title: Potyvirus genome-linked protein (VPg) determines pea seed-borne mosaic virus pathotype-specific virulence in Pisum sativum.
abstract: The mechanism of Pisum sativum pathotype-specific resistance to pea seed-borne mosaic potyvirus (PSbMV) was investigated and the coding region determinant of PSbMV virulence was defined. Homozygous recessive sbm-1 peas are unable to support replication of PSbMV pathotype 1 (P-1), whereas biochemically and serologically related pathotype 4 (P-4) is fully infectious in the sbm-1/sbm-1 genotype. We were unable to detect viral coat protein or RNA with double antibody sandwich-enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction in sbm-1/sbm-1 P-1-inoculated protoplasts and plants. Lack of viral coat protein or RNA in P-1 transfected sbm-1/sbm-1 protoplasts suggests that sbm-1 resistance is occurring at the cellular level and that inhibition of cell-to-cell virus movement is not the operating form of resistance. In addition, because virus products were not detected at any time post-inoculation, resistance must either be constitutive or expressed very early in the virus infection process. P-1-resistant peas challenged with full-length, infectious P-1/P-4 recombinant clones demonstrated that a specific P-4 coding region, the 21-kDa, genome-linked protein (VPg), was capable of overcoming sbm-1 resistance, whereas clones containing the P-1 VPg coding region were noninfectious to sbm-1/sbm-1 peas. VPg is believed to be involved in potyvirus replication and its identification as the PSbMV determinant of infectivity in sbm-1/sbm-1 peas is consistent with disruption of an early P-1 replication event.
authors.affiliation: USDA-ARS, Horticultural Crops Research Laboratory, Oregon State University, Corvallis 97330, USA. kellerk@bcc.orst.edu
authors.forename: K E
authors.initials: KE
authors.lastname: Keller
authors.forename: I E
authors.initials: IE
authors.lastname: Johansen
authors.forename: R R
authors.initials: RR
authors.lastname: Martin
authors.forename: R O
authors.initials: RO
authors.lastname: Hampton
mesh_terms: D000595:Amino Acid Sequence; D005816:Genetic Complementation Test; D016679:Genome, Viral; D005838:Genotype; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000821:virology*; D017800:Potyvirus / Q000235:genetics*; D011523:Protoplasts; D016601:RNA-Binding Proteins / Q000235:genetics*; D012261:Ribonucleoproteins; D017386:Sequence Homology, Amino Acid; D017361:Viral Nonstructural Proteins / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D017361:Viral Nonstructural Proteins; C102206:genome-linked viral protein, potato virus Y