RNA interference (RNAi) is an elegant technique in which double-stranded RNA (dsRNA) can direct the degradation of homologous RNA species leading to post-transcriptional gene silencing. In the October 2 EMBO Journal Mette et al. extend dsRNA applications by showing that dsRNA corresponding to sequences from the nopaline synthase promoter (NOSpro) could disrupt transcriptional activation (EMBO Journal 2000, 19:5194-5201). The dsRNA trans-silencing was accompanied by induced methylation of the target NOSpro locus. The formation of a NOSpro RNA hairpin was essential for transcriptional silencing. Analysis revealed that the NOSpro dsRNA is degraded into small RNAs 23-25 nucleotides long, as has been observed for RNAi in animal systems. They show that this dsRNA trans-silencing technique functions in transgenic tobacco plants, as well as Arabidopsis lines, suggesting that it could be widely applied as a strategy to turn off plant genes.