Signalling in gene silencing

At present, the available data only allow us to speculate on the molecules and processes that are involved in PTGS. In a simplified model, PTGS can be considered as a mechanism in which a mobile signal exceeds a threshold. Although the nature of such a signal is unknown, it is thought that it contains dsRNA. However, degradation of dsRNA is assumed to be responsible for the removal of mRNA during PTGS, so it appears unlikely that the signal is an unprotected dsRNA molecule. It is worth investigation whether the signal molecules are protected by proteins or whether they can escape degradation, for example, by heteroduplex formation. To investigate the role of dsRNA in PTGS further, biolistic techniques for the transfer of dsRNA into plant cells could be very helpful.