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Bradley I. Hillman - One of the best experts on this subject based on the ideXlab platform.
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Genome analysis of Cryphonectria hypovirus 4, the most common hypovirus species in North America.
Virology, 2005Co-Authors: Daniela Linder-basso, Jasmin N. Dynek, Bradley I. HillmanAbstract:Many different viruses that reduce virulence and alter the phenotype to varying extents have been identified in the chestnut blight fungus Cryphonectria parasitica. Most viruses identified in this fungus fall within the Hypoviridae family of positive-sense RNA viruses, which contains one genus and four species. Different species predominate in different geographic locations in chestnut-growing areas around the world. In this paper, we describe the genome organization and some variants of Cryphonectria hypovirus 4 (CHV-4), the species most commonly found in eastern North America. CHV-4 is distinguished from other hypoviruses by having little effect on fungal virulence and colony morphology. The 9.1-kb genome of strain CHV-4/SR2 is the smallest of any member of the family characterized to date. Like the recently characterized species CHV-3, a single ORF was predicted from deduced translations of CHV-4/ SR2. Sequence analysis revealed the presence of a putative glucosyltransferase domain in both CHV-4 and in CHV-3, but no such homolog was detected in the more thoroughly examined CHV-1 or in CHV-2. Alignments with 8 other CHV-4 isolates from different regions of eastern North America revealed sequence diversity within the species and the likelihood that RNA recombination has led to this diversity.
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satellite and defective rnas of cryphonectria hypovirus 3 grand haven 2 a virus species in the family Hypoviridae with a single open reading frame
Virology, 2000Co-Authors: Bradley I. Hillman, R. Foglia, Weiming YuanAbstract:Abstract Cryphonectria parasitica hypovirus 3-Grand Haven 2 (CHV3-GH2) is the most recently characterized member of the Hypoviridae family of viruses associated with hypovirulence of the chestnut blight fungus. Isolates of CHV3-GH2 contain either three or four double-stranded (ds) RNAs that are visible on ethidium bromide-stained agarose or polyacrylamide gels. Only the largest dsRNA appears to be required for virus infectivity, and was characterized previously (C. D. Smart et al., 1999, Virology 265, 66–73). In this study, we report the cloning, sequencing, and analysis of the other three dsRNAs. Sizes of the accessory dsRNAs are 3.6 kb (dsRNA 2), 1.9 kb (dsRNA 3), and 0.9 kb (dsRNA 4), compared to 9.8 kb for the genomic dsRNA segment (dsRNA 1). All three accessory dsRNA species are polyadenylated on the 3′-end of one strand, as is genomic dsRNA. DsRNA 2 represents a defective form of dsRNA 1, with the 5′-terminal 1.4 kb derived from the 5′-end of dsRNA 1 and the 3′-terminal 2.2 kb from the 3′-end of dsRNA 1. A single major open reading frame (ORF) is evident from deduced translations of dsRNA 2. The deduced translation product is a 91-kDa protein that represents a fusion consisting of the entire N-terminal protease and the entire putative helicase domain. DsRNAs 3 and 4 represent satellite RNAs that share very little sequence with dsRNA 1 and 2. DsRNA 4 is 937 nucleotides, excluding the poly(A) + . The first AUG of the polyadenylated strand of dsRNA 4 occurs eight residues in from the 5′-terminus and would initiate the largest ORF on dsRNA 4, with the coding capacity for a 9.4-kDa protein. Within the deduced ORF and approximately 100 nucleotides from the 5′-end of dsRNA 4 is a 22-base sequence that is identical to sequences found in the nontranslated leaders of dsRNAs 1 and 2. DsRNA 3 accumulation in infected cultures varied, but it was less abundant than dsRNA 4. DsRNA 3 was found to represent a head-to-tail dimer of dsRNA 4 linked by a poly(A)/(U) stretch of 40–70 residues.
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Cryphonectria hypovirus 3, a Virus Species in the Family Hypoviridae with a Single Open Reading Frame
Virology, 1999Co-Authors: Christine D. Smart, Donald L. Nuss, Weiming Yuan, R. Foglia, D. W. Fulbright, Bradley I. HillmanAbstract:Isolate Grand Haven (GH) 2 is a naturally occurring isolate of the chestnut blight fungus, Cryphonectria parasitica, that is greatly reduced in virulence due to the presence of a double-stranded RNA virus. Unlike many other virus-infected, hypovirulent isolates, GH2 is not substantially reduced in pigmentation, conidiation, or laccase expression compared to its virus-free counterpart. The dsRNA genome of the GH2 virus was cloned, sequenced, and compared to hypovirulence-associated viruses of the family Hypoviridae. GH2 dsRNA is considerably smaller than previously characterized members of the family, 9.8 kb compared to 12.5–12.7 kb for other members. The genome organization of GH2 dsRNA reflected the substantial difference in genome size. Like other members of the family, one strand contained a poly(A)+ tail at the 3′ end and a long sequence with several minicistrons at the 5′ end of the same strand. Only a single open reading frame (ORF) of 8622 nucleotides was predicted from deduced translations of the poly(A)+-containing strand, however. This contrasts with the two-ORF structures of previously characterized members. Analysis of the deduced ORF of GH2 dsRNA revealed putative proteinase, RNA polymerase, and helicase domains similar to those previously identified in confirmed members of the virus family Hypoviridae. GH2 dsRNA was more distantly related to Cryphonectria hypovirus (CHV) 1-EP713 and CHV2-NB58 than the latter two were to each other but has features in common with each of those viruses. We propose that the GH2 virus be included in this taxon as a member of the genus Hypovirus, representing a strain of a new species, CHV3.
Donald L. Nuss - One of the best experts on this subject based on the ideXlab platform.
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hypovirus molecular biology from koch s postulates to host self recognition genes that restrict virus transmission
Advances in Virus Research, 2013Co-Authors: Angus L. Dawe, Donald L. NussAbstract:The idea that viruses can be used to control fungal diseases has been a driving force in mycovirus research since the earliest days. Viruses in the family Hypoviridae associated with reduced virulence (hypovirulence) of the chestnut blight fungus, Cryphonectria parasitica, have held a prominent place in this research. This has been due in part to the severity of the chestnut blight epidemics in North America and Europe and early reports of hypovirulence-mediated mitigation of disease in European forests and successful application for control of chestnut blight in chestnut orchards. A more recent contributing factor has been the development of a hypovirus/C. parasitica experimental system that has overcome many of the challenges associated with mycovirus research, stemming primarily from the exclusive intracellular lifestyle shared by all mycoviruses. This chapter will focus on hypovirus molecular biology with an emphasis on the development of the hypovirus/C. parasitica experimental system and its contributions to fundamental and practical advances in mycovirology and the broader understanding of virus-host interactions and fungal pathogenesis.
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hypovirulence mycoviruses at the fungal plant interface
Nature Reviews Microbiology, 2005Co-Authors: Donald L. NussAbstract:Whereas most mycoviruses lead 'secret lives', some reduce the ability of their fungal hosts to cause disease in plants. This property, known as hypovirulence, has attracted attention owing to the importance of fungal diseases in agriculture and the limited strategies that are available for the control of these diseases. Using one pathogen to control another is appealing, both intellectually and ecologically. The recent development of an infectious cDNA-based reverse genetics system for members of the Hypoviridae mycovirus family has enabled the analysis of basic aspects of this fascinating virus–fungus–plant interaction, including virus–host interactions, the mechanisms underlying fungal pathogenesis, fungal signalling pathways and the evolution of RNA silencing. Such systems also provide a means for engineering mycoviruses for enhanced biocontrol potential.
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contribution of protein p40 to hypovirus mediated modulation of fungal host phenotype and viral rna accumulation
Journal of Virology, 2002Co-Authors: Nobuhiro Suzuki, Donald L. NussAbstract:Members of the virus family Hypoviridae are distinguished by the ability to persistently attenuate virulence (hypovirulence) and stably alter complex biological processes upon infection of their fungal host, the chestnut blight fungus, Cryphonectria parasitica. Infection-related phenotypic changes can include reduced pigment production, suppressed asexual sporulation, altered colony morphology, loss of female fertility, and modified expression of specific host genes (1, 12, 22-25). Efforts to identify hypovirus symptom determinants have benefited from the complete nucleotide sequence determinations of four members of the family (7, 18, 28, 30) and construction of full-length infectious cDNA clones for two family members: the prototypic severe hypovirus isolate CHV1-EP713 (9) and the mild isolate CHV1-Euro7 (7). Using the robust transformation protocol available for C. parasitica (10), Choi and Nuss (8) showed that the 5′-proximal CHV1-EP713 coding domain, open reading frame (ORF) A, when expressed in C. parasitica transformants in the absence of virus infection, caused a subset of phenotypic changes exhibited by CHV1-EP713-infected strains, e.g., a white phenotype (reduction in orange pigmentation), reduced asexual sporulation, and a slight reduction in the production of fungal laccase activity. ORF A encodes a 69-kDa polyprotein (p69) that is autocatalytically processed into p29 and p40 by the action of a papain-like cysteine protease domain located in the p29 coding region. Craven et al. (11) subsequently mapped the ORF A suppressive activity to p29, located within the N-terminal portion of p69. By deleting all but the first 24 codons of p29 in the context of the CHV1-EP713 infectious cDNA clone (mutant virus Δp29), these authors were also able to show that 88% of the p29 coding domain is dispensable for viral replication and that p29 contributes to the suppression in orange pigment production and in conidiation but not to virulence attenuation. Suzuki et al. (31) subsequently devised a gain-of-function analysis involving progressive repair of the Δp29 mutant virus to map the p29 symptom determinant domain to a region extending from Phe(25) to Gln(73). These authors noted a moderate level of sequence similarity between this region of p29 and the N-terminal portion of the HC-Pro papain-like protease encoded by plant-infecting potyviruses, including four conserved cysteine residues, Cys(38), Cys(48), Cys(70), and Cys(72). While substitution of a glycine for Cys(38) and Cys(48) had no apparent phenotypic effect, replacement of Cys(72) resulted in reduction of symptoms approaching that observed for the Δp29 mutant. In contrast, replacement of Cys(70) resulted in a very severe phenotype that included significantly reduced mycelial growth and profoundly altered colony morphology. Given the proposed evolutionary relationship between hypoviruses and potyviruses (20), it will be instructive to compare p29- and HC-Pro-mediated modulation of specific cellular regulatory pathways in the respective fungal and plant hosts. Additional insights into the functional role of viral coding regions were indirectly provided during recent efforts to develop hypoviruses as gene expression vectors (32). The nucleotide sequence corresponding to the first 24 codons of p29 were found to be required for viral replication, while the remaining 598 codons of ORF A, including all of the p40 coding region, was found to be dispensable. Substantial alterations were also tolerated in the pentanucleotide UAAUG that contains the ORF A termination codon and the overlapping putative ORF B initiation codon. For example, replication competence was maintained following either a frameshift mutation that caused a two-codon extension of ORF A or a modification that produced a single-ORF genomic organization. The deduced p40 amino acid sequence is very basic (pKa = 11.96), indicative of a possible role in viral RNA binding or replication. Moreover, this protein is conserved between two major hypovirus species, CHV1 and CHV2 (30). Thus, the observation that p40 is not required for CHV1-EP713 replication (32) was surprising. We now report the consequences of p40 deletion for CHV1-EP713-mediated alteration of fungal phenotype, virulence, and viral RNA accumulation and also report the mapping of the functional domain of this highly basic protein to amino acid residues Thr(288) to Arg(312).
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Cryphonectria hypovirus 3, a Virus Species in the Family Hypoviridae with a Single Open Reading Frame
Virology, 1999Co-Authors: Christine D. Smart, Donald L. Nuss, Weiming Yuan, R. Foglia, D. W. Fulbright, Bradley I. HillmanAbstract:Isolate Grand Haven (GH) 2 is a naturally occurring isolate of the chestnut blight fungus, Cryphonectria parasitica, that is greatly reduced in virulence due to the presence of a double-stranded RNA virus. Unlike many other virus-infected, hypovirulent isolates, GH2 is not substantially reduced in pigmentation, conidiation, or laccase expression compared to its virus-free counterpart. The dsRNA genome of the GH2 virus was cloned, sequenced, and compared to hypovirulence-associated viruses of the family Hypoviridae. GH2 dsRNA is considerably smaller than previously characterized members of the family, 9.8 kb compared to 12.5–12.7 kb for other members. The genome organization of GH2 dsRNA reflected the substantial difference in genome size. Like other members of the family, one strand contained a poly(A)+ tail at the 3′ end and a long sequence with several minicistrons at the 5′ end of the same strand. Only a single open reading frame (ORF) of 8622 nucleotides was predicted from deduced translations of the poly(A)+-containing strand, however. This contrasts with the two-ORF structures of previously characterized members. Analysis of the deduced ORF of GH2 dsRNA revealed putative proteinase, RNA polymerase, and helicase domains similar to those previously identified in confirmed members of the virus family Hypoviridae. GH2 dsRNA was more distantly related to Cryphonectria hypovirus (CHV) 1-EP713 and CHV2-NB58 than the latter two were to each other but has features in common with each of those viruses. We propose that the GH2 virus be included in this taxon as a member of the genus Hypovirus, representing a strain of a new species, CHV3.
Jiatao Xie - One of the best experts on this subject based on the ideXlab platform.
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characterization of a novel megabirnavirus from sclerotinia sclerotiorum reveals horizontal gene transfer from single stranded rna virus to double stranded rna virus
Journal of Virology, 2015Co-Authors: Jiasen Cheng, Said A. Ghabrial, Huiquan Liu, Daohong Jiang, Minghong Wang, Yong Wang, Xiangzhong Sun, Jiatao XieAbstract:Mycoviruses have been detected in all major groups of filamentous fungi, and their study represents an important branch of virology. Here, we characterized a novel double-stranded RNA (dsRNA) mycovirus, Sclerotinia sclerotiorum megabirnavirus 1 (SsMBV1), in an apparently hypovirulent strain (SX466) of Sclerotinia sclerotiorum. Two similarly sized dsRNA segments (L1- and L2-dsRNA), the genome of SsMBV1, are packaged in rigid spherical particles purified from strain SX466. The full-length cDNA sequence of L1-dsRNA/SsMBV1 comprises two large open reading frames (ORF1 and ORF2), which encode a putative coat protein and an RNA-dependent RNA polymerase (RdRp), respectively. Phylogenetic analysis of the RdRp domain clearly indicates that SsMBV1 is related to Rosellinia necatrix megabirnavirus 1 (RnMBV1). L2-dsRNA/SsMBV1 comprises two nonoverlapping ORFs (ORFA and ORFB) encoding two hypothetical proteins with unknown functions. The 5′-terminal regions of L1- and L2-dsRNA/SsMBV1 share strictly conserved sequences and form stable stem-loop structures. Although L2-dsRNA/SsMBV1 is dispensable for replication, genome packaging, and pathogenicity of SsMBV1, it enhances transcript accumulation of L1-dsRNA/SsMBV1 and stability of virus-like particles (VLPs). Interestingly, a conserved papain-like protease domain similar to a multifunctional protein (p29) of Cryphonectria hypovirus 1 was detected in the ORFA-encoded protein of L2-dsRNA/SsMBV1. Phylogenetic analysis based on the protease domain suggests that horizontal gene transfer may have occurred from a single-stranded RNA (ssRNA) virus (hypovirus) to a dsRNA virus, SsMBV1. Our results reveal that SsMBV1 has a slight impact on the fundamental biological characteristics of its host regardless of the presence or absence of L2-dsRNA/SsMBV1. IMPORTANCE Mycoviruses are widespread in all major fungal groups, and they possess diverse genomes of mostly ssRNA and dsRNA and, recently, circular ssDNA. Here, we have characterized a novel dsRNA virus (Sclerotinia sclerotiorum megabirnavirus 1 [SsMBV1]) that was isolated from an apparently hypovirulent strain, SX466, of Sclerotinia sclerotiorum. Although SsMBV1 is phylogenetically related to RnMBV1, SsMBV1 is markedly distinct from other reported megabirnaviruses with two features of VLPs and conserved domains. Our results convincingly showed that SsMBV1 is viable in the absence of L2-dsRNA/SsMBV1 (a potential large satellite-like RNA or genuine genomic virus component). More interestingly, we detected a conserved papain-like protease domain that commonly exists in ssRNA viruses, including members of the families Potyviridae and Hypoviridae. Phylogenetic analysis based on the protease domain suggests that horizontal gene transfer might have occurred from an ssRNA virus to a dsRNA virus, which may provide new insights into the evolutionary history of dsRNA and ssRNA viruses.
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a novel mycovirus closely related to hypoviruses that infects the plant pathogenic fungus sclerotinia sclerotiorum
Virology, 2011Co-Authors: Jiatao Xie, Xueqiong Xiao, Jiasen Cheng, Huiquan Liu, Said A. GhabrialAbstract:Abstract Three dsRNA segments, two similarly sized at 9.5 kbp and a third one of approximately 3.6 kbp, were extracted from a hypovirulent strain SZ-150 of Sclerotinia sclerotiorum . The complete cDNA sequence of one of the two large dsRNA segment (10398 bp, excluding the poly (A) tail) reveals a single ORF that encodes a polyprotein with conserved domains of putative papain-like protease, UDP glucose/sterol glycosyltransferase, RNA-dependent RNA polymerase and viral RNA Helicase. This virus is closely related to Cryphonectria hypovirus (CHV) 3/GH2 and CHV4/SR2 in the family Hypoviridae and designated as Sclerotinia sclerotiorum hypovirus 1 (SsHV1/SZ-150). The satellite-like 3.6 kbp dsRNA segment (S-dsRNA) shares high sequence identity with the 5′-UTR of SsHV1/SZ-150. SsHV1/SZ-150 alone is not the primary causal agent for hypovirulence of strain SZ-150 since strains without the S-dsRNA show normal phenotype. This is the first report of a naturally occurring hypovirus that infects a fungus other than Cryphonectria parasitica .
Minghong Wang - One of the best experts on this subject based on the ideXlab platform.
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characterization of a novel megabirnavirus from sclerotinia sclerotiorum reveals horizontal gene transfer from single stranded rna virus to double stranded rna virus
Journal of Virology, 2015Co-Authors: Jiasen Cheng, Said A. Ghabrial, Huiquan Liu, Daohong Jiang, Minghong Wang, Yong Wang, Xiangzhong Sun, Jiatao XieAbstract:Mycoviruses have been detected in all major groups of filamentous fungi, and their study represents an important branch of virology. Here, we characterized a novel double-stranded RNA (dsRNA) mycovirus, Sclerotinia sclerotiorum megabirnavirus 1 (SsMBV1), in an apparently hypovirulent strain (SX466) of Sclerotinia sclerotiorum. Two similarly sized dsRNA segments (L1- and L2-dsRNA), the genome of SsMBV1, are packaged in rigid spherical particles purified from strain SX466. The full-length cDNA sequence of L1-dsRNA/SsMBV1 comprises two large open reading frames (ORF1 and ORF2), which encode a putative coat protein and an RNA-dependent RNA polymerase (RdRp), respectively. Phylogenetic analysis of the RdRp domain clearly indicates that SsMBV1 is related to Rosellinia necatrix megabirnavirus 1 (RnMBV1). L2-dsRNA/SsMBV1 comprises two nonoverlapping ORFs (ORFA and ORFB) encoding two hypothetical proteins with unknown functions. The 5′-terminal regions of L1- and L2-dsRNA/SsMBV1 share strictly conserved sequences and form stable stem-loop structures. Although L2-dsRNA/SsMBV1 is dispensable for replication, genome packaging, and pathogenicity of SsMBV1, it enhances transcript accumulation of L1-dsRNA/SsMBV1 and stability of virus-like particles (VLPs). Interestingly, a conserved papain-like protease domain similar to a multifunctional protein (p29) of Cryphonectria hypovirus 1 was detected in the ORFA-encoded protein of L2-dsRNA/SsMBV1. Phylogenetic analysis based on the protease domain suggests that horizontal gene transfer may have occurred from a single-stranded RNA (ssRNA) virus (hypovirus) to a dsRNA virus, SsMBV1. Our results reveal that SsMBV1 has a slight impact on the fundamental biological characteristics of its host regardless of the presence or absence of L2-dsRNA/SsMBV1. IMPORTANCE Mycoviruses are widespread in all major fungal groups, and they possess diverse genomes of mostly ssRNA and dsRNA and, recently, circular ssDNA. Here, we have characterized a novel dsRNA virus (Sclerotinia sclerotiorum megabirnavirus 1 [SsMBV1]) that was isolated from an apparently hypovirulent strain, SX466, of Sclerotinia sclerotiorum. Although SsMBV1 is phylogenetically related to RnMBV1, SsMBV1 is markedly distinct from other reported megabirnaviruses with two features of VLPs and conserved domains. Our results convincingly showed that SsMBV1 is viable in the absence of L2-dsRNA/SsMBV1 (a potential large satellite-like RNA or genuine genomic virus component). More interestingly, we detected a conserved papain-like protease domain that commonly exists in ssRNA viruses, including members of the families Potyviridae and Hypoviridae. Phylogenetic analysis based on the protease domain suggests that horizontal gene transfer might have occurred from an ssRNA virus to a dsRNA virus, which may provide new insights into the evolutionary history of dsRNA and ssRNA viruses.
Weiming Yuan - One of the best experts on this subject based on the ideXlab platform.
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satellite and defective rnas of cryphonectria hypovirus 3 grand haven 2 a virus species in the family Hypoviridae with a single open reading frame
Virology, 2000Co-Authors: Bradley I. Hillman, R. Foglia, Weiming YuanAbstract:Abstract Cryphonectria parasitica hypovirus 3-Grand Haven 2 (CHV3-GH2) is the most recently characterized member of the Hypoviridae family of viruses associated with hypovirulence of the chestnut blight fungus. Isolates of CHV3-GH2 contain either three or four double-stranded (ds) RNAs that are visible on ethidium bromide-stained agarose or polyacrylamide gels. Only the largest dsRNA appears to be required for virus infectivity, and was characterized previously (C. D. Smart et al., 1999, Virology 265, 66–73). In this study, we report the cloning, sequencing, and analysis of the other three dsRNAs. Sizes of the accessory dsRNAs are 3.6 kb (dsRNA 2), 1.9 kb (dsRNA 3), and 0.9 kb (dsRNA 4), compared to 9.8 kb for the genomic dsRNA segment (dsRNA 1). All three accessory dsRNA species are polyadenylated on the 3′-end of one strand, as is genomic dsRNA. DsRNA 2 represents a defective form of dsRNA 1, with the 5′-terminal 1.4 kb derived from the 5′-end of dsRNA 1 and the 3′-terminal 2.2 kb from the 3′-end of dsRNA 1. A single major open reading frame (ORF) is evident from deduced translations of dsRNA 2. The deduced translation product is a 91-kDa protein that represents a fusion consisting of the entire N-terminal protease and the entire putative helicase domain. DsRNAs 3 and 4 represent satellite RNAs that share very little sequence with dsRNA 1 and 2. DsRNA 4 is 937 nucleotides, excluding the poly(A) + . The first AUG of the polyadenylated strand of dsRNA 4 occurs eight residues in from the 5′-terminus and would initiate the largest ORF on dsRNA 4, with the coding capacity for a 9.4-kDa protein. Within the deduced ORF and approximately 100 nucleotides from the 5′-end of dsRNA 4 is a 22-base sequence that is identical to sequences found in the nontranslated leaders of dsRNAs 1 and 2. DsRNA 3 accumulation in infected cultures varied, but it was less abundant than dsRNA 4. DsRNA 3 was found to represent a head-to-tail dimer of dsRNA 4 linked by a poly(A)/(U) stretch of 40–70 residues.
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Cryphonectria hypovirus 3, a Virus Species in the Family Hypoviridae with a Single Open Reading Frame
Virology, 1999Co-Authors: Christine D. Smart, Donald L. Nuss, Weiming Yuan, R. Foglia, D. W. Fulbright, Bradley I. HillmanAbstract:Isolate Grand Haven (GH) 2 is a naturally occurring isolate of the chestnut blight fungus, Cryphonectria parasitica, that is greatly reduced in virulence due to the presence of a double-stranded RNA virus. Unlike many other virus-infected, hypovirulent isolates, GH2 is not substantially reduced in pigmentation, conidiation, or laccase expression compared to its virus-free counterpart. The dsRNA genome of the GH2 virus was cloned, sequenced, and compared to hypovirulence-associated viruses of the family Hypoviridae. GH2 dsRNA is considerably smaller than previously characterized members of the family, 9.8 kb compared to 12.5–12.7 kb for other members. The genome organization of GH2 dsRNA reflected the substantial difference in genome size. Like other members of the family, one strand contained a poly(A)+ tail at the 3′ end and a long sequence with several minicistrons at the 5′ end of the same strand. Only a single open reading frame (ORF) of 8622 nucleotides was predicted from deduced translations of the poly(A)+-containing strand, however. This contrasts with the two-ORF structures of previously characterized members. Analysis of the deduced ORF of GH2 dsRNA revealed putative proteinase, RNA polymerase, and helicase domains similar to those previously identified in confirmed members of the virus family Hypoviridae. GH2 dsRNA was more distantly related to Cryphonectria hypovirus (CHV) 1-EP713 and CHV2-NB58 than the latter two were to each other but has features in common with each of those viruses. We propose that the GH2 virus be included in this taxon as a member of the genus Hypovirus, representing a strain of a new species, CHV3.