 Not long after , plant virologists working on improving plant resistance to viral diseases observed a similar unexpected phenomenon . While it was known that plants expressing virus @-@ specific proteins showed enhanced tolerance or resistance to viral infection , it was not expected that plants carrying only short , non @-@ coding regions of viral RNA sequences would show similar levels of protection . Researchers believed that viral RNA produced by transgenes could also inhibit viral replication . The reverse experiment , in which short sequences of plant genes were introduced into viruses , showed that the targeted gene was suppressed in an infected plant . This phenomenon was labeled " virus @-@ induced gene silencing " ( VIGS ) , and the set of such phenomena were collectively called post transcriptional gene silencing . 
