Abstract
A novel mycovirus named Fusarium oxysporum alternavirus 1(FoAV1) was identified as infecting Fusarium oxysporum strain BH19, which was isolated from a fusarium wilt diseased stem of Lilium brownii. The genome of FoAV1 contains four double-stranded RNA (dsRNA) segments (dsRNA1, dsRNA 2, dsRNA 3 and dsRNA 4, with lengths of 3.3, 2.6, 2.3 and 1.8 kbp, respectively). Additionally, dsRNA1 encodes RNA-dependent RNA polymerase (RdRp), and dsRNA2- dsRNA3- and dsRNA4-encoded hypothetical proteins (ORF2, ORF3 and ORF4), respectively. A homology BLAST search, along with multiple alignments based on RdRp, ORF2 and ORF3 sequences, identified FoAV1 as a novel member of the proposed family “Alternaviridae”. Evolutionary relation analyses indicated that FoAV1 may be related to alternaviruses, thus dividing the family “Alternaviridae” members into four clades. In addition, we determined that dsRNA4 was dispensable for replication and may be a satellite-like RNA of FoAV1—and could perhaps play a role in the evolution of alternaviruses. Our results provided evidence for potential genera establishment within the proposed family “Alternaviridae”. Additionally, FoAV1 exhibited biological control of Fusarium wilt. Our results also laid the foundations for the further study of mycoviruses within the family “Alternaviridae”, and provide a potential agent for the biocontrol of diseases caused by F. oxysporum.
Highlights
Mycoviruses are a group of viruses that infect filamentous fungi, yeasts and oomycetes.Until recently, the National Center of Biotechnology Information (NCBI) database contained more than 300 mycoviral sequences, divided into at least 19 families by the InternationalCommittee for Taxonomy of Viruses (ICTV) [1]
Many hypovirulence-associated mycoviruses have been found in other plant pathogenic fungi, such as Botryosphaeria cinerea debilitation-related virus (BcDRV), Botryosphaeria dothidea Chrysovirus 1 (BdCV1), Rhizoctonia solani partitivirus 2 (RSPV2), Rhizoctonia solani endornavirus 1 (RsEV1) and Colletotrichum liriopes partitivirus 1 (ClPV1) [17,18,19,20]
BLAST searches revealed that ORF1, ORF2 and ORF3 were all
Summary
Mycoviruses are a group of viruses that infect filamentous fungi, yeasts and oomycetes. SsRV2 contains only one genomic RNA segment (5202 bp) and is a typical totivirus, based on the sequence characteristics identified and phylogenetic analysis with other known totiviruses [22]. Aoki et al (2009) reported a novel mycovirus, Alternaria alternata virus 1 (AaV1), from Alternaria alternata, which is similar to AsV341, following an analysis of its sequence characteristics and multiple alignment. In 2013, Kozlakidis et al [24] reported a novel mycovirus (Aspergillus foetidus virus (AfV)), which was similar to both AaV1 and AsV341, and proposed a new genus, Alternavirus, and a new family, “Alternaviridae”, to accommodate the three viruses. Sequencing and analysis of this dsRNA showed that it corresponded with a novel alternavirus—the first to be described that infects a F. oxysporum strain—which was provisionally named Fusarium oxysporium alternavirus 1 (FoAV1). We conducted genome characterization to elucidate the molecular features of FoAV1, investigate its impact on virulence and understand its biological properties in F. oxysporum
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