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Functional Analysis of Agaricus bisporus Serine Proteinase 1 Reveals Roles in Utilization of Humic Rich Substrates and Adaptation to the Leaf-Litter Ecological Niche

Summary

This research investigated how button mushrooms (Agaricus bisporus) break down complex organic matter in soil and compost using a special enzyme called SPR1. The study showed this enzyme is crucial for the mushroom’s ability to obtain nutrients and grow successfully. This has important implications for understanding soil health and carbon cycling in natural environments. Impacts on everyday life: • Helps explain how mushrooms contribute to natural decomposition and nutrient recycling in garden soil and compost • Provides insights into sustainable mushroom cultivation practices • Advances understanding of soil fertility and health in gardens and natural environments • Contributes to knowledge about carbon storage in soil which affects climate change • Demonstrates the importance of proper soil management to maintain beneficial fungal activity

Background

Agaricus bisporus is a secondary decomposer fungus that grows well on partially-decomposed plant material and is abundant in composted leaf and needle litter found in temperate forest soils. Serine proteinase activity has been identified as the major extracellular proteinase produced by A. bisporus mycelium growing in compost, where nitrogen is largely sequestered in protein and microbial biomass forms. The SPR1 enzyme is produced in response to humic-associated protein rather than other nitrogen sources, suggesting a nutritional role.

Objective

To elucidate the importance of humic-regulated serine proteinases in nutrient acquisition by conducting a transgenic analysis of the Spr1 gene in A. bisporus. The study aimed to understand the role of SPR1 in allowing the fungus to access nitrogen from complex sources and adapt to humic-rich environments.

Results

Transformation resulted in 39 stable transformants, of which 13 showed reduced protease production. Four transformants showed significantly lower serine proteinase activity compared to controls when grown with humic fraction as nitrogen source. A strong correlation was found between Spr1 transcript levels and enzyme activity. One transformant failed to colonize compost while four others showed significantly reduced mushroom yields, demonstrating SPR1’s crucial role in supporting growth on complex substrates.

Conclusion

SPR1 plays a critical role in A. bisporus adaptation to humic-rich substrates by enabling nutrient acquisition from complex sources. The enzyme is essential for normal colonization of compost and mushroom production. Results demonstrate that SPR1 is a key determinant in nitrogen and carbon cycles within the humic-rich ecological niche formed during plant material degradation in soil.
  • Published in:Environmental Microbiology,
  • Study Type:Experimental Study,
  • Source: 10.1111/1462-2920.13350
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