Format

Send to

Choose Destination
Nature. 2014 Apr 17;508(7496):411-5. doi: 10.1038/nature13069. Epub 2014 Mar 16.

miRNAs trigger widespread epigenetically activated siRNAs from transposons in Arabidopsis.

Author information

1
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
2
Delaware Biotechnology Institute and Department of Plant & Soil Sciences, 15 Innovation Way, University of Delaware, Newark, Delaware 19711, USA.
3
1] Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA [2] Howard Hughes Medical Institute-Gordon and Betty Moore Foundation, Cold Spring Harbor Laboratory, New York 11724, USA [3] Chaire Blaise Pascal, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), 75230 Paris, France.

Abstract

In plants, post-transcriptional gene silencing (PTGS) is mediated by DICER-LIKE 1 (DCL1)-dependent microRNAs (miRNAs), which also trigger 21-nucleotide secondary short interfering RNAs (siRNAs) via RNA-DEPENDENT RNA POLYMERASE 6 (RDR6), DCL4 and ARGONAUTE 1 (AGO1), whereas transcriptional gene silencing (TGS) of transposons is mediated by 24-nucleotide heterochromatic (het)siRNAs, RDR2, DCL3 and AGO4 (ref. 4). Transposons can also give rise to abundant 21-nucleotide 'epigenetically activated' small interfering RNAs (easiRNAs) in DECREASED DNA METHYLATION 1 (ddm1) and DNA METHYLTRANSFERASE 1 (met1) mutants, as well as in the vegetative nucleus of pollen grains and in dedifferentiated plant cell cultures. Here we show that easiRNAs in Arabidopsis thaliana resemble secondary siRNAs, in that thousands of transposon transcripts are specifically targeted by more than 50 miRNAs for cleavage and processing by RDR6. Loss of RDR6, DCL4 or DCL1 in a ddm1 background results in loss of 21-nucleotide easiRNAs and severe infertility, but 24-nucleotide hetsiRNAs are partially restored, supporting an antagonistic relationship between PTGS and TGS. Thus miRNA-directed easiRNA biogenesis is a latent mechanism that specifically targets transposon transcripts, but only when they are epigenetically reactivated during reprogramming of the germ line. This ancient recognition mechanism may have been retained both by transposons to evade long-term heterochromatic silencing and by their hosts for genome defence.

PMID:
24670663
PMCID:
PMC4074602
DOI:
10.1038/nature13069
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Nature Publishing Group Icon for PubMed Central
Loading ...
Support Center