Characterization of small RNAs originating from mitoviruses infecting the conifer pathogen Fusarium circinatum

Abstract

Deep sequencing of small RNAs has proved effective in the diagnosis of mycovirus infections. In this study, the presence of mycoviruses in ten isolates of the phytopathogenic fungus Fusarium circinatum was investigated by high-throughput sequencing (HTS) of small RNAs. The contigs resulting from de novo assembly of the reads were aligned to viral genome sequences. The presence of each mycovirus detected in the isolates was confirmed by RT-PCR analysis with four previously described primer pairs and seven new pairs designed on the basis of sequencing data. The findings demonstrate the potential use of HTS for reconstructing previously identified mitoviruses infecting F. circinatum.

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

“…A high rate of transmission was expected, as mitoviruses FcMV1 and FcMV2-2 are associated with the mitochondria that the offspring inherit from the parents [17]. The high transmission rates of mycoviruses are consistent with those reported for asexual spores of other fungal species such as Ustilaginoidea virens [26] and Epichloë festucae [27] whereas for other pathogens variable rates of virus transmission were observed, e.g., Heterobasidion annosum [13] and CHV1 hypovirus infecting Chryphonectria parasitica [28][29][30].…”

“…Another hypothesis could be that mycoviruses are no longer active or pathogen's parasites and remain in the mitochondria as symbionts, producing no effects on the host. However, this seems unlikely since Muñoz-Adalia [17] found evidences of viral replication detected by high-throughput sequencing such as antisense vsRNA reads. In other Fusarium species, the presence of mycoviruses has not been related to any morphological changes, although it was observed that Fusarium graminearum virus 1 (FgV1) causes hypovirulence [39].…”

“…In the Spanish population of F. circinatum, natural transmission between other species was studied by isolating other fungi in which the disease is commonly established, although no virus was detected in any other fungal species [62]. Although there is no clear pattern in the geographical distribution of mycoviruses hosted by F. circinatum in Spain [17], it is likely that the fungi that were introduced in Spain were harboring viruses at that time [18]. However, whether the mitoviruses were acquired when the fungus established in Spain or if they came along with the fungus when it was introduced represents a hypothesis that remains unknown.…”

“…These mitoviruses are common in F. circinatum isolates from northern Spain. They have been shown to be polymorphic [16] and their viral genome has recently been studied [17]. The main aim of the present study was to investigate how the probability and rate of transmission of these mitoviruses via microconidia vary in relation to the fungal isolate and strain of virus (FcMV1 and FcMV2-2).…”

Biological and Molecular Characterization of Chenopodium quinoa Mitovirus 1 Reveals a Distinct Small RNA Response Compared to Those of Cytoplasmic RNA Viruses

“…Differential sRNA accumulation and processing of AMV and CqMV1 in infected C. quinoa plants. A number of fungal mitoviruses have been discovered through sRNA characterization, suggesting that, at least in fungi, they are subject to RNA interference (RNAi) processing (28,29). In order to characterize the sRNA present in C. quinoa, we decided to compare three libraries of sRNA: (i) CqMV1-free BO25 infected by AMV (SRA accession no.…”