Subcellular targeting of the coat protein of African cassava mosaic geminivirus

The coat protein (CP) of geminiviruses is involved in a number of processes during the life cycle of the virus, The predominant function is encapsidat ion of single-stranded DNA and formation of the virus particle to protect v iral DNA during transmission. The CP of monopartite geminiviruses is absolu tely essential for virus movement, whereas CP mutants of bipartite geminivi ruses are able to infect some host plants systemically, indicating an invol vement of the CP in host specificity. During the life cycle of geminiviruse s, the viral DNA enters the nucleus of the infected cell where virus replic ation, transcription, and encapsidation occur, For systemic infection, the virus moves cell-to-cell from the site of inoculation to vascular tissue an d via phloem to other plant tissues. To move, viral DNA has to shuttle in a nd out of the nucleus and through plasmodesmata, Parts of the bipartite Afr ican cassava mosaic virus (ACMV) CP were fused with green fluorescent prote in (GFP) or beta -glucuronidase (GUS). CP domains were identified that medi ate both nuclear import and export, as well as targeting of CP-fusion prote ins to the cell periphery. These results indicate that domains of the CP fa cilitate several aspects of geminivirus movement, including nuclear import and export and transport of the viral genome to the cell periphery. (C) 200 1 Academic Press.