The presence of a nucleus is the principal feature that distinguishes eukaryotic from prokaryotic cells. The nucleus and its contents are separated from the cytoplasm by the nuclear membranes that serve as barriers controlling the passage of large molecules into and out of the nucleus. Small molecules, up to 40 kDa diffuse passively through the nuclear pore complex of the nuclear envelop,  while transport of large molecules occurs through an active mechanism which requires energy. Import of viral DNA into the plant host cell nucleus is essential for the successful replication of a small group of plant DNA viruses - the geminiviruses. To achieve this  goal, they have developed mechanisms  enabling them to cross the nuclear membranes.

In this article, we discuss suggested mechanisms for this nuclear import of geminiviruses and the role of viral karyophilic proteins in mediating the nuclear entry of the viral genomes.