Progress 07/01/06 to 06/30/11
Outputs
OUTPUTS: Research on Cereal Yellow Dwarf Luteovirus (CYDV) utilizing differential gel electrophoresis and tandem mass spectrophotometry identified 4 aphid proteins specifically correlated with vector transmission phenotype in efficient vector clones of Schizaphis graminum. Two proteins were identified as cyclophilin and luciferase-like proteins. Biological assays involving hemolymph recovery of virus and EM were used to verify transmission barriers in vector and nonvector aphid clones. Use of EDTA or sodium sulfite in virus purification eliminated CYDV aphid transmissibility and was used to identify CYDV-bound host plant proteins associated with efficient CYDV transmission. Indigenous clover-infecting strains of Soybean Dwarf Virus (SbDV) were identified and sequenced. Transmission studies of SbDV verified the newly introduced soybean aphid, Aphis glycines, is capable of transmitting SbDV from clover to soybean. PCR primers were developed and used to study the adaptation of SbDV to pea and soybean hosts following multiple sequential aphid transmissions. Host adaptation correlated with specific mutations of the SbDV replicase gene. However, bottle-necks associated with aphid transmission eliminated transmission from soybean to soybean preventing successful maintenance of SbDV in soybean hosts. Data suggests severe trade-off effects associated with adaptation to soybean. Research on Zucchini Yellow Mosaic Virus verified cucurbit seed transmission resulting in symptomless infected seedlings capable of sustaining aphid vector virus acquisition and initiating horizontal ZYMV transmissions by Myzus persicae. Studies indicated that PCR testing of cucurbit seed is essential for identifying low titer seedborne ZYMV. Field studies of the legume strain of Cucumber Mosaic Virus (CMV) identified 30 species of aphids visiting bean fields in NY and PA. Of these, 12 species were tested for vector transmission efficiency. Two species, including the newly invasive Aphis glycines, were identified as very efficient vectors. Statistical models based on multiple aphid transmission tests were developed and tested by single aphid transmission to verify the validity of models. Plum pox virus (PPV) research focused on identifying migrant aphid species entering stone fruit orchards and determining which of these aphid species were most competent for transmitting PPV from infected to healthy trees. Results identified Myzus persicae and Aphis spiraecola as the most efficient vectors in Pennsylvania, and density data suggested that A. spiraecola is by far the most prevalent vector and likely responsible for most PPV spread. Biocontainment Greenhouse studies verified PPV transmission from infected mature fruit to stone fruit seedling trees by different aphid species. We also demonstrated the ability of PPV to genetically adapt to other herbaceous plant species through mutation of the replicatase gene. PARTICIPANTS: Project leader for project 4141 entitled "Mechanisms regulating plant virus transmission by aphid vector populations" is F.E. Gildow. Departmental collaborators included post doctoral researcher, Dr. Kari Peter, Ph.D. candidate, Bin Tian, and staff research assistant, William Sackett. Interdepartmental research collaborators include Dr. Diana Cox-Foster and Dr. Shelby Fleischer, Dept. of Entomology; and Dr. A.G. Stephenson and Dr. H.E. Simmons, Dept. of Biology, Penn State University. External collaborators include Dr. Stewart Gray, Dr. Ted Thannhauser, and Dr. Michelle Cilia, USDA-ARS, Ithaca, NY; Dr. Bill Schneider and Dr. Vernon Damsteegt, USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, Frederick, MD; and Dr. Michelle Cilia, Cornell University, Ithaca, NY. Technical support personnel included William Sackett, Penn State University; and Andrew Stone and Diana Sherman, USDA Foreign Disease and Weed Lab, Ft. Detrick, MD. Funding supporting this research was from USDA CSREES NRI Grants (96-01120, 2005-35604-15446 and the USDA-ARS (Project 58-1920-5-557). TARGET AUDIENCES: Research on luteovirus vector specificity of CYDV and host and vector adaptations by SbDV are of primary interest to scientists and students in the area of cellular and molecular mechanisms regulating plant virus- insect vector specificity and plant virus microevolution. Research on legume strains of Cucumber Mosaic Virus, Plum Pox Virus, and Zucchini Yellow Mosaic Virus is of scientific interest for understanding epidemiological models for disease spread; and of practical value to plant breeders and extension educators for developing disease control strategies. Results with a scientific focus are disseminated through publications in professional journals such as the Journal of General Virology, Phytopathology, and Plant Disease; and by professional presentations at national and international scientific meetings such as those of the American Entomological Society, The International Plant Virus Epidemiology Symposia, the Plant Virus Ecology Network, and the American Phytopathological Society. Results with practical applications are disseminated through industry extension presentations, and meetings such as the annual Mid-Atlantic Vegetable Conference. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our studies of luteovirus-aphid vector specificity using CYDV and genetically similar F2 clones of Schizaphis graminum are among the most detailed studies of virus-vector transmission available. These studies utilize a combination of virus and aphid genetics, aphid proteomics, receptor recognition studies, and aphid ultrastructure to identify the route of luteovirus through aphid vectors and the molecular mechanisms controlling this cellular process. This pioneering work provides a model for subsequent studies of other virus-vector systems. Understanding these processes will be essential for developing genetically engineered solutions to plant virus diseases spread by insect vectors. Studies of SbDV were significant for increasing understanding of how this virus commonly infecting clovers throughout the eastern U.S. might adapt to other legume hosts, such as soybeans, and initiate disease epidemics in economically important crops. Results indicated that SbDV rapidly adapted to pea and soybean host measured by increased virus concentrations, increased symptom severity, and reduced time to symptom development. Fortunately, adaptation to the soybean host indicated by increasing virus concentrations was accompanied by a decrease in aphid transmission efficiency until aphid transmission ceased. Thus, a trade-off between virus titer and transmission would suggest that SbDV must overcome several genetic hurdles before adapting to soybean. Studies of seed transmission of ZYMV are significant in verifying that ZYMV is seedborne in cucurbit seeds from infected plants but can be detected reliably only through use of PCR diagnostic techniques. In addition, seedlings growing from ZYMV-infected seeds are typically symptomless with very low virus titers. However, these seedlings are fully capable of acting as reservoirs for aphid vector acquisition of ZYMV and transmission to other plants. It is suggested that testing for seedborne viruses rely more on PCR detections. Data from CMV studies on aphid species diversity and populations in bean crops coupled with aphid species CMV-transmission efficiency data is being used to develop management strategies for controlling CMV spread in bean production. Results of PPV studies on aphid vector identification, fruit transmission, and virus strain distribution are being used to develop eradication protocols by USDSA-APHIS-PPQ and Canadian CIFA.
Publications
- Schneider, W. L., V. D. Damsteegt, F. E. Gildow, A. L. Stone, D. J. Sherman, L. E. Levy, V. Mavrodieva, N. Richwine, R. Welliver, and D. G. Luster. 2011. Molecular, Ultrastructural, and Biological Characterization of Pennsylvania Isolates of Plum Pox virus. Phtypathology 101:627-636.
- Simmons, H. E., E. C. Holmes, F. E. Gildow, M. A. Bothe-Goralczyk, and A. G. Stephenson. 2011. Experimental verification of seed transmission of zucchini yellow mosaic virus. Plant Disease 95:751-754.
- Damsteegt, V. D., A. L. Stone, M. Kuhlmann, F. E. Gildow, L. L. Domier, D. J. Sherman, B. Tian, and W. L. Schneider. 2011. Acquisition and transmissibility of U.S. Soybean dwarf virus isolates by the soybean aphid, Aphis glycines. Plant Dis. 95:945-950.
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: Studies combining mass spectrometry, ultrastructural electron microscopy, and biological virus transmission studies were used to identify aphid proteins associated with transmission of cereal yellow dwarf luteovirus (CYDV). In addition, host plant proteins associated with purified CYDV were found to influence efficient virus transmission by aphid vectors. Use of EDTA and sodium sulfite in virus purification media reduced or eliminated specific host plant proteins associated with CYDV particles and reduced or eliminated virus transmission. Thus additives to virus purification protocols can influence critical virus-protein interactions required for biological competency. Hemolymph recovery assays, virus microinjection, and EM were used to verify CYDV acquisition and transmission barriers in vector and nonvector genetic clones of Schizaphis graminium. Work is underway to identify specific aphid proteins associated with virus recognition and transport through vector cells at the hindgut and salivary gland barriers regulating virus transmission. Studies of soybean dwarf luteoviruses are focused on the effects of new aphid vectors and new host species on virus transmission. Clover infecting indigenous strains of SbDV were transmitted effectively to pea by the clover aphid but only inefficiently to soybeans by the clover aphid and the newly introduced soybean aphid. Sequential transmission in pea resulted in increased virus titers and increased transmission efficiency. Sequential transmission in soybean also resulted in host adaptation indicated by increased virus titer (replication), but reduced transmission efficiency. Sequence analysis indicated that specific mutations in soybean associated with increased replication were also associated with loss of aphid transmission. These results suggest that soybeans are not a viable alternative host for SbDV and unlikely to support SbDV epidemics. PARTICIPANTS: Project leader for project 4141 entitled "Mechanisms regulating plant virus transmission by aphid vector populations" is F.E. Gildow. Departmental collaborators included post doctoral researcher, Dr. Kari Peter, Ph.D. candidate, Bin Tian, and staff research assistant, William Sackett. Interdepartmental research collaborators include Dr. Diana Cox-Foster and Dr. Shelby Fleischer, Department of Entomology, Penn State University. External collaborators include Dr. Stewart Gray and Dr. Ted Thannhauser, USDA-ARS, Ithaca, NY; Dr. Bill Schneider and Dr. Vernon Damsteegt, USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, Frederick, MD; and Dr. Michelle Cilia, Cornell University, Ithaca, NY. Technical support personnel included William Sackett, Penn State University; and Andrew Stone and Diana Sherman, USDA Foreign Disease and Weed Lab, Ft. Detrick, MD. Funding supporting this research was from USDA CSREES NRI Grants (96-01120, 2005-35604-15446 and the USDA-ARS (Project 58-1920-5-557). TARGET AUDIENCES: This research is of primary interest to scientists and students in the area of cellular and molecular mechanisms regulating plant virus-insect vector specificity. Results of our work are disseminated through publications in professional journals such as the Journal of General Virology or Phytopathology, and by professional presentations at national and international scientific meetings such as those of the American Entomological Society, The International Plant Virus Epidemiology Symposia, the Plant Virus Ecology Network, and the American Phytopathological Society. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Our research on molecular and cellular mechanisms regulating aphid transmission of plant luteoviruses, such as barley yellow dwarf virus and cereal yellow dwarf virus is some of the most detailed work available on vector specificity mechanisms. We are among the first researchers to discover and describe insect vector proteins associated with recognition, cellular movement, and transmission of viruses through insects. This information has relevance as a model system for studies of all insect vectored viruses infecting plants and animals. Understanding these mechanisms is essential for developing genetically engineered solutions to many plant virus diseases spread by homopteran insect vectors. Work on soybean dwarf virus is focused on understanding the probability of virus mutation in response to exposure to new hosts and new vector species. We are identifying specific genes and specific mutations associated with evolutionary adaptation to new pathogen environments. This work is important for understanding how viruses adapt under various selection pressures allowing virus epidemics. This work will allow development of models allowing better risk analysis of invasive viruses and vectors .
Publications
- Tian, B., W. L. Schneider, and F. E. Gildow. 2010. The effect of new aphid vectors on the evolution of soybean dwarf virus. Phytopathology 100:S126.
- Peter, K., M. Cilia, F. Gildow, T. Thannhauser, and S. Gray. 2010. Host proteins implicated in the aphid transmission of cereal yellow dwarf virus-RPV. Phytopathology 100:S100.
- Tian, B., W. L. Schneider, and F. E. Gildow. 2010. Adaptation of soybean dwarf virus to new host species. Proceedings of the 11th International Plant Virus Epidemiology Symposium. Cornell University, Ithaca, NY. June 20-24. p. 62. (Abstract).
- Schneider, W. L., A. L. Stone, B. Tian, F. E. Gildow, and V. D. Damsteegt. 2010. Balancing selection for replication and horizontal transmission by mimicking field conditions. Proceedings of the 11th International Plant Virus Epidemiology Symposium. Cornell University, Ithaca, NY. June 20-24. p. 54. (Abstract).
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Our studies focus on three virus-vector systems involving aphid transmission of cereal yellow dwarf luteovirus (CYDV), soybean dwarf luteovirus (SbDV), and legume-infecting strains of cucumber mosaic virus (CMV-Le). CMV is a reemerging invasive species of virus responsible for CMV epidemics reported throughout the eastern US in commercial snap bean crops. Multiple-vector transmission tests were used to develop statistical models for estimating vector transmission efficiency. These models and corresponding field studies have been used to identify the four major vectors of CMV in NY and PA. Studies of the temporal dispersal trends of different aphid vectors and the incidence of CMV in sequentially planted bean crops are being used to develop recommended control strategies. Greenhouse studies of bean cultivars currently grown in NY and PA failed to identify host resistance to CMV-Le. Studies of CYDV have identified a genetic basis for CYDV vector-specificity in vector and nonvector clones of the greenbug aphid, Schizaphis graminum. Mass spectrometry and ultrastructural studies have indicated several aphid proteins associated with ability of aphids to transmit CYDV and the aphid tissues associated with the route of CYDV circulating through vectors. Consistent alterations of the CYDV capsid protein resulting from virus purification protocols have indicated sites on the virus required for transmission. For SbDV studies, we have developed several DNA primers for use in PCR studies to identify strains of SbDV in the eastern U.S. The RNA genome of the MD6 isolate of SbDV collected from an infected clover plant surrounding USDA soybean breeding plots in Beltsville, MD has been sequenced. Studies are underway to identify genomic mutations of MD6 required for enhanced infection of new crop hosts, such as, soybean (Glycines max) and pea (Pisum sativum). Specific mutations associated with the adaptation of clover-infecting strains of SbDV to new hosts have been identified. Genetic bottle necks and selective pressures on SbDV by aphid species with different SBDV transmission efficiencies are in progress. The goals of these projects are to understand the molecular mechanisms regulating aphid vector-specificity for transmission of plant infecting viruses and to gain a better understanding of the role of vector-specificity in plant virus epidemiology. PARTICIPANTS: Project leader is F.E. Gildow. Departmental collaborators included post doctoral researcher, Dr. Kari Peter, Ph.D. candidate, Bin Tian, and staff research assistant, William Sackett. Interdepartmental research collaborators include Dr. Diana Cox-Foster and Dr. Shelby Fleischer, Dept. of Entomology, Penn State University. External collaborators include Dr. Stewart Gray, USDA-ARS, Ithaca, NY and Brian Nault and Denis Shaw, Cornell University, Ithaca, NY and Dr. Bill Schneider, USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, Frederick, MD. Technical support personnel included William Sackett, Penn State University; Andrew Stone and Diana Sherman, USDA Foreign Disease and Weed Lab, Ft. Detrick, MD. Funding supporting this research was from USDA CSREES NRI Grants (96-01120, 2005-35604-15446), The Pennsylvania Department of Agriculture (ME445583), the Pennsylvania Vegetable Growers Association, The New York Vegetable Research Council, and the USDA-ARS (Project 58-1920-5-557). TARGET AUDIENCES: Field studies of CMV in legume crops are being carried out in collaboration with County Extension personnel and with the assistance of personnel associated with Hanover Foods, Inc. Results of this work are being disseminated through Extension presentations to grower groups in NY and PA, and through regional meetings, such as, the Annual Mid-Atlantic Vegetable Conference held each January in Hersey, PA. Results of these studies are being published in scientific journals (Environ. Entomology and Phytopathology). Research results of interest to workers in the area of virus-vector interactions are being disseminated through publications in professional journals and professional presentations at national and international scientific meetings such as those of the American Entomological Society and the American Phytopathological Society (Phytopathology 99:S153). PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Previous work on CMV epidemics in snap beans developed statistical probability models allowing precise estimates of aphid vector efficiency associated with incidence of CMV in commercial bean fields. This work indicated that the newly introduced soybean aphid, Aphis glycines is an extremely effective vector of CMV, however, it is not the only vector of major concern. Current work has identified four principle aphid vectors of CMV in bean crops and indicated crop production techniques for effective controls. This information is being used in developing control recommendations for growers. This work was supported by the Pennsylvania Department of Agriculture, The PA Vegetable Growers Assoc., NY Vegetable Research Council, and Hanover Food Corporation. To date, outputs on SbDV and CYDV have been primarily outputs of scientific data to the scientific plant virus-vector community. Both of these projects are focused on accumulating new biological and molecular information to allow a better understanding of the cellular and molecular mechanisms regulating plant virus transmission by insect vectors. We believe that this knowledge will be required to develop new innovative control strategies to manage plant virus diseases spread by insect vectors.
Publications
- Nault, B.A., D.A. Shah, K.E. Straight, A.C. Bachmann, W.M. Sackett, S.J. Fleischer, and F.E. Gildow. 2009. Modeling temporal trends in aphid vector dispersal and cucumber mosaic virus epidemics in snap bean. Environ. Entomol. 38:1347-1359.
- Peter, K., F.E. Gildow, P. Palukaitis, and S.M. Gray. 2009. The C terminus of the Polerovirus P5 Readthrough domain limits virus infection to the phloem. J. Virology 83:5419-5429.
- Gildow, F.E. and S.M. Gray. 2009. Vector and virus proteins contributing to the regulation of yellow dwarf virus (Luteoviridae) transmission by aphids. Phytopathology 99:S153.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: The overall goals of this project are to understand the molecular mechanisms regulating aphid vector-specificity for transmission of plant infecting viruses and to gain a better understanding of the role of vector-specificity in plant virus epidemiology. Future development of targeted control strategies for plant diseases induced by viruses and modeling of plant virus epidemics will require detailed knowledge related to virus-vector interactions influencing virus survival and spread. Over the past year our studies have focused on three virus-vector systems involving aphid transmission of cereal yellow dwarf luteovirus (CYDV), soybean dwarf luteovirus (SbDV), and a legume-infecting strain of cucumber mosaic virus (CMV). Continued study of CMV has identified major vector species responsible for CMV epidemics reported throughout the eastern US in commercial snap bean crops. Recently, we have tested statistical models based on multiple-vector transmission tests for estimating vector transmission efficiency. These models were recently shown to accurately predict vector competency when tested. SbDV studies are focused on identifying the major vectors of North American strains of the virus infecting perennial legume crops, such as clovers. Surveys are underway to identify stains of SbDV indigenous to the Mid-Atlantic States. To date, 4 distinct strains have been identified in our lab that are vectored by at least 3 aphid species. New primers were developed allowing more effective PCR for identification of strains. Current experiments are focused on developing SbDV purification strategies for use in characterization and transmission studies; and on studies of SbDV mutations allowing potential adaptation and infection of soybean crops as a new host. Our third area of emphasis involves studies of aphid proteins correlated with genetic competence of the aphid Schizaphis graminum to transmit CYDV. We continue to identify additional proteins identified only in vector clones of S. graminum. These proteins are being characterized for subsequent synthesis and antibody production. Ultrastructural and immunohistochemical studies were initiated to identify cellular sites in aphid vectors that regulate circulative transmission. PARTICIPANTS: Project leader for project 4141 entitled "Mechanisms regulating plant virus transmission by aphid vector populations" is F.E. Gildow. Interdepartmental research collaborators include Dr. Diana Cox-Foster and Dr. Shelby Fleischer, Dept. of Entomology, Penn State University. External collaborators include Dr. Stewart Gray and Dr. Xiaolong Yang, USDA-ARS, Ithaca, NY and Brian Nault and Denis Shaw, Cornell University, Ithaca, NY and Dr. Bill Schneider, USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, Frederick, MD. Technical support personnel included William Sackett, Penn State University; and Andrew Stone and Diana Sherman, USDA Foreign Disease and Weed Lab, Ft. Detrick, MD. TARGET AUDIENCES: Field studies of CMV in legume crops are being carried out in collaboration with County Extension personnel and with the assistance of personnel associated with Hanover Foods, Inc. Results of this work are being disseminated through Extension presentations to grower groups and through meetings such as the annual Mid-Atlantic Vegetable Conference. Results of these studies are being published in scientific journals. Research results of interest to workers in the area of virus-vector interactions will be and are being disseminated through publications in professional journals and professional presentations at national and international scientific meetings such as those of the American Entomological Society and the American Phytopathological Society. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Recent publication of multiple- and single-vector transmission test data was used to develop statistical probability models allowing precise estimates of aphid vector efficiency associated with incidence of CMV in commercial bean fields. These models were used to determine which aphid species are associated with CMV epidemics in beans. This information is being used in additional studies of CMV epidemiology and in developing control recommendations for growers. This work indicated that the newly introduced soybean aphid, Aphis glycines is an extremely effective vector of CMV, however, it is not the only vector of major concern. This work was supported by the Pennsylvania Department of Agriculture and Hanover Food Corporation. For SbDV studies we have developed several effective primers for use in PCR studies to characterize various strains of SbDV in the eastern US. The enhanced PCR methods will allow more effective SbDV identification in ongoing surveys in MD, NY, and PA legume crops.
Publications
- Gildow, F.E., D.A. Shah, W.M. Sackett, T. Butzler, B.A. Nault, and S.J. Fleischer. 2008. Transmission efficiency of Cucumber mosaic virus by aphids associated with epidemics in snap beans. Phytopathology. 98: 1233-1241.
- Yang, X., T.W. Thannhauser, M. Burrows, D. Cox-Foster, F.E. Gildow, and S. M. Gray. 2008. Coupling Genetics and Proteomics To Identify Aphid Proteins Associated with Vector-Specific Transmission of Polerovirus (Luteoviridae). J. Virology. 82: 291-299.
- Peter, K., F. Gildow, P. Palukaitis, and S.M. Gray. 2008. Phloem limitation of potato leafroll virus is an asset and not a liability. Phytopathology. 98:S124.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Projects described here are to develop methods for the study of plant virus movement in aphid vectors and to utilize these methods for better understanding of mechanisms regulating vector-specific virus transmission. Transmission of viruses in the family Luteoviridae, such as cereal yellow dwarf virus (CYDV) and soybean dwarf virus SbDV), involve interactions between the virus and cell membranes in the aphid gut and salivary gland. Our studies have identified the sites of these interactions and their biological consequences. Little is known about the molecular mechanisms regulating vector specificity. The immediate objectives of these studies are (1) to identify vector populations transmitting Luteoviruses with high levels of vector-specificity, and (2) to develop methods for in situ studies of virus transport through aphid tissues utilizing fluorescent light microscopy and transmission electron microscopy coupled with proteomic studies. Utilizing CYDV-RPV and F2 generations
of Schiazphis graminum resulting from crosses of vector and nonvector populations, we have identified 4 aphid proteins specifically correlated with the vector transmission phenotype. Current work is focused on characterization of these proteins and localization in aphid vectors. In a second newly initiated project using SbDV, we have developed methods for mass rearing 5 species of legume feeding aphids to be used in SbDV vector tests. Our facility now houses a permanent collection of 18 geographically distinct aphid populations representing 12 species. We have began characterizing N. Am. strains of SbDV infecting indigenous clover plants adjacent to potentially vulnerable soybean crops. The SbDV strains have been sequenced and host range and purification studies initiated. We have developed a reliable vector test system utilizing purified virus acquisition through artificial membranes and plant bioassays. Preliminary aphid vector transmission tests are in progress to characterize
vector-specificity. A third project involves studies of legume infecting strains of cucumber mosaic virus (CMV) infecting snap beans. Completed vector efficiency studies of a legume-infecting strain of CMV (CMV-Le) by 15aphid populations, and initiated studies of a previously uncharacterized necosis-inducing strain of CMV (CMV-Nec). CMV-Le was sequenced and CMV-Nec sequencing is in progress. Differences between these two CMV strains in host range and in aphid vector efficiency have been completed. These two virus strains and their aphid vectors are being characterized in preparation for their use as a model system for studies of nonpersistent virus transmission not involving a virus encoded transmission helper component protein. The end goal of this research is to identify genes in virus and aphid populations regulating virus transmission.
PARTICIPANTS: Project leader is F.E. Gildow. Interdepartmental research collaborators include Dr. Diana Cox-Foster and Dr. Shelby Fleischer, Dept. of Entomology, Penn State University. External collaborators include Dr. Stewart Gray and Dr. Xiaolong Yang, USDA-ARS and Cornell University, Ithaca, NY and Dr. Bill Schneider, USDA-ARS, Foreign Disease and Weed Research Unit, Ft. Detrick, Frederick, MD. Technical support personnel included William Sackett, Penn State University; and Andrew Stone and Diana Sherman, USDA Foreign Disease and Weed Lab, Ft. Detrick, MD.
TARGET AUDIENCES: Field studies of CMV in legume crops are being carried out in collaboration with County Extension personnel and with the assistance of personnel associated with Hanover Foods, Inc. Results of this work are being disseminated through Extension presentations to grower groups and through meetings such as the annual Mid-Atlantic Vegetable Conference. Results of these studies will be published in scientific journals. Research results of interest to workers in the area of virus-vector interactions will be and are being disseminated through publications in professional journals and professional presentations at national and international scientific meetings such as those of the American Entomological Society and the American Phytopathological Society
Impacts
Recent epidemics of cucumber mosaic virus (CMV) in snap bean crops and the recent arrival of a new aphid species, the soybean aphid in the eastern U.S. prompted a new study to examine the potential role of the soybean aphid in transmitting CMV to commercial snap bean and soybean crops. Based on CMV transmission studies, we have identified several important aphid vectors of the legume strain of CMV common in NY and PA. The two most effective vectors were the cotton or melon aphid (Aphis gossypii) and the soybean aphid (Aphis glycines). Several additional species including the alfalfa aphid, Therioaphis trifolii, and the corn leaf aphid, Rhopalosiphum maidis, also were identified as common and effective vectors. A distinct difference was observed in the prevalence of CMV between NY and PA snapbean fields, even when the same efficient vector aphid species predominated. Although CMV did occur in PA snap bean crops, alfalfa mosaic virus and bean yellow mosaic virus
predominated. For soybean dwarf virus, four genetically distinct strains of SbDV recovered from naturally infected clovers have been sequenced. Vector transmission tests are underway to identify the most effective aphid vectors and those species most at risk for transmitting SbDV to soybean. Three effective aphid vector species have been identified to date and tests are continuing to study vector efficiency of several additional legume feeding aphid species. Ultrastructural tests are underway to identify tissue-specific sites regulating SbDV and cereal yellow dwarf virus transmission through aphids. We are currently developing fluorescent labeling techniques for virus movement in aphid vectors and localizing cellular sites in aphids associated with virus transmission. Because this is a new project, progress on these new objectives is limited.
Publications
- Wallis, C., W. Schneider, A. Stone, D. Sherman, V. Damsteegt, and F.E. Gildow. 2007. Identification of a mutation in the Plum pox potyvirus NIb gene associated with adaptation to pea (pisum sativum). J. Gen.Virology 88:2839-2845.
- Damsteegt, V.D., R. Scorza, A.L. Stone, W.L. Schneider, K. Webb, M. Demuth, and F.E. Gildow. 2007. Prunus host range of plum pox virus (PPV) in the United States by aphid and graft inoculation. Plant Disease 91:18-23.
- Kaplan, I., L. Lee, D. R. Ripoll, P. Palukaitis, F. Gildow, and S. M. Gray. 2007. Point mutations in the potato leafroll virus major capsid protein alter virion stability and aphid transmission. Virology 88:1821-1830.
- Overton, B.E., E.L. Stewart, X. Qu, F.E. Gildow, N.G. Wenner, and D.S. Grove. 2007. Development of a Real-Time RT-PCR SYBR(trademark) Green Assay for Tomato Ring Spot Virus in Grape. Plant Disease 91:1083-1088.
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Progress 01/01/06 to 12/31/06
Outputs
Continued studies in collaboration with S. Gray and colleagues (USDA/Cornell) of luteovirus vector-specificity utilizing vector and non-vector clones of Schizaphis graminum and their F2 progeny have identified 74 differentially expressed aphid proteins of interest. Thirty-seven of these proteins were either up-regulated or specific to the vector genotype. Genetic analysis of the F2 progeny indicated that 4 proteins were inherited only with the vector phenotype. Three of these proteins immunoprecipitated with purified Cereal Yellow Dwarf Luteovirus-RPV indicating that they bound to RPV virions. Using 2-d differential gel electrophoresis and tandam mass spectrometry, one of the proteins was characterized as a cyclophilin protein, and a second protein as a luciferase. Cyclophilins are reported to function in secretory pathways and are involved in HIV attachment to cells. Luciferase proteins possess targeting signals to membrane-bound vesicles. Our ultrastructural studies
have verified that luteoviruses are frequently observed attached to aphid cell membranes and that luteoviruses are transported into and through aphid gut and salivary cells in single membrane vesicles. Current work is aimed at sequencing these proteins and localizing them in specific aphid tissues to determine a role in luteovirus transmission. A newly initiated study is focused on the species composition of aphid population in bean fields related to epidemic spread of a legume strain of cucumber mosaic virus (CMV-L). Field trapping over 3 years has identified over 30 species of aphids. Twelve of the most common species were tested for their CMV-L vector transmission efficiency. Of these only one species (Sitobion avenae) was a non-vector. Vector efficiency ranged from 2 % up to 70% in multiple aphid transmission tests utilizing 25-50 aphids per plant. Single aphid transmission tests indicated that the efficient vectors Aphid gossypii, Aphis glycines, and Therioaphis trifolii could
transmit with probabilities of around 10%. Tests of A. glycines (soybean aphid) clones from three geographical locations ( MD, NY, PA) indicated no differences in ability to transmit CMV-L. Studies are underway to correlate CMV-L disease incidence in local epidemics to aphid vector species distribution, and to identify resistant bean cultivars.
Impacts
Few virus-vector systems are as well known as the luteoviruses. We have previously identified the route of luteoviruses through aphid vectors and reported on cellular mechanisms regulating luteovirus transmission. Our work is aimed at identifying the molecular mechanisms determining virus recognition by aphid vectors, the virus-protein interactions regulating luteovirus endocytotic uptake into aphid cells, and the transcellular transport mechanisms involved in virus movement. Results of this work will have value to understanding virus transmission in insect vector systems of both agricultural and medical importance. In the future genetically engineered peptides may be used to either interfere with virus transmission or to target lethal pesticides to specific vector species. Our work with CMV-L has more immediate value in identifying the major aphid vectors involved in CMV epidemics in late planted snap bean crops in NY and eastern PA. A recent major epidemic of CMV
coincided with the appearance of the newly introduced soybean aphid. Our studies have verified that the soybean aphid is a very efficient vector of CMV-L. It is likely that this newly introduced aphid may vector other indigenous viruses in field crops and alter the occurrence of virus epidemics. Our current tests for CMV-L resistance in bean will be of value to producers requiring resistant or tolerant cultivars for late planted crops which are most vulnerable to large migrating populations of soybean aphids developing on soybeans in mid to late summer.
Publications
- Yang, X., Burrows, M., Thannhauser, T., Cox-Foster, D., Gray, S. and Gildow, F. 2006. In search of proteins in the aphid Schizaphis graminum associated with vectoring luteoviruses: a proteomics approach. Abstract. Phytopathology 96: S127.
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