The answer to this question is not clear; however, diVerent authors had reported that such viral proteins are involved both in replication of the viral genome, and in transcriptional and post-transcriptional regulation of viral genome expression (Dang and Lee 1989; Pyper et al. 1998) . For example, some plants viruses are known to encode a protein designated movement protein, responsible for long-distance movement of the viral RNA through the phloem (Ryabov et al. 1999) . Movement strictly depends on the interaction of the viral movement protein with the nucleolus and the Cajal bodies, which contain snRNPs and snoR-NPs (Kim et al. 2007a, b) . The open reading frame (ORF) 3 of Groundnut rosette virus is one such protein; it is Wrst localized in Cajal bodies and forms Cajal body-like struc-tures, it is then localized in the nucleolus when the Cajal body-like structures fuse with the nucleolus, and Wnally it exits to the cytoplasm (Kim et al. 2007b) . Another study showed that this shuttling is indispensable to form the RNPs essential for systemic virus infection (Kim et al. 2007a) . In this process, the interaction of the viral ORF3 with Wbrillarin is absolutely required. Interestingly, silencing of the Wbrillarin gene blocks long-distance movement of the virus but does not aVect virus replication and movement via plasmodesmata. Because the mobility of nucleolar components depends on the interactions and functions of the components (Olson and Dundr 2005) , we suggest that targeting of viral proteins to the nucleolus could help viral protein traYc and diVusion of viral infection.