More than half of the recognized genera of positive strand RNA viruses employ polyprotein processing as one of the strategies for their genome expression. Normally, this processing is mediated by virus-encoded proteinases that belong to the trypsin-like or papain-like family. In particular, papain-like, leader proteinases were found in diverse families of human, animal, plant, and fungal positive strand RNA viruses. In addition to autocatalytic processing, these proteinases play a variety of roles in the virus life cycle. In plant potyviruses, a papain-like helper component-proteinase (HC-Pro) was implicated in genome amplification, cell-to-cell movement, long distance transport, and suppression of host defense. The p29 proteinase encoded by a fungal hypovirus CHV1 was found to be dispensable for virus replication, but it was identified as a major determinant of viral pathogenicity. In an animal equine aterivirus (EAV), a papain-like proteinase nspl was demonstrated to possess a putative zinc finger domain, which functions in subgenomic RNA synthesis, although it is not essential for virus replication. The Lab proteinase of the foot and mouse disease virus (FMDV) is involved in inhibition of cellular mRNA translation and in virus spread in infected animals. In general, it appears that functional plasticity of the papain-like leader proteinases played an important role in the evolution of viral diversity. Here, we examined the functions of a papain-like leader proteinase (L-Pro) in the life cycle of the beet yellows closterovirus (BYV). It was found that L-Pro is required for autoproteolytic processing, genome amplification, virus invasiveness and cell-to-cell movement for BYV. The gene swapping experiments involving several closterviruses, a potyvirus, as well as CHV1, FMDV, and EAV revealed complex functional profiles of the papain-like leader proteinases. The possible mechanisms that underlie L-Pro functions are discussed. / Graduation date: 2002

Coreplication experiments have revealed that replication of turnip yellow mosaic virus (TYMV) RNA in turnip protoplasts is cis-preferential. Genomes encoding mutant p141 or p66, proteins essential for virus replication, were inefficiently rescued by a helper genome. One model for the cis-preferential replication of TYMV is that p66 and p141 form a complex that associates with the RNA from which they are translated, limiting their availability in trans. Three types of experiments were used in this study in an attempt to obtain physical evidence for the hypothetical interaction between p66 and p141. Immunoprecipitations from in vitro translation reactions using antiserum that recognizes p66 (and its progenitor, p206) coprecipitate p141, indicating that the proteins form a complex in vitro. The results of coimmunoprecipitations of translation products with in-frame deletions did not lead to definitive information about interaction domains. p66 and the helicase domain of p141 do not detectably interact in the yeast two-hybrid system or in GST fusion interaction assays. Problems with the expression of full length p141 fusions make conclusions about the interaction of other p141 domains with p66 not possible at this time. Since the helicase domain of p141 does not appear to interact with p66, future experiments will focus on obtaining expression of smaller domains of p141, outside the helicase domain, and determining if they interact with p66. Variations to the model that do not necessitate the direct interaction between p66 and p141 are also considered. / Graduation date: 1997

Includes bibliographical references (leaves [102]-120). / 5, 120, [ca. 50] leaves, [3] leaves of plates : ill. ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the structure of the cucumber mosaic virus genome and the control of its expression. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1988

Bibliography: leaves 127-138. / v, 138 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / 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. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1997

Includes Appendix listing other publications by the author. / Includes bibliographical references (leaves 134-181). / vi, 182 leaves : ill., photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Alfalfa mosaic virus was isolated from lucerne (Medicago sativa) plants with a variety of disease symptoms. Experiments showed that each isolate was biologically distinct and that the host range and symptomatology of each isolate was affected by the environmental condition. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1990

Includes bibliographical references (leaves 108-123). / xi, 123 leaves : ill., photos ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The comparative studies carried out suggest that tomato aspermy virus and the Q strain of cucumber mosaic virus are sufficiently similar to be included in the same taxonomic group. Nevertheless, the two viruses are distinct and the present nomenclature should be retained. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1975

Typescript (photocopy) / Includes bibliographical references (leaves 84-94). / xi, 94 leaves, [35] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Eight cucumovirus isolates were examined with respect to their host range, antigenic properties and nucleic acid composition. / Thesis (Ph.D.)--Dept. of Plant Pathology, University of Adelaide, 1983

Bibliography: leaves 127-138. / v, 138 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / 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. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1997

Typescript (photocopy) / Includes bibliographical references (leaves 84-94). / xi, 94 leaves, [35] leaves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Eight cucumovirus isolates were examined with respect to their host range, antigenic properties and nucleic acid composition. / Thesis (Ph.D.)--Dept. of Plant Pathology, University of Adelaide, 1983

Includes bibliographical references (leaves 147-171). Studies factors affecting the rate of epidemic progress of cucumber mosaic virus in Lupinus angustifolius.