Isolation and characterization of a mycovirus in Lentinula edodes

Abstract

A mycovirus was isolated from an edible mushroom, Lentinula edodes, that was suffering from a severe epidemic. Fractionation of the diseased cell extract by isopycnic centrifugation with 50% CsCl revealed that the diseased mushroom was infected by Lentinula edodes spherical virus (LeSV), a new spherical virus with a diameter of 55 nm. The particle of LeSV encapsidated the 12 kb RNA genome by a 120 kDa coat protein. BLAST analysis of the partially sequenced LeSV genome showed 95% sequence identity with a putative RNA-dependent RNA polymerase (RdRp) gene of the mycovirus HKB, which was previously reported as being a double-stranded RNA (dsRNA) element. In contrast to HKB, the RNA genome in LeSV is encapsidated by the 120 kDa coat protein. To confirm that the LeSV coat protein is encoded by the viral genome, the N-terminal amino acid sequence of the coat protein was determined. The resulting N-terminal amino acid sequence, N-SALDVAPVVPELYFXXLEV-C, was found to be located in the middle of the HKB ORF1, suggesting that the LeSV coat protein was indeed encoded by the virus. To detect LeSV in L. edodes, a primer set targeting the RdRp gene was designed based on the partial sequence of the LeSV genome. RT-PCR analysis showed that 56 of the 84 commercially available dikaryotic cultivars carry LeSV. The transmission pattern of the virus was determined by analysing basidiospores from LeSV-infected and LeSV-free fruiting bodies. Nine out of 10 basidiospores from the LeSV-infected cultivars contained the virus while the spores from the LeSV-free parent were free of LeSV, suggesting that vertical transmission is the primary mode of LeSV propagation.

Vertical Transmission of Fusarium circinatum Mitoviruses FcMV1 and FcMV2-2 via Microconidia

“…In some species, usually ascomycetes, there appear to be barriers to the transmission of viruses during sexual reproduction and the formation of sexual spores [27]. While no virus-transmission was observed via sexual spores in C. parasitica [31] and of the root rot pathogens Helicobasidium mompa and Rosellinia necatrix [32], wide-ranging rates of transmission were reported for H. annosum, [33], H. parviporum [21], and Lentinula edodes [34]. The lack of repetition of the experiment limit us to draw conclusions about the variance and reproducibility of our methodology and to estimate standard errors on the transmission rate.…”

Characterization of a Novel Megabirnavirus from Sclerotinia sclerotiorum Reveals Horizontal Gene Transfer from Single-Stranded RNA Virus to Double-Stranded RNA Virus

“…The genomes of the three mycoviruses PgLV-1, LeMV, and LeSV comprise one large segment that encodes two putative proteins, but those vi- ruses appear to be capsidless based on previous reports (38,39,40). The RnMBV1 genome was previously reported to comprise two dsRNA segments (dsRNA1 and dsRNA2) (5).…”

Genome sequence of a novel mycovirus of Rhizoctonia solani, a plant pathogenic fungus

“…It is plausible that these viruses may have an ancient origin and symbiosis maintenance in their respective hosts. Won et al [21] reported an encapsidated virus from L. edodes, whose partial genomic attribute has a high sequence similarity, up to 95 %, with that of the virus LeV-HKB. Additionally, N-terminal amino acid sequencing of the capsid protein (120 kDa) of the encapsidated virus (LeSV) identified some peptides that are located in the middle of the hypothetical protein encoded by HKB ORF1.…”