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Relevant bibliographies by topics / Plant Virus

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Academic literature on the topic 'Plant Virus'

Author: Grafiati

Published: 4 June 2021

Last updated: 9 June 2025

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Journal articles on the topic "Plant Virus"

1

Roossinck, Marilyn J. "Plant Virus Ecology." PLoS Pathogens 9, no. 5 (May 23, 2013): e1003304. http://dx.doi.org/10.1371/journal.ppat.1003304.

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Francki, R. I. B. "Plant Virus Satellites." Annual Review of Microbiology 39, no. 1 (October 1985): 151–74. http://dx.doi.org/10.1146/annurev.mi.39.100185.001055.

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Pedro, Filho Noronha Souza. "Plant Virus Interaction: Layers of Plant Antiviral Immunity." International Journal of Plant Science and Horticulture 1, no. 2 (April 24, 2019): 89–94. https://doi.org/10.36811/ijpsh.2019.110010.

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Plant defense mechanisms are divided into two phases; (1) the Pathogen-Triggered Immunity (PTI), which is basal resistance and; (2) Effector-Triggered Immunity (ETI) or induced resistance, the second line of defense of plants [1,2]. The PTI response is rapidly active by plants after recognizing pathogens effectors, which could be MAMPS or PAMPs (Microbe/pathogen-associated molecular patterns, e.g., bacterial flagellin), DAMPs (Damage-associated molecular patterns, e.g., fungal haustorium), and VAMPs (Viral-associated molecular patterns, e.g., double-stranded RNA of viruses). The recognition of pathogens effectors is performed by Pattern Recognition Receptors (PRR) [3-6].

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Roossinck, Marilyn J., Darren P. Martin, and Philippe Roumagnac. "Plant Virus Metagenomics: Advances in Virus Discovery." Phytopathology® 105, no. 6 (June 2015): 716–27. http://dx.doi.org/10.1094/phyto-12-14-0356-rvw.

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In recent years plant viruses have been detected from many environments, including domestic and wild plants and interfaces between these systems—aquatic sources, feces of various animals, and insects. A variety of methods have been employed to study plant virus biodiversity, including enrichment for virus-like particles or virus-specific RNA or DNA, or the extraction of total nucleic acids, followed by next-generation deep sequencing and bioinformatic analyses. All of the methods have some shortcomings, but taken together these studies reveal our surprising lack of knowledge about plant viruses and point to the need for more comprehensive studies. In addition, many new viruses have been discovered, with most virus infections in wild plants appearing asymptomatic, suggesting that virus disease may be a byproduct of domestication. For plant pathologists these studies are providing useful tools to detect viruses, and perhaps to predict future problems that could threaten cultivated plants.

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Moffat, A. S. "Plant Pathology: ATCC Plant-Virus Collection Threatened." Science 275, no. 5307 (March 21, 1997): 1733b—0. http://dx.doi.org/10.1126/science.275.5307.1733b.

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Bethencourt, Victor. "Virus stalls Genzyme plant." Nature Biotechnology 27, no. 8 (August 2009): 681. http://dx.doi.org/10.1038/nbt0809-681a.

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Hefferon, Kathleen. "Repurposing Plant Virus Nanoparticles." Vaccines 6, no. 1 (February 14, 2018): 11. http://dx.doi.org/10.3390/vaccines6010011.

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Zaitlin, M., and R. Hull. "Plant Virus-Host Interactions." Annual Review of Plant Physiology 38, no. 1 (June 1987): 291–315. http://dx.doi.org/10.1146/annurev.pp.38.060187.001451.

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Roossinck, Marilyn J. "Plant RNA virus evolution." Current Opinion in Microbiology 6, no. 4 (August 2003): 406–9. http://dx.doi.org/10.1016/s1369-5274(03)00087-0.

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Carrington, James C. "Reinventing plant virus movement." Trends in Microbiology 7, no. 8 (August 1999): 312–13. http://dx.doi.org/10.1016/s0966-842x(99)01559-0.

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Dissertations / Theses on the topic "Plant Virus"

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Ratcliff, Frank Giles. "Novel aspects of plant-virus interactions." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302040.

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Chewachong, Godwill Mih. "Engineering Plant Virus " Vaccines" Using Pepino mosaic virus as a Model." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1384203201.

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Tungadi, Trisna Dewi. "Cucumber mosaic virus modifies plant-aphid interactions." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708288.

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van, Zyl Albertha R. "Development of plant-produced Bluetongue virus vaccines." Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/28248.

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Bluetongue is a disease of domestic and wild ruminants caused by Bluetongue virus (BTV). It has caused several serious outbreaks, the most recent occurring in Northern Europe in 2006 during which high mortality rates of livestock were reported. The only vaccines currently approved and commercially available for use are live-attenuated or inactivated virus strains and although these are effective, there is the risk of reversion in the case of live-attenuated strains to more virulent forms by recombination. Another drawback associated with the use of live-attenuated virus vaccines is that they are not DIVA (differentiate infected from vaccinated animals) compliant, this means that naturally infected animals cannot be distinguished from vaccinated animals. Recombinantly produced vaccines would be preferable to minimize the risks associated with live-attenuated virus vaccines and also enable the development of candidate vaccines that are DIVA-compliant. A number of recombinant vaccine candidates have been developed against BTV, with the most promising vaccine consisting of BTV virus-like particles (VLPs). BTV VLPs were successfully produced in insect cells by the co-expression of the four BTV capsid proteins (VP2, VP3, VP5 and VP7). Sheep vaccinated with insect cell-produced BTV VLPs were shown to be protected against challenge with wild type virus. However, the high costs associated with the production and scale-up of BTV VLPs in insect cells has possibly limited their widespread application. Plants – such as N. benthamiana – provides a safe, efficient and cost effective system for the production of recombinant proteins. In this study the best plant expression vector with which to co-express the four BTV serotype 8 (BTV-8) VPs – which direct formation of BTV-8 VLPs – was identified. Expression and purification of the BTV-8 VLPs was optimised with the aim of producing a VLP-based vaccine for BTV-8. It was further undertaken to develop two novel second generation plant-produced protein body (PB) vaccines that are DIVA compliant. Mice were immunised with the plantproduced VLP and PB vaccines in order to analyse their ability to elicit humoral immune responses.

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Murray, Abner A. "Plant Virus Nanoparticle In Situ Cancer Immunotherapies." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1532370850718292.

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Aitken, Angus Iain. "Membrane interactions of plant virus movement proteins." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/15617.

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Plant viruses post a significant risk to both global food security, and industrial agriculture, however very little is known regarding their molecular mechanisms. Despite intensive study since the discovery of a multitude of plant virtual movement proteins, it remains unknown how they transverse the plasmodesmata, and thus move between cells. The CMV virus is widespread, infecting over a thousand plant species, and yet the means by which the movement protein CMV 3a associates to cellular membranes, targets itself and viral genomes to plasmodesmata have not been described. This study initially attempted to purify the CMV 3a protein from bacterial expression for structural and biophysical studies to examine viral protein and host membrane interactions. The study also began mapping the CMV 3a protein surface to investigate protein localisation and membrane attachment in planta, identifying structural features, including two potentially amphipathic helices which bear further investigation for potential roles in membrane association. Finally, this thesis examined the potential for the lipid modification S-acylation (Palmitoylation) as a membrane anchor, across a range of viral movement proteins. Describing this modification of viral movement proteins for the first time, S-acylation was demonstrated to not only be widespread, but potentially play different roles across a range of plant virus movement systems. This information is vital for the advancement of the field's understanding of the cell to cell movement of plant viruses, and the potential development of control strategies; and hence the safeguarding of global food security.

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Soards, Avril Jacqueline. "The Cucumber mosaic virus 2b protein : influences on the plant-virus interaction." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619971.

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Gaafar, Yahya Zakaria Abdou [Verfasser]. "Plant virus identification and virus-vector-host interactions / Yahya Zakaria Abdou Gaafar." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1220909262/34.

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Chun, Elizabeth M. "Developing a Recombinant Plant Virus Nanoparticle Vaccine for Rift Valley Fever Virus." Scholarship @ Claremont, 2019. https://scholarship.claremont.edu/scripps_theses/1345.

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Rift Valley Fever (RVF) is an emerging infectious disease found in both livestock and humans. RVF is associated with high abortion and mortality rates in livestock and can be fatal in humans. As such, RVF is economically and socially significant to affected smallholder and subsistence farmers, those infected, and national livestock industries. However, Rift Valley Fever virus (RVFV) vaccines are not commercially available outside of endemic areas or for humans, and current vaccines are limited in their safety and efficacy. A plant-based, viral nanoparticle vaccine offers a more affordable alternative to conventional vaccines that is safe, rapidly producible, and easily scalable, better meeting the needs of impacted communities. This project focuses on assessing the potential of using a Nicotiana benthamiana plant expression system to generate recombinant tobacco mosaic virus (TMV) nanoparticles displaying RVFV glycoprotein epitopes. Eight TMV-RVFV glycoprotein constructs were designed. Five TMV-RVFV constructs were successfully cloned, and four recombinant TMV constructs were successfully expressed in planta. The antigenicity of these constructs was examined for their possible use in RVFV vaccine development.

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Chare, Elizabeth R. "Recombination in RNA viruses and plant virus evolution." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433381.

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Books on the topic "Plant Virus"

1

Roossinck, Marilyn J., ed. Plant Virus Evolution. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75763-4.

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Kleinow, Tatjana, ed. Plant-Virus Interactions. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-25489-0.

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Roossinck, Marilyn J. Plant virus evolution. Berlin: Springer, 2008.

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Michael, Thresh J., ed. Plant virus epidemiology. Amsterdam: Academic Press/Elsevier, 2006.

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Fontes, Elizabeth P. B., and Kristiina Mäkinen, eds. Plant-Virus Interactions. New York, NY: Springer US, 2024. http://dx.doi.org/10.1007/978-1-0716-3485-1.

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A, Hadidi, Khetarpal R. K, and Koganezawa H, eds. Plant virus disease control. St. Paul, Minn: APS Press, 1998.

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T, Plumb R., ed. Plant virus vector interactions. San Diego: Academic Press, 2002.

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F, Harris Kerry, Smith Oney P. 1954-, and Duffus James E, eds. Virus-insect-plant interactions. San Diego, Calif: Academic, 2001.

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Sreenivasulu, P. Physiology of virus infected plants. New Delhi: South Asian Publishers, 1989.

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Matthews, R. E. F. 1921-, ed. Diagnosis of plant virus diseases. Boca Raton: CRC Press, 1993.

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Book chapters on the topic "Plant Virus"

1

Melcher, Ulrich, and Akhtar Ali. "Virus–Virus Interactions in Plants." In Plant Viruses, 249–66. Boca Raton: CRC Press, 2018. http://dx.doi.org/10.1201/9781315162287-15.

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Parthasarathy, S. "Virus." In Fundamentals of Plant Pathology, 203–26. London: CRC Press, 2023. http://dx.doi.org/10.1201/9781032711881-16.

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Walkey, David G. A. "Virus Symptoms." In Applied Plant Virology, 71–102. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3090-5_3.

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Walkey, David G. A. "Virus Purification." In Applied Plant Virology, 121–32. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3090-5_5.

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Walkey, David G. A. "Virus Identification." In Applied Plant Virology, 133–67. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3090-5_6.

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Hull, R., and A. J. Maule. "Virus Multiplication." In The Plant Viruses, 83–115. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4937-2_4.

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van Vloten-Doting, L. "Virus Genetics." In The Plant Viruses, 117–61. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4937-2_5.

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Hamilton, R. I. "Virus Transmission." In The Plant Viruses, 245–67. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4684-4937-2_8.

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Parthasarathy, S., P. Lakshmidevi, V. K. Satya, and C. Gopalakrishnan. "Virus." In Plant Pathology and Disease Management, 130–40. London: CRC Press, 2023. http://dx.doi.org/10.1201/9781032711973-16.

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Yadav, Sunita, and Anju K. Chhibbar. "Plant–Virus Interactions." In Molecular Aspects of Plant-Pathogen Interaction, 43–77. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7371-7_3.

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Conference papers on the topic "Plant Virus"

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"Genetic incongruity in the genomes of dahlia mosaic virus and dahlia common mosaic virus." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-071.

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"A new blackberry virus in the U.S." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-236.

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"Improved Virus Detection Procedures for Strawberry Certification Programs." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-074.

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"RNA-Sequencing-Based Virus Discovery in Florida Citrus Pests." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-018.

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"Genetic Diversity of Wheat Streak Mosaic Virus in Texas." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-279.

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"A Complex Association of Tomato Chlorosis Virus and Tomato Yellow Leaf Curl Virus in Cultivated Tomato (Solanum lycopersicum L.) in the Southern USA." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-143.

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"Characterization of birch toti-like virus infecting ornamental European birch." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-235.

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Silva-Martins, Guilherme. "Jasmonic acid regulates Argonaute 5-mediated defense against virus infection." In ASPB PLANT BIOLOGY 2020. USA: ASPB, 2020. http://dx.doi.org/10.46678/pb.20.1051755.

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"Genome characterization of seed-transmitted bean common mosaic virus tepary bean isolates." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-282.

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"Molecular characterization of two tobacco necrosis virus-A variants identified in sugar beet." In Plant Health 2024. American Phytopathological Society, 2024. http://dx.doi.org/10.1094/aps-ph24-228.

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Reports on the topic "Plant Virus"

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Palukaitis, Peter, Amit Gal-On, Milton Zaitlin, and Victor Gaba. Virus Synergy in Transgenic Plants. United States Department of Agriculture, March 2000. http://dx.doi.org/10.32747/2000.7573074.bard.

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Transgenic plants expressing viral genes offer novel means of engendering resistance to those viruses. However, some viruses interact synergistically with other viruses and it is now known that transgenic plants expressing particular genes of one virus may also mediate synergy with a second virus. Thus, our specific objectives were to (1) determine if transgenic plants resistant to one virus showed synergy with another virus; (2) determine what viral sequences were essential for synergy; and (3) determine whether one of more mechanisms were involved i synergy. This project would also enable an evaluation of the risks of synergism associated with the use of such transgenic plants. The conclusion deriving from this project are as follows: - There is more than one mechanism of synergy. - The CMV 2b gene is required for synergistic interactions. - Synergy between a potyvirus and CMV can break natural resistance limiting CMV movement. - Synergy operates at two levels - increase in virus accumulation and increase in pathology - independently of each other. - Various sequences of CMV can interact with the host to alter pathogenicity and affect virus accumulation. - The effect of synergy on CMV satellite RNA accumulatio varies in different systems. - The HC-Pro gene may only function in host plant species to induce synergy. - The HC-Pro is a host range determinant of potyviruses. - Transgenic plants expressing some viral sequences showed synergy with one or more viruses. Transgenic plants expressing CMV RNA 1, PVY NIb and the TMV 30K gene all showed synergy with at least one unrelated virus. - Transgenic plants expressing some viral sequences showed interference with the infection of unrelated viruses. Transgenic plants expressing the TMV 30K, 54K and 126K genes, the PVY NIb gene, or the CMV 3a gene all showed some level of interference with the accumulation (and in some cases the pathology) of unrelated viruses. From our observations, there are agricultural implications to the above conclusions. It is apparent that before they are released commercially, transgenic plants expressing viral sequences for resistance to one virus need to be evaluated fro two properties: - Synergism to unrelated viruses that infect the same plant. Most of these evaluations can be made in the greenhouse, and many can be predicted from the known literature of viruses known to interact with each other. In other cases, where transgenic plants are being generated from new plant species, the main corresponding viruses from the same known interacting genera (e.g., potexviruses and cucumoviruses, potyviruses and cucumoviruses, tobamoviruses and potexviruses, etc.) should be evaluated. - Inhibition or enhancement of other resistance genes. Although it is unlikely that plants to be released would be transformed with HC-Pro or 2b genes, there may be other viral genes that can affect the expression of plant genes encoding resistance to other pathogens. Therefore, transgenic plants expressing viral genes to engender pathogen-derived resistance should be evaluated against a spectrum of other pathogens, to determine whether those resistance activities are still present, have been lost, or have been enhanced!

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Pirone, Thomas, Arieh Rosner, I. Harpaz, and Yehuda Stram. Molecular Basis of a Plant Virus-Insect Interaction. United States Department of Agriculture, December 1990. http://dx.doi.org/10.32747/1990.7599665.bard.

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Gal-On, Amit, Shou-Wei Ding, Victor P. Gaba, and Harry S. Paris. role of RNA-dependent RNA polymerase 1 in plant virus defense. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597919.bard.

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Objectives: Our BARD proposal on the impact of RNA-dependent RNA polymerase 1 (RDR1) in plant defense against viruses was divided into four original objectives. 1. To examine whether a high level of dsRNA expression can stimulate RDR1 transcription independent of salicylic acid (SA) concentration. 2. To determine whether the high or low level of RDR1 transcript accumulation observed in virus resistant and susceptible cultivars is associated with viral resistance and susceptibility. 3. To define the biogenesis and function of RDR1-dependent endogenous siRNAs. 4. To understand why Cucumber mosaic virus (CMV) can overcome RDR1-dependent resistance. The objectives were slightly changed due to the unique finding that cucumber has four different RDR1 genes. Background to the topic: RDR1 is a key plant defense against viruses. RDR1 is induced by virus infection and produces viral and plant dsRNAs which are processed by DICERs to siRNAs. siRNAs guide specific viral and plant RNA cleavage or serve as primers for secondary amplification of viral-dsRNA by RDR. The proposal is based on our preliminary results that a. the association of siRNA and RDR1 accumulation with multiple virus resistance, and b. that virus infection induced the RDR1-dependent production of a new class of endogenous siRNAs. However, the precise mechanisms underlying RDR1 induction and siRNA biogenesis due to virus infection remain to be discovered in plants. Major conclusions, solutions and achievements: We found that in the cucurbit family (cucumber, melon, squash, watermelon) there are 3-4 RDR1 genes not documented in other plant families. This important finding required a change in the emphasis of our objectives. We characterized 4 RDR1s in cucumber and 3 in melon. We demonstrated that in cucumber RDR1b is apparently a new broad spectrum virus resistance gene, independent of SA. In melon RDR1b is truncated, and therefore is assumed to be the reason that melon is highly susceptible to many viruses. RDR1c is dramatically induced due to DNA and RNA virus infection, and inhibition of RDR1c expression led to increased virus accumulation which suggested its important on gene silencing/defense mechanism. We show that induction of antiviral RNAi in Arabidopsis is associated with production of a genetically distinct class of virus-activated siRNAs (vasiRNAs) by RNA dependent RNA polymerase-1 targeting hundreds of host genes for RNA silencing by Argonaute-2. Production of vasiRNAs is induced by viruses from two different super groups of RNA virus families, targeted for inhibition by CMV, and correlated with virus resistance independently of viral siRNAs. We propose that antiviral RNAi activate broad-spectrum antiviral activity via widespread silencing of host genes directed by vasiRNAs, in addition to specific antiviral defense Implications both scientific and agricultural: The RDR1b (resistance) gene can now be used as a transcription marker for broad virus resistance. The discovery of vasiRNAs expands the repertoire of siRNAs and suggests that the siRNA-processing activity of Dicer proteins may play a more important role in the regulation of plant and animal gene expression than is currently known. We assume that precise screening of the vasiRNA host targets will lead in the near future for identification of plant genes associate with virus diseases and perhaps other pathogens.

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Jordan, Ramon L., Abed Gera, Hei-Ti Hsu, Andre Franck, and Gad Loebenstein. Detection and Diagnosis of Virus Diseases of Pelargonium. United States Department of Agriculture, July 1994. http://dx.doi.org/10.32747/1994.7568793.bard.

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Pelargonium (Geranium) is the number one pot plant in many areas of the United States and Europe. Israel and the U.S. send to Europe rooted cuttings, foundation stocks and finished plants to supply a certain share of the market. Geraniums are propagated mainly vegetatively from cuttings. Consequently, viral diseases have been and remain a major threat to the production and quality of the crop. Among the viruses isolated from naturally infected geraniums, 11 are not specific to Pelargonium and occur in other crops while 6 other viruses seem to be limited to geranium. However, several of these viruses are not sufficiently characterized to conclude that they are distinct agents and their nomenclature and taxonomy are confusing. The ability to separate, distinguish and detect the different viruses in geranium will overcome obstacles te developing effective detection and certification schemes. Our focus was to further characterize some of these viruses and develop better methods for their detection and control. These viruses include: isolates of pelargonium line pattern virus (PLPV), pelargonium ringspot virus (PelRSV), pelargonium flower break virus (PFBV), pelargonium leaf curl (PLCV), and tomato ringspot virus (TomRSV). Twelve hybridoma cell lines secreting monoclonal antibodies specific to a geranium isolate of TomRSV were produced. These antibodies are currently being characterized and will be tested for the ability to detect TomRSV in infected geraniums. The biological, biochemical and serological properties of four isometric viruses - PLPV, PelRSV, and PFBV (and a PelRSV-like isolate from Italy called GR57) isolated from geraniums exhibiting line and ring pattern or flower break symptoms - and an isolate ol elderbeny latent virus (ELV; which the literature indicates is the same as PelRSV) have been determined Cloned cDNA copies of the genomic RNAs of these viruses were sequenced and the sizes and locations of predicted viral proteins deduced. A portion of the putative replicase genes was also sequenced from cloned RT-PCR fragments. We have shown that, when compared to the published biochemical and serological properties, and sequences and genome organizations of other small isometric plant viruses, all of these viruses should each be considered new, distinct members of the Carmovirus group of the family Tombusviridae. Hybridization assays using recombinant DNA probes also demonstrated that PLPV, PelRSV, and ELV produce only one subgenomic RNA in infected plants. This unusual property of the gene expression of these three viruses suggests that they are unique among the Carmoviruses. The development of new technologies for the detection of these viruses in geranium was also demonstrated. Hybridization probes developed to PFBV (radioactively-labeled cRNA riboprobes) and to PLPV (non-radioactive digoxigenin-labeled cDNAs) were generally shown to be no more sensitive for the detection of virus in infected plants than the standard ELISA serology-based assays. However, a reverse transcriptase-polymerase chain reaction assay was shown to be over 1000 times more sensitive in detecting PFBV in leaf extracts of infected geranium than was ELISA. This research has lead to a better understanding of the identity of the viruses infecting pelargonium and to the development of new tools that can be used in an improved scheme of providing virus-indexed pelargonium plants. The sequence information, and the serological and cloned DNA probes generated from this work, will allow the application of these new tools for virus detection, which will be useful in domestic and international indexing programs which are essential for the production of virus-free germplasm both for domestic markets and the international exchange of plant material.

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Whitham, Steven A., Amit Gal-On, and Tzahi Arazi. Functional analysis of virus and host components that mediate potyvirus-induced diseases. United States Department of Agriculture, March 2008. http://dx.doi.org/10.32747/2008.7591732.bard.

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The mechanisms underlying the development of symptoms in response to virus infection remain to be discovered in plants. Insight into symptoms induced by potyviruses comes from evidence implicating the potyviral HC-Pro protein in symptom development. In particular, recent studies link the development of symptoms in infected plants to HC-Pro's ability to interfere with small RNA metabolism and function in plant hosts. Moreover, mutation of the highly conserved FRNK amino acid motif to FINK in the HC-Pro of Zucchini yellow mosaic virus (ZYMV) converts a severe strain into an asymptomatic strain, but does not affect virus accumulation in cucurbit hosts. The ability of this FINK mutation to uncouple symptoms from virus accumulation creates a unique opportunity to study symptom etiology, which is usually confounded by simultaneous attenuation of both symptoms and virus accumulation. Our goal was to determine how mutations in the conserved FRNK motif affect host responses to potyvirus infection in cucurbits and Arabidopsis thaliana. Our first objective was to define those amino acids in the FRNK motif that are required for symptoms by mutating the FRNK motif in ZYMV and Turnip mosaic virus (TuMV). Symptom expression and accumulation of resulting mutant viruses in cucurbits and Arabidopsis was determined. Our second objective was to identify plant genes associated with virus disease symptoms by profiling gene expression in cucurbits and Arabidopsis in response to mutant and wild type ZYMV and TuMV, respectively. Genes from the two host species that are differentially expressed led us to focus on a subset of genes that are expected to be involved in symptom expression. Our third objective was to determine the functions of small RNA species in response to mutant and wild type HC-Pro protein expression by monitoring the accumulation of small RNAs and their targets in Arabidopsis and cucurbit plants infected with wild type and mutant TuMV and ZYMV, respectively. We have found that the maintenance of the charge of the amino acids in the FRNK motif of HC-Pro is required for symptom expression. Reduced charge (FRNA, FRNL) lessen virus symptoms, and maintain the suppression of RNA silencing. The FRNK motif is involved in binding of small RNA species including microRNAs (miRNA) and short interfering RNAs (siRNA). This binding activity mediated by the FRNK motif has a role in protecting the viral genome from degradation by the host RNA silencing system. However, it also provides a mechanism by which the FRNK motif participates in inducing the symptoms of viral infection. Small RNA species, such as miRNA and siRNA, can regulate the functions of plant genes that affect plant growth and development. Thus, this binding activity suggests a mechanism by which ZYMVHC-Pro can interfere with plant development resulting in disease symptoms. Because the host genes regulated by small RNAs are known, we have identified candidate host genes that are expected to play a role in symptoms when their regulation is disrupted during viral infections. As a result of this work, we have a better understanding of the FRNK amino acid motif of HC-Pro and its contribution to the functions of HC-Pro, and we have identified plant genes that potentially contribute to symptoms of virus infected plants when their expression becomes misregulated during potyviral infections. The results set the stage to establish the roles of specific host genes in viral pathogenicity. The potential benefits include the development of novel strategies for controlling diseases caused by viruses, methods to ensure stable expression of transgenes in genetically improved crops, and improved potyvirus vectors for expression of proteins or peptides in plants.

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Wang, X. F., and M. Schuldiner. Systems biology approaches to dissect virus-host interactions to develop crops with broad-spectrum virus resistance. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2020. http://dx.doi.org/10.32747/2020.8134163.bard.

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More than 60% of plant viruses are positive-strand RNA viruses that cause billion-dollar losses annually and pose a major threat to stable agricultural production, including cucumber mosaic virus (CMV) that infects numerous vegetables and ornamental trees. A highly conserved feature among these viruses is that they form viral replication complexes (VRCs) to multiply their genomes by hijacking host proteins and remodeling host intracellular membranes. As a conserved and indispensable process, VRC assembly also represents an excellent target for the development of antiviral strategies that can be used to control a wide-range of viruses. Using CMV and a model virus, brome mosaic virus (BMV), and relying on genomic tools and tailor-made large-scale resources specific for the project, our original objectives were to: 1) Identify host proteins that are required for viral replication complex assembly. 2) Dissect host requirements that determine viral host range. 3) Provide proof-of-concept evidence of a viral control strategy by blocking the viral replication complex-localized phospholipid synthesis. We expect to provide new ways and new concepts to control multiple viruses by targeting a conserved feature among positive-strand RNA viruses based on our results. Our work is going according to the expected timeline and we are progressing well on all aims. For Objective 1, among ~6,000 yeast genes, we have identified 96 hits that were possibly play critical roles in viral replication. These hits are involved in cellular pathways of 1) Phospholipid synthesis; 2) Membrane-shaping; 3) Sterol synthesis and transport; 4) Protein transport; 5) Protein modification, among many others. We are pursuing several genes involved in lipid metabolism and transport because cellular membranes are primarily composed of lipids and lipid compositional changes affect VRC formation and functions. For Objective 2, we have found that CPR5 proteins from monocotyledon plants promoted BMV replication while those from dicotyledon plants inhibited it, providing direct evidence that CPR5 protein determines the host range of BMV. We are currently examining the mechanisms by which dicot CPR5 genes inhibit BMV replication and expressing the dicot CPR5 genes in monocot plants to control BMV infection. For Objective 3, we have demonstrated that substitutions in a host gene involved in lipid synthesis, CHO2, prevented the VRC formation by directing BMV replication protein 1a (BMV 1a), which remodels the nuclear membrane to form VRCs, away from the nuclear membrane, and thus, no VRCs were formed. This has been reported in Journal of Biological Chemistry. Based on the results from Objective 3, we have extended our plan to demonstrate that an amphipathic alpha-helix in BMV 1a is necessary and sufficient to target BMV 1a to the nuclear membrane. We further found that the counterparts of the BMV 1a helix from a group of viruses in the alphavirus-like superfamily, such as CMV, hepatitis E virus, and Rubella virus, are sufficient to target VRCs to the designated membranes, revealing a conserved feature among the superfamily. A joint manuscript describing these exciting results and authored by the two labs will be submitted shortly. We have also successfully set up systems in tomato plants: 1) to efficiently knock down gene expression via virus-induced gene silencing so we could test effects of lacking a host gene(s) on CMV replication; 2) to overexpress any gene transiently from a mild virus (potato virus X) so we could test effects of the overexpressed gene(s) on CMV replication. In summary, we have made promising progress in all three Objectives. We have identified multiple new host proteins that are involved in VRC formation and may serve as good targets to develop antiviral strategies; have confirmed that CPR5 from dicot plants inhibited viral infection and are generating BMV-resistance rice and wheat crops by overexpressing dicot CPR5 genes; have demonstrated to block viral replication by preventing viral replication protein from targeting to the designated organelle membranes for the VRC formation and this concept can be further employed for virus control. We are grateful to BARD funding and are excited to carry on this project in collaboration.

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Citovsky, Vitaly, and Yedidya Gafni. Nuclear Import of the Tomato Yellow Curl Leaf Virus in Tomato Plants. United States Department of Agriculture, September 1994. http://dx.doi.org/10.32747/1994.7568765.bard.

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Tomato yellow leaf curl geminivirus (TYLCV) is a major pathogen of cultivated tomato, causing up to 100% crop loss in many parts of the world. In Israel the disease is well known and has an economic significance. In recent years viral symptoms were found in countries of the "New World" and since 1997, in Florida. Surprisingly, little is known about the molecular mechanisms of TYLCV interaction with the host plant cells. This proposal was aimed at expanding our understanding of the molecular mechanisms by which TYLCV enters the host cell nucleus. The main objective was to elucidate the TYLCV protein(s) involved in transport of the viral genomic DNA into the host cell nucleus. This goal was best served by collaboration between our laboratories one of which (V.C.) was already investigating the nuclear import of the T-DNA ofAgrobacterium tumefaciens, and the other (Y.G.) was studying the effect of TYLCV capsid protein (CP) in transgenic plants, hypothesizing its involvement in the viral nuclear entry. Three years of our collaborative work have provided signifcant data that strongly support our original hypothesis of the involvement of TYLCtr CP in viral nuclear import. Furthermore, our results have laid a foundation to study fundamental, but as yet practically unresolved, questions about the role ofthe host cell factors in the nuclear import of geminiviruses within their host plant. As a result, this research may lead to development of new approaches for plant protection based on control of TYLCV import to the host plant cell nucleus.

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Loebenstein, Gad, William Dawson, and Abed Gera. Association of the IVR Gene with Virus Localization and Resistance. United States Department of Agriculture, August 1995. http://dx.doi.org/10.32747/1995.7604922.bard.

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We have reported that localization of TMV in tobacco cultivars with the N gene, is associated with a 23 K protein (IVR) that inhibited replication of several plant viruses. This protein was also found in induced resistant tissue of Nicotiana glutinosa x Nicotiana debneyi. During the present grant we found that TMV production is enhanced in protoplasts and plants of local lesion responding tobacco cultivars exposed to 35oC, parallel to an almost complete suppression of the production of IVR. We also found that IVR is associated with resistance mechanisms in pepper cultivars. We succeeded to clone the IVR gene. In the first attempt we isolated a clone - "101" which had a specific insert of 372 bp (the full length gene for the IVR protein of 23 kD should be around 700 bp). However, attempts to isolate the full length gene did not give clear cut results, and we decided not to continue with this clone. The amino acid sequence of the N-terminus of IVR was determined and an antiserum was prepared against a synthetic peptide representing amino acids residues 1-20 of IVR. Using this antiserum as well as our polyclonal antiserum to IVR a new clone NC-330 was isolated using lamba-ZAP library. This NC-330 clone has an insert of about 1 kB with an open reading frame of 596 bp. This clone had 86.6% homology with the first 15 amino acids of the N-terminal part of IVR and 61.6% homology with the first 23 amino acids of IVR. In the QIA expression system and western blotting of the expressed protein, a clear band of about 21 kD was obtained with IVR antiserum. This clone was used for transformation of Samsun tobacco plants and we have presently plantlets which were rooted on medium containing kanamycin. Hybridization with this clone was also obtained with RNA from induced resistant tissue of Samsun NN but not with RNA from healthy control tissue of Samsun NN, or infected or healthy tissue of Samsun. This further strengthens the previous data that the NC 330 clone codes for IVR. In the U.S. it was shown that IVR is induced in plants containing the N' gene when infected with mutants of TMV that elicit the HR. This is a defined system in which the elicitor is known to be due to permutations of the coat protein which can vary in elicitor strength. The objective was to understand how IVR synthesis is induced after recognition of elicitor coat protein in the signal transduction pathway that leads to HR. We developed systems to manipulate induction of IVR by modifying the elicitor and are using these elicitor molecules to isolate the corresponding plant receptor molecules. A "far-western" procedure was developed that found a protein from N' plants that specifically bind to elicitor coat proteins. This protein is being purified and sequenced. This objective has not been completed and is still in progress. We have reported that localization of TMV in tobacco cultivars with the N gene, is associated with a 23 K protein (IVR) that inhibited replication of several plant viruses. This protein was also found in induced resistant tissue of Nicotiana glutinosa x Nicotiana debneyi.

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Ullman, Diane E., Benjamin Raccah, John Sherwood, Meir Klein, Yehezkiel Antignus, and Abed Gera. Tomato Spotted Wilt Tosporvirus and its Thrips Vectors: Epidemiology, Insect/Virus Interactions and Control. United States Department of Agriculture, November 1999. http://dx.doi.org/10.32747/1999.7573062.bard.

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Objectives. The major aim of the proposed research was to study thrips-TSWV relationships and their role in the epidemiology of the virus with the aim of using this knowledge to reduce crop losses occurring due to epidemics. Our specific objectives were: To determine the major factors involved in virus outbreaks, including: a) identifying the thrips species involved in virus dissemination and their relative role in virus spread; b) determining the virus sources among wild and cultivated plants throughout the season and their role in virus spread, and, c) determining how temperature and molecular variations in isolates impact virus replication in plants and insects and impact the transmission cycle. Background to the topic. Tospoviruses are among the most important emerging plant viruses that impact production of agricultural and ornamental crops. Evolution of tospoviruses and their relationships with thrips vector species have been of great interest because of crop damage caused world wide and the complete absence of suitable methods of control. Tospoviruses threaten crops in Israel and the United States. By understanding the factors contributing to epidemics and the specific relationships between thrips species and particular tospoviruses we hope that new strategies for control can be developed that will benefit agriculture in both Israel and the United States. Major conclusions, solutions, achievements. We determined that at least three tospoviruses were involved in epidemics in Israel and the United States, tomato spotted wilt virus (TSWV), impatiens necrotic spot virus (INSV) and iris yellow spot virus (IYSV). We detected and characterized INSV for the first time in Israel and, through our efforts, IYSV was detected and characterized for the first time in both countries. We demonstrated that many thrips species were present in commercial production areas and trap color influenced thrips catch. Frankliniella occidentalis was the major vector species of INSV and TSWV and populations varied in transmission efficiency. Thrips tabaci is the sole known vector of IYSV and experiments in both countries indicated that F. occidentalis is not a vector of this new tospovirus. Alternate plant hosts were identified for each virus. A new monitoring system combining sticky cards and petunia indicator plants was developed to identify sources of infective thrips. This system has been highly successful in the U.S. and was used to demonstrate to growers that removal of plant sources of infective thrips has a dramatic impact on virus incidence. Finally, a putative thrips receptor mediating acquisition of TSWV was discovered. Implications, scientific and agricultural. Our findings have contributed to new control measures that will benefit agriculture. Identification of a putative thrips receptor for TSWV and our findings relative to thrips/tospovirus specificity have implications for development of innovative new control strategies.

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Gera, Abed, Abed Watad, P. Ueng, Hei-Ti Hsu, Kathryn Kamo, Peter Ueng, and A. Lipsky. Genetic Transformation of Flowering Bulb Crops for Virus Resistance. United States Department of Agriculture, January 2001. http://dx.doi.org/10.32747/2001.7575293.bard.

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Objectives. The major aim of the proposed research was to establish an efficient and reproducible genetic transformation system for Easter lily and gladiolus using either biolistics or Agrobacterium. Transgenic plants containing pathogen-derived genes for virus resistance were to be developed and then tested for virus resistance. The proposal was originally aimed at studying cucumber mosaic virus (CMV) resistance in plants, but studies later included bean yellow mosaic virus (BYMV). Monoclonal antibodies were to be tested to determine their effectiveness in interning with virus infection and vector (aphid) transmission. Those antibodies that effectively interfered with virus infection and transmission were to be cloned as single chain fragments and used for developing transgenic plants with the potential to resist virus infection. Background to the topic. Many flower crops, as lily and gladiolus are propagated vegetatively through bulbs and corms, resulting in virus transmission to the next planting generation. Molecular genetics offers the opportunity of conferring transgene-mediated disease resistance to flower crops that cannot be achieved through classical breeding. CMV infects numerous plant species worldwide including both lilies and gladioli. Major conclusions, solutions and achievements. Results from these for future development of collaborative studies have demonstrated the potential transgenic floral bulb crops for virus resistance. In Israel, an efficient and reproducible genetic transformation system for Easter lily using biolistics was developed. Transient as well as solid expression of GUS reporter gene was demonstrated. Putative transgenic lily plantlets containing the disabled CMV replicase transgene have been developed. The in vitro ability of monoclonal antibodies (mAbs) against CMV to neutralize virus infectivity and block virus transmission by M. persicae were demonstrated. In the US, transgenic Gladiolus plants containing either the BYMV coat protein or antisense coat protein genes have been developed and some lines were found to be virus resistant. Long-term expression of the GUS reporter gene demonstrated that transgene silencing did not occur after three seasons of dormancy in the 28 transgenic Gladiolus plants tested. Selected monoclonal antibody lines have been isolated, cloned as single chain fragments and are being used in developing transgenic plants with CMV resistance. Ornamental crops are multi-million dollar industries in both Israel and the US. The increasing economic value of these floral crops and the increasing ban numerous pesticides makes it more important than ever that alternatives to chemical control of pathogens be studied to determine their possible role in the future. The cooperation resulted in the objectives being promoted at national and international meetings. The cooperation also enabled the technology transfer between the two labs, as well as access to instrumentation and specialization particular to the two labs.

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