Analysis of the Subculture Effect on the Auricularia heimuer Strain ‘HWS1908’ Based on Transcriptome

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.