Functional characterization of a catalase gene PtCat associated with sclerotia formation in Pleurotus tuber-regium.

Abstract

Pleurotus tuber-regium (Fr.) Sing. can evade oxygen by forming sclerotia under oxidative stress, consequently averting the development of hyperoxidative state, during which the expression level of catalase gene (PtCat) is significantly up-regulated. To investigate the relationship between the catalase gene and sclerotia formation, over-expression and interference strains of the PtCat gene were obtained by Agrobacterium tumefaciens-mediated transformation for phenotypic analysis. In the absence of hydrogen peroxide (H₂O₂) stress, a minor difference was observed in the mycelial growth rate and the activity of antioxidant enzymes between the over-expression and interference strains. However, when exposed to 1-2 mM H₂O₂, the colony diameter of the over-expression strain was approximately 2-3× that of the interference strain after 8 days of culturing. The catalase activity of the over-expression strain increased by 1000 U/g under 2 mM H₂O₂ stress, while the interference strain increased by only 250 U/g. After one month of cultivation, the interference strain formed an oval sclerotium measuring 3.5 cm on the long axis and 2 cm on the short axis, while the over-expression strain did not form sclerotia. Therefore, it is concluded that catalase activity regulates the formation of sclerotia in P. tuber-regium.