Post-transcriptional gene silencing across kingdoms

Post-transcriptional gene silencing (PTGS) as a consequence of the introduc tion of either transgenes or double-stranded RNA molecules has been found t o occur in a number of species. In the past year, studies in different syst ems have greatly enhanced our understanding of the molecular mechanisms of these phenomena. The ubiquitous presence of PTGS in both the plant and anim al kingdoms and the finding of common genetic mechanisms suggest that PTGS is a universal gene-regulation system fundamental in biological processes s uch as protection against viruses and transposons.