The Metacaspase Gene PoMCA1 Enhances the Mycelial Heat Stress Tolerance and Regulates the Fruiting Body Development of Pleurotus ostreatus

Pleurotus ostreatus is one of the most cultivated edible mushrooms worldwide, of which the fruiting body development is a highly complex process involving the precise genetic regulatory network and suitable environmental factors. Metacaspases play important roles in developmental processes and programmed cell death (PCD) induced by some environmental stress in many organisms. In this study, a type I metacaspase, PoMCA1, was identified via the analysis of the enzyme domain and alignment with homologous metacaspases. PoMCA1 overexpression and RNAi mutants were generated via Agrobacterium tumefaciens-mediated transformation (ATMT) into the P. ostreatus mycelium. The roles of the PoMCA1 gene in heat stress and fruiting body development were examined. The results show that both of the overexpression transformants were more tolerant to heat stress than the wild-type strain, while the opposite phenomenons were found for the two RNAi strains. Compared with the wild-type strain, the overexpression strain OE-7 had faster formation of the fruiting body, while the two RNAi strains produced significantly more primordia and young fruiting bodies, and presented morphological deformities and slower fruiting body development. All of the results suggest that the PoMCA1 gene is involved in the positive regulation of heat stress tolerance and fruiting body development in P. ostreatus.