Nucleocytoplasmic trafficking of geminiviral proteins

The bidirectional movement of geminiviruses across the nuclear envelope is essential for this small group of plant viruses, as, not like the majority of plant viruses, they replicate in the nucleus. In plant cells, as in all eukaryotic 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 envelope, while transport of large molecules occurs through an active mechanism which requires energy. To achieve import and export of their genome into and out of the host cell nucleus, geminiviruses have developed mechanisms enabling them to cross the nuclear membranes. In this article, I discuss suggested mechanisms for this nuclear import/export shuttling of geminiviruses and the role of viral proteins in mediating these processes.