Endogenous Small RNA Mediates Meiotic Silencing of a Novel DNA Transposon

This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Genetics Society of America. The published article can be found at:http://www.g3journal.org/Supporting information available online at: http://g3journal.org/content/5/10/1949/suppl/DC1Genome defense likely evolved to curtail the spread of transposable elements and invading\ud viruses. A combination of effective defense mechanisms has been shown to limit colonization of the Neurospora\ud crassa genome by transposable elements. A novel DNA transposon named Sly1-1 was discovered\ud in the genome of the most widely used laboratory “wild-type” strain FGSC 2489 (OR74A). Meiotic silencing\ud by unpaired DNA, also simply called meiotic silencing, prevents the expression of regions of the genome\ud that are unpaired during karyogamy. This mechanism is posttranscriptional and is proposed to involve the\ud production of small RNA, so-called masiRNAs, by proteins homologous to those involved in RNA\ud interference - silencing pathways in animals, fungi, and plants. Here, we demonstrate production of small\ud RNAs when Sly1-1 was unpaired in a cross between two wild-type strains. These small RNAs are dependent\ud on SAD-1, an RNA-dependent RNA polymerase necessary for meiotic silencing. We present the first case of\ud endogenously produced masiRNA from a novel N. crassa DNA transposable element