Geminiviruses encode two movement proteins that are essential for systemic infection of their host but dispensable for replication and encapsidation.

1: The geminivirus BL1 movement protein is associated with endoplasmic reticulum-derived tubules in developing phloem cells. Ward BM, Medville R, Lazarowitz SG, Turgeon R; J Virol 1997;71:3726-3733. PMID:9094647