Studies on purification and properties of potato virus M (PVM) were carried out using an isolate found in British Columbia. The narrow host range of the virus was confirmed, and no new susceptible species was discovered. Potato cultivars failed to develop symptomps even in plants produced by tubers of inoculated plants, but none was immune. An attempt to demonstrate transmissibility of the virus by plant contact was unsuccessful. In undiluted potato sap the virus had a thermal inactivation point (TIP) of 65 to 70°C, and a longevity in vitro (LIV) of 2 to 4 days. The dilution end point (DEP) was 10⁻⁴. The LIV and DEP of the virus in tomato sap were similar to those in potato sap. Crude sap diluted to 10⁻¹ induced more lesions on Red Kidney bean than undiluted sap. An efficient purification procedure for PVM was developed. The virus was purified from leaves of potato (Solanum tuberosum L.), by extraction with 0.5 M borate buffer, pH 7.8, clarification with ammonium sulfate (20%), and concentration with ammonium sulfate (30%). Further concentration was carried out by high speed centrifugation followed by polyethylene glycol (PEG 6000) precipitation and high speed centrifugation. Final purification was by sucrose density gradient centrifugation. The yield obtained from this procedure was 3.7 to 4.1 mg per Kg of infected leaves. The purified preparations contained rod-shaped particles 651 nm normal length and 13.4 nm average width. The particles had an A₂₆₀/A₂₈₀ratio of ]^3' an A max/A min ratio of 1.24, a maximum ultraviolet light absorption at 260 nm, a minimum absorption at 245 nm, and a buoyant density in CsCl of 1.304 (suggesting an RNA content of 6.2%). The molecular weight of the protein subunit was about 39,300 daltons. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

Previous studies have detected the presence of the capsid protein (CP) and CP RNA of PVX in chloroplasts of transgenic plants expressing the PVX CP and 8kD genes from nuclear transgenes. CP RNA was also found in the chloroplasts of transgenic plants with mutations that eliminated either the CP or the 8kD protein. To further investigate the potential “RNA Tractor” activity of the PVX RNA, various constructs containing limited regions of the PVX 8kD and CP genes were produced and used to transform tobacco plants. RT-PCR analyses of chloroplastic RNA ascertained the presence of the RNA transcript within chloroplasts when as little as 125bp of the PVX sequence was used to transform plants. From this, it was concluded that the PVX proteins did not contribute to the movement of the viral RNA and that a region within the 125bp PVX sequence is acting as a chloroplastic “RNA Tractor”.

Previous studies have detected the presence of the capsid protein (CP) and CP RNA of PVX in chloroplasts of transgenic plants expressing the PVX CP and 8kD genes from nuclear transgenes. CP RNA was also found in the chloroplasts of transgenic plants with mutations that eliminated either the CP or the 8kD protein. To further investigate the potential “RNA Tractor” activity of the PVX RNA, various constructs containing limited regions of the PVX 8kD and CP genes were produced and used to transform tobacco plants. RT-PCR analyses of chloroplastic RNA ascertained the presence of the RNA transcript within chloroplasts when as little as 125bp of the PVX sequence was used to transform plants. From this, it was concluded that the PVX proteins did not contribute to the movement of the viral RNA and that a region within the 125bp PVX sequence is acting as a chloroplastic “RNA Tractor”.

Thesis (Ph. D., Entomology)--University of Idaho, December 2008. / Major professor: Juan Manuel Alvarez. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

Reciprocal interference experiments between Potato virus Y (PVY) and Pepper mottle virus (PeMV) in Capsicum annuum L. 'Tabasco' and 'Special pepper' (a selection of Anaheim chilli peppers), showed suppression of local lesion production in both directions but incomplete suppression of challenge virus replication (incomplete cross protection). However, suppression was reduced by increasing the concentration of the challenge virus. The source of inoculum of the viruses did not have a significant effect on the subsequent interference between the viruses. A direct relationship was established between counts of local lesions and virus particles counted using the electron microscope. Tobacco etch virus (TEV) was transmitted from one Capsicum annuum L. 'Tabasco' plant to another in the same pot within 4 days after infection of the test plant. Transmission probably took place via root grafts, as the necrotic roots of the test plants intertwined with the uninoculated Tabasco plants. Mixed infections of PVY and PeMV resulted in the production of PVY-N, a new strain of PVY. The new strain, which could be recognized by changes in biological and serological properties, was produced only in mixed infections and was stable after six serial transfers in several hosts. Evidence suggests that the development of the new strain is host dependent. Potato Virus Y in mixed infections with PeMV or TEV in C. annuum L. 'Anaheim' did not induce local lesions, systemic necrosis nor death of Special pepper, while PeMV alone induced the death of Tabasco. The behavior of TEV in Tabasco in a mixed infection was temperature dependent, while TEV alone induced wilt and death of Tabasco irrespective of the greenhouse temperature and season of the year.

No description available.

No description available.

Les protéines sont des acteurs majeurs dans les processus moléculaires et cellulaires d’un organisme. La remise en question des modalités associées aux fonctions de ces macromolécules a récemment été apportée par le concept de désordre intrinsèque. Celui-ci définit l’absence (transitoire ou permanente) de structure tridimensionnelle de certaines protéines ou régions protéiques comme étant directement liée à leurs fonctions. Chez les virus à ARN, les propriétés des protéines ou régions désordonnées semblent associées aux capacités de ces micro-organismes à détourner la machinerie cellulaire de l’hôte en interagissant avec de multiples partenaires, et à s’adapter aux nombreuses contraintes auxquelles ils doivent faire face en tant que parasites obligatoires. Ce travail porte sur les potyvirus, figurant parmi les pathogènes de plantes les plus dommageables étudiés à ce jour. L'objectif de cette thèse a été d’explorer les fonctions associées au désordre intrinsèque dans le cycle infectieux des potyvirus ainsi que dans le processus d’adaptation. Notre approche a ainsi démontré que : i) le désordre est ubiquitaire chez le genre Potyvirus ; ii) les régions de désordre conservées chez plusieurs protéines de potyvirus semblent être associées à leur(s) fonction(s) pendant l'infection ; iii) les régions désordonnées sont généralement associées à moins de contraintes évolutives, suggérant ainsi leur implication dans les processus adaptatifs des potyvirus ; iv) les régions prédites comme désordonnées semblent privilégier l’apparition de mutations et donc la capacité d’un virus à accumuler de la diversité génétique au cours de l'évolution sur son hôte naturel ; v) ce travail a permis de corréler le taux en désordre de la protéine viral genome-linked (VPg) du Potato virus Y à sa capacité à s’adapter à la résistance récessive pvr23 du piment. / Proteins are essential actors involved in a majority of molecular and cellular processes. The features associated with the functions of these macromolecules have been recently questioned with the emergence of the intrinsic disorder concept. It defines the transitory or permanent lack of 3D structure in some proteins or regions as directly related to their functions. Among RNA viruses, the properties of disordered proteins may be linked to the ability of these microorganisms to hijack the host machinery by interacting with multiple partners, as well as to adapt to the multiple constraints they must face as obligatory parasites. This work focuses on the Potyvirus genus, which includes some of the most damaging plant pathogens studied to date. The goal of this thesis was to explore the functions associated with intrinsic disorder in the infectious cycle of this viral genus as well as in its process of adaptation. Our studies have shown that i) intrinsic disorder is ubiquitous in potyviruses; ii) intrinsically disordered regions (IDR) of some of potyviral proteins are likely to be associated with important functions for the viral cycle ; iii) IDR are generally less evolutionary constrained, suggesting an adaptive potential of these regions ; iv) predicted IDR seem to favor the appearance of mutations and therefore virus ability to accumulate genetic diversity during its evolution in natural host ; v) an experimental disorder modulation within the Viral genome-linked (VPg) protein has been demonstrated as positively correlated with the adaptive ability of the Potato virus Y to overcome the pvr23 recessive resistance in pepper.