High-temperature stress is a key factor that reduces the yields of edible fungi. Auricularia heimuer (A. heimuer) is a nutrient-rich edible fungus that is widely cultivated in China. In this study, we analyzed the physiological, transcriptomic, and metabolomic results of A. heimuer (variety “Hei29”) under high-temperature stress. Our findings revealed that high temperatures (30 °C and 35 °C) significantly reduced hyphal growth, increased malondialdehyde content and antioxidant enzyme activity, and enhanced the accumulation of secondary metabolites, such as phenolic compounds and flavonoids. A total of 15 candidate genes potentially responsive to high-temperature stress were identified through transcriptomic analysis, including those involved in regulating antioxidant defense, heat shock response, sugar metabolism, amino acid metabolism, and accumulating secondary metabolites. Metabolomic analysis identified three candidate metabolites potentially responsive to high-temperature stress, including kinetin, flavonoids, and caffeic acid, as well as several metabolic pathways, including nucleotide metabolism, ABC transporters, and cofactor biosynthesis. These mechanisms help mitigate oxidative damage to cellular structures and energy deficits caused by elevated temperatures, enabling the fungus to maintain cellular stability, metabolic function, and growth under heat stress. This study is the first to explore the molecular mechanism of A. heimuer in response to high-temperature stress. The results provide valuable insights into the molecular mechanisms of heat stress tolerance in A. heimuer, highlighting potential targets for developing heat-tolerant strains for industrial application.

Morels (Morchella spp.) are medicinal and edible mushrooms, renowned for their distinctive taste and appearance. Due to the low yields and difficulty of foraging wild morels, artificial cultivation has significant economic value. Outdoor cultivation yields are influenced by factors such as weather and diseases, which can result in crop instability or failure, thereby causing losses to farmers. Previous studies have typically concentrated on either the fungal or bacterial communities. In this study, we investigated the ecological relationships between morel growth and both the fungi and bacteria in soil, analyzed over multiple trophic levels. We investigated three soil types: soil in which morel death was observed (DM), soil in which no morels emerged (UM), and soil that is suitable for normal fruiting (NM). We used high-throughput ITS and 16S rDNA amplicon sequencing, alongside assessment of soil physicochemical properties, to investigate factors contributing to morel emergence and death. The results indicated that the richness and diversity of both fungal and bacterial communities in the normal fruiting soil (NM) were significantly higher than those in the non-fruiting soils (DM and UM). The bacterial community was primarily composed of Proteobacteria and Bacteroidota, while the fungal community was dominated by Ascomycota and Mucoromycota. Furthermore, Morchella was significantly enriched in NM, indicating that it had successfully colonized and could develop into fruiting bodies. The morel mycelium in NM effectively utilized external nutrient bags, enhancing the soil nitrogen and organic matter content while reducing the consumption of available phosphorus and potassium. LEfSe and random forest analyses identified Pedobacter and Massilia as biomarkers of NM, potentially associated with the symbiosis of Morchella, which may promote its growth. Furthermore, the construction of the fungal-bacterial co-occurrence network revealed that the NM soil exhibited a higher number of nodes and greater network stability, suggesting that its complex microbial community structure may play a crucial role in the successful cultivation of Morchella. Our results indicate that the failures in morel production were due to inadequate management practices. Elevated greenhouse temperatures may have promoted pathogen proliferation, hindering the effective utilization of external nutrient bags by morel mycelium. Consequently, the mycelium was unable to accumulate nutrients efficiently, leading to the inability of Morchella to fruit or resulting in developmental failures. This study offers valuable insights into the interactions between morel mycelium and soil microorganisms, elucidating the reasons for morel cultivation failure and suggesting strategies for optimizing morel cultivation.

Lepista sordida is a type of high-quality rare edible and medicinal mushroom, and its research boom is just beginning. More than 80 million tons of grain crop residues are produced each year in Heilongjiang Province. To realize the exploration and utilization of wild L. sordida mushrooms and also provide a theoretical support for the high-value utilization of these resources in Heilongjiang Province, we evaluated the cultivation of L. sordida mushrooms using rice straw, corncob, and soybean straw as substrates. L. sordida grew on all three substrates, and the biological efficiency and yield of the mushrooms grown on soybean straw and corncob were 32.33 ± 1.78% and 4.20 ± 0.23 kg m⁻², and 30.15 ± 0.93% and 3.92 ± 0.12 kg m⁻², respectively, which increased by 9.38% and 2.08% compared with that on the rice straw substrate with 3.84 ± 0.12 kg m⁻² and 29.56 ± 0.89%. The time it took for the mycelia to colonize and initiate primordia on the soybean straw substrate was 22.33 ± 0.58 d and 19.67 ± 0.58 d, respectively, which was delayed by 2 d and 3 d compared with that on the rice straw substrate with 20.67 ± 2.08 d and 16.33 ± 0.58 d, respectively. The fruiting bodies grown on corncob and soybean straw substrates were relatively larger than those on the rice straw substrate. The highest amount of crude protein was 57.38 ± 0.08 g 100 g⁻¹, and the lowest amount of crude polysaccharide was 6.03 ± 0.01 g 100 g⁻¹. They were observed on mushrooms collected from the corncob substrate. The contents of the heavy metal mercury, lead, arsenic, and cadmium in the fruiting bodies grown on each substrate were within the national safety range.

In this study, the molecular mechanism underlying melanin synthesis within the fermentation broth of Auricularia heimuer (A. heimuer) was explored. The absorbance at 500 nm, melanin yield, and tyrosinase activity in the fermentation broth were assessed across different fermentation durations. Mycelia samples were gathered on the 4th (R1), 8th (R2), and 10th (R3) days of liquid fermentation for transcriptome sequencing. As fermentation progressed, the absorbance, melanin yield, and tyrosinase activity in the broth rose. A total of 5915 differentially expressed genes (DEGs) were detected, with 1136 DEGs between R2 and R1, 3717 between R3 and R1, and 2950 between R3 and R2. Gene Ontology (GO) analysis showed that DEGs were significantly enriched in oxidoreductase activity and ribosome structural constituent terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed significant enrichment of DEGs in ribosome and amino acid metabolism pathways. Key DEGs, including transcription factors, glycosidases, P450 enzymes, laccases, and glutamate dehydrogenase, were identified during melanin production in the fermentation broth. These DEGs may play crucial roles in melanin synthesis. This study offers a foundation for further exploring the melanin synthesis mechanism in A. heimuer fermentation broth.

Mudanjiang is a major producer of black wood ear (Auricularia heimuer) mushrooms in China. It has been estimated that more than 1.5 million tons of spent substrates of A. heimuer (SSA) are produced each year. Most of these are discarded or burned and have become an important source of pollution, which urgently merits research to find appropriate uses for them. To explore the feasibility of SSA as a substrate for cultivating Lepista sordida mushrooms, experiments were conducted to assess the effects of the addition of 0, 40%, 73%, and 98% SSA on the days required for the mycelia to fully colonize the substrate and initiate primordia, biological efficiency (BE), yield, and composition of the chemical biomass of the L. sordida fruiting bodies. The yield of fruiting bodies with 0, 40%, 73%, and 98% SSA supplementation for three flushes was 3.90 ± 0.74 kg m⁻², 4.06 ± 0.77 kg m⁻², 4.03 ± 0.62 kg m⁻², and 4.51 ± 0.65 kg m⁻², respectively. The addition of 98% SSA significantly delayed the number of days for the mycelia to fully colonize and form primordia by 6 and 3 d, respectively. This treatment also significantly increased the yield and BE by 15.64% compared with that of the control group. The crude polysaccharide content of 25.64 ± 0.38 g 100 g⁻¹ was higher in the samples grown on the 98% SSA substrate, which was shown to increase by 78.93% compared with that of the control substrate with 73% corn straw (14.33 ± 0.03 g 100 g⁻¹). The content of crude protein of 51.10 ± 0.08 g 100 g⁻¹ was higher in the samples grown on the 40% SSA substrate, which increased by 11.14% compared with the protein content of the control group. This study reveals that SSA would be a good substrate for the cultivation of L. sordida and is an efficient, promising, and cost-effective substrate additive that can improve the quality and yield of these mushrooms, while substantially reducing the problems of disposing of SSA.

The molecular mechanisms of mycelial degeneration during subculturing of Auricularia heimuer strain ‘HWS1908’ were investigated across generations G1 to G20. With successive subculturing, mycelial growth rate and compactness declined, cellulase and laccase activities decreased significantly, whereas antioxidant enzyme activities increased. Comparative transcriptome analysis between G1 and G20 identified 2643 differentially expressed genes (DEGs). Gene Ontology (GO) analysis indicated that the DEGs were significantly enriched in terms associated with protein refolding, response to reactive oxygen species, and ferroxidase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed significant enrichment of DEGs in pathways including phenylpropanoid biosynthesis, peroxisome, fatty acid degradation, and longevity-regulating pathways. Key DEGs, including transcription factors, glycoside hydrolases, lignin-modifying enzymes, chitin synthases, chitinases, ornithine decarboxylase, and Ras/Rho signaling pathway components (Sos, Ras, Rac1), were identified. These genes may be associated with the progressive decline of mycelial vigor, cell wall integrity, and substrate utilization capacity. These findings provide a basis for further exploration of the molecular mechanisms of strain degeneration in A. heimuer, and a practical recommendation to limit subcultures to within 20 generations for maintaining high vitality.