconversion pathways and improve biodegradation efficiency in Basidiomycetes.

In order to effectively utilize Stropharia rugosoannulata residue,the effects of in-situ returning of S. rugosoannulata residue on soil nutrient（organic matter and nitrogen,phosphorus,potassium） content,soil enzyme（phosphatase and dehydrogenase） activities,and soil fungal diversity were studied.The results showed that compared with CK,returning of S. rugosoannulata residue significantly reduced soil pH,neutralized soil acidity and alkalinity,and significantly increased the organic matter content of the field soil,as well as the content of total nitrogen,available nitrogen,total phosphorus,available phosphorus,total potassium and available potassium.The soil phosphatase and soil dehydrogenase activities of the treatment group with S. rugosoannulata residue were significantly higher than those of CK,with increases of over 30% and over 40%,respectively.The soil fungal diversity of S. rugosoannulata residue treatment group was lower than that of CK soil.The dominant bacterial groups in the soil of treatment group were Hypocreales,Russulaceae,Pezizales,Saccharomycetales and Bursaria;and the dominant bacterial groups in CK soil were Pseudoplatyophyra,Aleuria,Onygenales,Trichosporon,Sordariomycetes,Sordariales and Basidiomycota.

This study evaluates the chemical structure of a heteropolysaccharide (SP-1a) from the fruiting bodies of Stro-pharia rugosoannulata and the antioxidant activity and enzyme inhibitory activity of its derivatives. The results showed that SP-1a (2.29 x104 Da) contained fucose, glucose and galactose, and possessed the backbone of [-> 3)-alpha-D-Glcp-(1 ->] and [-> 3,6)-alpha-D-Glcp-(1 ->] with side chains [-> 6)-alpha-D-Galp-(1 ->] and T-alpha-D-Galp. Furthermore, carboxymethylated and phosphorylated modification of SP-1a (named as CSP-1a and PSP-1a) had good thermal stability and strong rehydration. Moreover, CSP-1a displayed stable DPPH scavenging ability (46.77%) and reducing power ability (0.434), as well as alpha-glucosidase inhibitory activity (60.98%) and alpha-amylase inhibitory activity (67.20%). Besides, PSP-1a presented significant hydroxyl radical scavenging ability (94.18%). The findings suggested that appropriate chemical modifications can improve the physicochemical properties and biological activities of polysaccharides from Stropharia rugosoannulata, providing hints and theoretical supports for further development of corresponding drug or food ingredients.

The cultivation of Agaricus bisporus was investigated with two commercial strains, A15 and W192. Nitrogen and lignocellulose were analyzed in absolute amounts based on mass balance to accurately compare the degradation efficiency of the compost, and the correlation between the degradation efficiency and extracellular enzyme activity of the mycelium was analyzed. Lignocellulose utilization efficiency positively correlated with mushroom yield. For the same strain, the compost with high lignocellulose content resulted in high utilization efficiency, which increased the yield of A. bisporus. For the same compost, the lignocellulose utilization efficiency of A15 was higher than that of W192. The activities of manganese-dependent peroxidase and β-glucosidase indicated that W192 may have a higher demand for lignin and cellulose. Therefore, a higher yield of W192 was obtained with high-lignocellulose compost. The metabolism of cellulose and hemicellulose in the mycelial growth stage seemed to be conducive to high mushroom yield.

To prepare zinc and selenium modified polysaccharides derivatives (ZnLEP-1a and SeLEP-1a), a novel poly-saccharide (LEP-1a) isolated from Lachnum YM38 was chosen. Following that, the structural characterization and in vitro bioactivities of LEP-1, ZnLEP-1a and SeLEP-1a were investigated. Results revealed that LEP-1a had a molecular weight of 5.69 x 104 Da and was composed of mannose, galactose and glucose. The linkage types of LEP-1a were proved to be (1 ->)-alpha-D-Manp, (1 -> 3)-alpha-D-Manp, (1 -> 2)-alpha-D-Galp, (1 -> 2)-alpha-D-Glcp, (1 -> 2,6)-alpha-D-Manp. Zinc content of ZnLEP-1a was 0.69 mg/g, while selenium content of SeLEP-1a was 206.99 mu g/g. Compared with LEP-1a, ZnLEP-1a and SeLEP-1a had a lower molecular weight, same monosaccharides in different molar ratios. The results of FT-IR, DSC, NMR, SEM and AFM suggested that there were obvious changes in structural characteristics after LEP-1a was modified with zinc and selenium. ZnLEP-1a and SeLEP-1a had stronger anti-oxidant, hypoglycemic, antitumor activities in vitro in comparison with LEP-1a. As a result, ZnLEP-1a and SeLEP-1a showed great potential to develop into a natural antioxidant, hypoglycemic and low-toxic antitumor drug.

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.

Umami peptides can supplement and enhance the overall taste of food, making it more harmonious, soft, and full-bodied. Stropharia rugoso-annulata mushroom is famous for its umami and pleasant flavor, however, there were no report on its umami peptides. In this study, umami peptides from S. rugoso-annulata were isolated and characterized, as well as to analyze the action mechanism in silico molecular docking approach. By ultrafiltration, gel filtration chromatography, HPLC, and UHPLC-Q-Orbitrap-MS2, five peptides, EPLCNQ, SGCVNEL, PHEMQ, SEPSHF, and ESCAPQL were identified. According to the sensory evaluation and electronic tongue analysis, they had good umami activity and their umami threshold values were in the range of 0.167-0.390 mmol/L. EPLCNQ and SGCVNEL had higher umami intensity than others. Molecular docking of the identified peptides with the umami taste receptor T1R1/T1R3 indicated that the peptides can enter the binding pocket in the Venus flytrap domain of T1R3 cavity, wherein Glu45, Ser104, and His145 may play major roles in the binding interactions of peptides and receptor, forming more stable hydrogen bonds to producing strong umami taste. The study expands the source range of umami peptides and potential raw material of value-added umamiflavorings, and provides further insight into understanding the flavor mechanisms of mushrooms.

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.