title: Structure of the mature P3-virus particle complex of cauliflower mosaic virus revealed by cryo-electron microscopy.
abstract: The cauliflower mosaic virus (CaMV) has an icosahedral capsid composed of the viral protein P4. The viral product P3 is a multifunctional protein closely associated with the virus particle within host cells. The best-characterized function of P3 is its implication in CaMV plant-to-plant transmission by aphid vectors, involving a P3-virion complex. In this transmission process, the viral protein P2 attaches to virion-bound P3, and creates a molecular bridge between the virus and a putative receptor in the aphid's stylets. Recently, the virion-bound P3 has been suggested to participate in cell-to-cell or long-distance movement of CaMV within the host plant. Thus, as new data accumulate, the importance of the P3-virion complex during the virus life-cycle is becoming more and more evident. To provide a first insight into the knowledge of the transmission process of the virus, we determined the 3D structures of native and P3-decorated virions by cryo-electron microscopy and computer image processing. By difference mapping and biochemical analysis, we show that P3 forms a network around the capsomers and we propose a structural model for the binding of P3 to CaMV capsid in which its C terminus is anchored deeply in the inner shell of the virion, while the N-terminal extremity is facing out of the CaMV capsid, forming dimers by coiled-coil interactions. Our results combined with existing data reinforce the hypothesis that this coiled-coil N-terminal region of P3 could coordinate several functions during the virus life-cycle, such as cell-to-cell movement and aphid-transmission.
authors.affiliation: Université Rennes I, UMR 6026 CNRS, Campus de Beaulieu, 35042 Rennes, France.
authors.forename: Célia
authors.initials: C
authors.lastname: Plisson
authors.forename: Marilyne
authors.initials: M
authors.lastname: Uzest
authors.forename: Martin
authors.initials: M
authors.lastname: Drucker
authors.forename: Rémy
authors.initials: R
authors.lastname: Froissart
authors.forename: Christian
authors.initials: C
authors.lastname: Dumas
authors.forename: James
authors.initials: J
authors.lastname: Conway
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomas
authors.forename: Stéphane
authors.initials: S
authors.lastname: Blanc
authors.forename: Patrick
authors.initials: P
authors.lastname: Bron
mesh_terms: D017796:Caulimovirus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D014771:Virion / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*