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Articoli di riviste sul tema "Plant viruses Genetics"

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Fraser, R. S. S. "The Genetics of Resistance to Plant Viruses". Annual Review of Phytopathology 28, n. 1 (settembre 1990): 179–200. http://dx.doi.org/10.1146/annurev.py.28.090190.001143.

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de Jager, C. P. "Plant resistance to viruses". Physiological and Molecular Plant Pathology 36, n. 3 (marzo 1990): 265–66. http://dx.doi.org/10.1016/0885-5765(90)90032-s.

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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 e Mark P. Zwart. "The Evolutionary Genetics of Emerging Plant RNA Viruses". Molecular Plant-Microbe Interactions® 24, n. 3 (marzo 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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Roossinck, Marilyn J. "Lifestyles of plant viruses". Philosophical Transactions of the Royal Society B: Biological Sciences 365, n. 1548 (27 giugno 2010): 1899–905. http://dx.doi.org/10.1098/rstb.2010.0057.

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The vast majority of well-characterized eukaryotic viruses are those that cause acute or chronic infections in humans and domestic plants and animals. However, asymptomatic persistent viruses have been described in animals, and are thought to be sources for emerging acute viruses. Although not previously described in these terms, there are also many viruses of plants that maintain a persistent lifestyle. They have been largely ignored because they do not generally cause disease. The persistent viruses in plants belong to the family Partitiviridae or the genus Endornavirus . These groups also have members that infect fungi. Phylogenetic analysis of the partitivirus RNA-dependent RNA polymerase genes suggests that these viruses have been transmitted between plants and fungi. Additional families of viruses traditionally thought to be fungal viruses are also found frequently in plants, and may represent a similar scenario of persistent lifestyles, and some acute or chronic viruses of crop plants may maintain a persistent lifestyle in wild plants. Persistent, chronic and acute lifestyles of plant viruses are contrasted from both a functional and evolutionary perspective, and the potential role of these lifestyles in host evolution is discussed.
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Ali, Zahir, e Magdy M. Mahfouz. "CRISPR/Cas systems versus plant viruses: engineering plant immunity and beyond". Plant Physiology 186, n. 4 (12 maggio 2021): 1770–85. http://dx.doi.org/10.1093/plphys/kiab220.

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Abstract Molecular engineering of plant immunity to confer resistance against plant viruses holds great promise for mitigating crop losses and improving plant productivity and yields, thereby enhancing food security. Several approaches have been employed to boost immunity in plants by interfering with the transmission or lifecycles of viruses. In this review, we discuss the successful application of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) (CRISPR/Cas) systems to engineer plant immunity, increase plant resistance to viruses, and develop viral diagnostic tools. Furthermore, we examine the use of plant viruses as delivery systems to engineer virus resistance in plants and provide insight into the limitations of current CRISPR/Cas approaches and the potential of newly discovered CRISPR/Cas systems to engineer better immunity and develop better diagnostics tools for plant viruses. Finally, we outline potential solutions to key challenges in the field to enable the practical use of these systems for crop protection and viral diagnostics.
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Marwal, Avinash, e Rajarshi Kumar Gaur. "Host Plant Strategies to Combat Against Viruses Effector Proteins". Current Genomics 21, n. 6 (16 settembre 2020): 401–10. http://dx.doi.org/10.2174/1389202921999200712135131.

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Viruses are obligate parasites that exist in an inactive state until they enter the host body. Upon entry, viruses become active and start replicating by using the host cell machinery. All plant viruses can augment their transmission, thus powering their detrimental effects on the host plant. To diminish infection and diseases caused by viruses, the plant has a defence mechanism known as pathogenesis- related biochemicals, which are metabolites and proteins. Proteins that ultimately prevent pathogenic diseases are called R proteins. Several plant R genes (that confirm resistance) and avirulence protein (Avr) (pathogen Avr gene-encoded proteins [effector/elicitor proteins involved in pathogenicity]) molecules have been identified. The recognition of such a factor results in the plant defence mechanism. During plant viral infection, the replication and expression of a viral molecule lead to a series of a hypersensitive response (HR) and affect the host plant’s immunity (pathogen-associated molecular pattern–triggered immunity and effector-triggered immunity). Avr protein renders the host RNA silencing mechanism and its innate immunity, chiefly known as silencing suppressors towards the plant defensive machinery. This is a strong reply to the plant defensive machinery by harmful plant viruses. In this review, we describe the plant pathogen resistance protein and how these proteins regulate host immunity during plant–virus interactions. Furthermore, we have discussed regarding ribosome- inactivating proteins, ubiquitin proteasome system, translation repression (nuclear shuttle protein interacting kinase 1), DNA methylation, dominant resistance genes, and autophagy-mediated protein degradation, which are crucial in antiviral defences.
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Keese, Paul, e Adrian Gibbs. "Plant viruses: master explorers of evolutionary space". Current Opinion in Genetics & Development 3, n. 6 (gennaio 1993): 873–77. http://dx.doi.org/10.1016/0959-437x(93)90007-c.

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Kasschau, Kristin D., e James C. Carrington. "A Counterdefensive Strategy of Plant Viruses". Cell 95, n. 4 (novembre 1998): 461–70. http://dx.doi.org/10.1016/s0092-8674(00)81614-1.

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Kridl, Jean C., e Robert M. Goodman. "Transcriptional regulatory sequences from plant viruses". BioEssays 4, n. 1 (gennaio 1986): 4–8. http://dx.doi.org/10.1002/bies.950040103.

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THRESH, J. M. "The ecology of tropical plant viruses". Plant Pathology 40, n. 3 (settembre 1991): 324–39. http://dx.doi.org/10.1111/j.1365-3059.1991.tb02386.x.

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Tesi sul tema "Plant viruses Genetics"

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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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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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Zambrano, Mendoza Jose Luis. "Genetic Architecture of Resistance to Phylogenetically Diverse Viruses in Maize". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1373285155.

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Torok, Valeria Anna. "Biological and molecular variation among isolates of pea seed borne mosaic virus". Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pht686.pdf.

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Corrigendum inserted at the back. Includes bibliographical references (leaves 133-158). Ch. 1. General introduction -- ch. 2. General materials and methods -- ch. 3. Biological characterisation of Australian PSbMV isolates -- ch. 4. Developing nucleic acid based diagnostics for PSbMV -- ch. 5. Detection of PSbMV isolates by RT-PCR and RFLP analysis -- ch. 6. Developing an internal control for PSbMV RT-PCR -- ch. 7. Molecular analysis of the PSbMV VPG -- ch. 8. PSbMV sequence and phylogenetic analysis -- ch. 9. General discussion Sixteen pea seed borne mosaic virus (PSbMV) isolates were collected between 1995 and 1998. These isolates were biologically distinct yet serologically indistinguishable. The conclusion is that PSbMV is widespread and occurs at a low incidence in Australia. Reports sequence information on new isolates of PSbMV which has allowed genomic regions to be identified which distinguish PSbMV pathotypes and isolates; and, to the development of PSbMV nucleic acid hybridisation and RT-PCR assays.
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Malan, Stefanie. "Real time PCR as a versatile tool for virus detection and transgenic plant analysis". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1921.

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Thesis (MSc (Genetics))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: South Africa is regarded as one of the top wine producing countries in the world. One of the threats to the sustainability of the wine industry is viral diseases of which Grapevine leafroll-associated virus 3 (GLRaV-3) and Grapevine virus A (GVA) are considered to be the most important and wide spread. Scion material is regularly tested for viruses; however scion material is often grafted onto rootstocks that have questionable phytosanitary status. Virus detection in rootstocks is challenging due to low and varying titres, but is imperative as a viral control mechanism. An additional viral control mechanism is the use of transgenic grapevine material which offers resistance to grapevine infection. The objective of this project was to establish a detection system using real time PCR (qPCR) techniques, to accurately and routinely detect GLRaV-3 and GVA in rootstock propagation material. qPCR would furthermore be used to perform molecular characterisation of transgenic plants containing a GLRaV-3 antiviral ΔHSP-Mut construct. A severely infected vineyard (Nietvoorbij farm) in the Stellenbosch area was screened throughout the grapevine growing season to investigate virus prevalence throughout the season and to determine the optimal time for sensitive virus detection. A large scale screening of nursery propagation material for GLRaV-3 infection was also conducted. The qRT-PCR results were compared to DAS-ELISA results to compare the efficacy and sensitivity of the two techniques. For the severely infected vineyard, the ability to detect GLRaV-3 increased as the season progressed towards winter. qRT-PCR was more sensitive and accurate in detecting GLRaV-3 than DASELISA, as the latter technique delivered numerous false positive results later in the season. The best time to screen for GLRaV-3 in the Western Cape region was from the end of July to September. For the nursery screenings, our qRT-PCR results were compared to the results of the DAS-ELISA performed by the specific nurseries. No GLRaV-3 infection was detected in the specific samples received from the two different nurseries. The results for all the samples correlated between the two techniques. This confirms that the propagation material of these nurseries has a healthy phytosanitary status with regards to GLRaV-3. However, the detection of GVA in the severely infected vineyard yielded inconsistent results. Detection ability fluctuated throughout the season and no specific trend in seasonal variation and virus titre fluctuation could be established. The highest percentage of GVA infected samples were detected during September, April and the end of July. Previously published universal primers were used for the detection of GVA, but further investigation indicated that they might not be suitable for sensitive detection of specific GVA variants present in South Africa. Vitis vinifera was transformed with a GLRaV-3 antiviral construct, ΔHSP-Mut. SYBR Green Real time PCR (qPCR) and qRT-PCR were utilised as alternative methods for molecular characterisation of transgenic plants. The qPCR and Southern blot results correlated for 76.5% of the samples. This illustrated the ability of qPCR to accurately estimate transgene copy numbers. Various samples were identified during qRT-PCR amplification that exhibited high mRNA expression levels of the transgene. These samples are ideal for further viral resistance studies. This study illustrated that the versatility of real time PCR renders it a valuable tool for accurate virus detection as well as copy number determination.
AFRIKAANSE OPSOMMING: Suid Afrika word geag as een van die top wyn produserende lande ter wereld. Die volhoubaarheid van die wynbedryf word onder andere bedreig deur virus-infeksies. Grapevine leafroll associated virus 3 (GLRaV-3) en Grapevine virus A (GVA) is van die mees belangrike virusse wat siektes veroorsaak in Suid-Afrikaanse wingerde. Wingerd bo-stok materiaal word gereeld getoets vir hierdie virusse, maar hierdie materiaal word meestal geënt op onderstokmateriaal waarvan die virus status onbekend is. Virus opsporing in onderstokke word egter gekompliseer deur baie lae en variërende virus konsentrasies, maar opsporing in voortplantingsmateriaal is ‘n noodsaaklike beheermeganisme vir virus-infeksie. Die doel van die projek was om ‘n opsporingsisteem te ontwikkel via kwantitatiewe PCR (qPCR) tegnieke vir akkurate en gereelde toetsing van GLRaV-3 en GVA in onderstokmateriaal. qPCR sal ook verder gebruik word vir molekulêre karakterisering van transgeniese plante wat ‘n GLRaV-3 antivirale ΔHSP-Mut konstruk bevat. ‘n Hoogs geïnfekteerde wingerd was regdeur die seisoen getoets om seisoenale fluktuasies in viruskonsentrasie te ondersoek en om die optimale tydstip vir sensitiewe virus opsporing te bepaal. ‘n Grootskaalse toetsing van kwekery voortplantingsmateriaal vir GLRaV-3 infeksie was ook uitgevoer. Die qRT-PCR resultate is met die DAS-ELISA resultate vergelyk om die effektiwiteit en sensitiwiteit van die twee tegnieke te vergelyk. Vir die hoogs geïnfekteerde wingerd het die GLRaV-3 opsporing toegeneem met die verloop van die seisoen tot en met winter. qRT-PCR was meer sensitief en akkuraat as DAS-ELISA in die opsporing van GLRaV-3, weens verskeie vals positiewe resultate wat later in die seisoen deur die laasgenoemde tegniek verkry is. Die beste tyd om vir GLRaV-3 te toets is vanaf einde Julie tot September. Tydens die kwekery toetsings was qRT-PCR resultate met die DAS-ELISA resultate van die spesifieke kwekerye vergelyk. Geen GLRaV-3 infeksie was waargeneem in die spesifieke monsters wat vanaf die kwekerye ontvang is nie. Die resultate van die twee tegnieke het ooreengestem vir al die monsters wat v getoets is. Dit het bevestig dat die voortplantingsmateriaal van hierdie kwekerye gesonde fitosanitêre status met betrekking tot GLRaV-3 gehad het. Die opsporing van GVA in die geïnfekteerde wingerd het egter wisselvallige resultate gelewer. Opsporing van die virus het ook regdeur die seisoen gefluktueer en geen spesifieke neiging in seisoenale opsporingsvermoë kon gemaak word nie. Die hoogste persentasie GVA geïnfekteerde monsters was waargeneem tydens September, April en die einde van Julie. Voorheen gepubliseerde universele inleiers was gebruik vir die opsporing van GVA, maar verdere ondersoeke het getoon dat hierdie inleiers nie noodwendig geskik is vir sensitiewe opsporing van GVA variante wat teenwoordig is in Suid-Afrika nie. Vitis vinifera was getransformeer met ‘n GLRaV-3 antivirale konstruct, ΔHSP-Mut. SYBR Green Real time PCR (qPCR) en qRT-PCR was ingespan as alternatiewe metodes vir molekulêre karaterisering van transgeniese plante. Die qPCR en Southern-klad resultate het ooreengestem vir 76.5% van die monsters. Dit illustreer die vermoë van qPCR om akkurate kopie-getalle van transgene te bepaal. Verskeie plante is geïdentifiseer tydens qRT-PCR amplifisering wat hoë vlakke van transgeen mRNA uitdrukking getoon het. Hierdie monsters is ideaal vir verdere virus weerstandbiedendheids studies. Hierdie studie het die veelsydigheid van real time PCR bewys en getoon dat dit ‘n kosbare tegniek is vir akkurate virus opsporing sowel as kopie-getal bepaling.
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Rathjen, John Paul. "Aspects of luteovirus molecular biology in relation to the interaction between BYDV-PAV and the Yd2 resistance gene of barley /". Title page, contents and summary only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phr2342.pdf.

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Li, Sizhun. "SnRK1-eIF4E Interaction in Translational Control and Antiviral Defense". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417694518.

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Maree, H. J. (Hans Jacob). "The expression of Dianthin 30, a ribosome inactivating protein". Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53633.

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Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Ribosome inactivating proteins (RIPs) are currently classified as rRNA N-glycosidases, but also have polynucleotide: adenosine glycosidase activity. RIPs are believed to have anti-viral and anti-fungal properties, but the exact mechanism of these proteins still need to be elucidated.The mechanism of resistance however, appears to be independent of the pathogen. For resistance the RIP terminates virus infected plant cells and stops the reproduction and spread of the virus. Transgenic plants containing RIPs should thus be resistant to a wide range of viruses. The ultimate goal of the larger project of which this forms part is the development of virus resistant plants. To monitor the expression of a RIP in a transgenic plant a detection method had to be developed. Antibody detection of the RIP was decided upon as the most cost effective method. The RIP, Dianthin 30 from Dianthus caryophyllus (carnation), was used and expressed in bacterial and insect expression systems. The bacterial expression experiments were done using the pET expression system in BL21(DE3)pLysS cells. The expression in this system yielded recombinant protein at a very low concentration. Expression experiments were also performed in insect tissue culture with the baculovirus vector BAC-TO-BAC™.With this system the expression was also too low to be used for the production of antibodies. A Dianthin 30 specific peptide was then designed and then produced by Bio-Synthesis. This peptide was then used to raise antibodies to detect Dianthin 30. These antibodies were tested on Dianthus caryophyllus proteins. To establish if this detection method was effective to monitor the expression in plants, tobacco plants were transformed with Agrobacterium tumefaciens containing Dianthin 30 in the pART27 plant expression vector. The putative transformed plants were analysed with peR and Southern blots.
AFRIKAANSE OPSOMMING: Tans word Ribosomale-inaktiverende proteïene (RIPs) geklassifiseer as rRNA N-glikosidase wat ook polinukleotied: adenosien glikosidase aktiwiteit bevat. Daar word geglo dat RIPs anti-virale en anti-fungus eienskappe bevat, maar die meganisme van beskerming word nog nie ten volle verstaan nie. Dit is wel bewys dat die meganisme van weerstand onafhanklik is van die patogeen. Virus geinfekteerde plantselle word deur die RIP gedood om die voortplanting en verspreiding te bekamp en sodoende word weerstand bewerkstellig. Transgeniese plante wat dan 'n RIP bevat sal dus weerstandbiedend wees teen 'n wye spektrum virusse. Die hoofdoel van die breër projek, waarvan die projek deel uitmaak: is die ontwikkeling van virusbestande plante. Om die uitdrukking van die RIP in die transgeniese plante te kontroleer, moes 'n deteksie metode ontwikkel word. Die mees koste effektiewe deteksie metode is met teenliggame. Die RIP, Dianthin 30 from Dianthus caryophyllus (angelier) was gebruik vir uitdrukking in bakteriele- en insekweefselkultuur. Die bakteriele uitdrukkingseksperimente was gedoen met die pET uitdrukkings sisteem III BL21(DE3)pLysS selle. Die uitdrukking in die sisteem het slegs rekombinante proteïene gelewer in uiters lae konsentrasies. Uitdrukkingseksperimente was ook gedoen in insekweefselkultuur met die baculovirus vektor BAC-To- BACTM. Met die sisteem was die uitdrukking ook veels te laag om bruikbaar te wees vir die produksie van teenliggame. Daar is toe 'n peptied ontwerp wat Dianthin 30 kan verteenwoordig vir die produksie van teenliggame. Die teenliggame is getoets teen Dianthus caryophyllus proteïene. Om vas te stel of die deteksiemetode wel die uitdrukking van Dianthin 30 sal kan monitor, is tabak ook getransformeer met Dianthin 30. Die transformasies is gedoen met die hulp van Agrobacterium tumefaciens en die pART27 plant uitdrukkings vektor. Die plante is getoets met die polimerase ketting reaksie en Southern klad tegnieke.
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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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Vaitkunas, Katrina Emilee. "The genetics of TCV resistance". Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0428103-102720.

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Libri sul tema "Plant viruses Genetics"

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Hull, Roger. Comparative plant virology: Fundamentals of plant virology. 2a ed. Burlington, MA: Elsevier Academic Press, 2009.

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P, Pirone T., Shaw John G e Symposium on Viral Genes and Plant Pathogenesis (1989 : Lexington, Ky.), a cura di. Viral genes and plant pathogenesis. New York: Springer-Verlag, 1990.

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Uyeda, Ichiro, e Chikara Masuta. Plant virology protocols: New approaches to detect viruses and host responses. New York: Humana Press, 2015.

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A, Wilson T. Michael, e Davies Jeffrey W, a cura di. Genetic engineering with plant viruses. Boca Raton: CRC Press, 1992.

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R, Crute I., Holub E. B, Burdon J. J e British Society for Plant Pathology., a cura di. The gene-for-gene relationship in plant-parasite interactions. Wallington, UK: CAB International, 1997.

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Warmbrodt, Robert D. Biotechnology, plant protection from agents other than viruses: January 1988 - March 1991. Beltsville, Md: National Agricultural Library, 1991.

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M, Kyle Molly, a cura di. Resistance to viral diseases of vegetables: Genetics & breeding. Portland, Or: Timber Press, 1993.

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Ponce, Claudia Ortega. Relaciones sociales y de genes: El primer vegetal transgénico mexicano. México, D.F: Universidad Autónoma del Estado de México, Facultad de Ciencias Políticas y Sociales, 2010.

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Thompson, Winston M. O. The Whitefly, Bemisia tabaci (Homoptera: Aleyrodidae) Interaction with Geminivirus-Infected Host Plants: Bemisia tabaci, Host Plants and Geminiviruses. Dordrecht: Springer Science+Business Media B.V., 2011.

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King, Robert C. Handbook of Genetics: Plants, Plant Viruses, and Protists. Springer, 2013.

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Capitoli di libri sul tema "Plant viruses Genetics"

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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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Fraser, R. S. S. "Genetics of Plant Resistance to Viruses". In Ciba Foundation Symposium 133 - Plant Resistance to Virus, 6–22. Chichester, UK: John Wiley & Sons, Ltd., 2007. http://dx.doi.org/10.1002/9780470513569.ch2.

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Fraser, R. S. S. "Genetics of Host Resistance to Viruses and of Virulence". In Mechanisms of Resistance to Plant Diseases, 62–79. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5145-7_4.

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Ricci, Angela, Silvia Sabbadini, Laura Miozzi, Bruno Mezzetti e Emanuela Noris. "Host-induced gene silencing and spray-induced gene silencing for crop protection against viruses." In RNAi for plant improvement and protection, 72–85. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789248890.0008.

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Abstract Since the beginning of agriculture, plant virus diseases have been a strong challenge for farming. Following its discovery at the very beginning of the 1990s, the RNA interference (RNAi) mechanism has been widely studied and exploited as an integrative tool to obtain resistance to viruses in several plant species, with high target-sequence specificity. In this chapter, we describe and review the major aspects of host-induced gene silencing (HIGS), as one of the possible plant defence methods, using genetic engineering techniques. In particular, we focus our attention on the use of RNAi-based gene constructs to introduce stable resistance in host plants against viral diseases, by triggering post-transcriptional gene silencing (PTGS). Recently, spray-induced gene silencing (SIGS), consisting of the topical application of small RNA molecules to plants, has been explored as an alternative tool to the stable integration of RNAi-based gene constructs in plants. SIGS has great and innovative potential for crop defence against different plant pathogens and pests and is expected to raise less public and political concern, as it does not alter the genetic structure of the plant.
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Ricci, Angela, Silvia Sabbadini, Laura Miozzi, Bruno Mezzetti e Emanuela Noris. "Host-induced gene silencing and spray-induced gene silencing for crop protection against viruses." In RNAi for plant improvement and protection, 72–85. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789248890.0072.

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Abstract Since the beginning of agriculture, plant virus diseases have been a strong challenge for farming. Following its discovery at the very beginning of the 1990s, the RNA interference (RNAi) mechanism has been widely studied and exploited as an integrative tool to obtain resistance to viruses in several plant species, with high target-sequence specificity. In this chapter, we describe and review the major aspects of host-induced gene silencing (HIGS), as one of the possible plant defence methods, using genetic engineering techniques. In particular, we focus our attention on the use of RNAi-based gene constructs to introduce stable resistance in host plants against viral diseases, by triggering post-transcriptional gene silencing (PTGS). Recently, spray-induced gene silencing (SIGS), consisting of the topical application of small RNA molecules to plants, has been explored as an alternative tool to the stable integration of RNAi-based gene constructs in plants. SIGS has great and innovative potential for crop defence against different plant pathogens and pests and is expected to raise less public and political concern, as it does not alter the genetic structure of the plant.
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Fraenkel-Conrat, H. "Viruses". In Genetic Flux in Plants, 3–10. Vienna: Springer Vienna, 1985. http://dx.doi.org/10.1007/978-3-7091-8765-4_1.

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García-Arenal, F., A. Fraile e J. M. Malpica. "Genetic Variability and Evolution". In Molecular Biology of Plant Viruses, 143–59. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-1-4615-5063-1_6.

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Whitham, Steven A., e M. R. Hajimorad. "Plant Genetic Resistance to Viruses". In Current Research Topics in Plant Virology, 87–111. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32919-2_4.

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Ali, Akhtar, e Marilyn J. Roossinck. "Genetic Bottlenecks". In Plant Virus Evolution, 123–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-75763-4_7.

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Verma, Rakesh Kumar, Ritesh Mishra e Rajarshi Kumar Gaur. "Potato Virus Y Genetic Variability: A Review". In Plant Viruses: Evolution and Management, 205–14. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1406-2_12.

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Atti di convegni sul tema "Plant viruses Genetics"

1

"Bacillus bacteria in the resistance of potato plants to viruses". In 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/plantgen2019-035.

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"Endophytic bacteria of the Bacillus induce resistance of potato plants to viruses". In Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Novosibirsk ICG SB RAS 2021, 2021. http://dx.doi.org/10.18699/plantgen2021-029.

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"Efficient eradication of potato viruses by induction of posttranscriptional gene silencing in transgenic potato". In 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/plantgen2019-009.

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"VirHunter: a deep learning-based method for detection of novel viruses in plant sequencing data". In Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Novosibirsk ICG SB RAS 2021, 2021. http://dx.doi.org/10.18699/plantgen2021-196.

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Marii, Liliana, Larisa Andronic, Svetlana Smerea e Natalia Balasova. "Evaluarea rolului genotipului în răspunsul antioxidativ la tomatele infectate cu virusuri". In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.41.

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Studying the particularities of manifestation of defensive indicators – POX and PPO in case of in-fection with 2 types of viruses of different virus-host combinations (sensitive, tolerant, resistant) was per-formed in basis of analysis of variance. The obtained results denote a significant contribution of all ana-lyzed factors in the variability of PPO and POX indices, the major contribution returning to the genotype, followed by viral infection, the type of viral infection with a variable dose of contribution depending on the applied matrix. The PPO index expressed a higher specificity of the genotype response depending on the virus applied compared to POX. At the same time, it was found that TAV had a higher contribution in the variability of POX and PPO, compared to TMV.
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"Potential of ribonuclease-sinthesizing plant growth promoting rhizobacteria in plant defence against viruses". In Current Challenges in Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences Novosibirsk State University, 2019. http://dx.doi.org/10.18699/icg-plantgen2019-24.

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Салтанович, Татьяна, Людмила Анточ e А. Дончилэ. "Особенности мужского гаметофита томата в условиях вирусного патогенеза и водного дефицита". In VIIth International Scientific Conference “Genetics, Physiology and Plant Breeding”. Institute of Genetics, Physiology and Plant Protection, Republic of Moldova, 2021. http://dx.doi.org/10.53040/gppb7.2021.25.

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On the example of F1 hybrid combinations and tomato varieties, the possibility of the assessing method for pollen selection on the responses of male gametophytes under conditions of viral pathogenesis and drought has been shown. It was found the action of factors on the pollen viability and on the rate of pollen tubes growth, leading to the manifestation of differential reactions. The viruses are the main sources of variability of the pollen functional traits, while the effect of water deficit and genotype are considerably weaker. Genotypes that combine the high viability of pollen with the ability to form longer pollen tubes under the complementary action of viruses and water deficit have been identified, suggesting the prospect of these genotypes using in further breeding studies.
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"Development of a new method for eradication of viruses by induction of posttranscriptional gene silencing in transgenic potato plants". In Current Challenges in Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences Novosibirsk State University, 2019. http://dx.doi.org/10.18699/icg-plantgen2019-46.

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"Drought resistance in some Prunus persica (L.) Batsch cultivars damaged with Plum Pox Virus". In 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/plantgen2019-034.

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"Plant virus genome studies using novel databases and bioinformatics tools for text compression and entropy". In Plant Genetics, Genomics, Bioinformatics, and Biotechnology. Novosibirsk ICG SB RAS 2021, 2021. http://dx.doi.org/10.18699/plantgen2021-080.

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Rapporti di organizzazioni sul tema "Plant viruses Genetics"

1

Dawson, William O., e Moshe Bar-Joseph. Creating an Ally from an Adversary: Genetic Manipulation of Citrus Tristeza. United States Department of Agriculture, gennaio 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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Mawassi, Munir, e Valerian V. Dolja. Role of the viral AlkB homologs in RNA repair. United States Department of Agriculture, giugno 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 e Munir Mawassi. Role of Defective RNAs in Citrus Tristeza Virus Diseases. United States Department of Agriculture, settembre 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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Gera, Abed, Abed Watad, P. Ueng, Hei-Ti Hsu, Kathryn Kamo, Peter Ueng e A. Lipsky. Genetic Transformation of Flowering Bulb Crops for Virus Resistance. United States Department of Agriculture, gennaio 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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Ullman, Diane, James Moyer, Benjamin Raccah, Abed Gera, Meir Klein e Jacob Cohen. Tospoviruses Infecting Bulb Crops: Evolution, Diversity, Vector Specificity and Control. United States Department of Agriculture, settembre 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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Dolja, Valerian V., Amit Gal-On e Victor Gaba. Suppression of Potyvirus Infection by a Closterovirus Protein. United States Department of Agriculture, marzo 2002. http://dx.doi.org/10.32747/2002.7580682.bard.

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

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Abstract (sommario):
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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Levin, Ilan, John Thomas, Moshe Lapidot, Desmond McGrath e Denis Persley. Resistance to Tomato yellow leaf curl virus (TYLCV) in tomato: molecular mapping and introgression of resistance to Australian genotypes. United States Department of Agriculture, ottobre 2010. http://dx.doi.org/10.32747/2010.7613888.bard.

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Abstract (sommario):
Tomato yellow leaf curl virus (TYLCV) is one of the most devastating viruses of cultivated tomatoes. Although first identified in the Mediterranean region, it is now distributed world-wide. Sequence analysis of the virus by the Australian group has shown that the virus is now present in Australia. Despite the importance of the disease and extensive research on the virus, very little is known about the resistance genes (loci) that determine host resistance and susceptibility to the virus. A symptom-less resistant line, TY-172, was developed at the Volcani Center which has shown the highest resistance level among all tested varieties. Preliminary results show that TY-172 is a good candidate to confer resistance to both TYLCV and to Tomato leaf curl virus (ToLCV) in Queensland conditions. Furthermore, Segregation analysis has previously indicated that the resistance is determined by 2-3 genes. In this proposal we aimed to substantiate that TY-172 can contribute to resistance breeding against TYLCV in Queensland, to develop DNA markers to advance such resistance breeding in both Israel and Queensland, and to exploit these markers for resistant breeding in Australian and Israeli lines. To map quantitative trait loci (QTLs) controlling TYLCVresistance in TY172, appropriate segregating populations were analyzed using 69 polymorphic DNA markers spanning the entire tomato genome. Results show that TYLCV resistance in TY172 is controlled by a previously unknown major QTL, originating from the resistant line, and four additional minor QTLs. The major QTL, termed Ty-5, maps to chromosome 4 and accounts for 39.7-to-46.6% of the variation in symptom severity among segregating plants (LOD score: 33-to-35). The minor QTLs, originated either from the resistant or susceptible parents, were mapped to chromosomes 1, 7, 9 and 11, and contributed 12% to the variation in symptom severity in addition to Ty-5. Further analysis of parental lines as well as large F₁, BC₁F₁, F₂ and BC₁F₂ populations originating from crosses carried out, in reciprocal manner, between TY172 and the susceptible processing line M-82 (LA3475) during spring-summer 2010, indicated that: (1) the minor QTLs we have previously identified are in effect not reproducible, (2)Ty-5 alone can yield highly resistant plants with practically no extra-chromosomal effects, and (3) the narrow-sense heritability estimate of resistance levels, attributed to additive factors responsive to selection, does not significantly deviate from 1. All of these results point to Ty-5 as the sole resistance locus in TY172 thus significantly increasing the likelihood of its successful molecular dissection. The DNA markers developed during the course of this study were transferred together with the TY172 genotype to Queensland. TY172 was crossed to a panel of Australian genotypes and the resulting populations were subjected to segregation analysis. Results showed that resistant locus, Ty-5, is highly reproducible in the Australian conditions as well. The Australian group was also able to make improvements to the marker assays by re-designing primer pairs to provide more robust PCR fragments. The Ty-5 locus has now been introgressed into elite Australian germplasm and selection for TYLCV resistance has begun. Cumulatively, our results show that Ty-5 can be effectively used, together with the TY172 genotype to expedite TYLCV resistance breeding and improve our understanding of the genetics that underline the response of tomato to TYLCV. Contributions to agriculture include: (1) the development of tools for more efficient resistance breeding, allowing the incorporation of resistance to local tomato varieties in Australia, Israel and elsewhere; and (2) establish a solid framework for a future attempt to clone the genes that encode such resistance. The latter will enable to decipher the resistance mechanisms that could be applied to other geminiviruses in tomato and possibly in other plant species.
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Mawassi, Munir, Baozhong Meng e Lorne Stobbs. Development of Virus Induced Gene Silencing Tools for Functional Genomics in Grapevine. United States Department of Agriculture, luglio 2013. http://dx.doi.org/10.32747/2013.7613887.bard.

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Abstract (sommario):
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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10

Avni, Adi, e Kirankumar S. Mysore. Functional Genomics Approach to Identify Signaling Components Involved in Defense Responses Induced by the Ethylene Inducing Xyalanase Elicitor. United States Department of Agriculture, dicembre 2009. http://dx.doi.org/10.32747/2009.7697100.bard.

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Abstract (sommario):
Plant-microbe interactions involve a large number of global regulatory systems, which are essential for plants to protect themselves against pathogen attack. An ethylene-inducing xylanase (EIX) of Trichoderma viride is a potent elicitor of plant defense responses, like hypersensitive response (HR), in specific cultivars of tobacco (Nicotiana tabacum) and tomato (Lycopersicon esculentum). The central goal of this proposal was to investigate the molecular mechanisms that allow plants to specifically activate defense responses after EIX treatment. We proposed to identify cellular signaling components involved in the induction of HR by the EIX elicitor. The molecular genetic analysis of the signal transduction pathway that modulates hypersensitive responses is an important step in understanding the induction of plant defense responses. The genes that mediate LeEIX2-EIX dependent activation of resistance mechanisms remain to be identified. We used two approaches to identify the cellular signaling components that induce HR mediated by the EIX elicitor. In the first approach, we performed a yeast two-hybrid screening using LeEix2 as bait to identify plant proteins that interact with it. In the second approach, we used virus-induced gene silencing (VIGS) for a high-throughput screen to identify genes that are required for the induction of LeEIX2-EIX mediated HR. VIGS will also be used for functional characterization of genes that will be identified during the yeast two-hybrid screen. This investigation will shed light on cellular processes and signaling components involved in induction of general plant defense against pathogens and will provide the basis for future biotechnological approaches to improve plant resistance to pathogens. Several genes were indentified by the two approaches. We used the VIGS and yeast two hybrid approaches to confirm that activity of the genes initially identified by different procedure. Two genes inhibit the induction of HR by the fungal elicitor in the different systems; Tobacco-Harpin binding protein 1 and cyclopropyl isomerase.
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