title: Mutation of a Short Variable Region in HCpro Protein of Potato virus A Affects Interactions with a Microtubule-Associated Protein and Induces Necrotic Responses in Tobacco.
abstract: Helper component proteinase (HCpro) is a multifunctional protein of potyviruses (genus Potyvirus). HCpro of Potato virus A (PVA) interacts with the microtubule-associated protein HIP2 in host cells, and depletion of HIP2 reduces virus accumulation. This study shows that HCpro of Potato virus Y and Tobacco etch virus also interact with HIP2. The C-proximal portion of PVA HCpro determines the interaction with HIP2 and was found to contain a stretch of six residues comprising a highly variable region (HVR) in potyviruses. Mutations in HVR reduced PVA accumulation in tobacco plants and induced necrotic symptoms novel to PVA. Microarray and quantitative reverse transcription polymerase chain reaction analyses revealed induction of many defense-related genes including ethylene- and jasmonic acid-inducible pathways in systemically infected leaves at necrosis onset. Salicylic acid-mediated signaling was dispensable for the response. Genes related to microtubule functions were down-regulated. Structural modeling of HCpro suggested that all mutations in HVR caused conformational changes in adjacent regions containing functionally important motifs conserved in potyviruses. Those mutations, which also caused conformational changes in HVR, led to the greatest reduction of fitness. Our results implicate HVR in the regulation of HCpro conformation and virus-host interactions and suggest that mutation of HVR induces host defense.
authors.affiliation: Department of Agricultural Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland.
authors.forename: Tuuli
authors.initials: T
authors.lastname: Haikonen
authors.forename: Minna-Liisa
authors.initials: ML
authors.lastname: Rajamäki
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Tian
authors.forename: Jari P T
authors.initials: JP
authors.lastname: Valkonen
mesh_terms: D000595:Amino Acid Sequence; D003517:Cyclopentanes / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D005030:Ethylenes / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D054883:Oxylipins / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology / Q000821:virology*; D057865:Plant Immunity; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000821:virology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017800:Potyvirus / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000276:immunology / Q000821:virology*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D003517:Cyclopentanes; D005030:Ethylenes; D008869:Microtubule-Associated Proteins; D054883:Oxylipins; D010940:Plant Proteins; D014764:Viral Proteins; C011006:jasmonic acid; C036216:ethylene; D003546:Cysteine Endopeptidases; C072775:HC-Pro protein, potyvirus