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Telengech P, Hyodo K, Ichikawa H, Kuwata R, Kondo H, Suzuki N. Replication of single viruses across the kingdoms, Fungi, Plantae, and Animalia. Proc Natl Acad Sci U S A 2024; 121:e2318150121. [PMID: 38865269 PMCID: PMC11194502 DOI: 10.1073/pnas.2318150121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 05/10/2024] [Indexed: 06/14/2024] Open
Abstract
It is extremely rare that a single virus crosses host barriers across multiple kingdoms. Based on phylogenetic and paleovirological analyses, it has previously been hypothesized that single members of the family Partitiviridae could cross multiple kingdoms. Partitiviridae accommodates members characterized by their simple bisegmented double-stranded RNA genome; asymptomatic infections of host organisms; the absence of an extracellular route for entry in nature; and collectively broad host range. Herein, we show the replicability of single fungal partitiviruses in three kingdoms of host organisms: Fungi, Plantae, and Animalia. Betapartitiviruses of the phytopathogenic fungusRosellinia necatrix could replicate in protoplasts of the carrot (Daucus carota), Nicotiana benthamiana and Nicotiana tabacum, in some cases reaching a level detectable by agarose gel electrophoresis. Moreover, betapartitiviruses showed more robust replication than the tested alphapartitiviruses. One of the fungal betapartitiviruses, RnPV18, could persistently and stably infect carrot plants regenerated from virion-transfected protoplasts. Both alpha- and betapartitiviruses, although with different host preference, could replicate in two insect cell lines derived from the fall armyworm Spodoptera frugiperda and the fruit fly Drosophila melanogaster. Our results indicate the replicability of single partitiviruses in members of three kingdoms and provide insights into virus adaptation, host jumping, and evolution.
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Affiliation(s)
- Paul Telengech
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
| | - Kiwamu Hyodo
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
| | - Hiroaki Ichikawa
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki305-8634, Japan
| | - Ryusei Kuwata
- Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Ehime794-8555, Japan
| | - Hideki Kondo
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
| | - Nobuhiro Suzuki
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
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Sato Y, Kondo H, Suzuki N. Argonaute-independent, Dicer-dependent antiviral defense against RNA viruses. Proc Natl Acad Sci U S A 2024; 121:e2322765121. [PMID: 38865263 PMCID: PMC11194562 DOI: 10.1073/pnas.2322765121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Accepted: 05/07/2024] [Indexed: 06/14/2024] Open
Abstract
Antiviral RNA interference (RNAi) is conserved from yeasts to mammals. Dicer recognizes and cleaves virus-derived double-stranded RNA (dsRNA) and/or structured single-stranded RNA (ssRNA) into small-interfering RNAs, which guide effector Argonaute to homologous viral RNAs for digestion and inhibit virus replication. Thus, Argonaute is believed to be essential for antiviral RNAi. Here, we show Argonaute-independent, Dicer-dependent antiviral defense against dsRNA viruses using Cryphonectria parasitica (chestnut blight fungus), which is a model filamentous ascomycetous fungus and hosts a variety of viruses. The fungus has two dicer-like genes (dcl1 and dcl2) and four argonaute-like genes (agl1 to agl4). We prepared a suite of single to quadruple agl knockout mutants with or without dcl disruption. We tested these mutants for antiviral activities against diverse dsRNA viruses and ssRNA viruses. Although both DCL2 and AGL2 worked as antiviral players against some RNA viruses, DCL2 without argonaute was sufficient to block the replication of other RNA viruses. Overall, these results indicate the existence of a Dicer-alone defense and different degrees of susceptibility to it among RNA viruses. We discuss what determines the great difference in susceptibility to the Dicer-only defense.
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Affiliation(s)
- Yukiyo Sato
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
| | - Hideki Kondo
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
| | - Nobuhiro Suzuki
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama710-0046, Japan
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Zhou Q, Yao Z, Cao X, Chen Y, Zou C, Chen B. Fusarium sacchari hypovirus 1, a Member of Hypoviridae with Virulence Attenuation Capacity in Phytopathogenic Fusarium Species. Viruses 2024; 16:608. [PMID: 38675949 PMCID: PMC11054305 DOI: 10.3390/v16040608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Revised: 04/05/2024] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
In a survey of mycoviruses in Fusarium species that cause sugarcane Pokkah boeng disease, twelve Fusarium strains from three Fusarium species (F. sacchari, F. andiyazi, and F. solani) were found to contain Fusarium sacchari hypovirus 1 (FsHV1), which we reported previously. The genomes of these variants range from 13,966 to 13,983 nucleotides, with 98.6% to 99.9% nucleotide sequence identity and 98.70% to 99.9% protein sequence similarity. Phylogenetic analysis placed these FsHV1 variants within the Alphahypovirus cluster of Hypoviridae. Intriguingly, no clear correlation was found between the geographic origin and host specificity of these viral variants. Additionally, six out of the twelve variants displayed segmental deletions of 1.5 to 1.8 kilobases, suggesting the existence of defective viral dsRNA. The presence of defective viral dsRNA led to a two-thirds reduction in the dsRNA of the wild-type viral genome, yet a tenfold increase in the total viral dsRNA content. To standardize virulence across natural strains, all FsHV1 strains were transferred into a single, virus-free Fusarium recipient strain, FZ06-VF, via mycelial fusion. Strains of Fusarium carrying FsHV1 exhibited suppressed pigment synthesis, diminished microspore production, and a marked decrease in virulence. Inoculation tests revealed varying capacities among different FsHV1 variants to modulate fungal virulence, with the strain harboring the FsHV1-FSA1 showing the lowest virulence, with a disease severity index (DSI) of 3.33, and the FsHV1-FS1 the highest (DSI = 17.66). The identification of highly virulent FsHV1 variants holds promise for the development of biocontrol agents for Pokkah boeng management.
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Affiliation(s)
- Qiujuan Zhou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Ministry and Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China
| | - Ziting Yao
- Plant Protection Research Institute, Guangxi Academy of Agriculture Science, Nanning 530007, China
| | - Xueying Cao
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China
| | - Yuejia Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Ministry and Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China
| | - Chengwu Zou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Ministry and Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China
| | - Baoshan Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Ministry and Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China
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Ahmad F, Tomada S, Poonsiri T, Baric S. Molecular genetic variability of Cryphonectria hypovirus 1 associated with Cryphonectria parasitica in South Tyrol (northern Italy). Front Microbiol 2024; 15:1291542. [PMID: 38476955 PMCID: PMC10927965 DOI: 10.3389/fmicb.2024.1291542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Cryphonectria hypovirus 1 (CHV-1) has been widely studied and used as a biocontrol agent because of its ability to infect the chestnut blight fungus, Cryphonectria parasitica, and to reduce its virulence. Knowledge about the hypovirus, its presence, and diversity is completely lacking in South Tyrol (northern Italy), which may obstruct biocontrol measures for chestnut blight based on CHV-1. This work aimed to study the occurrence of CHV-1 infecting C. parasitica in South Tyrol and to perform a genetic characterization of the hypovirus. In South Tyrol, CHV-1 was found to occur in 29.2% of the fungal isolates investigated, varying in frequency between different regions and chestnut stands. Twenty-three haplotypes based on partial cDNA (complementary DNA) sequences of open reading frame (ORF)-A and 30 haplotypes based on partial cDNA sequences of ORF-B were identified among 47 and 56 hypovirulent fungal isolates, respectively. Phylogenetic analysis showed that all the haplotypes belonged to the Italian subtype of CHV-1 and that they were closely related to the populations of Italy, Switzerland, Croatia and Slovenia. Evidence of recombination was not found in the sequences and point mutations were the main source of diversity. Overall, this study indicated that the prevalence of CHV-1 in South Tyrol is low compared to many other central and western European populations and determined a need to actively impose biocontrol measures. Using sequence analysis, we identified some variants of interest of CHV-1 that should be studied in detail for their potential use in biocontrol.
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Affiliation(s)
- Farooq Ahmad
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
| | - Selena Tomada
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
| | - Thanalai Poonsiri
- Department of Pathobiology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Sanja Baric
- Laboratory for Phytopathology, Faculty of Agricultural, Environmental and Food Sciences, Free University of Bozen-Bolzano, Bolzano, Italy
- Competence Centre for Plant Health, Free University of Bozen-Bolzano, Bolzano, Italy
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Three-Layered Complex Interactions among Capsidless (+)ssRNA Yadokariviruses, dsRNA Viruses, and a Fungus. mBio 2022; 13:e0168522. [PMID: 36040032 PMCID: PMC9600902 DOI: 10.1128/mbio.01685-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously discovered a virus neo-lifestyle exhibited by a capsidless positive-sense (+), single-stranded (ss) RNA virus YkV1 (family Yadokariviridae) and an unrelated double-stranded (ds) RNA virus YnV1 (proposed family "Yadonushiviridae") in a phytopathogenic ascomycete, Rosellinia necatrix. YkV1 has been proposed to replicate in the capsid provided by YnV1 as if it were a dsRNA virus and enhance YnV1 replication in return. Recently, viruses related to YkV1 (yadokariviruses) have been isolated from diverse ascomycetous fungi. However, it remains obscure whether such viruses generally show the YkV1-like lifestyle. Here, we identified partner viruses for three distinct yadokariviruses, YkV3, YkV4a, and YkV4b, isolated from R. necatrix that were coinfected with multiple dsRNA viruses phylogenetically distantly related to YnV1. We first established transformants of R. necatrix carrying single yadokarivirus cDNAs and fused them with infectants by single partner candidate dsRNA viruses. Consequently, YkV3 and YkV4s replicated only in the presence of RnMBV3 (family Megabirnaviridae) and RnMTV1 (proposed family "Megatotiviridae"), respectively. The partners were mutually interchangeable between the two YkV4 strains and three RnMTV1 strains but not between other combinations involving YkV1 or YkV3. In contrast to YkV1 enhancing YnV1 accumulation, YkV4s reduced RnMTV1 accumulation to different degrees according to strains. Interestingly, YkV4 rescued the host R. necatrix from impaired growth induced by RnMTV1. YkV3 exerted no apparent effect on its partner (RnMBV3) or host fungus. Overall, we revealed that while yadokariviruses generally require partner dsRNA viruses for replication, each yadokarivirus partners with a different dsRNA virus species in the three diverse families and shows a distinct symbiotic relation in a fungus. IMPORTANCE A capsidless (+)ssRNA virus YkV1 (family Yadokariviridae) highjacks the capsid of an unrelated dsRNA virus YnV1 (proposed family "Yadonushiviridae") in a phytopathogenic ascomycete, while YkV1 trans-enhances YnV1 replication. Herein, we identified the dsRNA virus partners of three yadokariviruses (YkV3, YkV4a, and YkV4b) with genome organization different from YkV1 as being different from YnV1 at the suborder level. Their partners were mutually interchangeable between the two YkV4 strains and three strains of the partner virus RnMTV1 (proposed family "Megatotiviridae") but not between other combinations involving YkV1 or YkV3. Unlike YkV1, YkV4s reduced RnMTV1 accumulation and rescued the host fungus from impaired growth induced by RnMTV1. YkV3 exerted no apparent effect on its partner (RnMBV3, family Megabirnaviridae) or host fungus. These revealed that while each yadokarivirus has a species-specific partnership with a dsRNA virus, yadokariviruses collectively partner extremely diverse dsRNA viruses and show three-layered complex mutualistic/antagonistic interactions in a fungus.
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In-Tree Behavior of Diverse Viruses Harbored in the Chestnut Blight Fungus, Cryphonectria parasitica. J Virol 2021; 95:JVI.01962-20. [PMID: 33361433 DOI: 10.1128/jvi.01962-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/17/2020] [Indexed: 12/20/2022] Open
Abstract
The ascomycete Cryphonectria parasitica causes destructive chestnut blight. Biological control of the fungus by virus infection (hypovirulence) has been shown to be an effective control strategy against chestnut blight in Europe. To provide biocontrol effects, viruses must be able to induce hypovirulence and spread efficiently in chestnut trees. Field studies using living trees to date have focused on a selected family of viruses called hypoviruses, especially prototypic hypovirus CHV1, but there are now known to be many other viruses that infect C. parasitica Here, we tested seven different viruses for their hypovirulence induction, biocontrol potential, and transmission properties between two vegetatively compatible but molecularly distinguishable fungal strains in trees. The test included cytosolically and mitochondrially replicating viruses with positive-sense single-stranded RNA or double-stranded RNA genomes. The seven viruses showed different in planta behaviors and were classified into four groups. Group I, including CHV1, had great biocontrol potential and could protect trees by efficiently spreading and converting virulent to hypovirulent cankers in the trees. Group II could induce high levels of hypovirulence but showed much smaller biocontrol potential, likely because of inefficient virus transmission. Group III showed poor performance in hypovirulence induction and biocontrol, while efficiently being transmitted in the infected trees. Group IV could induce hypovirulence and spread efficiently but showed poor biocontrol potential. Nuclear and mitochondrial genotyping of fungal isolates obtained from the treated cankers confirmed virus transmission between the two fungal strains in most isolates. These results are discussed in view of dynamic interactions in the tripartite pathosystem.IMPORTANCE The ascomycete Cryphonectria parasitica causes destructive chestnut blight, which is controllable by hypovirulence-conferring viruses infecting the fungus. The tripartite chestnut/C. parasitica/virus pathosystem involves the dynamic interactions of their genetic elements, i.e., virus transmission and lateral transfer of nuclear and mitochondrial genomes between fungal strains via anastomosis occurring in trees. Here, we tested diverse RNA viruses for their hypovirulence induction, biocontrol potential, and transmission properties between two vegetatively compatible but molecularly distinguishable fungal strains in live chestnut trees. The tested viruses, which are different in genome type (single-stranded or double-stranded RNA) and organization, replication site (cytosol or mitochondria), virus form (encapsidated or capsidless) and/or symptomatology, have been unexplored in the aforementioned aspects under controlled conditions. This study showed intriguing different in-tree behaviors of the seven viruses and suggested that to exert significant biocontrol effects, viruses must be able to induce hypovirulence and spread efficiently in the fungus infecting the chestnut trees.
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Identification of an RNA Silencing Suppressor Encoded by a Symptomless Fungal Hypovirus, Cryphonectria Hypovirus 4. BIOLOGY 2021; 10:biology10020100. [PMID: 33572564 PMCID: PMC7912522 DOI: 10.3390/biology10020100] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 01/28/2021] [Indexed: 12/14/2022]
Abstract
Simple Summary Host antiviral defense/viral counter-defense is an interesting topic in modern virology. RNA silencing is the primary antiviral mechanism in insects, plants, and fungi, while viruses encode and utilize RNA silencing suppressors against the host defense. Hypoviruses are positive-sense single-stranded RNA viruses with phylogenetic affinity to the picorna-like supergroup, including animal poliovirus and plant potyvirus. The prototype hypovirus Cryphonectria hypovirus 1, CHV1, is one of the best-studied fungal viruses. It is known to induce hypovirulence in the chestnut blight fungus, Cryphonectria parasitica, and encode an RNA silencing suppressor. CHV4 is another hypovirus asymptomatically that infects the same host fungus. This study shows that the N-terminal portion of the CHV4 polyprotein, termed p24, is a protease that autocatalytically cleaves itself from the rest of the viral polyprotein, and functions as an antiviral RNA silencing suppressor. Abstract Previously, we have reported the ability of a symptomless hypovirus Cryphonectria hypovirus 4 (CHV4) of the chestnut blight fungus to facilitate stable infection by a co-infecting mycoreovirus 2 (MyRV2)—likely through the inhibitory effect of CHV4 on RNA silencing (Aulia et al., Virology, 2019). In this study, the N-terminal portion of the CHV4 polyprotein, termed p24, is identified as an autocatalytic protease capable of suppressing host antiviral RNA silencing. Using a bacterial expression system, CHV4 p24 is shown to cleave autocatalytically at the di-glycine peptide (Gly214-Gly215) of the polyprotein through its protease activity. Transgenic expression of CHV4 p24 in Cryphonectria parasitica suppresses the induction of one of the key genes of the antiviral RNA silencing, dicer-like 2, and stabilizes the infection of RNA silencing-susceptible virus MyRV2. This study shows functional similarity between CHV4 p24 and its homolog p29, encoded by the symptomatic prototype hypovirus CHV1.
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Bian R, Andika IB, Pang T, Lian Z, Wei S, Niu E, Wu Y, Kondo H, Liu X, Sun L. Facilitative and synergistic interactions between fungal and plant viruses. Proc Natl Acad Sci U S A 2020; 117:3779-3788. [PMID: 32015104 PMCID: PMC7035501 DOI: 10.1073/pnas.1915996117] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Plants and fungi are closely associated through parasitic or symbiotic relationships in which bidirectional exchanges of cellular contents occur. Recently, a plant virus was shown to be transmitted from a plant to a fungus, but it is unknown whether fungal viruses can also cross host barriers and spread to plants. In this study, we investigated the infectivity of Cryphonectria hypovirus 1 (CHV1, family Hypoviridae), a capsidless, positive-sense (+), single-stranded RNA (ssRNA) fungal virus in a model plant, Nicotiana tabacum CHV1 replicated in mechanically inoculated leaves but did not spread systemically, but coinoculation with an unrelated plant (+)ssRNA virus, tobacco mosaic virus (TMV, family Virgaviridae), or other plant RNA viruses, enabled CHV1 to systemically infect the plant. Likewise, CHV1 systemically infected transgenic plants expressing the TMV movement protein, and coinfection with TMV further enhanced CHV1 accumulation in these plants. Conversely, CHV1 infection increased TMV accumulation when TMV was introduced into a plant pathogenic fungus, Fusarium graminearum In the in planta F. graminearum inoculation experiment, we demonstrated that TMV infection of either the plant or the fungus enabled the horizontal transfer of CHV1 from the fungus to the plant, whereas CHV1 infection enhanced fungal acquisition of TMV. Our results demonstrate two-way facilitative interactions between the plant and fungal viruses that promote cross-kingdom virus infections and suggest the presence of plant-fungal-mediated routes for dissemination of fungal and plant viruses in nature.
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Affiliation(s)
- Ruiling Bian
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Ida Bagus Andika
- College of Plant Health and Medicine, Qingdao Agricultural University, 266109 Qingdao, China
| | - Tianxing Pang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Ziqian Lian
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Shuang Wei
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Erbo Niu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Yunfeng Wu
- Key Laboratory of Integrated Pest Management on Crops In Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, 712100 Yangling, China
| | - Hideki Kondo
- Institute of Plant Science and Resources, Okayama University, 710-0046 Kurashiki, Japan
| | - Xili Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China
| | - Liying Sun
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, 712100 Yangling, China;
- Key Laboratory of Integrated Pest Management on Crops In Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, 712100 Yangling, China
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Krstin L, Katanić Z, Repar J, Ježić M, Kobaš A, Ćurković-Perica M. Genetic Diversity of Cryphonectria hypovirus 1, a Biocontrol Agent of Chestnut Blight, in Croatia and Slovenia. MICROBIAL ECOLOGY 2020; 79:148-163. [PMID: 31053974 DOI: 10.1007/s00248-019-01377-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 04/03/2019] [Indexed: 06/09/2023]
Abstract
Transmissible hypovirulence associated with Cryphonectria hypovirus 1 (CHV1) has been used for biological control of chestnut blight, devastating disease of chestnut caused by the fungus Cryphonectria parasitica. The main aims of this study were to provide molecular characterization of CHV1 from Croatia and Slovenia and to reveal its genetic variability, phylogeny, and diversification of populations. Fifty-one CHV1 haplotypes were detected among 54 partially sequenced CHV1 isolates, all belonging to Italian subtype (I). Diversity was mainly generated by point mutations while evidence of recombination was not found. The level of conservation over analyzed parts of ORF-A proteins p29 and p40 varied, but functional sites were highly conserved. Phylogenetic analysis revealed close relatedness and intermixing of Croatian and Slovenian CHV1 populations. Our CHV1 isolates were also related to Swiss and Bosnian hypoviruses supporting previously suggested course of CHV1 invasion in Europe. Overall, this study indicates that phylogeny of CHV1 subtype I in Europe is complex and characterized with frequent point mutations resulting in many closely related variants of the virus. Possible association between variations within CHV1 ORF-A and growth of the hypovirulent fungal isolates is tested and presented.
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Affiliation(s)
- Ljiljana Krstin
- Department of Biology, Josip Juraj Strossmayer University of Osijek, HR-31000, Osijek, Croatia
| | - Zorana Katanić
- Department of Biology, Josip Juraj Strossmayer University of Osijek, HR-31000, Osijek, Croatia
| | - Jelena Repar
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Marin Ježić
- Department of Biology, Faculty of Science, University of Zagreb, HR-10000, Zagreb, Croatia
| | - Ana Kobaš
- Department of Biology, Josip Juraj Strossmayer University of Osijek, HR-31000, Osijek, Croatia
| | - Mirna Ćurković-Perica
- Department of Biology, Faculty of Science, University of Zagreb, HR-10000, Zagreb, Croatia.
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Aulia A, Andika IB, Kondo H, Hillman BI, Suzuki N. A symptomless hypovirus, CHV4, facilitates stable infection of the chestnut blight fungus by a coinfecting reovirus likely through suppression of antiviral RNA silencing. Virology 2019; 533:99-107. [PMID: 31146252 DOI: 10.1016/j.virol.2019.05.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/14/2019] [Accepted: 05/14/2019] [Indexed: 01/10/2023]
Abstract
Field-collected US strain C18 of Cryphonectria parasitica, the chestnut blight fungus, was earlier reported to be infected by a double-stranded RNA virus, mycoreovirus 2 (MyRV2). Next-generation sequencing has revealed co-infection of C18 by a positive-strand RNA virus, hypovirus 4 (CHV4). The current molecular and genetic analyses showed interesting commensal interactions between the two viruses. CHV4 facilitated the stable infection and enhanced vertical transmission of MyRV2, which was readily lost during subculturing and showed reduced vertical transmission in single infections. Deletion of a key antiviral RNA silencing gene, dcl2, in isolate C18 increased stability of MyRV2 in single infections. The ability of CHV4 to facilitate stable infection with MyRV2 appears to be associated with the inhibitory effect of CHV4 on RNA silencing via compromising the induction of transcriptional up-regulation of dcl2. These results suggest that natural infection of isolate C18 by MyRV2 in the field was facilitated by CHV4 co-infection.
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Affiliation(s)
- Annisa Aulia
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan; Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan
| | - Ida Bagus Andika
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan
| | - Hideki Kondo
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan
| | - Bradley I Hillman
- Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, 08901, USA
| | - Nobuhiro Suzuki
- Institute of Plant Science and Resources (IPSR), Okayama University, Kurashiki, 710-0046, Japan.
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Dicer functions transcriptionally and posttranscriptionally in a multilayer antiviral defense. Proc Natl Acad Sci U S A 2019; 116:2274-2281. [PMID: 30674672 DOI: 10.1073/pnas.1812407116] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In antiviral RNA interference (RNAi), Dicer plays a primary role in processing double-stranded RNA (dsRNA) molecules into small-interfering RNAs (siRNAs) that guide Argonaute effectors to posttranscriptional suppression of target viral genes. Here, we show a distinct role for Dicer in the siRNA-independent transcriptional induction of certain host genes upon viral infection in a filamentous fungus. Previous studies have shown that the two key players, dicer-like 2 (dcl2) and argonaute-like 2 (agl2), of antiviral RNAi in a phytopathogenic ascomycete, Cryphonectria parasitica, are highly transcriptionally induced upon infection with certain RNA mycoviruses, including the positive-stranded RNA hypovirus mutant lacking the RNAi suppressor (Cryphonectria hypovirus 1-Δp69, CHV1-Δp69). This induction is regulated by the Spt-Ada-Gcn5 acetyltransferase (SAGA) complex, a well-known transcriptional coactivator. The present study shows that diverse host genes, in addition to dcl2 and agl2, were up-regulated more than 10-fold by SAGA upon infection with CHV1-Δp69. Interestingly, DCL2, but not AGL2, was essential for SAGA-mediated global gene up-regulation. Moreover, deletion of certain virus-induced genes enhanced a CHV1-Δp69 symptom (growth rate) but not its accumulation. Constitutive, modest levels of dcl2 expression drastically reduced viral siRNA accumulation but were sufficient for full-scale up-regulation of host genes, suggesting that high induction of dcl2 and siRNA production are not essential for the transcriptional up-regulation function of DCL2. These data clearly demonstrate the dual functionality of DCL2: as a dsRNA-specific nuclease in posttranscriptional antiviral RNA silencing and as a key player in SAGA-mediated host gene induction, which independently represses viral replication and alleviates virus-induced symptom expression.
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Mlinarec J, Nuskern L, Ježić M, Rigling D, Ćurković-Perica M. Molecular evolution and invasion pattern of Cryphonectria hypovirus 1 in Europe: Mutation rate, and selection pressure differ between genome domains. Virology 2018; 514:156-164. [PMID: 29179038 DOI: 10.1016/j.virol.2017.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 11/13/2017] [Accepted: 11/14/2017] [Indexed: 01/08/2023]
Abstract
Understanding virus evolution is a fundamental goal of virology, evolutionary biology, and disease epidemiology. We provide a detailed analysis of evolution and origin of Cryphonectria hypovirus 1 (CHV1) populations in Europe, based on the complete genome sequence of all European subtypes. Phylogenetic analyses divided European strains into two closely related clades. Strains of the subtype I belong to the first, while strains of the subtypes F1, D and E belong to the second clade suggesting that the subtypes F1, D and E are more closely related than previously thought. Strains of the subtype F2 appeared to be recombinant; subtypes F1/D/E contributed a larger fraction of sequence while subtype I contributed a smaller fraction. The p29 was the most variable domain, while the replication-associated large ORF B protein was the most conserved domain within the CHV1. Low sequence similarity, predominant negative selection and frequent recombination characterise the evolution of CHV1.
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Affiliation(s)
- Jelena Mlinarec
- Department of Biology, Faculty of Science, University of Zagreb, Marulićev trg 9a, HR-10 000 Zagreb, Croatia
| | - Lucija Nuskern
- Department of Biology, Faculty of Science, University of Zagreb, Marulićev trg 9a, HR-10 000 Zagreb, Croatia
| | - Marin Ježić
- Department of Biology, Faculty of Science, University of Zagreb, Marulićev trg 9a, HR-10 000 Zagreb, Croatia
| | - Daniel Rigling
- WSL Swiss Federal Research Institute, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland
| | - Mirna Ćurković-Perica
- Department of Biology, Faculty of Science, University of Zagreb, Marulićev trg 9a, HR-10 000 Zagreb, Croatia.
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SAGA complex mediates the transcriptional up-regulation of antiviral RNA silencing. Proc Natl Acad Sci U S A 2017; 114:E3499-E3506. [PMID: 28400515 DOI: 10.1073/pnas.1701196114] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Pathogen recognition and transcriptional activation of defense-related genes are crucial steps in cellular defense responses. RNA silencing (RNAi) functions as an antiviral defense in eukaryotic organisms. Several RNAi-related genes are known to be transcriptionally up-regulated upon virus infection in some host organisms, but little is known about their induction mechanism. A phytopathogenic ascomycete, Cryphonectria parasitica (chestnut blight fungus), provides a particularly advantageous system to study RNAi activation, because its infection by certain RNA viruses induces the transcription of dicer-like 2 (dcl2) and argonaute-like 2 (agl2), two major RNAi players. To identify cellular factors governing activation of antiviral RNAi in C. parasitica, we developed a screening protocol entailing multiple transformations of the fungus with cDNA of a hypovirus mutant lacking the RNAi suppressor (CHV1-Δp69), a reporter construct with a GFP gene driven by the dcl2 promoter, and a random mutagenic construct. Screening for GFP-negative colonies allowed the identification of sgf73, a component of the SAGA (Spt-Ada-Gcn5 acetyltransferase) complex, a well-known transcriptional coactivator. Knockout of other SAGA components showed that the histone acetyltransferase module regulates transcriptional induction of dcl2 and agl2, whereas histone deubiquitinase mediates regulation of agl2 but not dcl2 Interestingly, full-scale induction of agl2 and dcl2 by CHV1-Δp69 required both DCL2 and AGL2, whereas that by another RNA virus, mycoreovirus 1, required only DCL2, uncovering additional roles for DCL2 and AGL2 in viral recognition and/or RNAi activation. Overall, these results provide insight into the mechanism of RNAi activation.
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Du Y, Lin Y, Zhou X, Wang K, Fang S, Deng Q. Full-length sequence and genome analysis of CHV1-CN280, a North China isolate of cryphonectria hypovirus 1. Arch Virol 2017; 162:1811-1818. [PMID: 28247097 DOI: 10.1007/s00705-017-3296-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 02/13/2017] [Indexed: 11/29/2022]
Abstract
CHV1-CN280 is a North China isolate of cryphonectria hypovirus 1 (CHV1), which has high horizontal transmission ability. The complete genomic sequence of CHV1-CN280 was determined and analyzed. Compared with other reported CHV1s, the genome of CHV1-CN280 shows some significantly different characteristics. The junction of the two open reading frames (ORFs) of CHV1-CN280 is AUGUAUAA, while in other reported CHV1s, it is UAAUG. The genomic sequence of CHV1-CN280 shows a high level of similarity to other reported CHV1s in the 3' portion, but in some sections of the 5' portion (the region around the start codon of ORFA, the region around the predicted cleavage site of p29 and p40, and the 5'-portion of p48 coding region), the nucleotide sequence identity is lower than 50%. The p29 of CHV1-CN280 shares only about 60% identity with other sequenced CHV1 isolates at the amino acid level. Full-length genomic recombination analysis suggests that several recombination events have occurred in the ORFB coding region between CHV1-CN280 and two subtype I CHV1 isolates (CHV1-Euro7 or CHV1-EP721). RT-PCR primers were designed according to the genomic sequence of CHV1-CN280 to study the genetic diversity of CHV1 in East Asia. Phylogenetic analysis showed that the East Asian CHV1s were quite different from the five assigned subtypes in Europe, and seven new CHV1 subtypes were identified in this study.
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Affiliation(s)
- Yanan Du
- Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, College of Agriculture, Yangtze University, Ministry of Education, Jingzhou, 434025, Hubei, China
| | - Yuan Lin
- Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, College of Agriculture, Yangtze University, Ministry of Education, Jingzhou, 434025, Hubei, China
| | - Xuan Zhou
- Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, College of Agriculture, Yangtze University, Ministry of Education, Jingzhou, 434025, Hubei, China
| | - Kerong Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Shouguo Fang
- Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, College of Agriculture, Yangtze University, Ministry of Education, Jingzhou, 434025, Hubei, China
| | - Qingchao Deng
- Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, College of Agriculture, Yangtze University, Ministry of Education, Jingzhou, 434025, Hubei, China.
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Zhong J, Chen D, Zhu HJ, Gao BD, Zhou Q. Hypovirulence of Sclerotium rolfsii Caused by Associated RNA Mycovirus. Front Microbiol 2016; 7:1798. [PMID: 27891121 PMCID: PMC5103162 DOI: 10.3389/fmicb.2016.01798] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 10/26/2016] [Indexed: 11/21/2022] Open
Abstract
Mycoviruses associated with hypovirulence are potential biological control agents and could be useful to study the pathogenesis of fungal host pathogens. Sclerotium rolfsii, a pathogenic fungus, causes southern blight in a wide variety of crops. In this study, we isolated a series of dsRNAs from a debilitated S. rolfsii strain, BLH-1, which had pronounced phenotypic aberrations including reduced pathogenicity, mycelial growth and deficient sclerotia production. Virus-curing and horizontal transmission experiments that eliminated or transmitted, respectively, all dsRNA elements showed that the dsRNAs were involved in the hypovirulent traits of BLH-1. Ultrastructure examination also showed hyphae fracture and cytoplasm or organelle degeneration in BLH-1 hyphal cells compared to the virus-free strain. Three assembled cDNA contigs generated from the cDNA library cloned from the purified dsRNA indicated that strain BLH-1 was infected by at least three novel mycoviruses. One has similarity to the hypovirulence-associated Sclerotinia sclerotiorum hypovirus 2 (SsHV2) in the family Hypoviridae, and the other two are related to two different unclassified dsRNA mycovirus families. To our knowledge, this is the first report of S. rolfsii hypovirulence that was correlated with its associated dsRNA.
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Affiliation(s)
- Jie Zhong
- Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University Changsha, China
| | - Dan Chen
- Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University Changsha, China
| | - Hong J Zhu
- Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University Changsha, China
| | - Bi D Gao
- Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University Changsha, China
| | - Qian Zhou
- Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests, Hunan Agricultural University Changsha, China
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16
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Chiba S, Suzuki N. Highly activated RNA silencing via strong induction of dicer by one virus can interfere with the replication of an unrelated virus. Proc Natl Acad Sci U S A 2015; 112:E4911-8. [PMID: 26283371 PMCID: PMC4568273 DOI: 10.1073/pnas.1509151112] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Viruses often coinfect single host organisms in nature. Depending on the combination of viruses in such coinfections, the interplay between them may be synergistic, apparently neutral with no effect on each other, or antagonistic. RNA silencing is responsible for many cases of interference or cross-protection between viruses, but such antagonistic interactions are usually restricted to closely related strains of the same viral species. In this study, we present an unprecedented example of RNA silencing-mediated one-way interference between unrelated viruses in a filamentous model fungus, Cryphonectria parasitica. The replication of Rosellinia necatrix victorivirus 1 (RnVV1; Totiviridae) was strongly impaired by coinfection with the prototypic member of the genus Mycoreovirus (MyRV1) or a mutant of the prototype hypovirus (Cryphonectria hypovirus 1, CHV1) lacking the RNA silencing suppressor (CHV1-Δp69). This interference was associated with marked transcriptional induction of key genes in antiviral RNA silencing, dicer-like 2 (dcl2) and argonaute-like 2 (agl2), following MyRV1 or CHV1-Δp69 infection. Interestingly, the inhibition of RnVV1 replication was reproduced when the levels of dcl2 and agl2 transcripts were elevated by transgenic expression of a hairpin construct of an endogenous C. parasitica gene. Disruption of dcl2 completely abolished the interference, whereas that of agl2 did not always lead to its abolishment, suggesting more crucial roles of dcl2 in antiviral defense. Taken altogether, these results demonstrated the susceptible nature of RnVV1 to the antiviral silencing in C. parasitica activated by distinct viruses or transgene-derived double-stranded RNAs and provide insight into the potential for broad-spectrum virus control mediated by RNA silencing.
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Affiliation(s)
- Sotaro Chiba
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Nobuhiro Suzuki
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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17
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Marzano SYL, Hobbs HA, Nelson BD, Hartman GL, Eastburn DM, McCoppin NK, Domier LL. Transfection of Sclerotinia sclerotiorum with in vitro transcripts of a naturally occurring interspecific recombinant of Sclerotinia sclerotiorum hypovirus 2 significantly reduces virulence of the fungus. J Virol 2015; 89:5060-71. [PMID: 25694604 PMCID: PMC4403457 DOI: 10.1128/jvi.03199-14] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/16/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED A recombinant strain of Sclerotinia sclerotiorum hypovirus 2 (SsHV2) was identified from a North American Sclerotinia sclerotiorum isolate (328) from lettuce (Lactuca sativa L.) by high-throughput sequencing of total RNA. The 5'- and 3'-terminal regions of the genome were determined by rapid amplification of cDNA ends. The assembled nucleotide sequence was up to 92% identical to two recently reported SsHV2 strains but contained a deletion near its 5' terminus of more than 1.2 kb relative to the other SsHV2 strains and an insertion of 524 nucleotides (nt) that was distantly related to Valsa ceratosperma hypovirus 1. This suggests that the new isolate is a heterologous recombinant of SsHV2 with a yet-uncharacterized hypovirus. We named the new strain Sclerotinia sclerotiorum hypovirus 2 Lactuca (SsHV2L) and deposited the sequence in GenBank with accession number KF898354. Sclerotinia sclerotiorum isolate 328 was coinfected with a strain of Sclerotinia sclerotiorum endornavirus 1 and was debilitated compared to cultures of the same isolate that had been cured of virus infection by cycloheximide treatment and hyphal tipping. To determine whether SsHV2L alone could induce hypovirulence in S. sclerotiorum, a full-length cDNA of the 14,538-nt viral genome was cloned. Transcripts corresponding to the viral RNA were synthesized in vitro and transfected into a virus-free isolate of S. sclerotiorum, DK3. Isolate DK3 transfected with SsHV2L was hypovirulent on soybean and lettuce and exhibited delayed maturation of sclerotia relative to virus-free DK3, completing Koch's postulates for the association of hypovirulence with SsHV2L. IMPORTANCE A cosmopolitan fungus, Sclerotinia sclerotiorum infects more than 400 plant species and causes a plant disease known as white mold that produces significant yield losses in major crops annually. Mycoviruses have been used successfully to reduce losses caused by fungal plant pathogens, but definitive relationships between hypovirus infections and hypovirulence in S. sclerotiorum were lacking. By establishing a cause-and-effect relationship between Sclerotinia sclerotiorum hypovirus Lactuca (SsHV2L) infection and the reduction in host virulence, we showed direct evidence that hypoviruses have the potential to reduce the severity of white mold disease. In addition to intraspecific recombination, this study showed that recent interspecific recombination is an important factor shaping viral genomes. The construction of an infectious clone of SsHV2L allows future exploration of the interactions between SsHV2L and S. sclerotiorum, a widespread fungal pathogen of plants.
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Affiliation(s)
| | - Houston A Hobbs
- Department of Crop Sciences, University of Illinois, Urbana, Illinois, USA
| | - Berlin D Nelson
- Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, USA
| | - Glen L Hartman
- Department of Crop Sciences, University of Illinois, Urbana, Illinois, USA United States Department of Agriculture/Agricultural Research Service, Urbana, Illinois, USA
| | - Darin M Eastburn
- Department of Crop Sciences, University of Illinois, Urbana, Illinois, USA
| | - Nancy K McCoppin
- United States Department of Agriculture/Agricultural Research Service, Urbana, Illinois, USA
| | - Leslie L Domier
- Department of Crop Sciences, University of Illinois, Urbana, Illinois, USA United States Department of Agriculture/Agricultural Research Service, Urbana, Illinois, USA
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Eusebio-Cope A, Suzuki N. Mycoreovirus genome rearrangements associated with RNA silencing deficiency. Nucleic Acids Res 2015; 43:3802-13. [PMID: 25800742 PMCID: PMC4402544 DOI: 10.1093/nar/gkv239] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 03/06/2015] [Indexed: 01/31/2023] Open
Abstract
Mycoreovirus 1 (MyRV1) has 11 double-stranded RNA genome segments (S1 to S11) and confers hypovirulence to the chestnut blight fungus, Cryphonectria parasitica. MyRV1 genome rearrangements are frequently generated by a multifunctional protein, p29, encoded by a positive-strand RNA virus, Cryphonectria hypovirus 1. One of its functional roles is RNA silencing suppression. Here, we explored a possible link between MyRV1 genome rearrangements and the host RNA silencing pathway using wild-type (WT) and mutant strains of both MyRV1 and the host fungus. Host strains included deletion mutants of RNA silencing components such as dicer-like (dcl) and argonaute-like (agl) genes, while virus strains included an S4 internal deletion mutant MyRV1/S4ss. Consequently, intragenic rearrangements with nearly complete duplication of the three largest segments, i.e. S1, S2 and S3, were observed even more frequently in the RNA silencing-deficient strains Δdcl2 and Δagl2 infected with MyRV1/S4ss, but not with any other viral/host strain combinations. An interesting difference was noted between genome rearrangement events in the two host strains, i.e. generation of the rearrangement required prolonged culture for Δagl2 in comparison with Δdcl2. These results suggest a role for RNA silencing that suppresses genome rearrangements of a dsRNA virus.
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Affiliation(s)
- Ana Eusebio-Cope
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Nobuhiro Suzuki
- Agrivirology Laboratory, Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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Eusebio-Cope A, Sun L, Tanaka T, Chiba S, Kasahara S, Suzuki N. The chestnut blight fungus for studies on virus/host and virus/virus interactions: From a natural to a model host. Virology 2015; 477:164-175. [DOI: 10.1016/j.virol.2014.09.024] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Revised: 09/15/2014] [Accepted: 09/26/2014] [Indexed: 01/03/2023]
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Mutagenesis of the catalytic and cleavage site residues of the hypovirus papain-like proteases p29 and p48 reveals alternative processing and contributions to optimal viral RNA accumulation. J Virol 2014; 88:11946-54. [PMID: 25100848 DOI: 10.1128/jvi.01489-14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The positive-stranded RNA genome of the prototypic virulence-attenuating hypovirus CHV-1/EP713 contains two open reading frames (ORF), each encoding an autocatalytic papain-like leader protease. Protease p29, derived from the N-terminal portion of ORF A, functions as a suppressor of RNA silencing, while protease p48, derived from the N-terminal portion of ORF B, is required for viral RNA replication. The catalytic and cleavage site residues required for autoproteolytic processing have been functionally mapped in vitro for both proteases but not confirmed in the infected fungal host. We report here the mutagenesis of the CHV-1/EP713 infectious cDNA clone to define the requirements for p29 and p48 cleavage and the role of autoproteolysis in the context of hypovirus replication. Mutation of the catalytic cysteine and histidine residues for either p29 or p48 was tolerated but reduced viral RNA accumulation to ca. 20 to 50% of the wild-type level. Mutation of the p29 catalytic residues caused an accumulation of unprocessed ORF A product p69. Surprisingly, the release of p48 from the ORF B-encoded polyprotein was not prevented by mutation of the p48 catalytic and cleavage site residues and was independent of p29. The results show that, while dispensable for hypovirus replication, the autocatalytic processing of the leader proteases p29 and p48 contributes to optimal virus RNA accumulation. The role of the predicted catalytic residues in autoproteolytic processing of p29 was confirmed in the infected host, while p48 was found to also undergo alternative processing independent of the encoded papain-like protease activities. Importance: Hypoviruses are positive-strand RNA mycoviruses that attenuate virulence of their pathogenic fungal hosts. The prototypic hypovirus CHV-1/EP713, which infects the chestnut bight fungus Cryphonetria parasitica, encodes two papain-like autocatalytic leader proteases, p29 and p48, that also have important functions in suppressing the RNA silencing antiviral defense response and in viral RNA replication, respectively. The mutational analyses of the CHV-1/EP713 infectious cDNA clone, reported here, define the requirements for p29 and p48 cleavage and the functional importance of autoproteolysis in the context of hypovirus replication and exposed an alternative p48 processing pathway independent of the encoded papain-like protease activities. These findings provide additional insights into hypovirus gene expression, replication, and evolution and inform ongoing efforts to engineer hypoviruses for interrogating and modulating fungal virulence.
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Dawe AL, Nuss DL. Hypovirus molecular biology: from Koch's postulates to host self-recognition genes that restrict virus transmission. Adv Virus Res 2013; 86:109-47. [PMID: 23498905 DOI: 10.1016/b978-0-12-394315-6.00005-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
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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Affiliation(s)
- Angus L Dawe
- Department of Biology, New Mexico State University, Las Cruces, NM, USA
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A novel victorivirus from a phytopathogenic fungus, Rosellinia necatrix, is infectious as particles and targeted by RNA silencing. J Virol 2013; 87:6727-38. [PMID: 23552428 DOI: 10.1128/jvi.00557-13] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
A novel victorivirus, termed Rosellinia necatrix victorivirus 1 (RnVV1), was isolated from a plant pathogenic ascomycete, white root rot fungus Rosellinia necatrix, coinfected with a partitivirus. The virus was molecularly and biologically characterized using the natural and experimental hosts (chestnut blight fungus, Cryphonectria parasitica). RnVV1 was shown to have typical molecular victorivirus attributes, including a monopartite double-stranded RNA genome with two open reading frames (ORFs) encoding capsid protein (CP) and RNA-dependent RNA polymerase (RdRp), a UAAUG pentamer presumed to facilitate the coupled termination/reinitiation for translation of the two ORFs, a spherical particle structure ~40 nm in diameter, and moderate levels of CP and RdRp sequence identity (34 to 58%) to those of members of the genus Victorivirus within the family Totiviridae. A reproducible transfection system with purified RnVV1 virions was developed for the two distinct fungal hosts. Transfection assay with purified RnVV1 virions combined with virus elimination by hyphal tipping showed that the effects of RnVV1 on the phenotype of the natural host were negligible. Interestingly, comparison of the RNA silencing-competent (standard strain EP155) and -defective (Δdcl-2) strains of C. parasitica infected with RnVV1 showed that RNA silencing acted against the virus to repress its replication, which was restored by coinfection with hypovirus or transgenic expression of an RNA silencing suppressor, hypovirus p29. Phenotypic changes were observed in the Δdcl-2 strain but not in EP155. This is the first reported study on the host range expansion of a Totiviridae member that is targeted by RNA silencing.
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Variations in hypovirus interactions with the fungal-host RNA-silencing antiviral-defense response. J Virol 2012; 86:12933-9. [PMID: 22993160 DOI: 10.1128/jvi.00961-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Hypoviruses Cryphonectria hypovirus 1 (CHV-1)/EP713, CHV-1/Euro7, and CHV-1/EP721, which infect the chestnut blight fungus Cryphonectria parasitica, differ in their degrees of virulence attenuation (hypovirulence), symptom expression, and viral RNA accumulation, even though they share between 90% and 99% amino acid sequence identity. In this report we examine whether this variability is influenced by interactions with the C. parasitica Dicer gene dcl2-dependent RNA-silencing antiviral defense response. The mild symptoms exhibited by strains infected with CHV-1/Euro7 and CHV-1/EP721 relative to those with severe hypovirus CHV-1/EP713 did not correlate with a higher induction of the RNA-silencing pathway. Rather, dcl2 transcripts accumulated to a higher level (∼8-fold) following infection by CHV-1/EP713 than following infection by CHV-1/Euro7 (1.2-fold) or CHV-1/EP721 (1.4-fold). The differences in dcl2 transcript accumulation in response to CHV-1/EP713 and CHV-1/EP721 were unrelated to the suppressor of RNA silencing, p29, encoded by the two viruses. Moreover, the coding strand viral RNA levels increased by 33-, 32-, and 16-fold for CHV-1/EP713, CHV-1/Euro7, and CHV-1/EP721, respectively, in Δdcl2 mutant strains. This indicates that a very robust antiviral RNA-silencing response was induced against all three viruses, even though significant differences in the levels of dcl2 transcript accumulation were observed. Unexpectedly, the severe debilitation previously reported for CHV-1/EP713-infected Δdcl2 mutant strains, and observed here for the CHV-1/Euro7-infected Δdcl2 mutant strains, was not observed with infection by CHV-1/EP721. By constructing chimeric viruses containing portions of CHV-1/EP713 and CHV-1/EP721, it was possible to map the region that is associated with the severe debilitation of the Δdcl2 mutant hosts to a 4.1-kb coding domain located in the central part of the CHV-1/EP713 genome.
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Tanaka T, Eusebio-Cope A, Sun L, Suzuki N. Mycoreovirus genome alterations: similarities to and differences from rearrangements reported for other reoviruses. Front Microbiol 2012; 3:186. [PMID: 22675320 PMCID: PMC3365852 DOI: 10.3389/fmicb.2012.00186] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/04/2012] [Indexed: 11/13/2022] Open
Abstract
The family Reoviridae is one of the largest virus families with genomes composed of 9-12 double-stranded RNA segments. It includes members infecting organisms from protists to humans. It is well known that reovirus genomes are prone to various types of genome alterations including intragenic rearrangement and reassortment under laboratory and natural conditions. Recently distinct genetic alterations were reported for members of the genus Mycoreovirus, Mycoreovirus 1 (MyRV1), and MyRV3 with 11 (S1-S11) and 12 genome segments (S1-S12), respectively. While MyRV3 S8 is lost during subculturing of infected host fungal strains, MyRV1 rearrangements undergo alterations spontaneously and inducibly. The inducible MyRV1 rearrangements are different from any other previous examples of reovirus rearrangements in their dependence on an unrelated virus factor, a multifunctional protein, p29, encoded by a distinct virus Cryphonectria parasitica hypovirus 1 (CHV1). A total of 5 MyRV1 variants with genome rearranged segments (S1-S3, S6 and S10) are generated in the background of a single viral strain in the presence of CHV1 p29 supplied either transgenically or by coinfection. MyRV1 S4 and S10 are rearranged, albeit very infrequently, in a CHV1 p29 independent fashion. A variant of MyRV1 with substantial deletions in both S4 and S10, generated through a combined reassortment and rearrangement approach, shows comparable replication levels to the wild-type MyRV1. In vivo and in vitro interactions of CHV1 p29 and MyRV1 VP9 are implicated in the induction of MyRV1 rearrangements. However, the mechanism underlying p29-mediated rearrangements remains largely unknown. MyRV1 S4 rearrangements spontaneously occurred independently of CHV1 p29. In the absence of reverse genetics systems for mycoreoviruses, molecular and biological characterization of these MyRV1 and MyRV3 variants contribute to functional analyses of the protein products encoded by those rearranged segments.
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Affiliation(s)
- Toru Tanaka
- Agrivirology Laboratory, Institute of Plant Science and Bioresources, Okayama University Kurashiki, Okayama, Japan
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Abstract
Viruses are widespread in all major groups of fungi. The transmission of fungal viruses occurs intracellularly during cell division, sporogenesis, and cell fusion. They apparently lack an extracellular route for infection. Recent searches of the collections of field fungal isolates have detected an increasing number of novel viruses and lead to discoveries of novel genome organizations, expression strategies and virion structures. Those findings enhanced our understanding of virus diversity and evolution. The majority of fungal viruses have dsRNA genomes packaged in spherical particles, while ssRNA mycoviruses, possessing or lacking the ability to form particles, have increasingly been reported. This review article discusses the current status of mycovirus studies and virocontrol (biocontrol) of phytopathogenic fungi using viruses that infect them and reduce their virulence. Selected examples of virocontrol-associated systems include the chestnut/chestnut blight/hypovirus and fruit trees/white root rot fungus/mycoviruses. Natural dissemination and artificial introduction of hypovirulent fungal strains efficiently contributed to virocontrol of chestnut blight in European forests. Attempts to control white root rot with hypovirulence-conferring mycoviruses are now being made in Japan.
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Transmission of Fusarium boothii mycovirus via protoplast fusion causes hypovirulence in other phytopathogenic fungi. PLoS One 2011; 6:e21629. [PMID: 21738738 PMCID: PMC3126848 DOI: 10.1371/journal.pone.0021629] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2011] [Accepted: 06/03/2011] [Indexed: 11/19/2022] Open
Abstract
There is increasing concern regarding the use of fungicides to control plant diseases, whereby interest has increased in the biological control of phytopathogenic fungi by the application of hypovirulent mycoviruses as a possible alternative to fungicides. Transmission of hypovirulence-associated double-stranded RNA (dsRNA) viruses between mycelia, however, is prevented by the vegetative incompatibility barrier that often exists between different species or strains of filamentous fungi. We determined whether protoplast fusion could be used to transmit FgV1-DK21 virus, which is associated with hypovirulence on F. boothii (formerly F. graminearum strain DK21), to F. graminearum, F. asiaticum, F. oxysporum f. sp. lycopersici, and Cryphonectria parasitica. Relative to virus-free strains, the FgV1-DK21 recipient strains had reduced growth rates, altered pigmentation, and reduced virulence. These results indicate that protoplast fusion can be used to introduce FgV1-DK21 dsRNA into other Fusarium species and into C. parasitica and that FgV1-DK21 can be used as a hypovirulence factor and thus as a biological control agent.
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Tanaka T, Sun L, Tsutani K, Suzuki N. Rearrangements of mycoreovirus 1 S1, S2 and S3 induced by the multifunctional protein p29 encoded by the prototypic hypovirus Cryphonectria hypovirus 1 strain EP713. J Gen Virol 2011; 92:1949-1959. [PMID: 21508189 DOI: 10.1099/vir.0.031138-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Mycoreovirus 1 (MyRV1), a member of the family Reoviridae possessing a genome consisting of 11 dsRNA segments (S1-S11), infects the chestnut blight fungus and reduces its virulence (hypovirulence). Studies have previously demonstrated reproducible induction of intragenic rearrangements of MyRV1 S6 (S6L: almost full-length duplication) and S10 (S10ss: internal deletion of three-quarters of the ORF), mediated by the multifunctional protein p29 encoded by the prototype hypovirus, Cryphonectria hypovirus 1 (CHV1) strain EP713, of the family Hypoviridae with ssRNA genomes. The current study showed that CHV1 p29 also induced rearrangements of the three largest MyRV1 segments, S1, S2 and S3, which encode structural proteins. These rearranged segments involved in-frame extensions of almost two-thirds of the ORFs (S1L, S2L and S3L, respectively), which is rare for a reovirus rearrangement. MyRV1 variants carrying S1L, S2L or S3L always contained S10ss (MyRV1/S1L+S10ss2, MyRV1/S2L+S10ss2 or MyRV1/S3L+S10ss2). Levels of mRNAs for the rearranged and co-existing unaltered genome segments in fungal colonies infected with each of the MyRV1 variants appeared to be comparable to those for the corresponding normal segments in wild-type MyRV1-infected colonies, suggesting that the rearranged segments were fully competent for packaging and transcription. Protein products of the rearranged segments were detectable in fungal colonies infected with S2L MyRV1/S2L+S10ss2 and S3L MyRV1/S3L+S10ss2, whilst S1L-encoded protein remained undetectable. S1L, S2L and S3L were associated with enhancement of the aerial hyphae growth rate. This study has provided additional examples of MyRV1 intragenic rearrangements induced by p29, and suggests that normal S1, S2 and S3 are required for the symptoms caused by MyRV1.
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Affiliation(s)
- Toru Tanaka
- Agrivirology Laboratory, Institute of Plant Science and Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Liying Sun
- Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, PR China
| | - Kouhei Tsutani
- Agrivirology Laboratory, Institute of Plant Science and Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Nobuhiro Suzuki
- Agrivirology Laboratory, Institute of Plant Science and Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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Popov AP, Belov AA, Ivanushkina NE, Tsvetkov IL, Konichev AS. Molecular genetic determinants of intraspecific polymorphism of the phytopathogenic fungus Cryphonectria parasitica. RUSS J GENET+ 2011. [DOI: 10.1134/s1022795411030112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
In contrast to viruses of plants and animals, viruses of fungi, mycoviruses, uniformly lack an extracellular phase to their replication cycle. The persistent, intracellular nature of the mycovirus life cycle presents technical challenges to experimental design. However, these properties, coupled with the relative simplicity and evolutionary position of the fungal host, also provide opportunities for examining fundamental aspects of virus-host interactions from a perspective that is quite different from that pertaining for most plant and animal virus infections. This chapter presents support for this view by describing recent advances in the understanding of antiviral defense responses against one group of mycoviruses for which many of the technical experimental challenges have been overcome, the hypoviruses responsible for hypovirulence of the chestnut blight fungus Cryphonectria parasitica. The findings reveal new insights into the induction and suppression of RNA silencing as an antiviral defense response and an unexpected role for RNA silencing in viral RNA recombination.
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Affiliation(s)
- Donald L Nuss
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland, USA
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A novel bipartite double-stranded RNA Mycovirus from the white root rot Fungus Rosellinia necatrix: molecular and biological characterization, taxonomic considerations, and potential for biological control. J Virol 2009; 83:12801-12. [PMID: 19828620 DOI: 10.1128/jvi.01830-09] [Citation(s) in RCA: 205] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
White root rot, caused by the ascomycete Rosellinia necatrix, is a devastating disease worldwide, particularly in fruit trees in Japan. Here we report on the biological and molecular properties of a novel bipartite double-stranded RNA (dsRNA) virus encompassing dsRNA-1 (8,931 bp) and dsRNA-2 (7,180 bp), which was isolated from a field strain of R. necatrix, W779. Besides the strictly conserved 5' (24 nt) and 3' (8 nt) terminal sequences, both segments show high levels of sequence similarity in the long 5' untranslated region of approximately 1.6 kbp. dsRNA-1 and -2 each possess two open reading frames (ORFs) named ORF1 to -4. Although the protein encoded by 3'-proximal ORF2 on dsRNA-1 shows sequence identities of 22 to 32% with RNA-dependent RNA polymerases from members of the families Totiviridae and Chrysoviridae, the remaining three virus-encoded proteins lack sequence similarities with any reported mycovirus proteins. Phylogenetic analysis showed that the W779 virus belongs to a separate clade distinct from those of other known mycoviruses. Purified virions approximately 50 nm in diameter consisted of dsRNA-1 and -2 and a single major capsid protein of 135 kDa, which was shown by peptide mass fingerprinting to be encoded by dsRNA-1 ORF1. We developed a transfection protocol using purified virions to show that the virus was responsible for reduction of virulence and mycelial growth in several host strains. These combined results indicate that the W779 virus is a novel bipartite dsRNA virus with potential for biological control (virocontrol), named Rosellinia necatrix megabirnavirus 1 (RnMBV1), that possibly belongs to a new virus family.
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Guo LH, Sun L, Chiba S, Araki H, Suzuki N. Coupled termination/reinitiation for translation of the downstream open reading frame B of the prototypic hypovirus CHV1-EP713. Nucleic Acids Res 2009; 37:3645-59. [PMID: 19364811 PMCID: PMC2699510 DOI: 10.1093/nar/gkp224] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cryphonectria hypovirus 1 (CHV1), associated with the picorna-like superfamily, infects the chestnut blight fungus and attenuates the virulence of the host fungus. The genomic RNA of the virus has two continuous open reading frames, A and B, separated by the pentanucleotide UAAUG. We present here evidence suggesting that ORF B is translated from genome-sized virus mRNA by a coupled termination/reinitiation mechanism mediated by the pentamer. In the coupled translation, the overlapping UAA and AUG triplets serve as the stop codon of ORF A and the initiator of ORF B, respectively. This was established by the use of a luciferase assay with a basic construct containing the ORF A sequence and the firefly luciferase gene while retaining the pentamer between the two coding sequences. The proportion of ribosomes reinitiating translation after terminating was determined to be 2.5–4.4% by three independent assay systems in fungal and insect cells. Use of a series of mutant constructs identified two sequence elements, the pentamer and the p40 sequence, that affect the efficiency of coupled translation and virus replication. Together, these results provide the first example of coupled translation facilitated by the pentanucleotide UAAUG in the kingdom Fungi. The mechanism by which the preceding p40-coding sequence promotes reinitiation is discussed.
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Affiliation(s)
- Li-hua Guo
- State Key Lab of Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Yuanmingyuan West 2, Beijing 100094, China
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TrehanPati N, Geffers R, Sukriti, Hissar S, Riese P, Toepfer T, Buer J, Kumar M, Guzman CA, Sarin SK. Gene expression signatures of peripheral CD4+ T cells clearly discriminate between patients with acute and chronic hepatitis B infection. Hepatology 2009; 49:781-90. [PMID: 19185001 DOI: 10.1002/hep.22696] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
UNLABELLED CD4+ T and regulatory T cells (Tregs) seem to play a key role in persistence of hepatitis B virus (HBV) infection. However, the molecular events by which Tregs exert their modulatory activity are largely unknown. The transcriptional profiles of CD4+ T cells of healthy controls (HCs) and patients affected by acute hepatitis B (AVH-B) or chronic hepatitis B (CHB) infection were established using a custom expression array consisting of 350 genes relevant for CD4+ T cell and Treg function. These studies were complemented by real-time reverse-transcription polymerase chain reaction. Peripheral blood mononuclear cells (PBMCs) were also analyzed for the presence of Tregs, which were more abundant in the acute stage of the disease (7%) than in HCs and CHB infection (HCs versus AVH-B, P = 0.003; AVH-B versus CHB, P = 0.04). One hundred eighteen genes (34%) intrinsically differentiate HBV-infected patients from HCs. Using gene ontology, we identified T cell receptor signaling and clusterization, mitogen-activated protein kinase kinase signaling, cell adhesion, cytokines and inflammatory responses, cell cycle/cell proliferation, and apoptosis as the most prominent affected modules. A higher expression of CCR1, CCR3, CCR4, CCR5, and CCR8 was seen in AVH-B than in CHB-infected patients and HCs. Annotation of the interconnected functional network of genes provided a unique representation of global immune activation during acute infection. Almost all genes were down-regulated in patients with CHB infection. CONCLUSION The fingerprints enable clear discrimination between patients suffering from AVH-B or CHB infection. The observed profiles suggest accumulation of effector T cells with a potential role in necro-inflammation during the acute stage. Subsequent down-regulated effector functions support the hypothesis of suppressed CD4+ effector T cells favoring viral persistence in the chronic infection stage.
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Abstract
Mycoviruses are widespread in all major groups of plant pathogenic fungi. They are transmitted intracellularly during cell division, sporogenesis, and cell fusion, but apparently lack an extracellular route for infection. Their natural host ranges are limited to individuals within the same or closely related vegetative compatibility groups. Recent advances, however, allowed the establishment of experimental host ranges for a few mycoviruses. Although the majority of known mycoviruses have dsRNA genomes that are packaged in isometric particles, an increasing number of usually unencapsidated mycoviruses with positive-strand RNA genomes have been reported. We discuss selected mycoviruses that cause debilitating diseases and/or reduce the virulence of their phytopathogenic fungal hosts. Such fungal-virus systems are valuable for the development of novel biocontol strategies and for gaining an insight into the molecular basis of fungal virulence. The availability of viral and host genome sequences and of transformation and transfection protocols for some plant pathogenic fungi will contribute to progress in fungal virology.
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Affiliation(s)
- Said A Ghabrial
- Plant Pathology Department, University of Kentucky, Lexington, Kentucky 40546, USA.
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Sun L, Suzuki N. Intragenic rearrangements of a mycoreovirus induced by the multifunctional protein p29 encoded by the prototypic hypovirus CHV1-EP713. RNA (NEW YORK, N.Y.) 2008; 14:2557-2571. [PMID: 18945807 PMCID: PMC2590959 DOI: 10.1261/rna.1125408] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Accepted: 09/01/2008] [Indexed: 05/26/2023]
Abstract
Mycoreovirus 1 (MyRV1), a member of the Reoviridae family possessing a genome consisting of 11 dsRNA segments (S1-S11), and the prototype hypovirus (CHV1-EP713) of the Hypoviridae family, which is closely related to the monopartite picorna-like superfamily with a ssRNA genome, infect the chestnut blight fungus and cause virulence attenuation and distinct phenotypic alterations in the host. Here, we present evidence for reproducible induction of intragenic rearrangements of MyRV1 S6 and S10, mediated by the multifunctional protein p29 encoded by CHV1. S6 and S10 underwent an almost full-length ORF duplication (S6L) and an internal deletion of three-fourths of the ORF (S10ss). No significant influence on symptom induction in the fungal host was associated with the S6L rearrangement. In contrast, S10-encoded VP10, while nonessential for MyRV1 replication, was shown to contribute to virulence reduction and reduced growth of aerial mycelia. Furthermore, p29 was found to copurify with MyRV1 genomic RNA and bind to VP9 in vitro and in vivo, suggesting direct interactions of p29 with the MyRV1 replication machinery. This study provides the first example of a viral factor involved in RNA genome rearrangements of a different virus and shows its usefulness as a probe into the mechanism of replication and symptom expression of a heterologous virus.
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Affiliation(s)
- Liying Sun
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University Kurashiki, Okayama 710-0046, Japan
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35
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Zhang X, Nuss DL. A host dicer is required for defective viral RNA production and recombinant virus vector RNA instability for a positive sense RNA virus. Proc Natl Acad Sci U S A 2008; 105:16749-54. [PMID: 18922782 PMCID: PMC2567904 DOI: 10.1073/pnas.0807225105] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Indexed: 01/14/2023] Open
Abstract
Defective interfering (DI) RNAs, helper virus-dependent deletion mutant RNAs derived from the parental viral genomic RNA during replication, have been described for most RNA virus taxonomic groups. We now report that DI RNA production in the chestnut blight fungus, Cryphonectria parasitica, persistently infected by virulence-attenuating positive sense RNA hypoviruses, depends on one of two host dicer genes, dcl-2. We further report that nonviral sequences that are rapidly deleted from recombinant hypovirus RNA virus vectors in wild-type and dicer gene dcl-1 deletion mutant strains are stably maintained and expressed in the Deltadcl-2 mutant strain. These results establish a requirement for dcl-2, the C. parasitica dicer gene responsible for antiviral defense and generation of virus-derived small interfering RNAs, in DI RNA production and recombinant virus vector RNA instability.
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Affiliation(s)
- Xuemin Zhang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
| | - Donald L. Nuss
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
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Hypovirus papain-like protease p48 is required for initiation but not for maintenance of virus RNA propagation in the chestnut blight fungus Cryphonectria parasitica. J Virol 2008; 82:6369-78. [PMID: 18448523 DOI: 10.1128/jvi.02638-07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The prototypic hypovirus CHV1-EP713, responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus Cryphonectria parasitica, encodes two papain-like proteases, p29 and p48. Protein p29 has been shown to be dispensable for hypovirus RNA replication and to act as a suppressor of RNA silencing. Here we describe a role for p48 in hypovirus RNA propagation. CHV1-EP713 infectious cDNA clones in which the p48 coding region was deleted, Delta p48, were unable to establish infection in C. parasitica when introduced as a DNA form by transformation or as a coding strand transcript by electroporation. However, the Delta p48 mutant virus RNA was rescued when p48 was provided in trans. Surprisingly, the Delta p48 mutant viruses retained replication competence in the apparent absence of p48 following transmission to wild-type C. parasitica and successive subculturing. The replicating Delta p48 mutant virus was reduced in RNA accumulation by 60% both in the absence and presence of p48 provided in trans and was transmitted through asexual spores (conidia) at a rate 3 to 8% of that for full-length CHV1-EP713. Complementary analysis of strains expressing p48 or containing the replicating Delta p48 mutant virus showed that like p29, p48 contributes to virus-mediated suppression of host pigmentation and conidiation, although to a lesser extent, and is dispensable for hypovirus-mediated hypovirulence. The combined results suggest that papain-like protease p48 plays an essential role in the initiation but not the maintenance of virus RNA propagation and also contributes to the regulation of viral RNA accumulation and vertical transmission.
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Zhang X, Segers GC, Sun Q, Deng F, Nuss DL. Characterization of hypovirus-derived small RNAs generated in the chestnut blight fungus by an inducible DCL-2-dependent pathway. J Virol 2008; 82:2613-9. [PMID: 18199652 PMCID: PMC2258980 DOI: 10.1128/jvi.02324-07] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Accepted: 01/04/2008] [Indexed: 12/27/2022] Open
Abstract
The disruption of one of two dicer genes, dcl-2, of the chestnut blight fungus Cryphonectria parasitica was recently shown to increase susceptibility to mycovirus infection (G. C. Segers, X. Zhang, F. Deng, Q. Sun, and D. L. Nuss, Proc. Natl. Acad. Sci. USA 104:12902-12906, 2007). We now report the accumulation of virus-derived small RNAs (vsRNAs) in hypovirus CHV1-EP713-infected wild-type and dicer gene dcl-1 mutant C. parasitica strains but not in hypovirus-infected dcl-2 mutant and dcl-1 dcl-2 double-mutant strains. The CHV1-EP713 vsRNAs were produced from both the positive and negative viral RNA strands at a ratio of 3:2 in a nonrandom distribution along the viral genome. We also show that C. parasitica responds to hypovirus and mycoreovirus infections with a significant increase (12- to 20-fold) in dcl-2 expression while the expression of dcl-1 is increased only modestly (2-fold). The expression of dcl-2 is further increased ( approximately 35-fold) following infection with a hypovirus CHV1-EP713 mutant that lacks the p29 suppressor of RNA silencing. The combined results demonstrate the biogenesis of mycovirus-derived small RNAs in a fungal host through the action of a specific dicer gene, dcl-2. They also reveal that dcl-2 expression is significantly induced in response to mycovirus infection by a mechanism that appears to be repressed by the hypovirus-encoded p29 suppressor of RNA silencing.
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Affiliation(s)
- Xuemin Zhang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, 9600 Gudelsky Dr., Rockville, MD 20850, USA
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A host factor involved in hypovirus symptom expression in the chestnut blight fungus, Cryphonectria parasitica. J Virol 2007; 82:740-54. [PMID: 17977965 DOI: 10.1128/jvi.02015-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The prototype hypovirus CHV1-EP713 causes virulence attenuation and severe suppression of asexual sporulation and pigmentation in its host, the chestnut blight fungus, Cryphonectria parasitica. We identified a factor associated with symptom induction in C. parasitica using a transformation of C. parasitica strain EP155 with a full-length cDNA clone from a mild mutant virus strain, Cys(72). This was accomplished by using mutagenesis of the transformant fungal strain TCys(72)-1 by random integration of plasmid pHygR, conferring hygromycin resistance. The mutant, namA (after nami-gata, meaning wave shaped), showed an irregular fungal morphology with reduced conidiation and pigmentation while retaining similar levels of virulence and virus accumulation relative to TCys(72)-1- or Cys(72)-infected strain EP155. However, the colony morphology of virus-cured namA (VC-namA) was indistinguishable from those of EP155 and virus-cured TCys(72)-1 [VC-TCys(72)-1]. The phenotypic difference between VC-namA and VC-TCys(72)-1 was found only when these strains infected with the wild type or certain mutant CHV1-EP713 strains but not when infected with Mycoreovirus 1. Sequence analysis of inverse-PCR-amplified genomic DNA fragments and cDNA identified the insertion site of the mutagenic plasmid in exon 8 of the nam-1 gene. NAM-1, comprising 1,257 amino acids, shows sequence similarities to counterparts from other filamentous fungi and possesses the CorA domain that is conserved in a class of Mg(2+) transporters from prokaryotes and eukaryotes. Complementation assays using the wild-type and mutant alleles and targeted disruption of nam-1 showed that nam-1 with an extension of the pHygR-derived sequence contributed to the altered phenotype in the namA mutant. The molecular mechanism underlying virus-specific fungal symptom modulation in VC-namA is discussed.
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Segers GC, Zhang X, Deng F, Sun Q, Nuss DL. Evidence that RNA silencing functions as an antiviral defense mechanism in fungi. Proc Natl Acad Sci U S A 2007; 104:12902-6. [PMID: 17646660 PMCID: PMC1937564 DOI: 10.1073/pnas.0702500104] [Citation(s) in RCA: 207] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The role of RNA silencing as an antiviral defense mechanism in fungi was examined by testing the effect of dicer gene disruptions on mycovirus infection of the chestnut blight fungus Cryphonectria parasitica. C. parasitica dicer-like genes dcl-1 and dcl-2 were cloned and shown to share a high level of predicted amino acid sequence identity with the corresponding dicer-like genes from Neurospora crassa [Ncdcl-1 (50.5%); Ncdcl-2 (38.0%)] and Magnaporthe oryzae [MDL-1 (45.6%); MDL-2 (38.0%)], respectively. Disruption of dcl-1 and dcl-2 resulted in no observable phenotypic changes relative to wild-type C. parasitica. Infection of Deltadcl-1 strains with hypovirus CHV1-EP713 or reovirus MyRV1-Cp9B21 resulted in phenotypic changes that were indistinguishable from that exhibited by wild-type strain C. parasitica EP155 infected with these same viruses. In stark contrast, the Deltadcl-2 and Deltadcl-1/Deltadcl-2 mutant strains were highly susceptible to mycovirus infection, with CHV1-EP713-infected mutant strains becoming severely debilitated. Increased viral RNA levels were observed in the Deltadcl-2 mutant strains for a hypovirus CHV1-EP713 mutant lacking the suppressor of RNA silencing p29 and for wild-type reovirus MyRV1-Cp9B21. Complementation of the Deltadcl-2 strain with the wild-type dcl-2 gene resulted in reversion to the wild-type response to virus infection. These results provide direct evidence that a fungal dicer-like gene functions to regulate virus infection.
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Affiliation(s)
- Gert C. Segers
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
| | - Xuemin Zhang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
| | - Fuyou Deng
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
| | - Qihong Sun
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
| | - Donald L. Nuss
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, Rockville, MD 20850
- To whom correspondence should be addressed at:
Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, 9600 Gudelsky Drive, Rockville, MD 20850. E-mail:
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Sun L, Nuss DL, Suzuki N. Synergism between a mycoreovirus and a hypovirus mediated by the papain-like protease p29 of the prototypic hypovirus CHV1-EP713. J Gen Virol 2006; 87:3703-3714. [PMID: 17098988 DOI: 10.1099/vir.0.82213-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Infection of the chestnut blight fungus, Cryphonectria parasitica, by the prototypic hypovirus Cryphonectria hypovirus 1-EP713 (CHV1-EP713) or by the type member, Mycoreovirus 1-Cp9B21 (MyRV1-Cp9B21), of a novel genus (Mycoreovirus) of the family Reoviridae results in hypovirulence, but with a different spectrum of phenotypic changes. The former virus depresses pigmentation and conidiation dramatically, whilst the latter virus has little effect on these processes. This study showed that double infection by the two viruses resulted in a phenotype similar to that of CHV1-EP713 singly infected colonies, but with further decreased levels of host conidiation and vegetative growth and increased levels of MyRV1-Cp9B21 genomic dsRNA accumulation (twofold) and vertical transmission (sixfold). In contrast, CHV1-EP713 RNA accumulation was not altered by MyRV1-Cp9B21 infection. It was also found that the papain-like cysteine protease p29, encoded by CHV1-EP713 ORF A, contributes to the phenotypic alterations and transactivation of MyRV1-Cp9B21 replication and transmission. Chromosomally expressed p29 was able to increase MyRV1-Cp9B21 vertical transmission by more than twofold and genomic RNA accumulation by 80 %. Transactivation was abolished by Cys-->Gly mutations at p29 residues 70 and 72 located within the previously identified symptom-determinant domain required for suppression of host pigmentation and sporulation and p29-mediated in trans enhancement of homologous Deltap29 mutant virus RNA replication. Transactivation was not altered by Ser substitutions at the p29 protease catalytic residue Cys(162). These results indicated a link between p29-mediated enhancement of heterologous virus accumulation and transmission and p29-mediated host symptom expression. The role of p29 as a suppressor of RNA silencing is discussed.
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Affiliation(s)
- Liying Sun
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Donald L Nuss
- Center for Biosystems Research, University of Maryland Biotechnology Institute, University of Maryland, College Park, MD 20742, USA
| | - Nobuhiro Suzuki
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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Lin H, Lan X, Liao H, Parsley TB, Nuss DL, Chen B. Genome sequence, full-length infectious cDNA clone, and mapping of viral double-stranded RNA accumulation determinant of hypovirus CHV1-EP721. J Virol 2006; 81:1813-20. [PMID: 17135313 PMCID: PMC1797589 DOI: 10.1128/jvi.01625-06] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryphonectria parasitica strain EP721 is infected with a strain of hypovirus CHV1, CHV1-EP721, and exhibits typical hypovirulence-associated traits such as reduced pigmentation and reduced asexual sporulation. However, the accumulation of the viral double-stranded RNA (dsRNA) in this hypovirus-infected C. parasitica strain is atypically low. We now report the complete nucleotide sequence and construction of a full-length infectious cDNA clone for hypovirus CHV1-EP721. The genome sequence of CHV1-EP721 was determined to be 12,724 bp in length and to share extensive homology with two other hypovirus strains, CHV1-Euro7 and CHV1-EP713, with an average of 99% and 90% identities at the nucleotide level and 99% and 92% identities at the amino acid level, respectively. CHV1-EP721 was successfully introduced into virus-free fungal host strain EP721(-v) by transfection with transcripts derived from a full-length viral cDNA. The transfected strain had a phenotype indistinguishable from that of EP721, and the accumulation of CHV1-EP721 dsRNA in the transfectant was lower than those transfected by CHV1-Euro7 and CHV1-EP713 transcripts. Through the construction of chimeric viruses by domain swapping using infectious cDNA clones of CHV1-EP721, CHV1-EP713, and CHV1-Euro7 hypoviruses, the determinant for the low level of viral dsRNA accumulation in CHV1-EP721 was mapped to the second of two CHV1-EP721 open reading frames (ORFs), ORF B. Further refined swapping of domains within ORF B identified a 2.5-kb coding region between p48 and the polymerase domain of CHV1-EP721 as being responsible for the low viral dsRNA accumulation. Evidence is also provided that low rates of hypovirus transmission through conidial spores correlates with low viral dsRNA accumulation.
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Affiliation(s)
- Haiyan Lin
- Guangxi Key Laboratory of Subtropical Bioresource Conservation and Utilization, Guangxi University, 100 Daxiu Road, Nanning, Guangxi 530004, People's Republic of China
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Xie J, Wei D, Jiang D, Fu Y, Li G, Ghabrial S, Peng Y. Characterization of debilitation-associated mycovirus infecting the plant-pathogenic fungus Sclerotinia sclerotiorum. J Gen Virol 2006; 87:241-249. [PMID: 16361437 DOI: 10.1099/vir.0.81522-0] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It was previously reported that three dsRNA segments, designated L, M and S, were isolated from Sclerotinia sclerotiorum strain Ep-1PN and that the M dsRNA segment was coincident with hypovirulence and debilitation of the fungal host. Here, the complete nucleotide sequence of the M dsRNA of 5419 nt, excluding the poly(A) tail, was determined. Sequence analysis revealed the occurrence of a single open reading frame (nt 93-5195) encoding a protein with significant similarity to the replicases of the 'alphavirus-like' supergroup of positive-strand RNA viruses. The M dsRNA-encoded putative replicase protein contained the conserved methyl transferase, helicase and RNA-dependent RNA polymerase (RdRp) domains characteristic of the replicases of potex-like plant viruses (flexiviruses) and Botrytis virus F (BVF), a flexuous rod mycovirus infecting the phytopathogenic fungus Botrytis cinerea. Furthermore, convincing evidence is presented showing that ascospore descendents derived from the debilitated strain Ep-1PN were devoid of dsRNA and exhibited normal colony morphology. Moreover, it was demonstrated that the debilitation phenotype was transmitted from the parental debilitated strain to its normal ascospore progeny via hyphal anastomosis. These results suggest that the M dsRNA from strain Ep-1PN is derived from the genomic RNA of a positive-strand RNA virus, which we designated Sclerotinia sclerotiorum debilitation-associated RNA virus (SsDRV). Although phylogenetic analysis of the conserved RdRp motifs verified that SsDRV is closely related to BVF and to the allexiviruses in the family Flexiviridae, SsDRV is distinct from these viruses, mainly based on the lack of coat protein and movement protein.
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Affiliation(s)
- Jun Xie
- National Key Laboratory of Agriculture Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China
- Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Dongmei Wei
- National Key Laboratory of Agriculture Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China
- Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Daohong Jiang
- National Key Laboratory of Agriculture Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China
- Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Yanping Fu
- Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Guoqing Li
- National Key Laboratory of Agriculture Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China
- Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
| | - Said Ghabrial
- Department of Plant Pathology, University of Kentucky, 201F Plant Science Building, 1405 Veterans Drive, University of Kentucky, Lexington, KY 40546-0312, USA
| | - Youliang Peng
- Department of Plant Pathology, China Agricultural University, Beijing 100092, PR China
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Abstract
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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Affiliation(s)
- Donald L Nuss
- Center for Biosystems Research, 5115 Plant Sciences Building, University of Maryland Biotechnology Institute, College Park, Maryland 20742, USA.
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Allen TD, Dawe AL, Nuss DL. Use of cDNA microarrays to monitor transcriptional responses of the chestnut blight fungus Cryphonectria parasitica to infection by virulence-attenuating hypoviruses. EUKARYOTIC CELL 2004; 2:1253-65. [PMID: 14665460 PMCID: PMC326648 DOI: 10.1128/ec.2.6.1253-1265.2003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hypoviruses are a family of cytoplasmically replicating RNA viruses of the chestnut blight fungus Cryphonectria parasitica. Members of this mycovirus family persistently alter virulence (hypovirulence) and related fungal developmental processes, including asexual and sexual sporulation. In order to gain a better understanding of the molecular basis for these changes, we have developed a C. parasitica cDNA microarray to monitor global transcriptional responses to hypovirus infection. In this report, a spotted DNA microarray representing approximately 2,200 C. parasitica genes was used to monitor changes in the transcriptional profile after infection by the prototypic hypovirus CHV1-EP713. Altered transcript abundance was identified for 295 clones (13.4% of the 2,200 unique cDNAs) as a result of CHV1-EP713 infection-132 up-regulated and 163 down-regulated. In comparison, less than 20 specific C. parasitica genes were previously identified by Northern analysis and mRNA differential display as being responsive to hypovirus infection. A 93% validation rate was achieved between real-time reverse transcription-PCR results and microarray predictions. Differentially expressed genes represented a broad spectrum of biological functions, including stress responses, carbon metabolism, and transcriptional regulation. These findings are consistent with the view that infection by a 12.7-kbp hypovirus RNA results in a persistent reprogramming of a significant portion of the C. parasitica transcriptome. The potential impact of microarray studies on current and future efforts to establish links between hypovirus-mediated changes in cellular gene expression and phenotypes is discussed.
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Affiliation(s)
- Todd D Allen
- Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, Maryland 20742-4450, USA
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Affiliation(s)
- Bradley I Hillman
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ 08901, USA
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Suzuki N, Maruyama K, Moriyama M, Nuss DL. Hypovirus papain-like protease p29 functions in trans to enhance viral double-stranded RNA accumulation and vertical transmission. J Virol 2003; 77:11697-707. [PMID: 14557655 PMCID: PMC229363 DOI: 10.1128/jvi.77.21.11697-11707.2003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The prototypic hypovirus CHV1-EP713 attenuates virulence (hypovirulence) and alters several physiological processes of the chestnut blight fungus Cryphonectria parasitica. The papain-like protease, p29, and the highly basic protein, p40, derived, respectively, from the N-terminal and C-terminal portions of the CHV1-EP713-encoded open reading frame (ORF) A polyprotein, p69, both contribute to reduced pigmentation and sporulation. The p29 coding region was shown to suppress pigmentation and asexual sporulation in the absence of virus infection in transformed C. parasitica, whereas transformants containing the p40-coding domain exhibited a wild-type, untransformed phenotype. Deletion of either p29 or p40 from the viral genome also results in reduced accumulation of viral RNA. We now show that p29, but not p40, functions in trans to enhance genomic RNA accumulation and vertical transmission of p29 deletion mutant viruses. The frequency of virus transmission through conidia was found to decrease with reduced accumulation of viral genomic double-stranded RNA (dsRNA): from almost 100% for wild-type virus to approximately 50% for Deltap29, and 10 to 20% for Deltap69. When expressed from a chromosomally integrated cDNA copy, p29 elevated viral dsRNA accumulation and transmission for Deltap29 mutant virus to the level shown by wild-type virus. Increased viral RNA accumulation levels were also observed for a Deltap69 mutant lacking almost the entire ORF A sequence. Such enhancements were not detected in transgenic fungal colonies expressing p40. Mutation of p29 residues Cys(70) or Cys(72), strictly conserved in hypovirus p29 and potyvirus HC-Pro, resulted in the loss of both p29-mediated suppressive activity in virus-free transgenic C. parasitica and in trans enhancement of RNA accumulation and transmission, suggesting a linkage between these functional activities. These results suggest that p29 is an enhancer of viral dsRNA accumulation and vertical virus transmission through asexual spores.
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Affiliation(s)
- Nobuhiro Suzuki
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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Deng F, Xu R, Boland GJ. Hypovirulence-Associated Double-Stranded RNA from Sclerotinia homoeocarpa Is Conspecific with Ophiostoma novo-ulmi Mitovirus 3a-Ld. PHYTOPATHOLOGY 2003; 93:1407-1414. [PMID: 18944069 DOI: 10.1094/phyto.2003.93.11.1407] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT The nucleotide sequence of the hypovirulence-associated double-stranded RNA (dsRNA) in hypovirulent isolate Sh12B of Sclerotinia homoeocarpa, the causal agent of dollar spot of turf grass, was determined. This large dsRNA (L-dsRNA) is 2,632 bp long and is A and U rich (61.0% A+U residues). One strand of this dsRNA contains an open reading frame (ORF) with the potential to encode a protein of 720 amino acids. This ORF contains 12 UGA codons, predicted to encode tryptophan in ascomycete mitochondria, and has a codon bias typical of mitochondrial genes, which is consistent with a mitochondrial localization of this dsRNA. The amino acid sequence contains conserved motifs typical of RNA-dependent RNA polymerases (RdRps). Sequence analyses of the nucleotide and RdRp-like protein revealed that the L-dsRNA is homologous with previously characterized mitochondrial viruses and dsRNAs from other phytopathogenic fungi, and shares 92.4% nucleotide and 95.1% amino acid sequence identities with the Ophiostoma novo-ulmi mitovirus 3a-Ld from Ophiostoma novo-ulmi, the causal agent of Dutch elm disease. The results indicate that these two dsRNAs are conspecific. This is the first report that a hypovirulence-associated dsRNA virus naturally occurs in two taxonomically distinct fungi, and indicates that horizontal transmission of this dsRNA virus may have occurred between these fungi.
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