Affiliation:
1. Laboratoire de Génétique Moléculaire, CNRS UMR 8541, Ecole Normale Supérieure, Paris, France
Abstract
ABSTRACT
The germ line genome of ciliates is extensively rearranged during development of the somatic macronucleus. Numerous sequences are eliminated, while others are amplified to a high ploidy level. In the
Paramecium aurelia
group of species, transformation of the maternal macronucleus with transgenes at high copy numbers can induce the deletion of homologous genes in sexual progeny, when a new macronucleus develops from the wild-type germ line. We show that this
trans
-nuclear effect correlates with homology-dependent silencing of maternal genes before autogamy and with the accumulation of ∼22- to 23-nucleotide (nt) RNA molecules. The same effects are induced by feeding cells before meiosis with bacteria containing double-stranded RNA, suggesting that small interfering RNA-like molecules can target deletions. Furthermore, experimentally induced macronuclear deletions are spontaneously reproduced in subsequent sexual generations, and reintroduction of the missing gene into the variant macronucleus restores developmental amplification in sexual progeny. We discuss the possible roles of the ∼22- to 23-nt RNAs in the targeting of deletions and the implications for the RNA-mediated genome-scanning process that is thought to determine developmentally regulated rearrangements in ciliates.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
127 articles.
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