Résumé
In plants, RNA interference constitutes an important defense mechanism against viruses, transposons,
and transgenes. Viruses, on the other hand, use suppressors to counteract silencing. In contrast to mammalian
systems, silencing in plants spreads systemically through the whole organism. Since also viruses spread
and consequently produce suppressors systemically, a race between silencing and virus replication occurs.
Apparently, successful viruses win the race, but only until they reach the tissue around the meristem. There,
the silencing mechanism is most capable by efficiently amplifying the silencing signal, bona fide 21-nt
siRNA, leading to the well-known phenomenon of meristem exclusion.