title: Mutations in the P3 protein of Soybean mosaic virus G2 isolates determine virulence on Rsv4-genotype soybean.
abstract: Two Soybean mosaic virus (SMV) G2 isolates, L and L-RB, sharing high-sequence similarly but differing in ability to break Rsv4-mediated resistance in soybean, were investigated. Infectious clones corresponding to these two isolates and their chimeric clones resulting from swapping different regions of genomic cDNA between L and L-RB were constructed. Only L-RB or chimeras containing the middle fragment of L-RB cDNA showed virulence on Rsv4-genotype soybean. Sequence comparison analysis revealed that the middle genomic region of L and L-RB encodes four different amino acids. Point mutagenesis demonstrated that a single amino acid substitution (Q1033K) in the P3 protein determined virulence toward Rsv4 resistance. In addition, six new SMV Rsv4 resistance-breaking isolates, variants of the second passage on Williams 82 infected with the chimeras or mutants noninfectious on soybean carrying Rsv4, were obtained. Sequencing data indicated that these new isolates contain either the Q1033K mutation or a new substitution (G1054R) in P3. Site-directed mutagenesis confirmed the virulence role of the G1054R mutation on Rsv4-genotype soybean. Taken together, these data suggest that P3 of the SMV G2 strain is an avirulent determinant for Rsv4 and one single nucleotide mutation in P3 may be sufficient to compromise its elicitor function.
authors.affiliation: Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, 1391 Sandford St., London, Ontario, N5V 4T3, Canada.
authors.forename: R V
authors.initials: RV
authors.lastname: Chowda-Reddy
authors.forename: Haiyue
authors.initials: H
authors.lastname: Sun
authors.forename: Hongyan
authors.initials: H
authors.lastname: Chen
authors.forename: Vaino
authors.initials: V
authors.lastname: Poysa
authors.forename: Hong
authors.initials: H
authors.lastname: Ling
authors.forename: Mark
authors.initials: M
authors.lastname: Gijzen
authors.forename: Aiming
authors.initials: A
authors.lastname: Wang
mesh_terms: D019943:Amino Acid Substitution; D001483:Base Sequence; D002678:Chimera / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010935:Plant Diseases / Q000821:virology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013025:Glycine max / Q000235:genetics / Q000821:virology*; D014774:Virulence
chemical_list: D018076:DNA, Complementary; D004279:DNA, Viral