Subcellular targeting domains of Abutilon mosaic geminivirus movement protein BC1

Abutilon mosaic geminivirus (AbMV) encodes two movement proteins, BV1 and BC1, which mediate the intra- and intercellular transport of viral DNA in plants cooperatively. It has been shown previously that singly expressed BC1, fused to green fluorescent protein (GFP), accumulates preferentially either at the cell periphery or around the nucleus in separate plant cells. To define the BC1 domains responsible for understanding the subcellular sorting, deletion mutants were fused to GFP and expressed transiently in epidermal cells of non-host (Allium cepa) as well as of host (Nicotiana benthamiana) plants with basically the same results in both species. BC1-mediated intracellular sorting was dependent on two protein domains, an "anchor domain" (amino acids 117 to 180) which is necessary and sufficient to fix GFP:BC1 at the cell periphery and the nuclear environment, and a "pilot domain" (amino acids 1 to 49) in the absence of which the fusion proteins were found at both sites in the same cell simultaneously.