The VP37 protein of Broad bean wilt virus 2 induces tubule-like structures in both plant and insect cells

VP37 protein of Broad bean wilt virus 2 (BBWV-2) is a multifunctional protein that binds single-strand nucleic acids, interacts with viral coat protein (CP) and potentiates the virus cell-to-cell movement in its host plant. In this study, tubule-like structures filled with virus-like particles were observed by Electron Microscopy in plasmodesmata in walls of Chenopodium quinoa leaf cells infected with BBWV-2. Immunogold labeling using VP37 protein specific antibody demonstrates that the VP37 is a component of the tubular structures. When VP37 was fused with the green fluorescent protein (VP37-GFP) and expressed in BY-2 protoplasts or in insect Tn cells, green fluorescent tubules of various lengths were produced, protruding from the surface of the expressing cells. These findings suggest that the movement of BBWV-2 between cells is mediated by the tubular structures that contain the VP37 protein, and the VP37 protein itself is capable of inducing these tubule-like structures in cells. Our results also suggest that the plant and insect cell factors involved in the tubule formation have conserved features.