title: Aggregation of TMV CP plays a role in CP functions and in coat-protein-mediated resistance.
abstract: Tobacco mosaic virus (TMV) coat protein (CP) in absence of RNA self-assembles into several different structures depending on pH and ionic strength. Transgenic plants that produce self-assembling CP are resistant to TMV infection, a phenomenon referred to as coat-protein-mediated resistance (CP-MR). The mutant CP Thr42Trp (CP(T42W)) produces enhanced CP-MR compared to wild-type CP. To establish the relationship between the formation of 20S CP aggregates and CP-MR, virus-like particles (VLPs) produced by TMV variants that yield high levels of CP-MR were characterized. We demonstrate that non-helical structures are found in VLPs formed in vivo by CP(T42W) but not by wild-type CP and suggest that the mutation shifts the intracellular equilibrium of aggregates from low to higher proportions of non-helical 20S aggregates. A similar shift in equilibrium of aggregates was observed with CP(D77R), another mutant that confers high level of CP-MR. The mutant CP(D50R) confers a level of CP-MR similar to wild-type CP and aggregates in a manner similar to wild-type CP. We conclude that increased CP-MR is correlated with a shift in intracellular equilibrium of CP aggregates, including aggregates that interfere with virus replication.
authors.affiliation: Donald Danforth Plant Science Center, 975 North Warson Road, St. Louis, MO 63132, USA. sasurmendi@cnia.inta.gov.ar
authors.forename: S
authors.initials: S
authors.lastname: Asurmendi
authors.forename: R H
authors.initials: RH
authors.lastname: Berg
authors.forename: T J
authors.initials: TJ
authors.lastname: Smith
authors.forename: M
authors.initials: M
authors.lastname: Bendahmane
authors.forename: R N
authors.initials: RN
authors.lastname: Beachy
mesh_terms: D019943:Amino Acid Substitution; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D020285:Cryoelectron Microscopy; D004279:DNA, Viral / Q000235:genetics; D024882:Drug Resistance, Viral; D014644:Genetic Variation; D008854:Microscopy, Electron; D008958:Models, Molecular; D011487:Protein Conformation; D014027:Tobacco Mosaic Virus / Q000502:physiology* / Q000648:ultrastructure; D014158:Transcription, Genetic
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral