Auricularia heimuer is a valuable traditional Chinese fungus used as food and medicine. Hei29 is a strain derived from wild A. heimuer through systematic domestication and selection. It has been the primary A. heimuer variety in Northeast China for 30 years and offers the advantages of high yield, good commercial property, and stable traits. This study used protoplast nucleation on Hei29 to produce two amiable and paired monokaryons, Hei29-D1 and Hei29-D2. The genome of Hei29 was sequenced utilizing the Illumina PE150 and PacBio Sequel sequencing platforms. Hei29-D1 and Hei29-D2 had genomic sizes of 47.54 Mb and 47.49 Mb, GC contents of 56.95% and 56.99%, and an N50 of 2.37 Mb and 4.28 Mb, respectively. Hei29’s genome possessed two phytoene synthase (PSY) protein genes, one of which—PSY encoded by g894—has a transmembrane domain. The phylogenetic tree showed that Hei29 shared the closest evolutionary relationship with Auricularia subglabra TFB-10046 SS5. Collinearity analysis showed that the correlation between the two monokaryons was as high as 90.81%. Cluster analysis revealed that Hei29 contains 12,362 core genes, 223 unique genes in Hei29-D1, and 228 unique genes in Hei29-D2. This study is the first to sequence two related and paired monokaryons from A. heimuer, which is critical for fully understanding the genetic composition and information of the characteristic strain of A. heimuer in Northeast China. It establishes the data and theoretical foundation for gene mining, usage, and molecular breeding. It further promotes the genetic breeding and active substance utilization of A. heimuer.

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.

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.

This paper systematically reviews the research progress on the physiological functions, gene cloning, classification basis, and expression regulation mechanisms of laccase in edible and medicinal fungi. Laccase is a copper-containing polyphenol oxidase widely distributed in these fungi, characterized by broad-spectrum substrate catalytic activity and redox properties. It plays a central role in lignin degradation, pigment synthesis, and environmental pollutant treatment. Regarding gene cloning, researchers have successfully isolated and identified laccase genes from multiple species using techniques such as transcriptome sequencing, RACE amplification, and gene knockout. Expression regulation studies have revealed that laccase genes exhibit stage-specific expression patterns during mycelial growth, fruiting body development, and lignin degradation. In recent years, breakthroughs in genomics, transcriptomics, and gene editing technologies have greatly advanced research into the cloning, classification, and regulatory mechanisms of laccase genes. This article systematically reviews the diversity, clonal classification, and regulatory mechanisms of these genes, aiming to provide a reference for further research and industrial development of laccase in edible and medicinal fungi.

Auricularia heimuer is an important cultivated edible mushroom in China. This study used the early maturity, chrysanthemum-shaped, high yield strain “8808” and the late-maturity, single-shaped, high-quality strain “HW15” as parental strains. The objective was to develop a new strain of A. heimuer combining early maturity with excellent quality through protoplast fusion. Protoplasts from the parental strains were fused using a polyethylene glycol (PEG)-mediated method. The obtained hybrids were identified through clamp connection, antagonism tests, esterase isozyme analysis, and Inter-Simple Sequence Repeat (ISSR) molecular marker techniques, followed by ultimate selection through cultivation. Among the evaluated hybrids, strain R33 exhibited desirable agronomic traits: primordium formation occurred 4 days earlier than the parental strain HW15, harvest time was advanced by 6 days, yield increased by 14.7%, and the ratio of absorbed water improved by 29.8%. Transcriptomic analysis revealed that starch and sucrose metabolism as well as amino acid metabolism pathways were significantly upregulated in R33, which may be associated with its early maturity and high-yield phenotype. Overall, protoplast fusion technology can be used to create promising candidate strains that combine early maturity, high yield, and excellent quality.