PriA is involved in Pleurotus ostreatus development and defense against Pseudomonas tolaasii.

Pleurotus ostreatus is a crucial commercial mushroom widely cultivated for diverse uses. Scientists have worked on breeding disease-resistant and high-yielding varieties to secure food supply. Studies on the molecular genetic mechanism of growth and development can provide valuable information to facilitate crop breeding programs by genetic engineering. Aegerolysins are pore-forming proteins widely distributed in both prokaryotes and eukaryotes, which are reported to have haemolytic activity and be involved in the early stages of fructification. The present study aimed to explore biological function of a differential expressed aegerolysin gene PriA in P. ostreatus. The expression level of PriA gene was higher in primordium and fruiting body than that in mycelium. The PriA expression in overexpression (OE) and RNAi interference (RNAi) strains was detected by qRT-PCR. The RNAi strains grew at slightly slower rates and advanced producing yellow pigments than the wild type, while OE strains showed no prominent phenotypic characteristics. Furthermore, Pseudomonas tolaasii infection assays showed that the PriA OE strains could enhance mycelia and caps resistance to P. tolaasii. These data demonstrate PriA from P. ostreatus play an essential role in mycelial development and increase antagonism against P. tolaasii. Our study provides some reference information on interactions between edible fungi and pathogenic bacteria and offers a new resistance-conferring gene for breeding.

Alternative oxidase is involved in oxidative stress resistance and melanin synthesis in Annulohypoxylon stygium, a companion fungus of Tremella fuciformis.

Annulohypoxylon stygium, a companion fungus of Tremella fuciformis, provides nutrition for growth and development of T. fuciformis. Alternative oxidase (AOX), which is the terminal oxidase of the alternative respiration pathway, functions to transfer electrons from ubiquinol to O2 with the production of H2O. In this study, an AOX encoded gene, Asaox, was cloned from A. stygium. The coding sequence of Asaox gene contains 1056 nucleotides and encodes 351 amino acids. RNA interference was used to study the function of Asaox in A. stygium. The Asaox-silenced strains were confirmed by PCR, quantitative real-time PCR, and Southern blot. The Asaox-silenced strains exhibited increased relative growth inhibition rates when inoculated on PDA plates with 50 mM H2O2, compared with wild-type strain. The growth rate in sawdust medium, melanin content, and laccase activity of Asaox-silenced strains were decreased. The expression levels of tyr and pks genes were decreased in Asaox-silenced strains, indicating that there might be two melanin synthesis pathways, DHN and DOPA, in A. stygium. In summary, the results have demonstrated that Asaox gene was involved in oxidative stress resistance and melanin synthesis in A. stygium.

Identification and physiological function of one microRNA (Po-MilR-1) in oyster mushroom Pleurotus ostreatus.

MicroRNAs are essential regulators of gene expression and have been extensively studied in plants and animals; however, few reports have been published in mushrooms. Po-MilR-1 is a novel microRNA with a length of 22 bp in Pleurotus ostreatus. The secondary structures of five precursors and the target genes of Po-MilR-1 were predicted. Expression profile analysis showed Po-MilR-1 had specific expression in the primordium and fruiting body. To explore its physiological function, Po-MilR-1 was overexpressed in P. ostreatus. The transformants showed slow mycelium growth rate and abnormal pileus with irregular edge, which suggested Po-MilR-1 plays an important role in P. ostreatus development. Additionally, Po-MilR-1 and one of its target hydrophobin genes POH1 had opposite temporal expression profiles in the primordium and fruiting body, which revealed that Po-MilR-1 may perform its physiological function through the negative regulation of POH1. This study explored the development-related function of a mushroom microRNA and will provide a reference for other microRNAs.