1. In-depth comparison of adeno-associated virus containing fractions after CsCl ultracentrifugation gradient separationMojca Janc, Kaja Zevnik, Ana Dolinar, Tjaša Jakomin, Maja Štalekar, Katarina Bačnik, Denis Kutnjak, Magda Tušek-Žnidarič, Lorena Zentilin, Dmitri G. Fedorov, David Dobnik, 2024, izvirni znanstveni članek Povzetek: Recombinant adeno-associated viruses (rAAVs) play a pivotal role in the treatment of genetic diseases. However, current production and purification processes yield AAV-based preparations that often contain unwanted empty, partially filled or damaged viral particles and impurities, including residual host cell DNA and proteins, plasmid DNA, and viral aggregates. To precisely understand the composition of AAV preparations, we systematically compared four different single-stranded AAV (ssAAV) and self-complementary (scAAV) fractions extracted from the CsCl ultracentrifugation gradient using established methods (transduction efficiency, analytical ultracentrifugation (AUC), quantitative and digital droplet PCR (qPCR and ddPCR), transmission electron microscopy (TEM) and enzyme-linked immunosorbent assay (ELISA)) alongside newer techniques (multiplex ddPCR, multi-angle light-scattering coupled to size-exclusion chromatography (SEC-MALS), multi-angle dynamic light scattering (MADLS), and high-throughput sequencing (HTS)). Suboptimal particle separation within the fractions resulted in unexpectedly similar infectivity levels. No single technique could simultaneously provide comprehensive insights in the presence of both bioactive particles and contaminants. Notably, multiplex ddPCR revealed distinct vector genome fragmentation patterns, differing between ssAAV and scAAV. This highlights the urgent need for innovative analytical and production approaches to optimize AAV vector production and enhance therapeutic outcomes. Ključne besede: recombinant adeno-associated viruses (rAAVs), CsCl ultracentrifugation gradient, analytical methods, digital droplet PCR (ddPCR), transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS), Illumina sequencing, virology Objavljeno v DiRROS: 07.08.2024; Ogledov: 92; Prenosov: 70
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2. Global advances in tomato virome research : current status and the impact of high-throughput sequencingMark Paul Selda Rivarez, Ana Vučurović, Nataša Mehle, Maja Ravnikar, Denis Kutnjak, 2021, pregledni znanstveni članek Povzetek: Viruses cause a big fraction of economically important diseases in major crops, including tomato. In the past decade (2011–2020), many emerging or re-emerging tomato-infecting viruses were reported worldwide. In this period, 45 novel viral species were identified in tomato, 14 of which were discovered using high-throughput sequencing (HTS). In this review, we first discuss the role of HTS in these discoveries and its general impact on tomato virome research. We observed that the rate of tomato virus discovery is accelerating in the past few years due to the use of HTS. However, the extent of the post-discovery characterization of viruses is lagging behind and is greater for economically devastating viruses, such as the recently emerged tomato brown rugose fruit virus. Moreover, many known viruses still cause significant economic damages to tomato production. The review of databases and literature revealed at least 312 virus, satellite virus, or viroid species (in 22 families and 39 genera) associated with tomato, which is likely the highest number recorded for any plant. Among those, here, we summarize the current knowledge on the biology, global distribution, and epidemiology of the most important species. Increasing knowledge on tomato virome and employment of HTS to also study viromes of surrounding wild plants and environmental samples are bringing new insights into the understanding of epidemiology and ecology of tomato-infecting viruses and can, in the future, facilitate virus disease forecasting and prevention of virus disease outbreaks in tomato. Objavljeno v DiRROS: 05.08.2024; Ogledov: 100; Prenosov: 104
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3. A primer on the analysis of high-throughput sequencing data for detection of plant virusesDenis Kutnjak, Lucie Tamisier, Ian Adams, Neil Boonham, Thierry Candresse, Michela Chiumenti, Kris De Jonghe, Jan F. Kreuze, Marie Lefebvre, Goncalo Silva, Martha Malapi-Wight, Paolo Margaria, Irena Mavrič Pleško, Sam McGreig, Laura Miozzi, Benoit Remenant, Jean-Sébastien Reynard, Johan Rollin, Mike Rott, Olivier Schumpp, Sébastien Massart, Annelies Haegeman, 2021, pregledni znanstveni članek Povzetek: High-throughput sequencing (HTS) technologies have become indispensable tools assisting plant virus diagnostics and research thanks to their ability to detect any plant virus in a sample without prior knowledge. As HTS technologies are heavily relying on bioinformatics analysis of the huge amount of generated sequences, it is of utmost importance that researchers can rely on efficient and reliable bioinformatic tools and can understand the principles, advantages, and disadvantages of the tools used. Here, we present a critical overview of the steps involved in HTS as employed for plant virus detection and virome characterization. We start from sample preparation and nucleic acid extraction as appropriate to the chosen HTS strategy, which is followed by basic data analysis requirements, an extensive overview of the in-depth data processing options, and taxonomic classification of viral sequences detected. By presenting the bioinformatic tools and a detailed overview of the consecutive steps that can be used to implement a well-structured HTS data analysis in an easy and accessible way, this paper is targeted at both beginners and expert scientists engaging in HTS plant virome projects. Ključne besede: plant virus, high-throughput sequencing, bioinformatics, detection, discovery Objavljeno v DiRROS: 05.08.2024; Ogledov: 95; Prenosov: 85
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4. Guidelines for the reliable use of high throughput sequencing technologies to detect plant pathogens and pestsSébastien Massart, Ian Adams, Maher Al Rwahnih, Steve Baeyen, Guillaume J. Bilodeau, Arnaud G. Blouin, Neil Boonham, Thierry Candresse, Anne Chandellier, Kris De Jonghe, Denis Kutnjak, Nataša Mehle, 2022, pregledni znanstveni članek Povzetek: High-throughput sequencing (HTS) technologies have the potential to become one of the most significant advances in molecular diagnostics. Their use by researchers to detect and characterize plant pathogens and pests has been growing steadily for more than a decade and they are now envisioned as a routine diagnostic test to be deployed by plant pest diagnostics laboratories. Nevertheless, HTS technologies and downstream bioinformatics analysis of the generated datasets represent a complex process including many steps whose reliability must be ensured. The aim of the present guidelines is to provide recommendations for researchers and diagnosticians aiming to reliably use HTS technologies to detect plant pathogens and pests. These guidelines are generic and do not depend on the sequencing technology or platform. They cover all the adoption processes of HTS technologies from test selection to test validation as well as their routine implementation. A special emphasis is given to key elements to be considered: undertaking a risk analysis, designing sample panels for validation, using proper controls, evaluating performance criteria, confirming and interpreting results. These guidelines cover any HTS test used for the detection and identification of any plant pest (viroid, virus, bacteria, phytoplasma, fungi and fungus-like protists, nematodes, arthropods, plants) from any type of matrix. Overall, their adoption by diagnosticians and researchers should greatly improve the reliability of pathogens and pest diagnostics and foster the use of HTS technologies in plant health. Objavljeno v DiRROS: 05.08.2024; Ogledov: 82; Prenosov: 112
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5. Next generation sequencing for detection and discovery of plant viruses and viroids : comparison of two approachesAnja Pecman, Denis Kutnjak, Ion Gutiérrez-Aguirre, Ian Adams, Adrian Fox, Neil Boonham, Maja Ravnikar, 2017, izvirni znanstveni članek Povzetek: Next generation sequencing (NGS) technologies are becoming routinely employed in different fields of virus research. Different sequencing platforms and sample preparation approaches, in the laboratories worldwide, contributed to a revolution in detection and discovery of plant viruses and viroids. In this work, we are presenting the comparison of two RNA sequence inputs (small RNAs vs. ribosomal RNA depleted total RNA) for the detection of plant viruses by Illumina sequencing. This comparison includes several viruses, which differ in genome organization and viroids from both known families. The results demonstrate the ability for detection and identification of a wide array of known plant viruses/viroids in the tested samples by both approaches. In general, yield of viral sequences was dependent on viral genome organization and the amount of viral reads in the data. A putative novel Cytorhabdovirus, discovered in this study, was only detected by analysing the data generated from ribosomal RNA depleted total RNA and not from the small RNA dataset, due to the low number of short reads in the latter. On the other hand, for the viruses/viroids under study, the results showed higher yields of viral sequences in small RNA pool for viroids and viruses with no RNA replicative intermediates (single stranded DNA viruses). Ključne besede: next generation sequencing, small RNA, ribosomal RNA depleted total RNA, detection, plant viruses, plant viroids Objavljeno v DiRROS: 25.07.2024; Ogledov: 114; Prenosov: 78
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6. Time-sampled population sequencing reveals the interplay of selection and genetic drift in experimental evolution of Potato virus YDenis Kutnjak, Santiago F. Elena, Maja Ravnikar, 2017, izvirni znanstveni članek Povzetek: RNA viruses are one of the fastest-evolving biological entities. Within their hosts, they exist as genetically diverse populations (i.e., viral mutant swarms), which are sculpted by different evolutionary mechanisms, such as mutation, natural selection, and genetic drift, and also the interactions between genetic variants within the mutant swarms. To elucidate the mechanisms that modulate the population diversity of an important plant-pathogenic virus, we performed evolution experiments with Potato virus Y (PVY) in potato genotypes that differ in their defense response against the virus. Using deep sequencing of small RNAs, we followed the temporal dynamics of standing and newly generated variations in the evolving viral lineages. A time-sampled approach allowed us to (i) reconstruct theoretical haplotypes in the starting population by using clustering of single nucleotide polymorphisms' trajectories and (ii) use quantitative population genetics approaches to estimate the contribution of selection and genetic drift, and their interplay, to the evolution of the virus. We detected imprints of strong selective sweeps and narrow genetic bottlenecks, followed by the shift in frequency of selected haplotypes. Comparison of patterns of viral evolution in differently susceptible host genotypes indicated possible diversifying evolution of PVY in the less-susceptible host (efficient in the accumulation of salicylic acid).
IMPORTANCE High diversity of within-host populations of RNA viruses is an important aspect of their biology, since they represent a reservoir of genetic variants, which can enable quick adaptation of viruses to a changing environment. This study focuses on an important plant virus, Potato virus Y, and describes, at high resolution, temporal changes in the structure of viral populations within different potato genotypes. A novel and easy-to-implement computational approach was established to cluster single nucleotide polymorphisms into viral haplotypes from very short sequencing reads. During the experiment, a shift in the frequency of selected viral haplotypes was observed after a narrow genetic bottleneck, indicating an important role of the genetic drift in the evolution of the virus. On the other hand, a possible case of diversifying selection of the virus was observed in less susceptible host genotypes. Ključne besede: Potato virus Y, experimental evolution, genetic drift, natural selection, sRNA deep sequencing Objavljeno v DiRROS: 24.07.2024; Ogledov: 143; Prenosov: 66
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7. High-throughput sequencing facilitates characterisation of a ʺforgottenʺ plant virus : the case of a henbane mosaic virus infecting tomatoAnja Pecman, Denis Kutnjak, Nataša Mehle, Magda Tušek-Žnidarič, Ion Gutiérrez-Aguirre, Patricija Pirnat, Ian Adams, Neil Boonham, Maja Ravnikar, 2018, izvirni znanstveni članek Povzetek: High-throughput sequencing has dramatically broadened the possibilities for plant virus research and diagnostics, enabling discovery of new or obscure viruses, and virus strains and rapid sequencing of their genomes. In this research, we employed high-throughput sequencing to discover a new virus infecting tomato, Henbane mosaic virus (Potyvirus, Potyviridae), which was first discovered at the beginning of 20th century in the United Kingdom in cultivated henbane. A field tomato plant with severe necrotic symptoms of unknown etiology was sampled in Slovenia and high-throughput sequencing analysis using small RNA and ribosomal RNA depleted total RNA approaches revealed a mixed infection with Potato virus M (Carlavirus, Betaflexiviridae), Southern tomato virus (Amalgavirus, Amalgamaviridae) and henbane mosaic virus in the sample. The complete genomic sequence of henbane mosaic virus was assembled from the sequencing reads. By re-inoculation of the infected material on selected test plants, henbane mosaic virus was isolated and a host range analysis was performed, demonstrating the virus was pathogenic on several plant species. Due to limited metadata in public repositories, the taxonomic identification of the virus isolate was initially putative. Thus, in the next step, we used small RNA sequencing to determine genomic sequences of four historic isolates of the virus, obtained from different virus collections. Phylogenetic analyses performed using this new sequence information enabled us to taxonomically position Henbane mosaic virus as a member of the Potyvirus genus within the chili veinal mottle virus phylogenetic cluster and define the relationship of the new tomato isolate with the historic ones, indicating the existence of at least four putative strains of the virus. The first detection of henbane mosaic virus in tomato and demonstration of its pathogenicity on this host is important for plant protection and commercial tomato production. Since the virus was initially present in a mixed infection, and its whole genome was not sequenced, it has probably been overlooked in routine diagnostics. This study confirms the applicability of a combination of high-throughput sequencing and classic plant virus characterization methods for identification and phylogenetic classification of obscure viruses and historical viral isolates, for which no or limited genome sequence data is available. Ključne besede: henbane mosaic virus, Tomato, high-throughput sequencing, host range analysis, phylogeny, Potyvirus Objavljeno v DiRROS: 24.07.2024; Ogledov: 123; Prenosov: 113
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8. Transmission modes affect the population structure of potato virus Y in potatoWashington da Silva, Denis Kutnjak, Yi Xu, Yimin Xu, James Giovannoni, Santiago F. Elena, Stewart Gray, 2020, izvirni znanstveni članek Povzetek: Transmission is a crucial part of a viral life cycle and transmission mode can have an important impact on virus biology. It was demonstrated that transmission mode can influence the virulence and evolution of a virus; however, few empirical data are available to describe the direct underlying changes in virus population structure dynamics within the host. Potato virus Y (PVY) is an RNA virus and one of the most damaging pathogens of potato. It comprises several genetically variable strains that are transmitted between plants via different transmission modes. To investigate how transmission modes affect the within-plant viral population structure, we have used a deep sequencing approach to examine the changes in the genetic structure of populations (in leaves and tubers) of three PVY strains after successive passages by horizontal (aphid and mechanical) and vertical (via tubers) transmission modes. Nucleotide diversities of viral populations were significantly influenced by transmission modes; lineages transmitted by aphids were the least diverse, whereas lineages transmitted by tubers were the most diverse. Differences in nucleotide diversities of viral populations between leaves and tubers were transmission mode-dependent, with higher diversities in tubers than in leaves for aphid and mechanically transmitted lineages. Furthermore, aphid and tuber transmissions were shown to impose stronger genetic bottlenecks than mechanical transmission. To better understand the structure of virus populations within the host, transmission mode, movement of the virus within the host, and the number of replication cycles after transmission event need to be considered. Collectively, our results suggest a significant impact of virus transmission modes on the within-plant diversity of virus populations and provide quantitative fundamental data for understanding how transmission can shape virus diversity in the natural ecosystems, where different transmission modes are expected to affect virus population structure and consequently its evolution. Objavljeno v DiRROS: 22.07.2024; Ogledov: 120; Prenosov: 130
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9. Viromics and infectivity analysis reveal the release of infective plant viruses from wastewater into the environmentKatarina Bačnik, Denis Kutnjak, Anja Pecman, Nataša Mehle, Magda Tušek-Žnidarič, Ion Gutiérrez-Aguirre, Maja Ravnikar, 2020, izvirni znanstveni članek Povzetek: Viruses represent one of the most important threats to agriculture. Several viral families include highly stable pathogens, which remain infective and can be transported long distances in water. The diversity of plant viruses in wastewater remains understudied; however, their potential impact is increasing with the increased irrigation usage of reclaimed wastewater. To determine the abundance, diversity and biological relevance of plant viruses in wastewater influents and effluents we applied an optimized virus concentration method followed by high-throughput sequencing and infectivity assays. We detected representatives of 47 plant virus species, including emerging crop threats. We also demonstrated infectivity for pathogenic and economically relevant plant viruses from the genus Tobamovirus (family Virgaviridae), which remain infective even after conventional wastewater treatment. These results demonstrate the potential of metagenomics to capture the diversity of plant viruses circulating in the environment and expose the potential risk of the uncontrolled use of reclaimed water for irrigation. Ključne besede: wastewater, virome, high-throughput sequencing, plant viruses, tobamoviruses, infectivity Objavljeno v DiRROS: 19.07.2024; Ogledov: 250; Prenosov: 150
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10. Virome analysis of signal crayfish (Pacifastacus leniusculus) along its invasion range reveals diverse and divergent RNA virusesKatarina Bačnik, Denis Kutnjak, Silvija Černi, Ana Bielen, Sandra Hudina, 2021, izvirni znanstveni članek Povzetek: Crayfish are a keystone species of freshwater ecosystems and a successful invasive species. However, their pathogens, including viruses, remain understudied. The aim of this study was to analyze the virome of the invasive signal crayfish (Pacifastacus leniusculus) and to elucidate the potential differences in viral composition and abundance along its invasion range in the Korana River, Croatia. By the high-throughput sequencing of ribosomal RNA, depleted total RNA isolated from the crayfish hepatopancreas, and subsequent sequence data analysis, we identified novel and divergent RNA viruses, including signal crayfish-associated reo-like, hepe-like, toti-like, and picorna-like viruses, phylogenetically related to viruses previously associated with crustacean hosts. The patterns of reads abundance and calculated nucleotide diversities of the detected viral sequences varied along the invasion range. This could indicate the possible influence of different factors and processes on signal crayfish virome composition: e.g., the differences in signal crayfish population density, the non-random dispersal of host individuals from the core to the invasion fronts, and the transfer of viruses from the native co-occurring and phylogenetically related crayfish species. The study reveals a high, previously undiscovered diversity of divergent RNA viruses associated with signal crayfish, and sets foundations for understanding the potential risk of virus transmissions as a result of this invader’s dispersal. Ključne besede: signal crayfish virome, RNA viruses, invasive alien species, invasion range, high-throughput sequencing Objavljeno v DiRROS: 19.07.2024; Ogledov: 209; Prenosov: 99
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