Schematic depiction of TE control in the different models. A. Transposon dynamics. Active TEs are transcribed and may integrate new TE copies into the host genome via several steps in the cytoplasm. B. Transcriptional silencing of TEs. Short transcripts are produced from heterochromatic regions of the genome, and these are processed into small RNAs (left panel). Alternatively, antisense RNA is produced from silenced TEs, which base pairs with mRNA and is then processed into small RNAs (right panel). In both cases small RNAs assist in heterochromatin formation. C. Post-transcriptional silencing of TEs. In the left panel, dsRNA is formed by RdRP from mRNA. In the middle panel, dsRNA is the result of sense-antisense annealing, and in the right panel mRNA hairpin formation leads to dsRNA. In all models the resulting dsRNA is cleaved into small RNAs. These small RNAs guide the degradation of base pair matching mRNA by RISC, and prime mRNA for dsRNA formation by RdRP (left panel only).