RRC ID 28167
Author Nosaka M, Itoh J, Nagato Y, Ono A, Ishiwata A, Sato Y.
Title Role of transposon-derived small RNAs in the interplay between genomes and parasitic DNA in rice.
Journal PLoS Genet
Abstract RNA silencing is a defense system against "genomic parasites" such as transposable elements (TE), which are potentially harmful to host genomes. In plants, transcripts from TEs induce production of double-stranded RNAs (dsRNAs) and are processed into small RNAs (small interfering RNAs, siRNAs) that suppress TEs by RNA-directed DNA methylation. Thus, the majority of TEs are epigenetically silenced. On the other hand, most of the eukaryotic genome is composed of TEs and their remnants, suggesting that TEs have evolved countermeasures against host-mediated silencing. Under some circumstances, TEs can become active and increase in copy number. Knowledge is accumulating on the mechanisms of TE silencing by the host; however, the mechanisms by which TEs counteract silencing are poorly understood. Here, we show that a class of TEs in rice produces a microRNA (miRNA) to suppress host silencing. Members of the microRNA820 (miR820) gene family are located within CACTA DNA transposons in rice and target a de novo DNA methyltransferase gene, OsDRM2, one of the components of epigenetic silencing. We confirmed that miR820 negatively regulates the expression of OsDRM2. In addition, we found that expression levels of various TEs are increased quite sensitively in response to decreased OsDRM2 expression and DNA methylation at TE loci. Furthermore, we found that the nucleotide sequence of miR820 and its recognition site within the target gene in some Oryza species have co-evolved to maintain their base-pairing ability. The co-evolution of these sequences provides evidence for the functionality of this regulation. Our results demonstrate how parasitic elements in the genome escape the host's defense machinery. Furthermore, our analysis of the regulation of OsDRM2 by miR820 sheds light on the action of transposon-derived small RNAs, not only as a defense mechanism for host genomes but also as a regulator of interactions between hosts and their parasitic elements.
Volume 8(9)
Pages e1002953
Published 2012-9-1
DOI 10.1371/journal.pgen.1002953
PMID 23028360
PMC PMC3459959
MeSH DNA Methylation / genetics DNA Transposable Elements / genetics* Epigenetic Repression Evolution, Molecular Gene Expression Regulation, Plant Gene Silencing Genome, Plant Host-Parasite Interactions / genetics* Interspersed Repetitive Sequences / genetics MicroRNAs* / genetics MicroRNAs* / metabolism Oryza / genetics* RNA, Small Interfering / genetics*
IF 5.175
Times Cited 48
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