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RNA viruses of the genera Ambivirus, Mitovirus, Sclerotimonavirus, and Partitivirus were found in a single isolate of Fusarium graminearum. The genomes of the mitovirus, sclerotimonavirus, and partitivirus were assigned to previously described viruses, whereas the ambivirus genome putatively represents a new species, named Fusarium graminearum ambivirus 1 (FgAV1). To investigate the effect of mycoviruses on the fungal phenotype, the spontaneous loss of mycoviruses during meiosis and the transmission of mycoviruses into a new strain via anastomosis were used to obtain isogenic F. graminearum strains both with and without mycoviruses. Notable effects observed in mycovirus-harboring strains were (i) the suppression of the synthesis of trichothecene mycotoxins and their precursor trichodiene, (ii) the suppression of the synthesis of the defense compound aurofusarin, (iii) the stimulation of the emission of 2-methyl-1-butanol and 3-methyl-1-butanol, and (iv) the increased attractiveness of fungal mycelia for fungivorous collembolans. The increased attractiveness of mycovirus-infected filamentous fungi to animal predators opens new perspectives on the ecological implications of the infection of fungi with viruses. [ABSTRACT FROM AUTHOR]

Introduction: The garden petunia, Petunia hybrida (Solanaceae) is a fertile, diploid, annual hybrid species (2n=14) originating from P. axillaris and P. inflata 200 years ago. To understand the recent evolution of the P. hybrida genome, we examined tandemly repeated or satellite sequences using bioinformatic and molecular cytogenetic analysis. Methods: Raw reads from available genomic assemblies and survey sequences of P. axillaris N (PaxiN), P. inflata S6, (PinfS6), P. hybrida (PhybR27) and the here sequenced P. parodii S7 (PparS7) were used for graph and k-mer based cluster analysis of TAREAN and RepeatExplorer. Analysis of repeat specific monomer lengths and sequence heterogeneity of the major tandem repeat families with more than 0.01% genome proportion were complemented by fluorescent in situ hybridization (FISH) using consensus sequences as probes to chromosomes of all four species. Results: Seven repeat families, PSAT1, PSAT3, PSAT4, PSAT5 PSAT6, PSAT7 and PSAT8, shared high consensus sequence similarity and organisation between the four genomes. Additionally, many degenerate copies were present. FISH in P. hybrida and in the three wild petunias confirmed the bioinformatics data and gave corresponding signals on all or some chromosomes. PSAT1 is located at the ends of all chromosomes except the 45S rDNA bearing short arms of chromosomes II and III, and we classify it as a telomere associated sequence (TAS). It is the most abundant satellite repeat with over 300,000 copies, 0.2% of the genomes. PSAT3 and the variant PSAT7 are located adjacent to the centromere or mid-arm of one to three chromosome pairs. PSAT5 has a strong signal at the end of the short arm of chromosome III in P. axillaris and P.inflata, while in P. hybrida additional interstitial sites were present. PSAT6 is located at the centromeres of chromosomes II and III. PSAT4 and PSAT8 were found with only short arrays. Discussion: These results demonstrate that (i) repeat families occupy distinct niches within chromosomes, (ii) they differ in the copy number, cluster organization and homogenization events, and that (iii) the recent genome hybridization in breeding P. hybrida preserved the chromosomal position of repeats but affected the copy number of repetitive DNA. [ABSTRACT FROM AUTHOR]

Asparagus samples were examined from growing areas of Germany and selected European as well as North, Central and South American countries. Overall, 474 samples were analyzed for Asparagus virus 1 (AV1) using DAS-ELISA. In our survey, 19 AV1 isolates were further characterized. Experimental transmission to 11 species belonging to Aizoaceae, Amarantaceae, Asparagaceae, and Solanaceae succeeded. The ultrastructure of AV1 infection in asparagus has been revealed and has been compared with the one in indicator plants. The cylindrical inclusion (CI) protein, a core factor in viral replication, localized within the cytoplasm and in systemic infections adjacent to the plasmodesmata. The majority of isolates referred to pathotype I (PI). These triggered a hypersensitive resistance in inoculated leaves of Chenopodium spp. and were incapable of infecting Nicotiana spp. Only pathotype II (PII) and pathotype III (PIII) infected Nicotiana benthamiana systemically but differed in their virulence when transmitted to Chenopodium spp. The newly identified PIII generated amorphous inclusion bodies and degraded chloroplasts during systemic infection but not in local lesions of infected Chenopodium spp. PIII probably evolved via recombination in asparagus carrying a mixed infection by PI and PII. Phylogeny of the coat protein region recognized two clusters, which did not overlap with the CI-associated grouping of pathotypes. These results provide evidence for ongoing modular evolution of AV1. [ABSTRACT FROM AUTHOR]

Tobamoviruses are among the most well-studied plant viruses and yet there is still a lot to uncover about them. On one side of the spectrum, there are damage-causing members of this genus: such as the tobacco mosaic virus (TMV), tomato brown rugose fruit virus (ToBRFV) and cucumber green mottle mosaic virus (CGMMV), on the other side, there are members which cause latent infection in host plants. New technologies, such as high-throughput sequencing (HTS), have enabled us to discover viruses from asymptomatic plants, viruses in mixed infections where the disease etiology cannot be attributed to a single entity and more and more researchers a looking at non-crop plants to identify alternative virus reservoirs, leading to new virus discoveries. However, the diversity of these interactions in the virosphere and the involvement of multiple viruses in a single host is still relatively unclear. For such host–virus interactions in wild plants, symptoms are not always linked with the virus titer. In this review, we refer to latent infection as asymptomatic infection where plants do not suffer despite systemic infection. Molecular mechanisms related to latent behavior of tobamoviruses are unknown. We will review different studies which support different theories behind latency. [ABSTRACT FROM AUTHOR]

Pararetroviruses, taxon Caulimoviridae , are typical of retroelements with reverse transcriptase and share a common origin with retroviruses and LTR retrotransposons, presumably dating back 1.6 billion years and illustrating the transition from an RNA to a DNA world. After transcription of the viral genome in the host nucleus, viral DNA synthesis occurs in the cytoplasm on the generated terminally redundant RNA including inter- and intra-molecule recombination steps rather than relying on nuclear DNA replication. RNA recombination events between an ancestral genomic retroelement with exogenous RNA viruses were seminal in pararetrovirus evolution resulting in horizontal transmission and episomal replication. Instead of active integration, pararetroviruses use the host DNA repair machinery to prevail in genomes of angiosperms, gymnosperms and ferns. Pararetrovirus integration – leading to Endogenous ParaRetroViruses, EPRVs – by illegitimate recombination can happen if their sequences instead of homologous host genomic sequences on the sister chromatid (during mitosis) or homologous chromosome (during meiosis) are used as template. Multiple layers of RNA interference exist regulating episomal and chromosomal forms of the pararetrovirus. Pararetroviruses have evolved suppressors against this plant defense in the arms race during co-evolution which can result in deregulation of plant genes. Small RNAs serve as signaling molecules for Transcriptional and Post-Transcriptional Gene Silencing (TGS, PTGS) pathways. Different populations of small RNAs comprising 21–24 nt and 18–30 nt in length have been reported for Citrus, Fritillaria, Musa, Petunia, Solanum and Beta. Recombination and RNA interference are driving forces for evolution and regulation of EPRVs. [ABSTRACT FROM AUTHOR]

Abstract: Electron microscopy of leaf samples displaying streak symptoms from enset (Ensete ventricosum), a banana‐like plant widely cultivated in Ethiopia, showed the presence of bacilliform shaped virions as known for badnaviruses. DNA extracts subjected to rolling circle amplification (RCA), polymerase chain reaction (PCR) and cloning and sequence analysis revealed that the virus has a circular double‐stranded DNA genome of 7,163 nucleotides encoding predicted proteins of 21.5 kDa, 14.5 kDa and 202.5 kDa, a genome organization known for badnaviruses. The virus is phylogenetically most closely related to Sugarcane bacilliform Guadeloupe D virus with a nucleotide sequence identity of 77.2% at the conserved RT/RNase‐H region and 73.6% for the whole genome. Following the current species demarcation criteria, the virus should be considered as an isolate of a new species in the genus Badnavirus for which the name Enset leaf streak virus (ELSV) is suggested. Leaf samples from enset and banana were screened using virus‐specific primers, and ELSV was detected in six of 40 enset but not found in any of 61 banana samples. On the other hand, Banana streak OL virus (BSOLV) was detected from the majority (60%) of symptomatic banana samples but not from enset samples. This paper reports the first full‐genome sequence of a putative new badnavirus species infecting plants in the genus Ensete. In addition, this is the first report of the occurrence of BSOLV in Ethiopia. [ABSTRACT FROM AUTHOR]

A combination of electron microscopy and genome sequencing is highly efficient in screening for latent virus infections independent of the virus morphology or genome. One example is hoya tobamovirus-2 (HoTV-2 genbank accession number: MT750216.1) that has been reported from symptomatic mixed infected samples in 2011 and also as single, asymptomatic, infection in several Hoya species in Germany. The virus induces no symptoms in experimental host plants including Chenopodium quinoa, N. tabacum 'Xanthi nc', N. benthamiana and N. tabacum 'Samsun nn'. 14 days post inoculation, plant sap homogenates were examined using negative staining. Rod shaped virions of 300nm length were detected in newly developing leaves, confirming systemic infection. The virions' morphology and size indicated presence of a tobamovirus. The virus titer was lower when compared to tobacco mosaic virus (TMV) infected plants. For virus species identification, RNA sequencing data were scanned for virus specific sequences. The assembled virus genome could be assigned to the genus Tobamovirus. Phylogenetic analysis showed it is closely related to Youcai mosaic virus (YoMV). Therefore, polyclonal antisera for YoMV (DSMZ number AS-0527) was used in immuno-electron microscopy. The heterologous antiserum reacted with HoTV-2, while other tobamovirus antisera used in routine tobamovirus detection did not. The binding of antibodies along the virion was irregular when compared to TMV and its homologous antisera. Mixed infected Hoya plants and HoTV-2 infected N. benthamiana leaves were embedded to study the ultrastructure of infected plants displaying latency linking in situ HoTV-2 structures. [ABSTRACT FROM AUTHOR]

The article offers information related to European Virus Archive (EVA) was created in 2008 in response to the need for a coordinated and readily accessible collection of human and animal viruses that could be made available to academia, public health organizations and industry. It report that EVA-GLOBAL collaborated with 38 academic institutions at the forefront of human, animal and plant research in Virology, associated with key Non- Governmental Organizations.

Endogenous plant pararetroviruses (EPRVs) were identified as integrated counterparts of most members of the plant virus family Caulimoviridae and represent repetitive elements that are ubiquitous in the plant kingdom. They are often located in pericentromeric regions of plant chromosomes in the vicinity of retrotransposon sequences. Depending on their structure and sequence integrity, some EPRVs are able to replicate and to initiate viral infection. However, conservation of integrated sequences in plant genomes might indicate benefits for the host during evolution. Understanding EPRV activation and control by the host could have important implications for plant breeding strategies to prevent viral disease caused by EPRVs in newly generated cultivars. [Copyright &y& Elsevier]

A number of cases of plant virus sequence integration into host plant genome have been reported. In at least two cases, endogenous pararetrovirus sequences are correlated strongly with subsequent episomal virus infection and there is circumstantial evidence that this also occurs for Petunia vein-clearing virus (PVCV). The detection of viruses is a critical component of plant health and therefore, it is important to have diagnostic procedures that differentiate between the detection of encapsidated viral DNA and homologous sequences in the host genome. PCR-based detection methods targeted at PVCV DNA have been tested and particular attention was paid to design controls that would indicate the existence of host DNA in the reaction. The use of ion-exchange chromatography for the partial purification of plant viruses from other cellular components, including chromosomal DNA, is described. The methods tested for PVCV detection are used to illustrate general principles for the specific detection of virus infections in host plants that carry homologous virus sequences in their genomes. [Copyright &y& Elsevier]

The article presents a study on exploration of the small RNA landscape in Petunia hybrida infected with latent viruses and a pospiviroid using high throughput sequencing. It reports the study will help to contribute to the knowledge of the collection of vsiRNAs for better reconstruction of the virome, shade light on the mechanism of vsiRNA action on host mRNA, contribute to the understanding of benefits for the host during symbiosis.

[Display omitted] • New baculovirus from olive moth, Palpita vitrealis, termed PaviNPV. • PaviNPV was isolated in 2005 and 2019 in Egypt in olive plantations. • PaviNPV represents a new species within group I of the Alphabaculovirus genus. • The genome is 117,533 bp and contains 131 ORFs. The olive leaf moth (jasmine moth), Palpita vitrealis (Lepidoptera: Crambidae), is an important insect pest of olives in several Mediterranean countries. A new alphabaculovirus was isolated from diseased larvae of P. vitrealis in Egypt, first in Giza in spring 2005 and again in Marsa Matrouh in 2019.The larvae exhibited typical symptoms of a baculovirus infection. Light and scanning electron microscopy studies revealed polyhedral occlusion bodies. Transmission electron microscopy of ultrathin sections of purified OBs revealed virions with multiple embedded nucleocapsids. The identity of the two virus isolates was confirmed by sequencing the partial polyhedrin and lef-8 genes, and sequence comparison suggested a relationship to group I alphabaculoviruses. Therefore, this virus was termed Palpita vitrealis nucleopolyhedrovirus (PaviNPV). Whole genome sequencing of the PaviNPV isolate from Giza (Gz05) revealed a genome of 117,533 bp, 131 open reading frames (ORFs) and four homologous repeat (hr) regions. Phylogenetic reconstruction and genetic distance analyses using 38 core genes indicated that PaviNPV should be considered to belong to a novel species within the genus Alphabaculovirus. In bioassays, PaviNPV was highly virulent against second-instar larvae of P. vitrealis. The study reports a novel baculovirus that might have potential as a biological control agent of the olive leaf moth. [ABSTRACT FROM AUTHOR]