Trans-acting siRNA Brett Johnson BMS265 Trans-acting siRNA is just like “normal” siRNA Trans-acting siRNA is just like “normal” siRNA …except for when its not. Discovery Biogenesis ta-siRNAs come from TAS genes Mechanism of Action Trans-acting siRNAs act in trans! Cellular Functions • All ta-siRNAs from a TAS gene tend to have similar targets. • Four TAS families in Arabidopsis: – TAS1 regulates at least 5 different targets of unknown function – TAS2 targets 2 Pentatricopeptide Repeat (PPR) proteins of disputed function – TAS3 targets three Auxin Response Factor (ARF) genes (tasiR-ARF) – TAS4 targets MYB transcripts (cell cycle, metabolism) Evolution and Conservation • TAS1 and TAS2 ta-siRNAs are unique to Arabidopsis • TAS3 is conserved in rice, Arabidopsis and maize (monocot vs. dicot lineages) • miR390 directed biogenesis of tasiRNAs is conserved in moss (400 million years) Potential as a Tool QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Replaced the ta-siRNAs in TAS1c and silenced FAD2 activity to levels comparable to a null mutant There’s More! There’s More! Read the wiki.