AGO1, QDE-2, and RDE-1 are related proteins required for post-transcriptional gene silencing in plants, quelling in fungi, and RNA interference in animals

Introduction of transgene DNA may lead to specific degradation of RNAs that are homologous to the transgene transcribed sequence through phenomena nam ed post-transcriptional gene silencing (PTGS) in plants, quelling in fungi, and RNA interference (RNAi) in animals. It was shown previously that PTGS. quelling, and RNAi require a set of related proteins (SCS2, QDE-1, and EGO -1, respectively). Here we report the isolation of Arabidopsis mutants impa ired in PTGS which are affected at the Argonaote1 (AGO1) locus. AGO1 is sim ilar to QDE-2 required for quelling and RDE-1 required for RNAi. Sequencing of ago1 mutants revealed one amino acid essential for PTGS that is also pr esent in QDE-2 and RDE-1 in a highly conserved motif. Taken together, these results confirm the hypothesis that these processes derive from a common a ncestral mechanism that controls expression of invading nucleic acid molecu les at the post-transcriptional level. As opposed to rde-1 and qde-2 mutant s, which are viable, ago1 mutants display several developmental abnormaliti es, including sterility. These results raise the possibility that PTGS. or at least some of its elements, could participate in the regulation of gene expression during development in plants.