Geminiviruses and RNA silencing.

Geminiviruses are single-stranded circular DNA viruses that cause economically significant diseases in a wide range of crop plants worldwide. In plants, post-transcriptional gene silencing (PTGS) acts as a natural anti-viral defense system and plays a role in genome maintenance and development. During the past decade there has been considerable evidence of PTGS suppression by viruses, which is often required to establish infection in plants. In particular, nuclear-replicating geminiviruses, which have no double-stranded RNA phase in their replication cycle, can induce and suppress the PTGS and become targets for PTGS. Here, we summarize recent developments in determining how these viruses trigger PTGS and how they suppress the induced PTGS, as well as how we can use the system to control these viruses in plants better and manipulate the system to study functional genomics in crop plants.