Abstract
Isogenic virus-cured and virus-infected fungal strains were previously obtained and compared to investigate mycoviral diseases and, specifically, the influence of viral infection on the vegetative growth of Pleurotus ostreatus. The present study demonstrated that infection with mycovirus PoV-ASI2792 (PoV) caused phenotypic and physiological changes in fungal cells and mycelia. The microscopically determined growth rate of the virus-infected strain was lower than that of the virus-cured strain, due to the conglomerate phenomenon during the mycelial growth process. An exploration of the viral effects of PoV on fruiting bodies yield showed significantly lower than that on virus-cured P. ostreatus. A colorimetric assay of polyphenol oxidase activity in the strains showed very weak activity in the virus-infected strain. To estimate the activity levels of enzymes related to the growth and fruiting body formation, the relative expression levels of genes encoding various extracellular enzymes such as Carbohydrate-Active Enzymes (CAZymes) were measured by quantitative RT-PCR. The expression levels of the assayed genes were significantly lower in virus-infected than in virus-cured P. ostreatus. Together, these results indicate that PoV infection affects the spawn growth and fruiting body formation of P. ostreatus via decreased expression and activity of some extracellular enzymes including lignocellulolytic enzymes.
Highlights
Isogenic virus-cured and virus-infected fungal strains were previously obtained and compared to investigate mycoviral diseases and, the influence of viral infection on the vegetative growth of Pleurotus ostreatus
For this comparative study of one PoV-infected line (POV) and the two virus-cured lines (POVF10 and P. ostreatus AS2792-VF12 (POVF12)), the presence or absence of the PoV mycovirus was verified for each strain via gel electrophoresis and RT-PCR using P. ostreatus mycelium
The results showed that the relative expression level of RNA-dependent RNA polymerase (RdRp) mRNA from PoV differed between the POV and P. ostreatus AS2792-VF10 (POVF10)/POVF12 strains
Summary
Isogenic virus-cured and virus-infected fungal strains were previously obtained and compared to investigate mycoviral diseases and, the influence of viral infection on the vegetative growth of Pleurotus ostreatus. The expression levels of the assayed genes were significantly lower in virus-infected than in virus-cured P. ostreatus Together, these results indicate that PoV infection affects the spawn growth and fruiting body formation of P. ostreatus via decreased expression and activity of some extracellular enzymes including lignocellulolytic enzymes. CAZymes secreted by fungi are classified into several families, including two high-priority classes, i.e., glycoside hydrolase (GH) and auxiliary activities (AA)[18] These enzymes assist in the acquisition of nutrients to enhance mycelial growth and fruiting body production in Pleurotus spp. There is little literature about the effect of mycoviruses on the gene expression levels and activities of extracellular enzymes, even though mycoviruses can cause drastically decreased fruiting body production in cultivated mushrooms, including Pleurotus spp
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