Co-Infection of Three Novel Deltaflexiviruses in an Isolate of the Edible Fungus Pleurotus ostreatus Reduces Fruiting Body Yield by Inhibiting Cellulase Activity.

Metadata-grounded summary

Citation abstract

Pleurotus ostreatus, a globally cultivated oyster mushroom, is susceptible to viral infections that threaten yield and quality. This study reports the identification and characterization of three novel viruses from a symptomatic P. ostreatus strain K3: Pleurotus ostreatus deltaflexivirus 2, 3, and 4 (PoDFV2, PoDFV3, PoDFV4). Complete genome sequencing revealed that they are single-stranded, positive-sense RNA viruses with lengths of 7809 nt, 7771 nt, and 7786 nt, encoding 5, 2, and 4 open reading frames (ORFs), respectively. The largest open reading frame (ORF1) encodes a putative replication-associated polyprotein (RP) containing three conserved domains-viral RNA methyltransferase (Mtr), viral RNA helicase (Hel), and RNA-dependent RNA polymerase (RdRp). Based on genomic sequence analysis, multiple sequence alignments, and phylogenetic analysis, PoDFV2-4 were identified as novel viruses of the genus Deltaflexivirus within the family Deltaflexiviridae. PoDFV2-4 had no significant effects on mycelial growth rate, plate mycelial biomass, or laccase activity. However, they significantly inhibited mycelial cellulase activity and resulted in malformed fruiting bodies, as well as a substantial reduction in yield.