title: Virus variants with differences in the P1 protein coexist in a Plum pox virus population and display particular host-dependent pathogenicity features.
abstract: Subisolates segregated from an M-type Plum pox virus (PPV) isolate, PPV-PS, differ widely in pathogenicity despite their high degree of sequence similarity. A single amino acid substitution, K109E, in the helper component proteinase (HCPro) protein of PPV caused a significant enhancement of symptom severity in herbaceous hosts, and notably modified virus infectivity in peach seedlings. The presence of this substitution in certain subisolates that induced mild symptoms in herbaceous hosts and did not infect peach seedlings suggested the existence of uncharacterized attenuating factors in these subisolates. In this study, we show that two amino acid changes in the P1 protein are specifically associated with the mild pathogenicity exhibited by some PS subisolates. Site-directed mutagenesis studies demonstrated that both substitutions, W29R and V139E, but especially W29R, resulted in lower levels of virus accumulation and symptom severity in a woody host, Prunus persica. Furthermore, when W29R and V139E mutations were expressed concomitantly, PPV infectivity was completely abolished in this host. In contrast, the V139E substitution, but not W29R, was found to be responsible for symptom attenuation in herbaceous hosts. Deep sequencing analysis demonstrated that the W29R and V139E heterogeneities already existed in the original PPV-PS isolate before its segregation in different subisolates by local lesion cloning. These results highlight the potential complexity of potyviral populations and the relevance of the P1 protein of potyviruses in pathogenesis and viral adaptation to the host.
authors.affiliation: Department of Plant Molecular Genetics, Centro Nacional de Biotecnología, Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Varvara I
authors.initials: VI
authors.lastname: Maliogka
authors.forename: Beatriz
authors.initials: B
authors.lastname: Salvador
authors.forename: Alberto
authors.initials: A
authors.lastname: Carbonell
authors.forename: Pilar
authors.initials: P
authors.lastname: Sáenz
authors.forename: David San
authors.initials: DS
authors.lastname: León
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Oliveros
authors.forename: Ma Otilia
authors.initials: MO
authors.lastname: Delgadillo
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: García
authors.forename: Carmen
authors.initials: C
authors.lastname: Simón-Mateo
mesh_terms: D019943:Amino Acid Substitution; D016297:Mutagenesis, Site-Directed; D017801:Plum Pox Virus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014774:Virulence
chemical_list: D014764:Viral Proteins