Electron microscopic studies on barley yellow dwarf virus infection in oats
Nass, Petra Hildegard
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Permalink
https://hdl.handle.net/2142/20140
Description
Title
Electron microscopic studies on barley yellow dwarf virus infection in oats
Author(s)
Nass, Petra Hildegard
Issue Date
1996
Doctoral Committee Chair(s)
D'Arcy, Cleora J.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Agriculture, Plant Pathology
Language
eng
Abstract
Barley yellow dwarf luteoviruses (BYDVs) cause significant economic losses worldwide due to damage to cereal crops such as oats, wheat and barley. The virus is transmitted by aphids that inject viral particles into the phloem of the host during the feeding process. BYDVs remain restricted to the phloem tissue and cause cytopathological alterations that ultimately lead to complete obliteration of the infected cell. Phloem cells are considered infected if they contain one or more of the following inclusions: Viral particles, filamentous material, virus-induced vesicles. In this project an in situ immunolocalization assay and an in situ hybridization assay were developed to determine the subcellular accumulation of two viral proteins, the coat protein and a single strand RNA binding protein (17 kDa protein), and the viral RNA. Viral coat protein was first detected in the cytoplasm surrounding clusters of filamentous material that was shown to contain viral RNA. It is suggested that viral coat protein is translated in these areas from viral RNA. Only at later stages was coat protein observed in the nucleus and it is concluded that the viral coat protein diffuses into the nucleus after its disruption during later stages of infection. Viral coat protein was not detected in any other cell organelle. The 17 kDa protein was always associated with filamentous material. Filaments in nuclear pores were also occasionally labeled. The role of the 17 kDa protein as a single strand RNA binding protein was confirmed. The in situ hybridization assay showed that the virus-induced filamentous material contains viral RNA. Minus- and plus-strand were detected in nucleus, cytoplasm, and virus-induced vesicles.
In the past the cytopathological changes induced by BYDVs had only been observed in highly susceptible hosts. These varieties are not economically relevant. In this project the cytopathological changes induced by BYDV-PAV in infected primary and flag leaves of several resistant and susceptible oat lines were compared. The flag leaves of resistant oat lines did not show any phloem obliteration whereas susceptible oat lines and one only weakly tolerant oat line contained obliterated phloem cells. No differences in the cytopathological changes indicative of resistance to the virus were found in the primary leaves. It is suggested that the ultrastructural damage to the host tissue of the flag leaf by BYDVs could be used to assess resistance of oat lines to BYDVs.
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