Integrated Transcriptomics and Metabolomics Provide Insight into Degeneration-Related Molecular Mechanisms of Morchella importuna During Repeated Subculturing

Summary

Morel mushrooms (Morchella importuna) lose quality when repeatedly grown from cultured samples, a process called strain degeneration. Scientists found that degenerated strains have lower levels of beneficial compounds called flavonoids, which normally protect mushroom cells from damage. By studying gene expression and metabolite changes, researchers identified a specific gene responsible for making these protective flavonoids, which becomes less active in degenerated strains. This research suggests that avoiding frequent reculturing and maintaining cold storage or adding antioxidants could help preserve healthy morel mushroom strains.

Background

Morchella importuna is a highly valued edible fungus that undergoes degeneration during repeated subculturing, manifesting as reduced mycelial growth, altered pigmentation, and decreased productivity. The specific molecular mechanisms underlying this degeneration remain poorly understood, though existing studies suggest involvement of viral infections, reduced enzyme synthesis, harmful substance accumulation, and genetic/epigenetic changes.

Objective

This study aimed to investigate the molecular mechanisms of M. importuna strain degeneration during repeated subculturing using integrated metabolomics and transcriptomics analyses, with particular focus on secondary metabolite biosynthesis and gene expression changes.

Results

Analysis identified 699 differentially expressed metabolites (DEMs) and 2691 differentially expressed genes (DEGs), with enrichment in secondary metabolite biosynthesis pathways, particularly flavonoid and indole alkaloid biosynthesis. A non-reducing polyketide synthase (NR-PKS) gene was identified as critical for flavonoid biosynthesis, showing significantly reduced expression in degenerated strains. Total flavonoid content was 1.43 times higher in normal mycelia, with 15 of 35 tested flavonoid compounds showing significantly decreased levels in degenerated strains.

Conclusion

M. importuna degeneration results from systemic dysregulation of gene expression networks and metabolic pathway reorganization, particularly in secondary metabolite biosynthesis. Decreased intracellular flavonoids weaken antioxidant capacity and cause oxidative damage leading to degeneration. Prevention strategies should include avoiding frequent subculturing and potentially employing low-temperature dormancy or antioxidant supplementation.
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