title: Virus-induced necrosis is a consequence of direct protein-protein interaction between a viral RNA-silencing suppressor and a host catalase.
abstract: Many plant host factors are known to interact with viral proteins during pathogenesis, but how a plant virus induces a specific disease symptom still needs further research. A lily strain of Cucumber mosaic virus (CMV-HL) can induce discrete necrotic spots on infected Arabidopsis (Arabidopsis thaliana) plants; other CMV strains can induce similar spots, but they are not as distinct as those induced by CMV-HL. The CMV 2b protein (2b), a known RNA-silencing suppressor, is involved in viral movement and symptom induction. Using in situ proximity ligation assay immunostaining and the protoplast assays, we report here that CMV 2b interacts directly with Catalase3 (CAT3) in infected tissues, a key enzyme in the breakdown of toxic hydrogen peroxide. Interestingly, CAT3, normally localized in the cytoplasm (glyoxysome), was recruited to the nucleus by an interaction between 2b and CAT3. Although overexpression of CAT3 in transgenic plants decreased the accumulation of CMV and delayed viral symptom development to some extent, 2b seems to neutralize the cellular catalase contributing to the host defense response, thus favoring viral infection. Our results thus provide evidence that, in addition to altering the type of symptom by disturbing microRNA pathways, 2b can directly bind to a host factor that is important in scavenging cellular hydrogen peroxide and thus interfere specifically with that host factor, leading to the induction of a specific necrosis.
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Inaba
authors.forename: Bo Min
authors.initials: BM
authors.lastname: Kim
authors.forename: Hanako
authors.initials: H
authors.lastname: Shimura
authors.forename: Chikara
authors.initials: C
authors.lastname: Masuta
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology / Q000235:genetics / Q000821:virology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000201:enzymology; D017799:Cucumovirus / Q000378:metabolism*; D060467:Disease Resistance / Q000276:immunology; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D006861:Hydrogen Peroxide / Q000378:metabolism; D009336:Necrosis; D010935:Plant Diseases / Q000276:immunology / Q000821:virology; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism / Q000821:virology; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021381:Protein Transport; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism / Q000821:virology; D034622:RNA Interference; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: C404227:2b protein, cucumber mosaic virus; D029681:Arabidopsis Proteins; D014764:Viral Proteins; D006861:Hydrogen Peroxide; C490323:CAT3 protein, Arabidopsis; D002374:Catalase