Fig 6 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Effect of MmPV1 on fungal virulence. (A) Survival rates of G. mellonella larvae following injection with conidial suspensions from Mm and Mm/MmPV1 strains. Control insects were treated with sterile water. (B) Mean lethal times (LT 50 ) of different strains after injection. (C) Survival rates of G. mellonella larvae following topical infection with conidial suspensions from different strains. Control insects were treated with sterile water. (D) The mean lethal times (LT 50 ) of different strains after topical application. **, P <0.01. https://doi.org/10.1371/journal.ppat.1011397.g006
Source publication
Mycoviruses are widely present in all major groups of fungi but those in entomopathogenic Metarhizium spp. remain understudied. In this investigation, a novel double-stranded (ds) RNA virus is isolated from Metarhizium majus and named Metarhizium majus partitivirus 1 (MmPV1). The complete genome sequence of MmPV1 comprises two monocistronic dsRNA s...
Contexts in source publication
Context 1
... survival rates of G. mellonella larvae following topical infection with Mm/MmPV1 were higher than with Mm (Fig 6A), resulting in LT 50 estimates of 10.59 ± 0.70 and 10.07 ± 0.20 days for Mm/MmPV1-1 and -2 as compared to 7.04 ± 0.33 days for Mm ( Fig 6B). However, ...
Context 2
... survival rates of G. mellonella larvae following topical infection with Mm/MmPV1 were higher than with Mm (Fig 6A), resulting in LT 50 estimates of 10.59 ± 0.70 and 10.07 ± 0.20 days for Mm/MmPV1-1 and -2 as compared to 7.04 ± 0.33 days for Mm ( Fig 6B). However, ...
Context 3
... LT 50 estimates via cuticle-bypassing infection (injection) revealed no significant differences between Mm and Mm/MmPV1 (Fig 6C-6D). These results indicate that MmPV1 attenuates virulence during the cuticle infection phase. ...
Context 4
... analysis revealed that 28 and 25 major metabolites were present respectively in Mm and Mm/MmPV1 (Fig 8 and S6 Fig). The levels of 22 metabolites were more than doubled (Table 1). ...
Context 5
... contrast, the gammapartitivirus Talaromyces marneffei partitivirus-1 (TmPV1) enhances virulence due to upregulation of genes encoding γ-aminobutyric acid transaminase, nitrite reductase and nitrate transporters and downregulation of genes associated with RNA interference (RNAi) [40]. Our results reveal a link between MmPV1, host hypovirulence and transcriptional suppression (Fig 6). Several virulence-related genes, which contribute to conidial hydrophobicity and adhesion, are vital for initial cuticle infection, while secretion of cuticle-degrading enzymes is essential for successful cuticle infection [47,48] (Fig 7). ...
Citations
... Most mycoviruses establish latent infections with no discernible impact on their fungal host. However, some mycoviruses can cause morphological alterations in their fungal hosts, such as hypovirulence (reduction of pathogenicity) or hypervirulence (significant increase in virulence) (Xie and Jiang, 2014;Kotta-Loizou and Coutts, 2017;Das et al., 2023;Wang et al., 2023). The mycoviruses associated with hypovirulence have the potential to control fungal diseases and offer valuable resources for investigating fungal biological mechanisms (Ghabrial and Suzuki, 2009;Kondo et al., 2022;Pedersen and Marzano, 2023;Hillman and Turina, 2024;Zhu et al., 2024). ...
Mycoviruses have been found in various fungal species across different taxonomic groups, while no viruses have been reported yet in the fungus Exserohilum rostratum. In this study, a novel orfanplasmovirus, namely Exserohilum rostratum orfanplasmovirus 1 (ErOrfV1), was identified in the Exserohilum rostratum strain JZ1 from maize leaf. The complete genome of ErOrfV1 consists of two positive single-stranded RNA segments, encoding an RNA-dependent RNA polymerase and a hypothetical protein with unknown function, respectively. Phylogenetic analysis revealed that ErOrfV1 clusters with other orfanplasmoviruses, forming a distinct phyletic clade. A new family, Orfanplasmoviridae, is proposed to encompass this newly discovered ErOrfV1 and its associated orfanplasmoviruses. ErOrfV1 exhibits effective vertical transmission through conidia, as evidenced by its 100% presence in over 200 single conidium isolates. Moreover, it can be horizontally transmitted to Exserohilum turcicum. Additionally, the infection of ErOrfV1 is cryptic in E. turcicum because there were no significant differences in mycelial growth rate and colony morphology between ErOrfV1-infected and ErOrfV1-free strains. This study represents the inaugural report of a mycovirus in E. rostratum, as well as the first documentation of the biological and transmission characteristics of orfanplasmovirus. These discoveries significantly contribute to our understanding of orfanplasmovirus.
... Mycoviruses, also known as fungal viruses, are widely present in fungi kingdom. While some mycovirus infections remain hidden, others have been associated with hypovirulence or hypervirulence, leading to significant effects on the growth, development, and reproduction of their fungal hosts [1][2][3][4]. The exploration of viral diversity within the virosphere has revolutionized our understanding of virus diversity and evolution [5]. ...
We investigated the prevalence and species diversity of dsRNA mycoviruses in Beauveria bassiana isolates from the China's Guniujiang Nature Preserve. Among the 28 isolates analyzed, electropherotyping revealed viral infections in 28.6 % (8 out of 28) of the isolates. Metatranscriptomic identification and RT-PCR confirmed the presence of six putative virus species, including two novel species: Beauveria bassiana victorivirus 2 (BbV-2) and Beauveria bassiana bipartite mycovirus 2 (BbBV-2). Four previously characterized mycoviruses were also identified: Beauveria bassiana polymycovirus 4 (BbPmV4), Beauveria bassiana partitivirus 1 (BbPV-1), Beauveria bassiana bipartite mycovirus 1 (BbBV-1), and Beauveria bassiana chrysovirus 2 (BbCV-2). BbPmV4 was found to be the prevailing mycovirus among the infected isolates, and three isolates showed co-infection with both BbPmV4 and BbBV-2. This study enhances our understanding of fungal viral taxonomy and diversity, providing insights into mycovirus infections in B. bassiana populations in China's Guniujiang Nature Preserve. Furthermore, the study on the diversity of B. bassiana viruses lays the foundation for recognizing fungal viruses as potential enhancers of biocontrol agents.
... To assay conidial adhesion, conidial adhesion assays were carried out according to previous reports (Wang et al. 2023b). 20 µL of conidia suspension (1 × 10 7 conidia/mL) were spread on a hydrophobic surface (diameter 3.5 cm), and stacked for 2-4 h, then blown dry. ...
Metarhizium robertsii, a vital entomopathogenic fungus for pest management, relies on various virulence-related proteins for infection. Identifying these proteins, especially those with unknown functions, can illuminate the fungus’s virulence mechanisms. Through RNA-seq, we discovered that the hypothetical protein MAA_07646 was significantly upregulated during appressorium formation in M. robertsii. In this study, we characterized MAA_07646, finding its presence in both the nucleus and cytoplasm. Surprisingly, it did not affect vegetative growth, conidiation, or chemical tolerance. However, it played a role in heat and UV radiation sensitivity. Notably, ΔMAA_07646 exhibited reduced virulence in Galleria mellonella larvae due to impaired appressorium formation and decreased expression of virulence-related genes. In conclusion, MAA_07646 contributes to thermotolerance, UV resistance, and virulence in M. robertsii. Understanding its function sheds light on the insecticidal potential of M. robertsii’s hypothetical proteins.
... Most mycoviruses are divided into single-stranded DNA (ssDNA), positive single-stranded RNA (+ssRNA), double-stranded RNA (dsRNA), and negative single-stranded RNA (-ssRNA) as the types of genomes [1,2,4]. Most dsRNA mycoviruses are classified into nine families (Amalgaviridae, Chrysoviridae, Curvulaviridae, Megabirnaviridae, Partitiviridae, Polymycoviridae, Quadriviridae, Spinareoviridae, Totiviridae) and one unassigned genus (Botybirnavirus) [5]. ...
Root rot as a result of Salvia miltiorrhiza is a common root disease caused by Fusarium spp., which has become one of the main diseases affecting the production of S. miltiorrhiza. Currently, several hypovirulence-related mycoviruses have been identified in many phytopathogenic fungi, including Fusarium spp., which show potential as biological controls. In this study, we report a new mycovirus, Fusarium oxysporum partitivirus 1 (FoPV1), isolated from F. oxysporum strain FCR51, which is a causal agent of S. miltiorrhiza dry rot. The FoPV1 genome contains two double-stranded RNA segments (dsRNA1 and dsRNA2). The size of dsRNA1 is 1773 bp, and it encodes a putative RNA-dependent RNA polymerase (RdRp). The dsRNA2 is 1570 bp in length, encoding a putative capsid protein (CP). Multiple sequence alignments and phylogenetic analyses based on the amino acid sequences of the RdRp and the CP proteins indicated that FoPV1 appears to be a new member of the family Partitiviridae that is related to members of the genus Gammapartitivirus. Pathogenicity assay showed that FoPV1 confers hypervirulence to its host, F. oxysporum. This is the first report of a partitivirus infecting F. oxysporum and the first hypovirulence-related mycovirus from the causal agent of S. miltiorrhiza dry rot.
... Within this family, the genus Gammapartitivirus is of particular interest, and it includes various viruses that infect ascomycetous fungi. While the majority of gammapartitiviruses induce latent infections, some, such as Talaromyces marneffei partitivirus 1 (TmPV1) and Metarhizium majus partitivirus 1 (MmPV1), affect the biological characteristics of their hosts [3,4]. ...
Penicillium oxalicum, an important biocontrol fungus in China, has been a subject of extensive study due to its role in combating various pathogenic fungi. Despite the prevalence of mycoviruses with double-stranded (ds) RNA genomes in filamentous fungi, there has been no screening of mycoviruses in P. oxalicum. In this report, we describe the identification and characterization of a novel dsRNA virus isolated from P. oxalicum, designated as "Penicillium oxalicum partitivirus 1" (PoPV1). The genome of PoPV1 consists of two dsRNA segments, dsRNA1 (1,770 bp) and dsRNA2 (1,584 bp), each containing a single open reading frame (ORF): ORF1 and ORF2. Comparative analysis revealed that the RdRp and CP amino acid sequences of PoPV1 share the highest identity (89.18% and 73.97%, respectively) with those of Penicillium aurantiogriseum partitivirus 1 (PaPV1). Motif analysis based on RdRp amino acid sequences places PoPV1 in the genus Gammapartitivirus within the family Partitiviridae, with a distinctive motif VI (R/KV/ILGDD). Phylogenetic analysis further established a close relationship of PoPV1 to PaPV1, forming a unique clade among the gammapartitiviruses. Consequently, we propose that Penicillium oxalicum partitivirus 1 represents a new species in the genus Gammapartitivirus. This is the first report of a dsRNA virus in P. oxalicum.
... The sexual fruiting bodies of the C. militaris WT and sector cultures were induced on a rice medium and the pupae of Chinese Tussah silkworm (Antheraea pernyi) by injection with 100 µl of 1 × 10 7 conidia/ml suspension per insect for 30 days as described before [27]. Total RNA was extracted from the two-week-old WT and sector PDA cultures using the TRIzol reagent (Thermo Fisher Scientific), treated with DNase I (New England Biolabs) and checked with 1% agarose gel to determine the presence or absence of mycovirus in each fungus [28]. ...
... In addition, some mycoviruses might participate in the interactions between biocontrol fungi and their host, such as mycoviruses in Trichoderma spp. (21), Metarhizium majus (22), and Beauveria bassiana (15). In addition, some mycoviruses can regulate the metabolite production, multistress tolerance, and drug resistance of their host fungi (11,23,24). ...
Colletotrichum is a kind of economically important phytopathogenic fungi that cause anthracnose disease in a variety of plant species worldwide. We found a novel mycovirus of the Gammapartitiviru s genus and Partitiviridae family from the phytopathogenic fungus Colletotrichum alienum and named it CaPV1. This study revealed that CaPV1 infection significantly decreased host virulence and fitness by affecting mycelial growth, appressorial development, and appressorium turgor. In addition, CaPV1 could also infect other Colletotrichum species, including C. fructicola , C. spaethianum , and C. gloeosporioides , by viral particle transfection and resulting in hypovirulence of these Colletotrichum species. Transcriptomic analysis showed that CaPV1 caused significant transcriptional rewiring of the host fungus C. alienum , especially the genes involved in vesicle transport. Moreover, endocytosis and gene knockout assays demonstrated that the mechanism underlying CaPV1-induced hypovirulence is, at least in part, caused by affecting the vesicle transport of the host fungus. This study provided insights into the mechanisms underlying the pathogenesis of Colletotrichum species and mycovirus-fungus interactions, linking the role of mycovirus and fungus vesicle transport systems in shaping fungal pathogenicity.
... Within Partitiviridae, the genus Gammapartitivirus is of particular interest, and it includes various members that infect ascomycetous fungi. While the majority of gammapartitiviruses induce latent infections, certain exceptions, such as Talaromyces marneffei partitivirus-1 (TmPV1) and Metarhizium majus partitivirus 1(MmPV1), impact the biological characteristics of their hosts [3,4]. ...
Penicillium oxalicum , an essential biocontrol fungus in China, has been a subject of extensive study due to its role in combating various pathogenic fungi. Despite the prevalence of mycoviruses with double-stranded (ds) RNA genomes in filamentous fungi, no instances of mycovirus infection have been reported in P. oxalicum . In this investigation, we present the identification and characterization of a novel dsRNA virus isolated from P. oxalicum , designated as "Penicillium oxalicum partitivirus 1" (PoPV1). The genome of PoPV1 consists of two dsRNA segments, dsRNA1 (1,770 bp) and dsRNA2 (1,584 bp), each hosting a single open reading frame (ORF): ORF1 and ORF2. Comparative analysis revealed that PoPV1's RdRp and CP sequences share the highest identity (89.18% and 73.97%, respectively) with Penicillium aurantiogriseum partitivirus 1 (PaPV1). Motif analysis based on RdRp amino acid sequences places PoPV1 in the genus Gammapartitivirus within the family Partitiviridae , with a distinctive motif VI (R/KV/ILGDD). Phylogenetic analysis further establishes PoPV1's close relationship with PaPV1, forming a unique clade within gammapartitiviruses. Consequently, we propose that Penicillium oxalicum partitivirus 1 represents a novel species in the genus Gammapartitivirus , marking the first reported case of dsRNA in P. oxalicum .
... Unfortunately, mycoviruses can also hypovirulence of entomopathogenic fungi. Wang et al. (2023) found that infection with partitivirus Metarhizium majus partitivirus 1 (MmPV1) decreased conidiation and tolerance to heat shock and UV-B irradiation, and especially hypovirulence toward the insect pest of the host entomogenous fungus Metarhizium majus [67]. However, there have been few reports on mycoviruses causing B. bassiana hypovirulence. ...
... Unfortunately, mycoviruses can also hypovirulence of entomopathogenic fungi. Wang et al. (2023) found that infection with partitivirus Metarhizium majus partitivirus 1 (MmPV1) decreased conidiation and tolerance to heat shock and UV-B irradiation, and especially hypovirulence toward the insect pest of the host entomogenous fungus Metarhizium majus [67]. However, there have been few reports on mycoviruses causing B. bassiana hypovirulence. ...
... In addition, biomass was significantly decreased following virus infection, which likely causes a decrease of physical damage and toxin metabolism. The hypovirulence mechanism of partitivirus MmPV1 toward host fungi was known to involve a decrease in toxin metabolism caused by infection, including effects on triterpenoids and metarhizins A and B [67]. Hence, interactions between mycoviruses and genes/ pathways related to insect epidermis penetration, fungal biomass and toxin metabolism may be involved in the mechanisms by which BbCV2 causes hypovirulence of B. bassiana, but this needs to be verified at the protein level though co-immunoprecipitation assays [80,81] and pulldown assays [82], both of which are efficient methods for probing virus-host interactions. ...
Background
The entomogenous fungus Beauveria bassiana is used as a biological insecticide worldwide, wild B. bassiana strains with high pathogenicity in the field play an important role in controlling insect pests via not only screening of highly virulent strains but also natural infection, but the pathogenicity degeneration of wild strains severely affected aforementioned effects. Previous studies have showed that multiple factors contributed to this phenomenon. It has been extensively proved that the mycovirus infection caused hypovirulence of phytopathogenic fungi, which has been used for plant disease biocontrol. However, it remains unknown whether the mycovirus epidemics is a key factor causing hypovirulence of B. bassiana naturally in the field.
Methods
Wild strains of B. bassiana were collected from different geographic locations in Jilin Province, China, to clarify the epidemic and diversity of the mycoviruses. A mycovirus Beauveria bassiana chrysovirus 2 (BbCV2) we have previously identified was employed to clarify its impact on the pathogenicity of host fungi B. bassiana against the larvae of insect pest Ostrinia furnacalis. The serological analysis was conducted by preparing polyclonal antibody against a BbCV2 coat protein, to determine whether it can dissociate outside the host fungal cells and subsequently infect new hosts. Transcriptome analysis was used to reveal the interactions between viruses and hosts.
Results
We surprisingly found that the mycovirus BbCV2 was prevalent in the field as a core virus in wild B. bassiana strains, without obvious genetic differentiation, this virus possessed efficient and stable horizontal and vertical transmission capabilities. The serological results showed that the virus could not only replicate within but also dissociate outside the host cells, and the purified virions could infect B. bassiana by co-incubation. The virus infection causes B. bassiana hypovirulence. Transcriptome analysis revealed decreased expression of genes related to insect epidermis penetration, hypha growth and toxin metabolism in B. bassiana caused by mycovirus infection.
Conclusion
Beauveria bassiana infected by hypovirulence-associated mycovirus can spread the virus to new host strains after infecting insects, and cause the virus epidemics in the field. The findings confirmed that mycovirus infection may be an important factor affecting the pathogenicity degradation of B. bassiana in the field.
... Since the coinfection of animal viruses and fungi can occur in the same host [63][64][65][66][67][68], it is worth questioning whether fungi can also acquire animal viruses during colonization. Notably, several animal viruses (mainly arthropod viruses) and fungal viruses show a close taxonomic relationship [69][70][71][72][73][74][75][76][77][78][79][80][81] (Fig 1). Moreover, in recent reports, several mycoviruses in the order Bunyavirales and the family Rhabdovirdae (order Mononegavirales) were identified to encode a putative precursor of glycoproteins or a glycoprotein similar to that encoded by animal-infecting viruses in the family Phenuiviridae or animal rhabdoviruses (subfamily Alpharhabdovirinae), respectively [75,77,82]. ...
Fungi are highly widespread and commonly colonize multicellular organisms that live in natural environments. Notably, studies on viruses infecting plant-associated fungi have revealed the interesting phenomenon of the cross-kingdom transmission of viruses and viroids from plants to fungi. This implies that fungi, in addition to absorbing water, nutrients, and other molecules from the host, can acquire intracellular parasites that reside in the host. These findings further suggest that fungi can serve as suitable alternative hosts for certain plant viruses and viroids. Given the frequent coinfection of fungi and viruses in humans/animals, the question of whether fungi can also acquire animal viruses and serve as their hosts is very intriguing. In fact, the transmission of viruses from insects to fungi has been observed. Furthermore, the common release of animal viruses into the extracellular space (viral shedding) could potentially facilitate their acquisition by fungi. Investigations of the cross-infection of animal viruses in fungi may provide new insights into the epidemiology of viral diseases in humans and animals.
