Complete nucleotide sequences of four dsRNAs associated with a new chrysovirus infecting Aspergillus fumigatus

Jiang

et al. 2014

J Virol

100

Botryosphaeria dothidea is an important pathogenic fungus causing fruit rot, leaf and stem ring spots and dieback, stem canker, stem death or stool mortality, and decline of pear trees. Seven double-stranded RNAs (dsRNAs; dsRNAs 1 to 7 with sizes of 3,654, 2,773, 2,597, 2,574, 1,823, 1,623, and 511 bp, respectively) were identified in an isolate of B. dothidea exhibiting attenuated growth and virulence and a sectoring phenotype. Characterization of the dsRNAs revealed that they belong to two dsRNA mycoviruses. The four largest dsRNAs (dsRNAs 1 to 4) are the genomic components of a novel member of the family Chrysoviridae (tentatively designated Botryosphaeria dothidea chrysovirus 1 [BdCV1]), a view supported by the morphology of the virions and phylogenetic analysis of the putative RNA-dependent RNA polymerases (RdRps). Two other dsRNAs (dsRNAs 5 and 6) are the genomic components of a novel member of the family Partitiviridae (tentatively designated Botryosphaeria dothidea partitivirus 1 [BdPV1]), which is placed in a clade distinct from other established partitivirus genera on the basis of the phylogenetic analysis of its RdRp. The smallest dsRNA, dsRNA7, seems to be a noncoding satellite RNA of BdPV1 on the basis of the conservation of its terminal sequences in BdPV1 genomic segments and its cosegregation with BdPV1 after horizontal transmission. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus. IMPORTANCEOur studies identified and characterized two novel mycoviruses, Botryosphaeria dothidea chrysovirus 1 (BdCV1) and Botryosphaeria dothidea partitivirus 1 (BdPV1), associated with the hypovirulence of an important fungus pathogenic to fruit trees. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus. BdCV1 appears to be a good candidate for the biological control of the serious disease induced by B. dothidea. Additionally, BdPV1 is placed in a clade distinct from the established genera. The BdCV1 capsid has two major structural proteins, and the capsid is distinct from that made up by a single polypeptide of the typical chrysoviruses. BdPV1 is the second partitivirus in which the putative capsid protein shares no significant identity with any mycovirus protein.A small accompanying dsRNA that is presumed to be a noncoding satellite RNA of BdPV1 is the first of its kind reported for a partitivirus.

Section: Discussionmentioning

confidence: 99%

Hypovirulence of the Phytopathogenic Fungus Botryosphaeria dothidea: Association with a Coinfecting Chrysovirus and a Partitivirus

Jiang

et al. 2014

J Virol

100

Proc. Natl. Acad. Sci. U.S.A.

“…Two of the profiles were found to be representatives of respectively a chrysovirus nominated Aspergillus fumigatus chrysovirus (AfuCV) (12) and a partitivirus nominated Aspergillus fumigatus partitivirus 1 (AfuPV-1) (13). Here, we report the sequence and characterization of the remaining profile of four uncharacterized dsRNA segments, which constitute the genome of a completely novel mycovirus nominated Aspergillus fumigatus tetramycovirus-1 (AfuTmV-1).…”

mentioning

confidence: 99%

A novel mycovirus from Aspergillus fumigatus contains four unique dsRNAs as its genome and is infectious as dsRNA

Kanhayuwa

Kotta‐Loizou

Özkan

et al. 2015

125

226

We report the discovery and characterization of a double-stranded RNA (dsRNA) mycovirus isolated from the human pathogenic fungus Aspergillus fumigatus, Aspergillus fumigatus tetramycovirus-1 (AfuTmV-1), which reveals several unique features not found previously in positive-strand RNA viruses, including the fact that it represents the first dsRNA (to our knowledge) that is not only infectious as a purified entity but also as a naked dsRNA. The AfuTmV-1 genome consists of four capped dsRNAs, the largest of which encodes an RNA-dependent RNA polymerase (RdRP) containing a unique GDNQ motif normally characteristic of negative-strand RNA viruses. The third largest dsRNA encodes an S-adenosyl methionine–dependent methyltransferase capping enzyme and the smallest dsRNA a P-A-S–rich protein that apparently coats but does not encapsidate the viral genome as visualized by atomic force microscopy. A combination of a capping enzyme with a picorna-like RdRP in the AfuTmV-1 genome is a striking case of chimerism and the first example (to our knowledge) of such a phenomenon. AfuTmV-1 appears to be intermediate between dsRNA and positive-strand ssRNA viruses, as well as between encapsidated and capsidless RNA viruses.

“…In the genus Aspergillus, the presence of dsRNA mycoviruses from the families Totiviridae, Partitiviridae and Chrysoviridae has been reported, and mixed infections are common [4,8,16]. More specifically, Aspergillus foetidus isolate IMI 41871 has been found to harbour at least two different types of isometric virus particles, designated as A. foetidus virus-fast (AfV-F) and -slow (AfV-S), based on their relative electrophoretic mobility [3,15].…”

Section: Introductionmentioning

confidence: 99%

Sequence determination of a satellite RNA isolated from Aspergillus foetidus

2015

Aspergillus foetidus virus (AfV) contains at least two distinct particle types designated as AfV-fast (F) and AfV-slow (S). AfV-S contains AfV-S1, a victorivirus, AfV-S2, an unclassified satellite RNA, and AfV-S3, a previously uncharacterized dsRNA element. Here we describe the complete sequence of AfV-S3, which is a short non-coding RNA with no known homologs. AfV-S3 is predicted to form extended secondary structure, shares a 5'-terminus with AfV-S2 and is a satellite RNA possibly dependent on both AfV-S1 and AfV-S2. This work concludes the sequencing of the A. foetidus virome.