Interactions between the tomato spotted wilt virus movement protein and plant proteins showing homologies to myosin, kinesin and DnaJ-like chaperones

The non-structural protein encoded by the M RNA segment (NSm) of tomato spotted wilt virus (TSWV) has been implicated in cell-to-cell movement of nucleocapsids through modified plasmodesmata. Recently, DnaJ-like proteins from Nicotiana tabacum (tobacco) and Arabidopsis thaliana have been identified as NSm interacting host proteins, implying an involvement of molecular chaperones during systemic spread of the virus or other, presently unknown NSm-mediated virus functions. Examination of additional TSWV host plants and improvement of yeast two-hybrid interaction trap experiments led to the isolation of a DnaJ-like protein from Lycopersicon esculentum (tomato) and the identification of a protein from A. thaliana sharing some homologies with myosin and kinesin-like polypeptides. Sequence alignments of the tomato DnaJ-like protein unveiled the corresponding gene as an orthologue to the tobacco and A. thaliana DnaJ genes, substantiating that NSm interacting DnaJ-like polypeptides, identified from three different TSWV host species, apparently form a subgroup distinct from archetypical DnaJ chaperones. Increased levels of DnaJ-like proteins could be detected in TSWV systemically infected leaves and in plants exposed to heat shock, showing that the NSm interacting DnaJ-like chaperones are inducible upon biotic and abiotic stress. All together, the identification of DnaJ-like proteins and a protein resembling myosin and kinesin as NSm interacting plant proteins is in accordance with results accomplished for movement proteins from other plant attacking viruses showing an involvement of molecular chaperones and the cytoskeleton in at least intracellular trafficking.