Molecular characterization of a novel mycovirus in Alternaria alternata manifesting two-sided effects: Down-regulation of host growth and up-regulation of host plant pathogenicity

Okada, Ryo; S, Ichinose; Takeshita, Kana; Urayama, Syun-ichi; Fukuhara, Teruyuki; Komatsu, Ken; Arie, Tsutomu; Ishihara, Atsushi; Egusa, Mayumi; Kodama, Motoichiro; Moriyama, Hiromitsu

doi:10.1016/j.virol.2018.03.027

Cited by 91 publications

(75 citation statements)

References 47 publications

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“…Briefly, the identified dsRNA viruses are three chrysoviruses, one totivirus, one endornavirus, one tetramycovirus and one virus that groups with a still undefined clade of viruses. With the exception of the chrysovirus identified in Alternaria alternata , which was already reported as Alternaria alternata chrysovirus 1 (Okada et al ., ), the other eight viruses have low identity with protein already reported in databases and hence are to be considered as new viral species. In specific, for dsRNA viruses, we observed identity percentages ranging from 77% for the putative coat protein of the totivirus and 64% of the RNA‐dependent RNA polymerase (RdRP) domain of the same virus, down to 28% of the endornavirus polyprotein.…”

Section: Resultsmentioning

confidence: 99%

“…In a more recent report, Okada et al . () reported mycovirus‐mediated effects on Alternaria alternata disease development in Japanese pear. Also in such case, thanks to the presence of a mycovirus, the fungus displayed the overproduction of an effector which enhanced its virulence in the host plant.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, infection by this virus was associated with enhanced sporulation, laccase activity and pigmentation in the fungus, highlighting possible positive interactions between viruses and their fungal hosts. In a more recent report, Okada et al (2018) reported mycovirusmediated effects on Alternaria alternata disease development in Japanese pear. Also in such case, thanks to the presence of a mycovirus, the fungus displayed the overproduction of an effector which enhanced its virulence in the host plant.…”

Section: Introductionmentioning

confidence: 99%

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Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

Nerva

Turina

Zanzotto

et al. 2019

Environmental Microbiology

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Summary Europe is the world largest grape producer, but in recent years, the report of diseases due to infection by grapevine trunk pathogens (GTPs) is becoming one of the main constraints for viticulture. Among grapevine trunk diseases (GTDs), esca syndrome is one of the most complex, characterized by simultaneous infection of several fungi, which leads to important reduction in yield and quality. Previous characterization of fungal isolates associated with esca syndrome leads to the recognition of at least three important players: Phaeocremonium minimum, Phaemoniella chlamydospora and Fomitiporia mediterranea. Here we isolated and characterized molecularly fungal endophytes directly from field wood tissues of plants showing or not esca symptoms. In addition, to better characterize such collection, a deep RNA sequencing (100 M reads in paired‐end) to screen for mycovirus presence was performed. Thirty‐nine viral genomes were detected, 38 of which were putative new viral species; some of these viruses infected GTPs, including P. minimum and F. mediterranea. In this work, we reported for the first time a curated collection of grapevine fungal endophytes identifying the associated mycoviruses some of which could be employed in future biotechnological exploitation as biological control agents for sustainable plant protection.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

Nerva

Turina

Zanzotto

et al. 2019

Environmental Microbiology

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“…Moreover, Okada et al . (Okada et al ., ) recently reported mycovirus‐mediated effects on Alternaria alternata disease development in Japanese pear. The authors demonstrated a Chrysovirus‐mediated enhancement of A. alternata pathogenicity through the overproduction of an effector (AK‐toxin), which is a host‐specific toxin able to induce necrotic spots in leaves.…”

Section: Resultsmentioning

confidence: 99%

Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus

Nerva

Chitarra

Siciliano

et al. 2018

Environmental Microbiology

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Summary To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus‐free ochratoxin A (OTA)‐producing isolate of Aspergillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses tested, only Aspergillus ochraceus virus (AoV), a partitivirus widespread in A. ochraceus, caused a specific interaction that led to an overproduction of OTA, which is regulated by the European Commission and is the second most important contaminant of food and feed commodities. Gene expression analysis failed to reveal a specific viral upregulation of the mRNA of genes considered to play a role in the OTA biosynthetic pathway. Furthermore, AoOTApks1, a polyketide synthase gene considered essential for OTA production, is surprisingly absent in the genome of our OTA‐producing isolate. The possible biological and evolutionary implications of the mycoviral regulation of mycotoxin production are discussed.

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“…AaCV1 was isolated from Alternaria alternate Japanese pear pathotype, which infects the susceptible pear cultivar ‘Nijisseiki’, produces AK-toxin and causes Alternaria black spot on the leaves. On the one hand, high titer of AaCV1 severely impaired the growth of A. alternata; on the other hand, it increased AK-toxin production and enhanced virulence of this fungus [35].…”

Section: Discussionmentioning

confidence: 99%

Did a novel virus contribute to late blight epidemics?

Cai

Myers

et al. 2018

Preprint

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Phytophthora infestans is the causal agent of potato and tomato late blight. In this study, we characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2). The PiRV-2 genome is 11,170 nt and lacks a polyA tail. It contains a single large open reading frame (ORF) with short 5’- and 3’-untranslated regions. The ORF is predicted to encode a polyprotein of 3710 aa (calculated molecular weight 410.94 kDa). This virus lacks significant similarity to any other known viruses, even in the conserved RNA-dependent RNA polymerase region. Comparing isogenic strains with or without the virus demonstrated that the virus stimulated sporangia production in P. infestans and appeared to enhance its virulence. Transcriptome analysis revealed that it achieved sporulation stimulation likely through down-regulation of ammonium and amino acid intake in P. infestans. This virus was faithfully transmitted through asexual reproduction. Survey of PiRV-2 presence in a P. infestans collection found it in most strains in the US-8 lineage, a very successful clonal lineage of P. infestans in North America. We suggest that PiRV-2 may have contributed to its success, raising the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.Author SummaryPotato late blight, the notorious plant disease behind the Irish Potato Famine, continues to pose a serious threat to potato and tomato production worldwide. While most studies on late blight epidemics focuses on pathogen virulence, host resistance, environmental factors and fungicide resistance, we present evidence in this study that a virus infecting the causal agent, Phytophthora infestans, may have played a role. We characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2) and examined its effects on its host. By comparing identical P. infestans strains except with or without the virus, we found that PiRV-2 stimulated sporulation of P. infestans (a critical factor in late blight epidemics) and increased its virulence. We also profiled gene expression in these strains and identified potential molecular mechanisms through which PiRV-2 asserted its sporulation stimulation effect. In a survey of PiRV-2 presence in a P. infestans collection, we found PiRV-2 in most isolates of the US-8 clonal lineage, a very successfull ineage that dominated potato fields in North America for several decades. We suggest that PiRV-2 may have contributed to its success. Our findings raise the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.

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Molecular characterization of a novel mycovirus in Alternaria alternata manifesting two-sided effects: Down-regulation of host growth and up-regulation of host plant pathogenicity

Cited by 91 publications

References 47 publications

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

Isolation, molecular characterization and virome analysis of culturable wood fungal endophytes in esca symptomatic and asymptomatic grapevine plants

Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus

Did a novel virus contribute to late blight epidemics?

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