RNA interference viral suppressor and RNA. Computer model showing the molecular structure of the p19 protein (blue) from a Tombusvirus, suppressing a double-stranded, small interfering RNA (siRNA) molecule (brown and orange). RNA interference, or RNA silencing, has developed in plants as a defence against viruses. However, some viruses have developed proteins such as p19, that inhibit the process and allow them to infect the host plant's cells.