title: Most microRNAs in the single-cell alga Chlamydomonas reinhardtii are produced by Dicer-like 3-mediated cleavage of introns and untranslated regions of coding RNAs.
abstract: We describe here a forward genetic screen to investigate the biogenesis, mode of action, and biological function of miRNA-mediated RNA silencing in the model algal species,Chlamydomonas reinhardtii Among the mutants from this screen, there were three at Dicer-like 3 that failed to produce both miRNAs and siRNAs and others affecting diverse post-biogenesis stages of miRNA-mediated silencing. The DCL3-dependent siRNAs fell into several classes including transposon- and repeat-derived siRNAs as in higher plants. The DCL3-dependent miRNAs differ from those of higher plants, however, in that many of them are derived from mRNAs or from the introns of pre-mRNAs. Transcriptome analysis of the wild-type and dcl3 mutant strains revealed a further difference from higher plants in that the sRNAs are rarely negative switches of mRNA accumulation. The few transcripts that were more abundant in dcl3 mutant strains than in wild-type cells were not due to sRNA-targeted RNA degradation but to direct DCL3 cleavage of miRNA and siRNA precursor structures embedded in the untranslated (and translated) regions of the mRNAs. Our analysis reveals that the miRNA-mediated RNA silencing in C. reinhardtii differs from that of higher plants and informs about the evolution and function of this pathway in eukaryotes.
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Valli
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Bruno A C M
authors.initials: BA
authors.lastname: Santos
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Silvia
authors.initials: S
authors.lastname: Hnatova
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Bassett
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Attila
authors.initials: A
authors.lastname: Molnar
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: Betty Y
authors.initials: BY
authors.lastname: Chung
authors.affiliation: Department of Plant Sciences, University of Cambridge CB2 3EA, Cambridge CB2 3EA, United Kingdom.
authors.forename: David C
authors.initials: DC
authors.lastname: Baulcombe
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism*; D002874:Chromosome Mapping; D018506:Gene Expression Regulation, Plant; D007438:Introns; D035683:MicroRNAs / Q000235:genetics*; D009154:Mutation; D034622:RNA Interference; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D020506:Untranslated Regions
chemical_list: D035683:MicroRNAs; D020506:Untranslated Regions; D043244:Ribonuclease III