Faculty Profiles - SUZUKI Nobuhiro

Editorial: Frontiers in Fungal Virus Research Reviewed

Liying Sun, Nobuhiro Suzuki, Daohong Jiang, Massimo Turina, Jiatao Xie

Frontiers in Cellular and Infection Microbiology 9 456 2020.1

Structure and assembly of double-stranded RNA mycoviruses Reviewed

Carlos P. Mata, Javier M. Rodríguez, Nobuhiro Suzuki, José R. Castón

Advances in Virus Research 108 213 - 247 2020.1

Language：English Publishing type：Part of collection (book)

Mycoviruses are a diverse group that includes ssRNA, dsRNA, and ssDNA viruses, with or without a protein capsid, as well as with a complex envelope. Most mycoviruses are transmitted by cytoplasmic interchange and are thought to lack an extracellular phase in their infection cycle. Structural analysis has focused on dsRNA mycoviruses, which usually package their genome in a 120-subunit T = 1 icosahedral capsid, with a capsid protein (CP) dimer as the asymmetric unit. The atomic structure is available for four dsRNA mycovirus from different families: Saccharomyces cerevisiae virus L-A (ScV-L-A), Penicillium chrysogenum virus (PcV), Penicillium stoloniferum virus F (PsV-F), and Rosellinia necatrix quadrivirus 1 (RnQV1). Their capsids show structural variations of the same framework, with asymmetric or symmetric CP dimers respectively for ScV-L-A and PsV-F, dimers of similar domains of a single CP for PcV, or of two different proteins for RnQV1. The CP dimer is the building block, and assembly proceeds through dimers of dimers or pentamers of dimers, in which the genome is packed as ssRNA by interaction with CP and/or viral polymerase. These capsids remain structurally undisturbed throughout the viral cycle. The T = 1 capsid participates in RNA synthesis, organizing the viral polymerase (1–2 copies) and a single loosely packaged genome segment. It also acts as a molecular sieve, to allow the passage of viral transcripts and nucleotides, but to prevent triggering of host defense mechanisms. Due to the close mycovirus-host relationship, CP evolved to allocate peptide insertions with enzyme activity, as reflected in a rough outer capsid surface.

DOI： 10.1016/bs.aivir.2020.08.001

Scopus

Neo-virology: The raison d'etre of viruses Reviewed International journal

Tokiko Watanabe, Nobuhiro Suzuki, Keizo Tomonaga, Hirofumi Sawa, Yoshiharu Matsuura, Yasushi Kawaguchi, Hideki Takahashi, Keizo Nagasaki, Yoshihiro Kawaoka

Virus Research 274 197751 - 197751 2019.12

Language：English Publishing type：Research paper (scientific journal)

Given that approximately 10 virus particles exist on Earth and all of them are parasitic in living organisms, it is not hard to imagine how virus infection might affect the physiology of hosts and their ecosystems. However, traditional virology research tends to focus on viral pathogenicity or the individual pathogenic viruses; hence, the significance of viruses and viral-mediated processes in the global ecosystem has been poorly understood. To identify the previously unrecognized “raison d'etre of viruses” in nature, we established a research community, designated as the ‘Neo-virology’ consortium. In this consortium, we define a virus as a component of the global ecosystem and our aim is to elucidate its key roles in host organisms, that is, the intra-host ecosystem. 31

DOI： 10.1016/j.virusres.2019.197751

ICTV Virus Taxonomy Profile: Megabirnaviridae. Reviewed International journal

Sato, Y, Miyazaki, N, Kanematsu, S, Ghabrial, S. A, Hillman, B. I, Suzuki, N, ICTV Report, Consortium

Journal of General Virology 100 ( 9 ) 269 - 1270 2019.9

Language：English Publishing type：Research paper (scientific journal)

Megabirnaviridae is a family of non-enveloped spherical viruses with dsRNA genomes of two linear segments, each of 7.2-8.9 kbp, comprising 16.1 kbp in total. The genus Megabirnavirus includes the species Rosellinia necatrix megabirnavirus 1, the exemplar isolate of which infects the white root rot fungus (Rosellinia necatrix) to which it confers hypovirulence. Megabirnaviruses are characterized by their bisegmented genome with large 5'-untranslated regions (1.6 kb) upstream of both 5'-proximal coding strand ORFs, and large protrusions on the particle surface. This is a summary of the ICTV Report on the family Megabirnaviridae, which is available at ictv.global/report/megabirnaviridae.This Profile is dedicated to the memory of our valued colleague Professor Said A. Ghabrial.

DOI： 10.1099/jgv.0.001297

Three ourmia-like viruses and their associated RNAs in Pyricularia oryzae Reviewed

Shuhei Ohkita, Yui Lee, Quyet Nguyen, Kenichi Ikeda, Nobuhiro Suzuki, Hitoshi Nakayashiki

Virology 534 25 - 35 2019.8

Publishing type：Research paper (scientific journal)

Three ourmia-like viruses, designated Pyricularia oryzae ourmia-like virus (PoOLV) 1 to 3, were identified in a wheat-infecting isolate of P. oryzae. The sizes of the full-length PoOLV1-3 genomes were determined to be 2,528, 1,671, and 2,557 nt. Interestingly, we also found two abundant single-stranded RNAs sharing their 5’ terminal 25 and 255 nt with PoOLV1 RNA and PoOLV3 RNA, respectively. The PoOLV1- and PoOLV3-associated RNAs (ARNA1 and ARNA3) were 639 and 514 nt in length, and possessed one and two small ORFs, respectively. In the field isolates of P. oryzae, PoOLVs and ARNAs were detectable at varying levels, and the levels of PoOLV1 and ARNA1 as well as those of PoOLV3 and ARNA3, were tightly correlated. In addition, gene silencing of PoOLV1 and PoOLV3 resulted in a reduction of ARNA1 and ARNA3, respectively. There results indicated that replication of ARNA1 and ARNA3 was associated with PoOLV1 and PoOLV3, respectively.

DOI： 10.1016/j.virol.2019.05.015

Two novel fungal negative-strand RNA viruses related to mymonaviruses and phenuiviruses in the shiitake mushroom (Lentinula edodes) Reviewed

Yu Hsin Lin, Miki Fujita, Sotaro Chiba, Kiwamu Hyodo, Ida Bagus Andika, Nobuhiro Suzuki, Hideki Kondo

Virology 533 125 - 136 2019.7

Publishing type：Research paper (scientific journal)

There is still limited information on the diversity of (−)ssRNA viruses that infect fungi. Here, we have discovered two novel (−)ssRNA mycoviruses in the shiitake mushroom (Lentinula edodes). The first virus has a monopartite RNA genome and relates to that of mymonaviruses (Mononegavirales), especially to Hubei rhabdo-like virus 4 from arthropods and thus designated as Lentinula edodes negative-strand RNA virus 1. The second virus has a putative bipartite RNA genome and is related to the recently discovered bipartite or tripartite phenui-like viruses (Bunyavirales) associated with plants and ticks, and designated as Lentinula edodes negative-strand RNA virus 2 (LeNSRV2). LeNSRV2 is likely the first segmented (−)ssRNA virus known to infect fungi. Its smaller RNA segment encodes a putative nucleocapsid and a plant MP-like protein using a potential ambisense coding strategy. These findings enhance our understanding of the diversity, evolution and spread of (−)ssRNA viruses in fungi.

DOI： 10.1016/j.virol.2019.05.008

Isolation and characterization of a novel mycovirus infecting an edible mushroom, Grifola frondosa Reviewed

Akiko Komatsu, Hideki Kondo, Masayuki Sato, Atsushi Kurahashi, Kozo Nishibori, Nobuhiro Suzuki, Fumihiro Fujimori

Mycoscience 60 ( 4 ) 211 - 220 2019.7

Publishing type：Research paper (scientific journal)

Grifola frondosa (Maitake mushroom) is an important cultivated mushroom due to its medicinal and nutrient values. In this study, we isolated and characterized a novel partitivirus (named Grifola frondosa partitivirus 1, GfPV1) infecting a standard G. frondosa strain Gf-N2. This virus has a two-segmented dsRNA genome (dsRNA1 and dsRNA2) with nucleotide lengths of 2.3 and 2.2 kbp, respectively. The coding strand of dsRNA1 and dsRNA2 segments carries single open reading frame encoding RNA-dependent RNA polymerase (RdRp) and a coat protein (CP), respectively. BLAST searches and phylogenetic analyses showed that GfPV1 is most closely related to a betapartitivirus, Lentinula edodes partitivirus 1 (RdRp <70% and CP <60% amino acid sequence identities), but the sequence divergence suggests that GfPV1 is classifiable as a new member of the genus Betapartitivirus, family Partitiviridae. The presence of GfPV1 does not affect colony morphology and fruiting body development of G. frondosa. This is the first report investigating the effects of a mycovirus infection on the colony morphology and fruiting body development of G. frondosa. Interestingly, GfPV1 accumulations markedly decreased along with the fruiting body maturation stages, suggesting the inhibition of virus multiplication during sexual phase of the G. frondosa life cycle.

DOI： 10.1016/j.myc.2019.01.005

Scopus

A symptomless hypovirus, CHV4, facilitates stable infection of the chestnut blight fungus by a coinfecting reovirus likely through suppression of antiviral RNA silencing Reviewed

Annisa Aulia, Ida Bagus Andika, Hideki Kondo, Bradley I. Hillman, Nobuhiro Suzuki

Virology 533 99 - 107 2019.7

Publishing type：Research paper (scientific journal) Publisher：Elsevier {BV}

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.

DOI： 10.1016/j.virol.2019.05.004

Novel victorivirus from a pakistani isolate of alternaria alternata lacking a typical translational stop/restart sequence signature Reviewed

Atif Jamal, Yukiyo Sato, Sabitree Shahi, Wajeeha Shamsi, Hideki Kondo, Nobuhiro Suzuki

Viruses 11 ( 6 ) 577 2019.6

Publishing type：Research paper (scientific journal) Publisher：MDPI} {AG

The family Totiviridae currently contains five genera Totivirus, Victorivirus, Leishmavirus, Trichomonasvirus, and Giardiavirus. Members in this family generally have a set of two-open reading frame (ORF) elements in their genome with the 5’-proximalORF (ORF1) encoding a capsid protein (CP) and the 3’-proximal one (ORF2) for RNA-dependent RNA polymerase (RdRp). How the downstream open reading frames (ORFs) are expressed is genus-specific. All victoriviruses characterized thus far appear to use the stop/restart translation mechanism, allowing for the expression of two separate protein products from bicitronic genome-sized viral mRNA, while the totiviruses use a -1 ribosomal frame-shifting that leads to a fusion product of CP and RdRp. We report the biological and molecular characterization of a novel victorivirus termed Alternaria alternata victorivirus 1 (AalVV1) isolated from Alternaria alternata in Pakistan. The phylogenetic and molecular analyses showed AalVV1 to be distinct from previously reported victoriviruses. AalVV1 appears to have a sequence signature required for the -1 frame-shifting at the ORF1/2 junction region, rather than a stop/restart key mediator. By contrast, SDS–polyacrylamide gel electrophoresis and peptide mass fingerprinting analyses of purified virion preparations suggested the expression of two protein products, not a CP-RdRp fusion product. How these proteins are expressed is discussed in this study. Possible effects of infection by this virus were tested in two fungal species: A. alternata and RNA silencing proficient and deficient strains of Cryphonectria parasitica, a model filamentous fungus. AalVV1 showed symptomless infection in all of these fungal strains, even in the RNA silencing deficient C. parasitica strain.

DOI： 10.3390/v11060577

Molecular and biological characterization of a novel botybirnavirus identified from a Pakistani isolate of Alternaria alternata Reviewed International journal

Wajeeha Shamsi, Yukiyo Sato, Atif Jamal, Sabitree Shahi, Hideki Kondo, Nobuhiro Suzuki, Muhammad Faraz Bhatti

Virus Research 263 119 - 128 2019.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier {BV}

Mycoviruses ubiquitously infect a wide range of fungal hosts in the world. The current study reports a novel double stranded RNA (dsRNA) virus, termed Alternaria alternata botybirnavirus 1 (AaBbV1), infecting a Pakistani strain, 4a, of a phytopathogenic ascomycetous fungus Alternaria alternata. A combined approach of next generation and conventional terminal end sequencing of the viral genome revealed that the virus is a distinct member of the genus Botybirnavirus. This virus comprised of two segments (dsRNA1 and dsRNA2) of sizes 6127 bp and 5860 bp respectively. The dsRNA1-encoded protein carrying the RNA-dependent RNA polymerase domain showed 61% identity to the counterpart of Botrytis porri botybirnavirus 1 and lower levels of amino acid similarity with those of other putative botybirnaviruses and the fungal dsRNA viruses such as members of the families Totiviridae, Chrysoviridae and Megabirnaviridae. The dsRNA2-encoded protein showed resemblance with corresponding proteins of botybirnaviruses. Electron microscopy showed AaBbV1 to form spherical particles of 40 nm in diameter. Biochemical analyses showed that two structural proteins encoded by dsRNA1 and dsRNA2 underwent processing to some extent during particle purification, resulting in the appearance of multiple smaller products. Phylogenetic analyses of structural proteins suggested that their coding region might have been duplicated once and maintained without recombination. Protoplast fusion technique allowed for the introduction of AaBbV1 into a virus free Japanese strain of A. alternata and demonstrated its symptomless infection by the virus. Interesting similarities and dissimilarities between AaBbV1 and other previously reported botybirnaviruses are also discussed.

DOI： 10.1016/j.virusres.2019.01.006

Investigation of Host Range of and Host Defense against a Mitochondrially Replicating Mitovirus Reviewed

A novel insect-infecting virga/nege-like virus group and its pervasive endogenization into insect genomes. Reviewed

Kondo H, Chiba S, Maruyama K, Andika IB, Suzuki N

Virus research 262 37 - 47 2019.3

"Integration of viral sequences into eukaryotic host genomes: legacy of ancient infections". Reviewed

Tomonaga K, Suzuki N, Berkhout B

Virus research 262 1 2019.3

Hijacking a host scaffold protein, RACK1, for replication of a plant RNA virus. Reviewed

Hyodo K, Suzuki N, Okuno T

The New phytologist 221 ( 2 ) 935 - 945 2019.1

Sabitree Shahi, Ana Eusebio-Cope, Hideki Kondo, Bradley I. Hillman, Nobuhiro Suzuki

Journal of Virology 93 ( 6 ) 2019.1

The biological attributes, genome architecture and packaging of diverse multi-component fungal viruses Reviewed International journal

Yukiyo Sato, Jos{\'{e, R Cast{\'{o } }n, Nobuhiro Suzuki

Current Opinion in Virology 33 55 - 65 2018.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier {BV}

Many fungal viruses or mycoviruses have multi-segmented, rather than single-segmented, genomes. This multi-segment nature is frequently possessed by double-stranded RNA viruses, which include members of the Chrysoviridae, Quadriviridae, Megabirnaviridae, Partitiviridae, and Reoviridae families, and unassigned groups. Their genome segments are often packaged separately with the exception of mycoreoviruses, which are multi-segmented but mono-particulate viruses. These multi-segmented fungal dsRNA viruses, as exemplified by reoviruses, have been extensively studied among structural biologists, and contributed to discoveries of novel virion structures. Multi-component systems, interactions of viruses with subviral agents such as satellite and defective RNAs as typified by the yeast killer, and the rule-breaking neo-virus lifestyle exhibited by a capsidless single-stranded RNA virus hosted in an unrelated double-stranded RNA virus are also discussed. Fungal multi-segmented viruses and multicomponent virus systems would continue to provide virologists with interesting future challenges.

DOI： 10.1016/j.coviro.2018.07.009