Plant epigenome alterations: an emergent player in viroid-host interactions.

It is well known that viroids promote significant alterations at diverse host regulatory levels. However the mechanisms by which these tiny RNAs subvert endogenous regulatory networks remain a to a large extent unsolved question. In the last years diverse studies have revealed the existence of a close interplay between viroid infection and host DNA methylation, suggesting that the modulation of the endogenous transcriptional activity by epigenetic alterations of the host genome may emerge as a novel player in plant-viroid interactions. Here, we summarize the more relevant findings related to alteration of the host DNA methylome in response to viroid infection and discus the potential strategies which may be exploited by these non-conventional pathogenic RNAs to hijack and redesign the plant epigenome.