Overexpression of cat2 restores antioxidant properties and production traits in degenerated strains of Volvariella volvacea

Strain degeneration is an important factor hindering the development of the edible fungus industry. Strain degeneration is associated with the excessive accumulation of reactive oxygen species (ROS) in vivo. Catalase (CAT), an important antioxidant enzyme, can promote the clearance of ROS. In this study, the cat2 gene of Volvariella volvacea was first cloned into an overexpression plasmid via homologous recombination. Finally, through Agrobacterium-mediated transformation, this plasmid was inserted into degenerated strains of V. volvacea T19. The physiological properties, antioxidant properties, ROS content, matrix degradation activity, and cultivation properties of the transformants were tested. The results showed that the cloned cat2 gene was 99.94% similar to the reference sequence. Screening revealed that six positive transformants were successfully obtained. After the overexpression of cat2, the growth rate and biomass of the mycelium increased significantly in the transformant strains (versus the V. volvacea T19 degenerated strains). Moreover, the accumulation of superoxide radical (O2•-) and hydrogen peroxide (H2O2) was significantly reduced, and the activity of the enzymes CAT, superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPX) was significantly increased. Meanwhile, the expression of cat2, Mnsod1, Mnsod2, gpx, and gr was significantly upregulated, and the activity of eight matrix degradation-related enzymes was increased to varying degrees. More importantly, the overexpression of the cat2 gene promoted the regrowth of fruiting bodies in degenerated strains of V. volvacea T19. This study provides a new biotechnological strategy to control the degeneration of V. volvacea and other edible fungi.