In vivo accumulation of Broad bean wilt virus 2 VP37 protein and its ability to bind single-stranded nucleic acid

The VP37 protein encoded by the RNA2 of Broad bean wilt virus 2 (BBWV2) was overexpressed in Escherichia coli. The protein was purified and a polyclonal antibody specific for the protein was produced. Time course studies by Western blot assays in BBWV2-infected Chenopodium quinoa leaves showed that the VP37 protein was present in cells of the inoculated leaves by 12 h post inoculation and in cells of systemically-infected leaves by 2 days post inoculation. The protein was able to accumulate to a high level in infected leaves at the late infection stage. Gel retardation and UV cross-linking assays demonstrated that the VP37 protein bound preferentially single-stranded (ss) RNA and DNA in a non-sequence-specific manner. The VP37 protein-RNA complex was stable in solutions containing less than 400 mM NaCl, but became fully dissociated in the solutions containing 800 mM NaCl. Sequence analysis of the VP37 protein and its ability to bind ssRNA and ssDNA suggest that the protein may play a role similar to the movement proteins reported for other plant viruses.