title: A biochemical framework for RNA silencing in plants.
abstract: RNA silencing phenomena were first discovered in plants, yet only the RNA interference pathway in animals has been subject to biochemical analysis. Here, we extend biochemical analysis to plant RNA silencing. We find that standard wheat germ extract contains Dicer-like enzymes that convert double-stranded RNA (dsRNA) into two classes of small interfering RNAs, as well as an RNA-dependent RNA polymerase activity that can convert exogenous single-stranded RNA into dsRNA. In this plant embryo extract, an endogenous microRNA (miRNA) that lacks perfect complementarity to its RNA targets nonetheless acts as a small interfering RNA. The miRNA guides an endonuclease to cleave efficiently wild-type Arabidopsis PHAVOLUTA mRNA, but not a dominant mutant previously shown to perturb leaf development. This finding supports the view that plant miRNAs direct RNAi and that miRNA-specified mRNA destruction is important for proper plant development. Thus, endonuclease complexes guided by small RNAs are a common feature of RNA silencing in both animals and plants.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
authors.forename: Guiliang
authors.initials: G
authors.lastname: Tang
authors.forename: Brenda J
authors.initials: BJ
authors.lastname: Reinhart
authors.forename: David P
authors.initials: DP
authors.lastname: Bartel
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Zamore
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics; D004722:Endoribonucleases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005799:Genes, Dominant; D018398:Homeodomain Proteins / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics*; D010936:Plant Extracts; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D043244:Ribonuclease III; D014908:Triticum / Q000196:embryology / Q000201:enzymology*
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; D035683:MicroRNAs; C114644:PHV protein, Arabidopsis; D010936:Plant Extracts; D010940:Plant Proteins; D012330:RNA, Double-Stranded; D018749:RNA, Plant; D034741:RNA, Small Interfering; D012324:RNA-Dependent RNA Polymerase; D004722:Endoribonucleases; D043244:Ribonuclease III