Posttranscriptional gene silencing is not compromised in the Arabidopsis CARPEL FACTORY (DICER-LIKE1) mutant, a homolog of Dicer-1 from Drosophila.
Posttranscriptional silencing (PTGS) in plants, nematodes, Drosophila, and perhaps all eukaryotes operates by sequence-specific degradation or translational inhibition of the target mRNA. These processes are mediated by duplexed RNA. In Drosophila and nematodes, double-stranded (ds)RNA or self-complementary RNA is processed into fragments of approximately 21 nt by Dicer-1. These small interfering RNAs (siRNAs) serve as guides to target degradation of homologous single-stranded (ss)RNA. In some cases, the approximately 21 nt guide fragments derived from endogenous, imperfectly self-complementary RNAs cause translational inhibition of their target mRNAs, with which they have substantial, but not perfect sequence complementarity. These small temporal RNAs (stRNAs) belong to a class of noncoding microRNAs (miRNAs), 20-24 nt in length, that are found in flies, plants, nematodes, and mammals. In nematodes, the Dicer-1 enzyme catalyzes the production of both siRNA and stRNA. Mutation of the Arabidopsis Dicer-1 homolog, CARPEL FACTORY (CAF), blocks miRNA production. Here, we report that the same caf mutant does not block either PTGS or siRNA production induced by self-complementary hairpin RNA. This suggests either that this mutation only impairs miRNA formation or, more interestingly, that plants have two distinct dicer-like enzymes, one for miRNA and another for siRNAi production.
Finnegan
E Jean
EJ
Commonwealth Scientific and Industrial Research Organisation, Plant Industry, P.O. Box 1600, Canberra ACT 2601, Australia. jean.finnegan@csiro.au
Margis
Rogerio
R
Waterhouse
Peter M
PM
D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics*; D004722:Endoribonucleases / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism; D005810:Multigene Family; D010802:Phylogeny; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D043244:Ribonuclease III
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D035683:MicroRNAs; D034741:RNA, Small Interfering; D004722:Endoribonucleases; C402383:DCL1 protein, Arabidopsis; D043244:Ribonuclease III