Heritable transposon silencing initiated by a naturally occurring transposon inverted duplication.
It has been suggested that gene silencing evolved as a defense against genomic parasites such as transposons. This idea is based on analysis of mutations that reactivate transposons that are stably silenced: they affect maintenance rather than initiation of silencing. Here we describe the cloning and characterization of a naturally occurring locus able to heritably silence the otherwise highly active MuDR transposon in maize. This locus, Mu killer (Muk), results from the inverted duplication of a partially deleted autonomous MuDR element located at the breakpoint of a genomic deletion. Muk produces a hybrid hairpin transcript that is processed into small RNAs, which are amplified when the target MuDR transcript is present. Muk provides the first example of a naturally occurring transposon derivative capable of initiating the heritable silencing of an active transposon family. Further, transposon-generated inverted duplications may be important for the generation of double-stranded RNAs used in gene silencing.
Slotkin
R Keith
RK
Department of Plant and Microbial Biology, 111 Koshland Hall, University of California Berkeley, Berkeley, California 94720, USA.
Freeling
Michael
M
Lisch
Damon
D
D004251:DNA Transposable Elements; D017353:Gene Deletion; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D008969:Molecular Sequence Data; D034741:RNA, Small Interfering; D003313:Zea mays / Q000235:genetics*
D004251:DNA Transposable Elements; D034741:RNA, Small Interfering