title: Plasmodesmal targeting and intercellular movement of potato mop-top pomovirus is mediated by a membrane anchored tyrosine-based motif on the lumenal side of the endoplasmic reticulum and the C-terminal transmembrane domain in the TGB3 movement protein.
abstract: Live-cell fluorescence microscopy was used to investigate the third triple gene block protein (TGB3) of potato mop-top pomovirus and its role in assisted targeting of TGB2 to plasmodesmata (PD). Wild-type and mutant TGB3 proteins were expressed under the control of the 35S promoter or from a virus reporter clone. Assisted targeting of TGB2 to PD was optimal when the proteins were expressed from a bicistronic plasmid in the relative ratios expected in a virus infection, suggesting that excess TGB3 inhibited PD localisation. Contrary to the generally accepted view, bimolecular fluorescence complementation showed that the TGB3 N terminus is located in the cytosol. Mutational analysis to dissect TGB3 sub domain functions showed that PD targeting was mediated by a composite signal comprising an ER-lumenal tyrosine-based motif and the C-terminal transmembrane domain. Mutation of either of these domains also abolished cell-to-cell movement of the virus. The results are discussed in the context of TGB3 membrane topology.
authors.affiliation: Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, DD2 5DA, UK.
authors.forename: J
authors.initials: J
authors.lastname: Tilsner
authors.forename: G H
authors.initials: GH
authors.lastname: Cowan
authors.forename: A G
authors.initials: AG
authors.lastname: Roberts
authors.forename: S N
authors.initials: SN
authors.lastname: Chapman
authors.forename: A
authors.initials: A
authors.lastname: Ziegler
authors.forename: E
authors.initials: E
authors.lastname: Savenkov
authors.forename: L
authors.initials: L
authors.lastname: Torrance
mesh_terms: D003600:Cytosol / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000821:virology*; D008856:Microscopy, Fluorescence; D053830:Plant Viral Movement Proteins / Q000378:metabolism*; D010942:Plant Viruses / Q000472:pathogenicity*; D031425:Plasmodesmata / Q000737:chemistry; D011485:Protein Binding; D021381:Protein Transport; D012328:RNA Viruses / Q000472:pathogenicity*; D011198:Solanum tuberosum / Q000821:virology*
chemical_list: D053830:Plant Viral Movement Proteins