Search Results (10)

Macrophomina phaseolina is a widely distributed soilborne phytopathogenic fungus that causes destructive diseases such as charcoal rot and stem canker, posing serious threats to crop yield and quality. In recent years, mycoviruses have gained attention as potential biological control agents. In this study, a novel double-stranded RNA (dsRNA) virus was identified from M. phaseolina strain 22C-8, isolated from sesame (Sesamum indicum L.) charcoal rot samples in Fuyang, Anhui Province, China. The viral genome comprised four dsRNA segments, each encoding a single open reading frame (ORF) predicted to encode RNA-dependent RNA polymerase (RdRp), coat protein (CP), and two hypothetical proteins. Phylogenetic analysis classified the virus as a new member of the genus Betachrysovirus in the family Chrysoviridae, and it was designated Macrophomina phaseolina chrysovirus 2 (MpChrV2). Pathogenicity assays in sesame seedlings revealed that MpChrV2 infection significantly reduced the virulence of M. phaseolina strain 22C-8. In contrast, virus-free derivatives (22C-8-VF18), obtained via protoplast regeneration, caused more severe symptoms and exhibited enhanced growth rates, indicating that MpChrV2 alters fungal physiology and pathogenicity. These findings suggest that MpChrV2 possesses a typical hypovirulence phenotype and holds promise as a biocontrol agent for sesame charcoal rot. Full article

Penicillium astrolabium is a primary pathogenic fungus that causes grape blue mold during postharvest, leading to substantial losses in the grape industry. Nevertheless, hypovirulence-associated mycoviruses can attenuate the virulence of postharvest grape-rot pathogens, thereby offering a promising biocontrol tool. Characterizing the mycovirus repertoire of P. astrolabium is imperative for grape protection, yet remains largely unexplored. Here, we screened six strains harboring viruses in 13 P. astrolabium isolates from rotted grapes. Using high-throughput sequencing, four novel dsRNA viruses and two +ssRNA viruses were identified from the six P. astrolabium strains. The dsRNA viruses belonged to two families—Chrysoviridae and Partitiviridae—and were designated to Penicillium astrolabium chrysovirus 1 (PaCV1), Penicillum astrolabium partitivirus 1′ (PaPV1′), Penicillum astrolabium partitivirus 2 (PaPV2), and Penicillum astrolabium partitivirus 3 (PaPV3). For the +ssRNA viruses, one was clustered into the Alphaflexiviridae family, while the other one was clustered into the Narnaviridae family. The two +ssRNA viruses were named Penicillium astrolabium alphaflexivirus 1 (PaAFV1) and Penicillium astrolabium narnavirus 1 (PaNV1), respectively. Moreover, several viral genomic contigs with non-overlapping and discontinuous sequences were identified in this study, which were probably representatives of five viruses from four families, including Discoviridae, Peribunyaviridae, Botourmiaviridae, and Picobirnaviridae. Taken together, our findings could expand the diversity of mycoviruses, advance the understanding of mycovirus evolution in P. astrolabium, and provide both potential biocontrol resources and a research system for dissecting virus–fungus–plant interactions. Full article

Chrysoviruses are isometric virus particles (35–50 nm in diameter) with a genome composed of double-stranded RNAs (dsRNA). These viruses belonged to the Chrysoviridae family, named after the first member isolated from Penicillium chrysogenum. Phylogenetic classification has divided the chrysoviruses into Alphachrysovirus and Betachrysovirus genera. Currently, these chrysoviruses have been found to infect many fungi, including Fusarium species, and cause changes in the phenotype and decline in the pathogenicity of the host. Thus, it is a microbial resource with great biocontrol potential against Fusarium species, causing destructive plant diseases and substantial economic losses. This review provides a comprehensive overview of three chrysovirus isolates (Fusarium graminearum virus 2 (FgV2), Fusarium graminearum virus-ch9 (FgV-ch9), and Fusarium oxysporum f. sp. dianthi mycovirus 1 (FodV1)) reported to decline the pathogenicity of Fusarium hosts. It also summarizes the recent studies on host response regulation, host RNA interference, and chrysovirus transmission. The information provided in the review will be a reference for analyzing the interaction of Fusarium species with chrysovirus and proposing opportunities for research on the biocontrol of Fusarium diseases. Finally, we present reasons for conducting further studies on exploring the interaction between chrysoviruses and Fusarium and improving the accumulation and transmission efficiency of these chrysoviruses. Full article

Pear ring rot disease is an important branch disease, caused by Botryosphaeria dothidea. With the discovery of fungal viruses, the use of their attenuated properties for biological control provides a new strategy for the biological control of fungal disease. RNA silencing is a major antiviral defense mechanism in plants, insects, and fungi. Viruses encode and utilize RNA silencing suppressors to suppress host defenses. Previous studies revealed that Botryosphaeria dothidea chrysovirus 1 (BdCV1) exhibited weak pathogenicity and could activate host gene silencing by infecting B. dothidea. The aim of our study was to investigate whether BdCV1 can encode a silencing suppressor and what effect it has on the host. In this study, the capability of silencing inhibitory activity of four BdCV1-encoded proteins was analyzed, and the P3 protein was identified as a BdCV1 RNA silencing suppressor in the exotic host Nicotiana benthamiana line 16c. In addition, we demonstrated that P3 could inhibit local silencing, block systemic RNA silencing, and induce the necrosis reaction of tobacco leaves. Furthermore, overexpression of P3 could slow down the growth rate and reduce the pathogenicity of B. dothidea, and to some extent affect the expression level of RNA silencing components and virus-derived siRNAs (vsiRNAs). Combined with transcriptomic analysis, P3 had an effect on the gene expression and biological process of B. dothidea. The obtained results provide new theoretical information for further study of interaction between BdCV1 P3 as a potential silencing suppressor and B. dothidea. Full article

Here, we report on a serendipitous finding of a chryso-like virus associated with Culex pipiens mosquitos in the course of study aimed to detect and characterize West Nile virus (WNV) circulating in mosquitos in Serbia, Southern Europe. Upon initial detection of unexpected product in a PCR protocol for partial WNV NS5 gene amplification, further confirmation and identification was obtained through additional PCR and Sanger sequencing experiments. Bioinformatic and phylogenetic analysis identified the obtained sequences as Xanthi chryso-like virus (XCLV). The finding is particular for the fact that it associates XCLV with a new potential vector species and documents a novel geographical area of its distribution. Full article

A lichen body is formed most often from green alga cells trapped in a net of ascomycetous fungi and accompanied by endolichenic or parasitic fungi, other algae, and symbiotic or free-living bacteria. The lichen’s microcosmos is inhabited by mites, insects, and other animals for which the lichen is a source of food or a place to live. Novel, four-segmented dsRNA viruses were detected in saxicolous Chrysothrix chlorina and Lepraria incana lichens. Comparison of encoded genome proteins revealed classification of the viruses to the genus Alphachrysovirus and a relationship to chrysoviruses from filamentous ascomycetous fungi. We propose the names Chrysothrix chrysovirus 1 (CcCV1) and Lepraria chrysovirus 1 (LiCV1) as acronyms for these viruses. Surprisingly, observation of Chrysothrix chlorina hybridization with fluorescent-labelled virus probe by confocal microscope revealed that the CcCV1 virus is not present in the lichen body-forming fungus but in accompanying endolichenic Penicillium citreosulfuratum fungus. These are the first descriptions of mycoviruses from a lichen environment. Full article

Magnaporthe oryzae, the fungus that causes rice blast, is the most destructive pathogen of rice worldwide. A number of M. oryzae mycoviruses have been identified. These include Magnaporthe oryzae. viruses 1, 2, and 3 (MoV1, MoV2, and MoV3) belonging to the genus, Victorivirus, in the family, Totiviridae; Magnaporthe oryzae. partitivirus 1 (MoPV1) in the family, Partitiviridae; Magnaporthe oryzae. chrysovirus 1 strains A and B (MoCV1-A and MoCV1-B) belonging to cluster II of the family, Chrysoviridae; a mycovirus related to plant viruses of the family, Tombusviridae (Magnaporthe oryzae. virus A); and a (+)ssRNA mycovirus closely related to the ourmia-like viruses (Magnaporthe oryzae. ourmia-like virus 1). Among these, MoCV1-A and MoCV1-B were the first reported mycoviruses that cause hypovirulence traits in their host fungus, such as impaired growth, altered colony morphology, and reduced pigmentation. Recently we reported that, although MoCV1-A infection generally confers hypovirulence to fungi, it is also a driving force behind the development of physiological diversity, including pathogenic races. Another example of modulated pathogenicity caused by mycovirus infection is that of Alternaria alternata chrysovirus 1 (AaCV1), which is closely related to MoCV1-A. AaCV1 exhibits two contrasting effects: Impaired growth of the host fungus while rendering the host hypervirulent to the plant, through increased production of the host-specific AK-toxin. It is inferred that these mycoviruses might be epigenetic factors that cause changes in the pathogenicity of phytopathogenic fungi. Full article

This study determined the effects of Aspergillus thermomutatus chrysovirus 1 (AthCV1), isolated from Aspergillus thermomutatus, on A. fumigatus, A. nidulans and A. niger. Protoplasts of virus-free isolates of A. fumigatus, A. nidulans and A. niger were transfected with purified AthCV1 particles and the phenotype, growth and sporulation of the isogenic AthCV1-free and AthCV1-infected lines assessed at 20 °C and 37 °C and gene expression data collected at 37 °C. AthCV1-free and AthCV1-infected A. fumigatus produced only conidia at both temperatures but more than ten-fold reduced compared to the AthCV1-infected line. Conidiation was also significantly reduced in infected lines of A. nidulans and A. niger at 37 °C. AthCV1-infected lines of A. thermomutatus and A. nidulans produced large numbers of ascospores at both temperatures, whereas the AthCV1-free line of the former did not produce ascospores. AthCV1-infected lines of all species developed sectoring phenotypes with sclerotia produced in aconidial sectors of A. niger at 37 °C. AthCV1 was detected in 18% of sclerotia produced by AthCV1-infected A. niger and 31% of ascospores from AthCV1-infected A. nidulans. Transcriptome analysis of the naturally AthCV1-infected A. thermomutatus and the three AthCV1-transfected Aspergillus species showed altered gene expression as a result of AthCV1-infection. The results demonstrate that AthCV1 can infect a range of Aspergillus species resulting in reduced sporulation, a potentially useful attribute for a biological control agent. Full article

Mycoviruses are viruses that naturally infect and replicate in fungi. They are widespread in all major fungal groups including plant and animal pathogenic fungi. Several dsRNA mycoviruses have been reported in Aspergillus fumigatus. Multiplex polymerase chain reaction (PCR) amplification is a version of PCR that enables amplification of different targets simultaneously. This technique has been widely used for detection and differentiation of viruses especially plant viruses such as those which infect tobacco, potato and garlic. For rapid detection, multiplex RT-PCR was developed to screen new isolates for the presence of A. fumigatus mycoviruses. Aspergillus fumigatus chrysovirus (AfuCV), Aspergillus fumigatus partitivirus (AfuPV-1), and Aspergillus fumigatus tetramycovirus-1 (AfuTmV-1) dsRNAs were amplified in separate reactions using a mixture of multiplex primer pairs. It was demonstrated that in the presence of a single infection, primer pair mixtures only amplify the corresponding single virus infection. Mixed infections using dual or triple combinations of dsRNA viruses were also amplified simultaneously using multiplex RT-PCR. Up until now, methods for the rapid detection of Aspergillus mycoviruses have been restricted to small scale dsRNA extraction approaches which are laborious and for large numbers of samples not as sensitive as RT-PCR. The multiplex RT-PCR assay developed here will be useful for studies on determining the incidence of A. fumigatus mycoviruses. This is the first report on multiplex detection of A. fumigatus mycoviruses. Full article

A novel double-stranded RNA (dsRNA) mycovirus, consisting of three dsRNA genome segments and possibly belonging to the family Chrysoviridae, was isolated from the filamentous phytopathogenic fungus Colletotrichum gloeosporioides and designated as Colletotrichum gloeosprioides chrysovirus 1 (CgCV1). The three dsRNAs of the CgCV1 genome with lengths of 3397, 2869, and 2630 bp (dsRNAs1–3) were found to contain a single open reading frame (ORF) putatively encoding the RNA-dependent RNA polymerase (RdRp), a capsid protein, and a protease, respectively, all of which exhibited some degree of sequence similarity to the comparable putative proteins encoded by the genus Chrysovirus. The 5′- and 3′-untranslated regions in each dsRNA segment contained similar sequences that were strictly conserved at the termini. Moreover, isometric virus-like particles (VLPs) with a diameter of approximately 40 nm were extracted from fungal mycelia. Phylogenetic analysis based on the conserved dsRNA1-encoded RdRp showed that CgCV1 is a new virus belonging to the Chrysoviridae family. BLAST analysis revealed the presence of CgCV1-like sequences in the chromosomes of Medicago truncatula and Solanum tuberosum. Moreover, some sequences in the transcriptome shotgun assembly (TSA) library and expressed sequence tag database (ESTdb) of other eudicot and monocot plants were also found to be related to CgCV1. Full article