title: The Importance of the KR-Rich Region of the Coat Protein of Ourmia melon virus for Host Specificity, Tissue Tropism, and Interference With Antiviral Defense.
abstract: The N-terminal region of the Ourmia melon virus (OuMV) coat protein (CP) contains a short lysine/arginine-rich (KR) region. By alanine scanning mutagenesis, we showed that the KR region influences pathogenicity and virulence of OuMV without altering viral particle assembly. A mutant, called OuMV6710, with three basic residue substitutions in the KR region, was impaired in the ability to maintain the initial systemic infection in Nicotiana benthamiana and to infect both cucumber and melon plants systemically. The integrity of this protein region was also crucial for encapsidation of viral genomic RNA; in fact, certain mutations within the KR region partially compromised the RNA encapsidation efficiency of the CP. In Arabidopsis thaliana Col-0, OuMV6710 was impaired in particle accumulation; however, this phenotype was abolished in dcl2/dcl4 and dcl2/dcl3/dcl4 Arabidopsis mutants defective for antiviral silencing. Moreover, in contrast to CPwt, in situ immunolocalization experiments indicated that CP6710 accumulates efficiently in the spongy mesophyll tissue of infected N. benthamiana and A. thaliana leaves but only occasionally infects palisade tissues. These results provided strong evidence of a crucial role for OuMV CP during viral infection and highlighted the relevance of the KR region in determining tissue tropism, host range, pathogenicity, and RNA affinity, which may be all correlated with a possible CP silencing-suppression activity.
authors.forename: Marika
authors.initials: M
authors.lastname: Rossi
authors.forename: Marta
authors.initials: M
authors.lastname: Vallino
authors.forename: Simona
authors.initials: S
authors.lastname: Abbà
authors.forename: Marina
authors.initials: M
authors.lastname: Ciuffo
authors.forename: Raffaella
authors.initials: R
authors.lastname: Balestrini
authors.forename: Andrea
authors.initials: A
authors.lastname: Genre
authors.forename: Massimo
authors.initials: M
authors.lastname: Turina
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000821:virology; D001120:Arginine / Q000378:metabolism; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D019662:Cucurbitaceae / Q000166:cytology / Q000821:virology*; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D008239:Lysine / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010935:Plant Diseases / Q000821:virology*; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000821:virology; D010942:Plant Viruses / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology / Q000648:ultrastructure; D021381:Protein Transport; D012367:RNA, Viral / Q000235:genetics; D014026:Nicotiana / Q000166:cytology / Q000821:virology; D018523:Tropism; D014771:Virion; D019065:Virus Assembly
chemical_list: D000998:Antiviral Agents; D036022:Capsid Proteins; D012367:RNA, Viral; D001120:Arginine; D008239:Lysine