Virus-specific proteins in cells infected with tomato black ring nepovirus: evidence for proteolytic processing in vivo

• Published in: Journal of general virology Vol. 73; no. 7; pp. 1609 - 1614
• Main Authors: Demangeat, G, Hemmer, O, Reinbolt, J, Mayo, M. A, Fritsch, C
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.07.1992; Society for General Microbiology
• Subjects: Amino Acid Sequence; Animals; Biological and medical sciences; Chenopodium quinoa; Fundamental and applied biological sciences. Psychology; Microbiology; Molecular Sequence Data; Nicotiana clevelandii; Plant Viruses - chemistry; Plant Viruses - metabolism; Rabbits; Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains; tomato black ring virus; Viral Proteins - analysis; Viral Proteins - metabolism; Virology; Virus; Proteins; Nepovirus; Molecular processing; Plant pathogen; Proteolysis; Immunoblotting assay; Infected cell; Aminoacid sequence
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/0022-1317-73-7-1609

1 Institut de Biologie Moléculaire des Plantes, 12 rue du Général Zimmer, 67000 Strasbourg 2 Institut de Biologie Moléculaire et Cellulaire, 15 rue Descartes, 67000 Strasbourg, France and 3 Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K. The synthesis of proteins encoded by the RNA of tomato black ring virus (TBRV) in vivo was studied in protoplasts by direct labelling with [ 35 S]methionine, and in protoplasts and plants by immunoblotting experiments with specific antisera. Comparison of the proteins synthesized in infected and mock-inoculated protoplasts suggested that proteins of M r 120K, 90K, 80K, 57K and 46K were virus-specific. The proteins derived from the RNA-1-encoded polyprotein detected by immunoblotting were a stable 120K protein and, only in protoplasts, small amounts of a 90K protein which contains the C-terminal part of the 120K protein and the polymerase domain. The results suggest that the polymerase and the adjacent protease function in vivo largely or solely when combined in a 120K protein. The proteins derived from the RNA-2-encoded polyprotein detected by immunoblotting were 59K and 57K proteins, which reacted with antiserum to TBRV particles, and a 46K protein. In extracts of infected Nicotiana clevelandii and Chenopodium quinoa made soon after inoculation, the 59K protein was more abundant than the 57K protein; later samples contained similar quantities of each protein. The 57K protein comigrated with protein extracted from virus particles. The results of amino acid sequencing suggested that the 57K protein is derived from the 59K protein by the loss of nine C-terminal amino acids. Antiserum to a peptide adjacent to the 57K protein in the 150K polyprotein detected a 46K protein in protoplasts and plant tissue. The results support the processing scheme for TBRV polyproteins proposed after analysis of the products of in vitro translation. Received 13 January 1992; accepted 16 March 1992.