Maternal piRNAs Are Essential for Germline Development following De Novo Establishment of Endo-siRNAs in Caenorhabditis elegans.
The Piwi-piRNA pathway represents a germline-specific transposon-defense system. C. elegans Piwi, prg-1, is a non-essential gene and triggers a secondary RNAi response that depends on mutator genes, endo-siRNAs (22G-RNAs), and the 22G-RNA-binding Argonaute protein HRDE-1. Interestingly, silencing of PRG-1 targets can become PRG-1 independent. This state, known as RNAe, is heritable and depends on mutator genes and HRDE-1. We studied how the transgenerational memory of RNAe and the piRNA pathway interact. We find that maternally provided PRG-1 is required for de novo establishment of 22G-RNA populations, especially those targeting transposons. Strikingly, attempts to re-establish 22G-RNAs in absence of both PRG-1 and RNAe memory result in severe germline proliferation defects. This is accompanied by a disturbed balance between gene-activating and -repressing 22G-RNA pathways. We propose a model in which CSR-1 prevents the loading of HRDE-1 and in which both PRG-1 and HRDE-1 help to keep mutator activity focused on the proper targets.
Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany; Graduate Program in Areas of Basic and Applied Biology, University of Porto, 4099-003 Porto, Portugal.
Bruno F M
BF
de Albuquerque
Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany.
Maria
M
Placentino
Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany. Electronic address: r.ketting@imb.de.
René F
RF
Ketting
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics; D020868:Gene Silencing; D017238:Genes, Helminth; D005854:Germ Cells / Q000254:growth & development* / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D018510:RNA, Helminth / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics
D029742:Caenorhabditis elegans Proteins; D004251:DNA Transposable Elements; D018510:RNA, Helminth; D034741:RNA, Small Interfering