Digitaria streak geminivirus replicative forms are abundant in S-phase nuclei of infected cells

We have analyzed the replication of Digitaria streak geminivirus (DSV) using flow cytometry. Nuclei from infected plants were sorted on the basis of their DNA content in the different phases of the cell cycle and viral DNA forms in them were analyzed. DSV replicative forms were much more abundant (up to 20 times in one experiment) in S-phase nuclei than in G0-G1 and G2 nuclei, while single-stranded viral DNA did not show such dramatic increase during any phase. DSV replicative forms constitute almost 90% of total viral DNA forms in S-phase nuclei. DSV replication seems to be synchronized with host DNA replication and might be primarily under control of host factors becoming available only at the G1/S boundary.