Genomes are highly dynamic units that often undergo events of reorganization which are formally called developmentally regulated genome rearrangements (DRGRs). DRGRs, like for example chromatin/chromosome elimination or chromatin diminution are widespread throughout eukaryotes (e.g., ciliates, animals, insects, kinetoplastids, foraminifera, entamoebae) and create diversity in genome architecture, often producing significant changes in the fate of the affected cells. The relevance and the consequences of DRGRs have to date received relatively little attention, one reason being that this type of events clash against a commonly, too simplistic, held view that the eukaryotic genome content essentially does not vary among nuclei during an organism’s lifetime. Here, we propose to study the evolution and biological significance of DRGRs by examining one of its best-known and peculiar examples, the massive elimination of so-called internal eliminated sequences (IESs) from the micronuclear DNA of the ciliate Paramecium. Paramecium is a powerful model system that because of its remarkable biological features and molecular tools represents an excellent system to elucidate the evolution of genome architecture. Given the wide phylogenetic distribution of DRGRs, our analysis not only will provide valuable insights about the rates and mechanisms of origin, evolution, and loss of IESs from multiple Paramecium species, possibly reveal the regulatory potential of these non-coding sequens, and improve our understanding of DRGRs in ciliates, but can also lead to the identification of aspects of DRGRs that could be cautiously generalized to other eukaryotic lineages. Notably, a number of features of ciliates that have initially been viewed as odd and unusual have already helped reveal universal molecular processes (e.g., self-splicing RNA, telomere addition).
Field of science
- /natural sciences/biological sciences/genetics and heredity/genome
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