EN
RNA-dependent processes control gene expression at the post-transcriptional and transcriptional levels in plants. There is a specific group of RNA molecules called small RNAs that play a significant role in the RNA degradation, methylation of genomes, inhibition of translation and, consequently, gene expression regulation. They consist of double ? stranded small interfering RNAs and single-stranded microRNAs. SiRNAs and miRNAs? functioning occurs when double-stranded RNAs of different origins appear in a cell. DsRNAs intermediate the process of gene silencing which has many implications for natural mechanisms of gene expression in plants and other eukaryotes. Furthermore, gene silencing initially thought to have been an effect of introducing transgenes into plants, now seems to be a defence mechanism against viruses and transposable elements.