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Littérature scientifique sur le sujet « RNA viruses Genetics »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 31 janvier 2023

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Articles de revues sur le sujet "RNA viruses Genetics"

Enami, Masayoshi. « Negative-strand RNA viruses. Reverse genetics of negative-strand RNA viruses. » Uirusu 45, n^o 2 (1995) : 145–57. http://dx.doi.org/10.2222/jsv.45.145.

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King, Andrew M. Q. « RNA viruses do it ». Trends in Genetics 3 (janvier 1987) : 60–61. http://dx.doi.org/10.1016/0168-9525(87)90173-9.

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Elena, Santiago F., Stéphanie Bedhomme, Purificación Carrasco, José M. Cuevas, Francisca de la Iglesia, Guillaume Lafforgue, Jasna Lalić, Àngels Pròsper, Nicolas Tromas et Mark P. Zwart. « The Evolutionary Genetics of Emerging Plant RNA Viruses ». Molecular Plant-Microbe Interactions® 24, n^o 3 (mars 2011) : 287–93. http://dx.doi.org/10.1094/mpmi-09-10-0214.

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Over the years, agriculture across the world has been compromised by a succession of devastating epidemics caused by new viruses that spilled over from reservoir species or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Viral emergence is usually associated with ecological change or with agronomical practices bringing together reservoirs and crop species. The complete picture is, however, much more complex, and results from an evolutionary process in which the main players are ecological factors, viruses' genetic plasticity, and host factors required for virus replication, all mixed with a good measure of stochasticity. The present review puts emergence of plant RNA viruses into the framework of evolutionary genetics, stressing that viral emergence begins with a stochastic process that involves the transmission of a preexisting viral strain into a new host species, followed by adaptation to the new host.

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Aubry, Fabien, Antoine Nougairède, Lauriane de Fabritus, Gilles Querat, Ernest A. Gould et Xavier de Lamballerie. « Single-stranded positive-sense RNA viruses generated in days using infectious subgenomic amplicons ». Journal of General Virology 95, n^o 11 (1 novembre 2014) : 2462–67. http://dx.doi.org/10.1099/vir.0.068023-0.

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Reverse genetics is a key methodology for producing genetically modified RNA viruses and deciphering cellular and viral biological properties, but methods based on the preparation of plasmid-based complete viral genomes are laborious and unpredictable. Here, both wild-type and genetically modified infectious RNA viruses were generated in days using the newly described ISA (infectious-subgenomic-amplicons) method. This new versatile and simple procedure may enhance our capacity to obtain infectious RNA viruses from PCR-amplified genetic material.

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Cuevas, Jose M., Pilar Domingo-Calap, Marianoel Pereira-Gomez et Rafael Sanjuan. « Experimental Evolution and Population Genetics of RNA Viruses ». Open Evolution Journal 3, n^o 1 (11 mai 2009) : 9–16. http://dx.doi.org/10.2174/1874404400903010009.

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Biacchesi, Stéphane. « The reverse genetics applied to fish RNA viruses ». Veterinary Research 42, n^o 1 (2011) : 12. http://dx.doi.org/10.1186/1297-9716-42-12.

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Wickner, Reed B. « PRIONS AND RNA VIRUSES OFSACCHAROMYCES CEREVISIAE ». Annual Review of Genetics 30, n^o 1 (décembre 1996) : 109–39. http://dx.doi.org/10.1146/annurev.genet.30.1.109.

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Froissart, Rémy, Claus O. Wilke, Rebecca Montville, Susanna K. Remold, Lin Chao et Paul E. Turner. « Co-infection Weakens Selection Against Epistatic Mutations in RNA Viruses ». Genetics 168, n^o 1 (septembre 2004) : 9–19. http://dx.doi.org/10.1534/genetics.104.030205.

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Turner, Paul E., et Lin Chao. « Sex and the Evolution of Intrahost Competition in RNA Virus φ6 ». Genetics 150, n^o 2 (1 octobre 1998) : 523–32. http://dx.doi.org/10.1093/genetics/150.2.523.

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Abstract Sex allows beneficial mutations that occur in separate lineages to be fixed in the same genome. For this reason, the Fisher-Muller model predicts that adaptation to the environment is more rapid in a large sexual population than in an equally large asexual population. Sexual reproduction occurs in populations of the RNA virus φ6 when multiple bacteriophages coinfect the same host cell. Here, we tested the model's predictions by determining whether sex favors more rapid adaptation of φ6 to a bacterial host, Pseudomonas phaseolicola. Replicate populations of φ6 were allowed to evolve in either the presence or absence of sex for 250 generations. All experimental populations showed a significant increase in fitness relative to the ancestor, but sex did not increase the rate of adaptation. Rather, we found that the sexual and asexual treatments also differ because intense intrahost competition between viruses occurs during coinfection. Results showed that the derived sexual viruses were selectively favored only when coinfection is common, indicating that within-host competition detracts from the ability of viruses to exploit the host. Thus, sex was not advantageous because the cost created by intrahost competition was too strong. Our findings indicate that high levels of coinfection exceed an optimum where sex may be beneficial to populations of φ6, and suggest that genetic conflicts can evolve in RNA viruses.

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Swaminathan, Gokul, Julio Martin-Garcia et Sonia Navas-Martin. « RNA viruses and microRNAs : challenging discoveries for the 21st century ». Physiological Genomics 45, n^o 22 (15 novembre 2013) : 1035–48. http://dx.doi.org/10.1152/physiolgenomics.00112.2013.

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RNA viruses represent the predominant cause of many clinically relevant viral diseases in humans. Among several evolutionary advantages acquired by RNA viruses, the ability to usurp host cellular machinery and evade antiviral immune responses is imperative. During the past decade, RNA interference mechanisms, especially microRNA (miRNA)-mediated regulation of cellular protein expression, have revolutionized our understanding of host-viral interactions. Although it is well established that several DNA viruses express miRNAs that play crucial roles in their pathogenesis, expression of miRNAs by RNA viruses remains controversial. However, modulation of the miRNA machinery by RNA viruses may confer multiple benefits for enhanced viral replication and survival in host cells. In this review, we discuss the current literature on RNA viruses that may encode miRNAs and the varied advantages of engineering RNA viruses to express miRNAs as potential vectors for gene therapy. In addition, we review how different families of RNA viruses can alter miRNA machinery for productive replication, evasion of antiviral immune responses, and prolonged survival. We underscore the need to further explore the complex interactions of RNA viruses with host miRNAs to augment our understanding of host-virus interplay.

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Thèses sur le sujet "RNA viruses Genetics"

Afsharifar, Alireza. « Characterisation of minor RNAs associated with plants infected with cucumber mosaic virus ». Title page, table of contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09pha2584.pdf.

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Bibliography: leaves 127-138. This thesis studies the minor double stranded RNAs (dsRNA) and single stranded RNAs (ssRNA) which are consistently associated with plants infected with Q strain of cucumber mosaic virus (Q-CMV). The investigations are focused on the structural elucidation of new RNAs which have been observed in single stranded and double stranded RNA profiles of Q strain of CMV.

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Upton, John H. « The role of RNA secondary structure in replication of Nodamura virus RNA2 ». To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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Wahyuni, Wiwiek Sri. « Variation among cucumber mosaic virus (CMV) isolates and their interaction with plants ». Title page, contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phw137.pdf.

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Includes appendix containing journal publications co-authored by the author. Includes bibliographical references (leaves 130-151). Eighteen strains of Cucumber mosaic virus, including forteen from Australia, two from the USA, and two from Japan were used in this study.

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Williams, Rhys Harold Verdon George. « Further studies on the structure and function of the cucumber mosaic virus genome : a thesis submitted to the University of Adelaide, South Australia for the degree of Doctor of Philosophy ». 1988, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phw7261.pdf.

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Chen, Baoshan. « Encapsidation of nucleic acids by cucumovirus coat proteins / ». Title page, contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phc5183.pdf.

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Shi, Bu-Jun. « Expression and function of cucumoviral genomes ». Title page, contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phs5546.pdf.

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Bibliography: leaves 104-130. The aim of this thesis is to characterise subgenomic RNAs of cucumoviruses and the functions of their encoding genes. Strains of cucumber mosaic virus (CMV) are classified into two major subgroups (I and II) on the basis of nucleotide sequence homology. The V strain of tomato aspermy virus (V-TAV) and a subgroup I CMV strain (WAII) are chosen to determine whether the 2b genes encoded by these viruses are expressed 'in vivo'. For further investigation of the 2b gene function, cDNA clones of three genomic RNAs of V-TAV are constructed. Using the infectious cDNA clones of V-TAV, a mutant virus containing only one of the two repeats is constructed.

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Ligat, Julio S. « Pathology and distribution in the host of pea seed-borne mosaic virus ». Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phl723.pdf.

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Includes bibliographical references (leaves 82-92). Five isolates of pea seed-borne mosaic virus were compared by host range and symptomatology on 16 pisum sativum cultivars lines, 21 lines of Lathyrus and Lens spp. and several indicator species

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Hajimorad, Mohammad Reza. « Variation in alfalfa mosaic virus with special reference to its immunochemical properties ». Title page, contents and summary only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phh154.pdf.

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Includes Appendix listing other publications by the author. Includes bibliographical references (leaves 134-181). Alfalfa mosaic virus was isolated from lucerne (Medicago sativa) plants with a variety of disease symptoms. Experiments showed that each isolate was biologically distinct and that the host range and symptomatology of each isolate was affected by the environmental condition.

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Wakeford, Laura 1956. « COMPLEMENTATION BETWEEN TEMPERATURE-SENSITIVE MUTANTS OF POLIOVIRUS ». Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276556.

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Conditional lethal mutants of poliovirus type 1 (Mahoney) were generated by treatment with the mutagen hydroxylamine. Temperature-sensitive mutants were selected by the replica plating technique at temperatures of 33°C (permissive) and 39°C (restrictive). New mutants were generated to achieve a larger population of mutants and also to generate additional RNA- mutants in this population. These mutants were characterized by two criteria: RNA synthesis and thermal stability. RNA synthesis is measured by the accumulation of labeled uridine incorporation into trichloroacetic acid (TCA) insoluble material. The thermal stability is determined by the difference in plaque forming units before and after treatment of the virion at 45°C. Complementation co-infections (5 MOI for each virus stock) were analyzed for the presence of the 150S virion particle of poliovirus after sedimentation through a linear sucrose gradient. Complementation is observed between RNA(+) mutants v.s. RNA(-) mutants, and between two RNA(-) mutants, but not between two RNA(+) mutants. Although reciprocal complementation has not been documented in this study some speculation on complementation is presented in this thesis.

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Sheldon, Candice Claire. « Hammerhead mediated self-cleavage of plant pathogenic RNAs / ». Title page, contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phs544.pdf.

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Livres sur le sujet "RNA viruses Genetics"

Perez, Daniel R., dir. Reverse Genetics of RNA Viruses. New York, NY : Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-6964-7.

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Bridgen, Anne, dir. Reverse Genetics of RNA Viruses. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.

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Luo, Ming. Negative strand RNA virus. Singapore : World Scientific, 2011.

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Holmes, Edward C. The evolution and emergence of RNA viruses. Oxford : Oxford University Press, 2009.

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The evolution and emergence of RNA viruses. Oxford : Oxford University Press, 2009.

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Bridgen, Anne. Reverse genetics of RNA viruses : Applications and perspectives. Chichester, West Sussex : John Wiley & Sons, 2012.

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Yechiel, Becker, dir. Viral messenger RNA : Transcription, processing, splicing, and molecular structure. Boston : Nijhoff, 1985.

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Kawaoka, Yoshihiro, dir. Biology of Negative Strand RNA Viruses : The Power of Reverse Genetics. Berlin, Heidelberg : Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-06099-5.

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1935-, Friedmann Theodore, et Rossi John J, dir. Gene transfer : Delivery and expression of DNA and RNA : a laboratory manual. Cold Spring Harbor, N.Y : Cold Spring Harbor Laboratory Press, 2007.

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Holland, John J., dir. Genetic Diversity of RNA Viruses. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77011-1.

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Chapitres de livres sur le sujet "RNA viruses Genetics"

Armesto, Maria, Kirsten Bentley, Erica Bickerton, Sarah Keep et Paul Britton. « Coronavirus Reverse Genetics ». Dans Reverse Genetics of RNA Viruses, 25–63. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch2.

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Goodfellow, Ian. « Calicivirus Reverse Genetics ». Dans Reverse Genetics of RNA Viruses, 91–112. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch4.

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Bordería, Antonio V., et Marco Vignuzzi. « Reverse Genetics and Quasispecies ». Dans Reverse Genetics of RNA Viruses, 319–49. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch11.

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Ghanem, Alexander, et Karl-Klaus Conzelmann. « Reverse Genetics of Rhabdoviruses ». Dans Reverse Genetics of RNA Viruses, 113–49. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch5.

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Boyce, Mark. « Bluetongue Virus Reverse Genetics ». Dans Reverse Genetics of RNA Viruses, 251–88. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch9.

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Bridgen, Anne. « Introduction ». Dans Reverse Genetics of RNA Viruses, 1–23. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch1.

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van den Hengel, Sanne K., Iris J. C. Dautzenberg, Diana J. M. van den Wollenberg, Peter A. E. Sillevis Smitt et Rob C. Hoeben. « Genetic Modification in Mammalian Orthoreoviruses ». Dans Reverse Genetics of RNA Viruses, 289–317. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch10.

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Bridgen, Anne. « Summary and Perspectives ». Dans Reverse Genetics of RNA Viruses, 350–74. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch12.

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Ploss, Alexander. « Reverse Genetic Tools to Study Hepatitis C Virus ». Dans Reverse Genetics of RNA Viruses, 64–90. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch3.

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Rennick, Linda J., et Paul Duprex. « Modification of Measles Virus and Application to Pathogenesis Studies ». Dans Reverse Genetics of RNA Viruses, 150–99. Chichester, UK : John Wiley & Sons, Ltd, 2012. http://dx.doi.org/10.1002/9781118405338.ch6.

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Actes de conférences sur le sujet "RNA viruses Genetics"

Brewer, Wesley H., Franzine D. Smith et John C. Sanford. « Information Loss : Potential for Accelerating Natural Genetic Attenuation of RNA Viruses ». Dans Proceedings of the Symposium. WORLD SCIENTIFIC, 2013. http://dx.doi.org/10.1142/9789814508728_0015.

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« Preventive role of Tomato bushy stunt virus RNA-interference suppressor protein in plant immune response ». Dans Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 2019. http://dx.doi.org/10.18699/plantgen2019-043.

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Al Khatib, Hebah A., Fatiha M. Benslimane, Israa El Bashir, Asmaa A. Al Thani et Hadi M. Yassine. « Within-Host Diversity of SARS-Cov-2 in COVID-19 Patients with Variable Disease Severities ». Dans Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0280.

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Background: The ongoing pandemic of SARS-COV-2 has already infected more than eight million people worldwide. The majority of COVID-19 patients are either asymptomatic or have mild symptoms. Yet, about 15% of the cases experience severe complications and require intensive care. Factors determining disease severity are not yet fully characterized. Aim: Here, we investigated the within-host virus diversity in COVID-19 patients with different clinical manifestations. Methods: We compared SARS-COV-2 genetic diversity in 19 mild and 27 severe cases. Viral RNA was extracted from nasopharyngeal samples and sequenced using Illumina MiSeq platform. This was followed by deep-sequencing analyses of SARS-CoV-2 genomes at both consensus and sub-consensus sequence levels. Results: Consensus sequences of all viruses were very similar, showing more than 99·8% sequence identity regardless of the disease severity. However, the sub-consensus analysis revealed significant differences in within-host diversity between mild and severe cases. Patients with severe symptoms exhibited a significantly (p-value 0.001) higher number of variants in coding and non-coding regions compared to mild cases. Analysis also revealed higher prevalence of some variants among severe cases. Most importantly, severe cases exhibited significantly higher within-host diversity (mean= 13) compared to mild cases (mean=6). Further, higher within-host diversity was observed in patients above the age of 60 compared to the younger age group. Conclusion: These observations provided evidence that within-host diversity might play a role in the development of severe disease outcomes in COVID19 patients; however, further investigations is required to elucidate this association.

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Rapports d'organisations sur le sujet "RNA viruses Genetics"

Dawson, William O., Moshe Bar-Joseph, Charles L. Niblett, Ron Gafny, Richard F. Lee et Munir Mawassi. Citrus Tristeza Virus : Molecular Approaches to Cross Protection. United States Department of Agriculture, janvier 1994. http://dx.doi.org/10.32747/1994.7570551.bard.

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Citrus tristeza virus (CTV) has the largest genomes among RNA viruses of plants. The 19,296-nt CTV genome codes for eleven open reading frames (ORFs) and can produce at least 19 protein products ranging in size from 6 to 401 kDa. The complex biology of CTV results in an unusual composition of CTV-specific RNAs in infected plants which includes multiple defective RNAs and mixed infections. The complex structure of CTV populations poses special problems for diagnosis, strain differentiation, and studies of pathogenesis. A manipulatable genetic system with the full-length cDNA copy of the CTV genome has been created which allows direct studies of various aspects of the CTV biology and pathology. This genetic system is being used to identify determinants of the decline and stem-pitting disease syndromes, as well as determinants responsible for aphid transmission.

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Mawassi, Munir, et Valerian V. Dolja. Role of the viral AlkB homologs in RNA repair. United States Department of Agriculture, juin 2014. http://dx.doi.org/10.32747/2014.7594396.bard.

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AlkB proteins that repair DNA via reversing methylation damage are conserved in a broad range of prokaryotes and eukaryotes including plants. Surprisingly, AlkB-domains were discovered in the genomes of numerous plant positive-strand RNA viruses, majority of which belong to the family Flexiviridae. The major goal of this research was to reveal the AlkB functions in the viral infection cycle using a range of complementary genetic and biochemical approaches. Our hypotheses was that AlkB is required for efficient replication and genetic stability of viral RNA genomes The major objectives of the research were to identify the functions of GVA AlkB domain throughout the virus infection cycle in N. benthamiana and grapevine, to investigate possible RNA silencing suppression activity of the viral AlkBs, and to characterize the RNA demethylation activity of the mutated GVA AlkBs in vitro and in vivo to determine methylation status of the viral RNA. Over the duration of project, we have made a very substantial progress with the first two objectives. Because of the extreme low titer of the virus particles in plants infected with the AlkB mutant viruses, we were unable to analyze RNA demethylation activity and therefore had to abandon third objective. The major achievements with our objectives were demonstration of the AlkB function in virus spread and accumulation in both experimental and natural hosts of GVA, discovery of the functional cooperation and physical interaction between AlkB and p10 AlkB in suppression of plant RNA silencing response, developing a powerful virus vector technology for grapevine using GLRaV-2-derived vectors for functional genomics and pathogen control in grapevine, and in addition we used massive parallel sequencing of siRNAs to conduct comparative analysis of the siRNA populations in grape plants infected with AlkB-containing GLRaV-3 versus GLRaV-2 that does not encode AlkB. This analysis revealed dramatically reduced levels of virus-specific siRNAs in plants infected with GLRaV-3 compared to that in GLRaV-2 infection implicating AlkB in suppression of siRNA formation. We are pleased to report that BARD funding resulted in 5 publications directly supported by BARD, one US patent, and 9 more publications also relevant to project. Moreover, two joint manuscripts that summarize work on GVA AlkB (led by Israeli PI) and on viral siRNAs in grapevine (led by US PI in collaboration with University of Basel) are in preparation.

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Bar-Joseph, Moshe, William O. Dawson et Munir Mawassi. Role of Defective RNAs in Citrus Tristeza Virus Diseases. United States Department of Agriculture, septembre 2000. http://dx.doi.org/10.32747/2000.7575279.bard.

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This program focused on citrus tristeza virus (CTV), the largest and one of the most complex RNA-plant-viruses. The economic importance of this virus to the US and Israeli citrus industries, its uniqueness among RNA viruses and the possibility to tame the virus and eventually turn it into a useful tool for the protection and genetic improvement of citrus trees justify these continued efforts. Although the overall goal of this project was to study the role(s) of CTV associated defective (d)-RNAs in CTV-induced diseases, considerable research efforts had to be devoted to the engineering of the helper virus which provides the machinery to allow dRNA replication. Considerable progress was made through three main lines of complementary studies. For the first time, the generation of an engineered CTV genetic system that is capable of infecting citrus plants with in vitro modified virus was achieved. Considering that this RNA virus consists of a 20 kb genome, much larger than any other previously developed similar genetic system, completing this goal was an extremely difficult task that was accomplished by the effective collaboration and complementarity of both partners. Other full-length genomic CTV isolates were sequenced and populations examined, resulting in a new level of understanding of population complexities and dynamics in the US and Israel. In addition, this project has now considerably advanced our understanding and ability to manipulate dRNAs, a new class of genetic elements of closteroviruses, which were first found in the Israeli VT isolate and later shown to be omnipresent in CTV populations. We have characterized additional natural dRNAs and have shown that production of subgenomic mRNAs can be involved in the generation of dRNAs. We have molecularly cloned natural dRNAs and directly inoculated citrus plants with 35S-cDNA constructs and have shown that specific dRNAs are correlated with specific disease symptoms. Systems to examine dRNA replication in protoplasts were developed and the requirements for dRNA replication were defined. Several artificial dRNAs that replicate efficiently with a helper virus were created from infectious full-genomic cDNAs. Elements that allow the specific replication of dRNAs by heterologous helper viruses also were defined. The T36-derived dRNAs were replicated efficiently by a range of different wild CTV isolates and hybrid dRNAs with heterologous termini are efficiently replicated with T36 as helper. In addition we found: 1) All CTV genes except of the p6 gene product from the conserved signature block of the Closteroviridae are obligate for assembly, infectivity, and serial protoplast passage; 2) The p20 protein is a major component of the amorphous inclusion bodies of infected cells; and 3) Novel 5'-Co-terminal RNAs in CTV infected cells were characterized. These results have considerably advanced our basic understanding of the molecular biology of CTV and CTV-dRNAs and form the platform for the future manipulation of this complicated virus. As a result of these developments, the way is now open to turn constructs of this viral plant pathogen into new tools for protecting citrus against severe CTV terms and development of virus-based expression vectors for other citrus improvement needs. In conclusion, this research program has accomplished two main interconnected missions, the collection of basic information on the molecular and biological characteristics of the virus and its associated dRNAs toward development of management strategies against severe diseases caused by the virus and building of novel research tools to improve citrus varieties. Reaching these goals will allow us to advance this project to a new phase of turning the virus from a pathogen to an ally.

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Chejanovsky, Nor, Diana Cox-Foster, Victoria Soroker et Ron Ophir. Honeybee modulation of infection with the Israeli acute paralysis virus, in asymptomatic, acutely infected and CCD colonies. United States Department of Agriculture, décembre 2013. http://dx.doi.org/10.32747/2013.7594392.bard.

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Honey bee (Apis mellifera) colony losses pose a severe risk to the food chain. The IAPV (Israeli acute paralysis virus) was correlated with CCD, a particular case of colony collapse. Honey bees severely infected with IAPV show shivering wings that progress to paralysis and subsequent death. Bee viruses, including IAPV, are widely present in honey bee colonies but often there are no pathological symptoms. Infestation of the beehive with Varroa mites or exposure to stress factors leads to significant increase in viral titers and fatal infections. We hypothesized that the honey bee is regulating/controlling IAPV and viral infections in asymptomatic infections and this control is broken through "stress" leading to acute infections and/or CCD. Our aims were: 1. To discover genetic changes in IAPV that may affect tissue tropism in the host, and/or virus infectivity and pathogenicity. 2. To elucidate mechanisms used by the host to regulate/ manage the IAPV-infection in vivo and in vitro. To achieve the above objectives we first studied stress-induced virus activation. Our data indicated that some pesticides, including myclobutanil, chlorothalonil and fluvalinate, result in amplified viral titers when bees are exposed at sub lethal levels by a single feeding. Analysis of the level of immune-related bee genes indicated that CCD-colonies exhibit altered and weaker immune responses than healthy colonies. Given the important role of viral RNA interference (RNAi) in combating viral infections we investigated if CCD-colonies were able to elicit this particular antiviral response. Deep-sequencing analysis of samples from CCD-colonies from US and Israel revealed high frequency of small interfering RNAs (siRNA) perfectly matching IAPV, Kashmir bee virus and Deformed wing virus genomes. Israeli colonies showed high titers of IAPV and a conserved RNAi pattern of targeting the viral genome .Our findings were further supported by analysis of samples from colonies experimentally infected with IAPV. Following for the first time the dynamics of IAPV infection in a group of CCD colonies that we rescued from collapse, we found that IAPV conserves its potential to act as one lethal, infectious factor and that its continuous replication in CCD colonies deeply affects their health and survival. Ours is the first report on the dominant role of IAPV in CCD-colonies outside from the US under natural conditions. We concluded that CCD-colonies do exhibit a regular siRNA response that is specific against predominant viruses associated with colony losses and other immune pathways may account for their weak immune response towards virus infection. Our findings: 1. Reveal that preventive measures should be taken by the beekeepers to avoid insecticide-based stress induction of viral infections as well as to manage CCD colonies as a source of highly infectious viruses such as IAPV. 2. Contribute to identify honey bee mechanisms involved in managing viral infections.

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Vakharia, Vikram, Shoshana Arad, Yonathan Zohar, Yacob Weinstein, Shamila Yusuff et Arun Ammayappan. Development of Fish Edible Vaccines on the Yeast and Redmicroalgae Platforms. United States Department of Agriculture, février 2013. http://dx.doi.org/10.32747/2013.7699839.bard.

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Betanodaviruses are causative agents of viral nervous necrosis (VNN), a devastating disease of cultured marine fish worldwide. Betanodavirus (BTN) genome is composed of two single-stranded, positive-sense RNA molecules. The larger genomic segment, RNA1 (3.1 kb), encodes the RNA-dependent RNA polymerase, while the smaller genomic segment, RNA 2 (1.4kb), encodes the coat protein. This structural protein is the host-protective antigen of VNN which assembles to form virus-like particles (VLPs). BTNs are classified into four genotypes, designated red-spotted grouper nervous necrosis virus (RGNNV), barfin flounder nervous necrosis virus (BFNNV), tiger puffer nervous necrosis virus (TPNNV), and striped jack nervous necrosis virus (SJNNV), based on phylogenetic analysis of the coat protein sequences. RGNNV type is quite important as it has a broad host-range, infecting warm-water fish species. At present, there is no commercial vaccine available to prevent VNN in fish. The general goal of this research was to develop oral fish vaccines in yeast and red microalgae (Porphyridium sp.) against the RGNNV genotype. To achieve this, we planned to clone and sequence the coat protein gene of RGNNV, express the coat protein gene of RGNNV in yeast and red microalgae and evaluate the immune response in fish fed with recombinantVLPs antigens produced in yeast and algae. The collaboration between the Israeli group and the US group, having wide experience in red microalgae biochemistry, molecular genetics and large-scale cultivation, and the development of viral vaccines and eukaryotic protein expression systems, respectively, was synergistic to produce a vaccine for fish that would be cost-effective and efficacious against the betanodavirus infection.

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Dawson, William O., et Moshe Bar-Joseph. Creating an Ally from an Adversary : Genetic Manipulation of Citrus Tristeza. United States Department of Agriculture, janvier 2004. http://dx.doi.org/10.32747/2004.7586540.bard.

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Citrus is one of the major agricultural crops common to Israel and the United States, important in terms of nutrition, foreign exchange, and employment. The economy of both citrus industries have been chronically plagued by diseases caused by Citrus tristeza virus (CTV). The short term solution until virus-resistant plants can be used is the use of mild strain cross-protection. We are custom designing "ideal" protecting viruses to immunize trees against severe isolates of CTV by purposely inoculating existing endangered trees and new plantings to be propagated as infected (protected) citrus budwood. We crossed the substantial technological hurdles necessary to accomplish this task which included developing an infectious cDNA clone which allows in vitro manipulation of the virus and methods to then infect citrus plants. We created a series of hybrids between decline-inducing and mild CTV strains, tested them in protoplasts, and are amplifying them to inoculate citrus trees for evaluation and mapping of disease determinants. We also extended this developed technology to begin engineering transient expression vectors based on CTV as tools for genetic improvement of tree crops, in this case citrus. Because of the long periods between genetic transformation and the ultimate assay of mature tree characteristics, there is a great need for an effective system that allows the expression or suppression of target genes in fruiting plants. Virus-based vectors will greatly expedite progress in citrus genetic improvement. We characterized several components of the virus that provides necessary information for designing virus-based vectors. We characterized the requirements of the 3 ’-nontranslated replication promoter and two 3 ’-ORF subgenomic (sg) mRNA controller elements. We discovered a novel type of 5’-terminal sgRNAs and characterized the cis-acting control element that also functions as a strong promoter of a 3 ’-sgRNA. We showed that the p23 gene controls negative-stranded RNA synthesis and expression of 3 ’ genes. We identified which genes are required for infection of plants, which are host range determinants, and which are not needed for plant infection. We continued the characterization of native dRNA populations and showed the presence of five different classes including class III dRNAs that consists of infectious and self-replicating molecules and class V dRNAs that contain all of the 3 ’ ORFs, along with class IV dRNAs that retain non-contiguous internal sequences. We have constructed and tested in protoplasts a series of expression vectors that will be described in this proposal.

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Ullman, Diane, James Moyer, Benjamin Raccah, Abed Gera, Meir Klein et Jacob Cohen. Tospoviruses Infecting Bulb Crops : Evolution, Diversity, Vector Specificity and Control. United States Department of Agriculture, septembre 2002. http://dx.doi.org/10.32747/2002.7695847.bard.

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Objectives. The overall goal of the proposed research was to develop a mechanistic understanding of tospovirus evolution, diversity and vector specificity that could be applied to development of novel methods for limiting virus establishment and spread. Our specific objectives were: 1) To characterize newly intercepted tospoviruses in onion, Hippeastrum and other bulb crops and compare them with the known tomato spotted wilt virus (TSWV) and its isolates; 2) To characterize intra- and interspecific variation in the virus transmission by thrips of the new and distinct tospoviruses. and, 3) To determine the basis of vector specificity using biological, cellular and molecular approaches. Background. New tospoviruses infecting bulb crops were detected in Israel and the US in the mid-90s. Their plant host ranges and relationships with thrips vectors showed they differed from the type member of the Tospovirus genus, tomato spotted wilt virus (TSWV). Outbreaks of these new viruses caused serious crop losses in both countries, and in agricultural and ornamental crops elsewhere. In the realm of plant infecting viruses, the tospoviruses (genus: Tospovirus , family: Bunyaviridae ) are among the most aggressive emerging viruses. Tospoviruses are transmitted by several species of thrips in a persistent, propagative fashion and the relationships between the viruses and their thrips vectors are often specific. With the emergence of new tospoviruses, new thrips vector/tospovirus relationships have also arisen and vector specificities have changed. There is known specificity between thrips vector species and particular tospoviruses, although the cellular and molecular bases for this specificity have been elusive. Major conclusions, solutions and achievements. We demonstrated that a new tospovirus, iris yellow spot virus (IYSV) caused "straw bleaching" in onion (Allium cepa) and lisianthus necrosis in lisianthus (Eustoma russellianum). Characterization of virus isolates revealed genetic diversity among US, Brazilian, Dutch and Israeli isolates. IYSV was not seed transmitted, and in Israel, was not located in bulbs of infected plants. In the US, infected plants were generated from infected bulbs. The relationship between IYSV and Thrips tabaci was shown to be specific. Frankliniella occidentalis, the primary vector of many other tospoviruses, did not transmit IYSV isolates in Israel or the US. Furthermore, 1': tabaci populations varied in their transmission ability. Transmission was correlated to IYSV presence in thrips salivary glands. In Israel, surveys in onion fields revealed that the onion thrips, Thrips tabaci Lindeman was the predominant species and that its incidence was strongly related to that of IYSV infection. In contrast, in the U.S., T. tabaci and F. occidentalis were present in high numbers during the times sampled. In Israel, insecticides reduced onion thrips population and caused a significant yield increase. In the US, a genetic marker system that differentiates non-thrips transmissible isolates from thrips transmissible isolate demonstrated the importance of the M RNA to thrips transmission of tospoviruses. In addition, a symbiotic Erwinia was discovered in thrips and was shown to cause significant artifacts in certain types of virus binding experiments. Implications, scientific and agricultural. Rapid emergence of distinct tospoviruses and new vector relationships is profoundly important to global agriculture. We advanced the understanding of IYSV in bulb crops and its relationships with thrips vector species. The knowledge gained provided growers with new strategies for control and new tools for studying the importance of particular viral proteins in thrips specificity and transmission efficiency.

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Mawassi, Munir, Baozhong Meng et Lorne Stobbs. Development of Virus Induced Gene Silencing Tools for Functional Genomics in Grapevine. United States Department of Agriculture, juillet 2013. http://dx.doi.org/10.32747/2013.7613887.bard.

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Grapevine is perhaps the most widely grown fruit crop. To understand the genetic make-up so as to improve the yield and quality of grapes and grape products, researchers in Europe have recently sequenced the genomes of Pinot noir and its inbred. As expected, function of many grape genes is unknown. Functional genomics studies have become the major focus of grape researchers and breeders. Current genetic approaches for gene function studies include mutagenesis, crossing and genetic transformation. However, these approaches are difficult to apply to grapes and takes long periods of time to accomplish. It is thus imperative to seek new ways for grape functional genomics studies. Virus-induced gene silencing (VIGS) offers an attractive alternative for this purpose and has proven highly effective in several herbaceous plant species including tomato, tobacco and barley. VIGS offers several advantages over existing functional genomics approaches. First, it does not require transformation to silence a plant gene target. Instead, it induces silencing of a plant gene through infection with a virus that contains the target gene sequence, which can be accomplished within a few weeks. Second, different plant genes can be readily inserted into the viral genome via molecular cloning and functions of a large number of genes can be identified within a short period of time. Our long-term goal of this research is to develop VIGS-based tools for grapevine functional genomics, made of the genomes of Grapevine virus A (GVA) from Israel and Grapevine rupestris stem pitting-associated virus (GRSPaV) from Canada. GVA and GRSPaV are members of the Flexiviridae. Both viruses have single-stranded, positive sense RNA genomes, which makes them easy to manipulate genetically and excellent candidates as VIGS vectors. In our three years research, several major breakthroughs have been made by the research groups involved in this project. We have engineered a cDNA clone of GVA into a binary vector that is infectious upon delivery into plantlets of micropropagated Vitis viniferacv. Prime. We further developed the GVA into an expression vector that successfully capable to silence endogenous genes. We also were able to assemble an infectious full-length cDNA clones of GRSPaV. In the following sections Achievements and Detailed description of the research activities, we are presenting the outcome and results of this research in details.

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Dolja, Valerian V., Amit Gal-On et Victor Gaba. Suppression of Potyvirus Infection by a Closterovirus Protein. United States Department of Agriculture, mars 2002. http://dx.doi.org/10.32747/2002.7580682.bard.

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The plant virus family Polyviridae is the largest and most destructive of all plant viruses. Despite the continuous effort to develop resistant plant varieties, there is a desperate need for novel approaches conferring wide-range potyvirus resistance. Based on experiments with the tobacco etch potyvirus (TEV)-derived gene expression vector, we suggested approach for screening of the candidate resistance genes. This approach relies on insertion of the genes into a virus vector and evaluation of the phenotypes of the resulting recombinant viruses. The genes which suppress infection by the recombinant virus are selected as candidates for engineering transgenic resistance. Our analysis of the TEV variants expressing proteins of the beet yellows closterovirus (BYV) revealed that one of those, the leader proteinase (L-Pro), strongly and specifically interfered with the hybrid TEV infection. Since closterovirus L-Pro is evolutionary related to potyviral helper component-proteinase (HC-Pro), we suggested that the L-Pro interfered with HC-Pro function via a trans-dominant inhibitory effect. Based on these findings, we proposed to test two major hypotheses. First, we suggested that L-Pro-mediated suppression of potyvirus infection is a general phenomenon effective against a range of potyviruses. The second hypothesis stated that the suppression effect can be reproduced in transgenic plants expressing L-Pro, and can be utilized for generation of resistance to potyviruses. In accord with these hypotheses, we developed two original objectives of our proposal: A) to determine the range of the closterovirus-derived suppression of potyviral infection, and B) to try and utilize the L-Pro-mediated suppression for the development of transgenic resistance to potyviruses. In the first phase of the project, we have developed all major tools and technologies required for successful completion of the proposed research. These included TEV and ZYMV vectors engineered to express several closteroviral L-Pro variants, and generation of the large collection of transgenic plants. To our satisfaction, characterization of the infection phenotypes exhibited by chimeric TEV and ZYMV variants confirmed our first hypothesis. For instance, similar to TEV-L- Pro(BYV) chimera, ZYMV-L-Pro(LIYV) chimera was debilitated in its systemic spread. In contrast, ZYMV-GUS chimera (positive control) was competent in establishing vigorous systemic infection. These and other results with chimeric viruses indicated that several closteroviral proteinases inhibit long-distance movement of the potyviruses upon co-expression in infected plants. In order to complete the second objective, we have generated ~90 tobacco lines transformed with closteroviral L-Pro variants, as well as ~100 lines transformed with BYV Hsp70-homolog (Hsp70h; a negative control). The presence and expression of the trans gene in each line was initially confirmed using RT-PCR and RNA preparations isolated from plants. However, since detection of the trans gene-specific RNA can not guarantee production of the corresponding protein, we have also generated L-Pro- and Hsp70h-specific antisera using corresponding synthetic peptides. These antisera allowed us to confirm that the transgenic plant lines produced detectable, although highly variable levels of the closterovirus antigens. In a final phase of the project, we tested susceptibility of the transgenic lines to TEV infection. To this end, we determined that the minimal dilution of the TEV inoculum that is still capable of infecting 100% of nontransgenic plants was 1:20, and used 10 plants per line (in total, ~2,000 plants). Unfortunately, none of the lines exhibited statistically significant reduction in susceptibility. Although discouraging, this outcome prompted us to expand our experimental plan and conduct additional experiments. Our aim was to test if closteroviral proteinases are capable of functioning in trans. We have developed agroinfection protocol for BYV, and tested if co- expression of the L-Pro is capable of rescuing corresponding null-mutant. The clear-cut, negative results of these experiments demonstrated that L-Pro acts only in cis, thus explaining the lack of resistance in our transgenic plants. We have also characterized a collection of the L-Pro alanine- scanning mutants and found direct genetic evidence of the requirement for L-Pro in virus systemic spread. To conclude, our research supported by BARD confirmed one but not another of our original hypotheses. Moreover, it provided an important insight into functional specialization of the viral proteinases and generated set of tools and data with which we will be able to address the molecular mechanisms by which these proteins provide a variety of critical functions during virus life cycle.

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Lapidot, Moshe, et Vitaly Citovsky. molecular mechanism for the Tomato yellow leaf curl virus resistance at the ty-5 locus. United States Department of Agriculture, janvier 2016. http://dx.doi.org/10.32747/2016.7604274.bard.

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Tomato yellow leaf curl virus (TYLCV) is a major pathogen of tomato that causes extensive crop loss worldwide, including the US and Israel. Genetic resistance in the host plant is considered highly effective in the defense against viral infection in the field. Thus, the best way to reduce yield losses due to TYLCV is by breeding tomatoes resistant or tolerant to the virus. To date, only six major TYLCV-resistance loci, termed Ty-1 to Ty-6, have been characterized and mapped to the tomato genome. Among tomato TYLCV-resistant lines containing these loci, we have identified a major recessive quantitative trait locus (QTL) that was mapped to chromosome 4 and designated ty-5. Recently, we identified the gene responsible for the TYLCV resistance at the ty-5 locus as the tomato homolog of the gene encoding messenger RNA surveillance factor Pelota (Pelo). A single amino acid change in the protein is responsible for the resistant phenotype. Pelo is known to participate in the ribosome-recycling phase of protein biosynthesis. Our hypothesis was that the resistant allele of Pelo is a “loss-of-function” mutant, and inhibits or slows-down ribosome recycling. This will negatively affect viral (as well as host-plant) protein synthesis, which may result in slower infection progression. Hence we have proposed the following research objectives: Aim 1: The effect of Pelota on translation of TYLCV proteins: The goal of this objective is to test the effect Pelota may or may not have upon translation of TYLCV proteins following infection of a resistant host. Aim 2: Identify and characterize Pelota cellular localization and interaction with TYLCV proteins: The goal of this objective is to characterize the cellular localization of both Pelota alleles, the TYLCV-resistant and the susceptible allele, to see whether this localization changes following TYLCV infection, and to find out which TYLCV protein interacts with Pelota. Our results demonstrate that upon TYLCV-infection the resistant allele of pelota has a negative effect on viral replication and RNA transcription. It is also shown that pelota interacts with the viral C1 protein, which is the only viral protein essential for TYLCV replication. Following subcellular localization of C1 and Pelota it was found that both protein localize to the same subcellular compartments. This research is innovative and potentially transformative because the role of Peloin plant virus resistance is novel, and understanding its mechanism will lay the foundation for designing new antiviral protection strategies that target translation of viral proteins. BARD Report - Project 4953 Page 2

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