Strain-specific P3 of Soybean mosaic virus elicits Rsv1-mediated extreme resistance, but absence of P3 elicitor function alone is insufficient for virulence on Rsv1-genotype soybean.
When challenged by mechanical inoculation, the Rsv1 gene of soybean invokes extreme resistance (ER) against Soybean mosaic virus (SMV) strain N, but not SMV-G7 and its experimentally evolved variant, SMV-G7d. SMV-G7 provokes a lethal systemic hypersensitive response (LSHR), whereas SMV-G7d induces systemic mosaic. Thus, for Rsv1-genotype soybean, SMV-G7 and SMV-G7d are both virulent virus strains. The elicitor function of SMV-G7 provoking Rsv1-mediated LSHR was recently mapped to P3, and the influence of amino acids 823, 953, and 1112 of the precursor polypeptide of SMV-G7d on evasion of Rsv1-mediated recognition provoking LSHR was demonstrated. We have now extended this study to SMV-N. Initially, amino acids corresponding to those of SMV-G7d at these positions were substituted, individually or in combinations. All the mutants remained replication competent on rsv1-genotype soybean; however, none lost the elicitor function provoking Rsv1-mediated ER. Subsequently, P3 of SMV-N was precisely replaced with P3 of SMV-G7 or SMV-G7d and vice versa. All the chimeras were replication competent on rsv1-genotype soybean, but surprisingly SMV-N/G7P3 and SMV-N/G7dP3 failed to gain virulence on Rsv1-genotype soybeans. However, SMV-G7/NP3 and SMV-G7d/NP3 lost virulence, and this loss of virulence function was mapped to the N-terminus domain of SMV-N P3. The data indicate that SMV strain-specific P3 provokes Rsv1-mediated ER; however, virulence on Rsv1-genotype soybean is not solely a consequence of the absence of the P3 elicitor functions provoking Rsv1-mediated ER and LSHR.
Hajimorad
M R
MR
Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, TN 37916, USA. mrh@utk.edu
Eggenberger
A L
AL
Hill
J H
JH
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000472:pathogenicity*; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009693:Nucleic Acid Hybridization; D010935:Plant Diseases / Q000821:virology*; D012367:RNA, Viral / Q000032:analysis; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D014774:Virulence / Q000235:genetics; D014779:Virus Replication
D012367:RNA, Viral; D014764:Viral Proteins