Transposon Invasion of the Paramecium Germline Genome Countered by a Domesticated PiggyBac Transposase and the NHEJ Pathway

Figure 2

Schematic representation of the structure of the MIC and MAC genomes in Paramecium. On the MIC chromosome displayed on top, genes (black boxes) are interrupted by short internal eliminated sequences (IESs, in red), some of which are also found in noncoding regions (thin line). Repeated germline sequences (transposons, minisatellites, etc.) are symbolized by a yellow double-headed arrow. During MAC development, each MIC chromosome is amplified ~400-fold and gives rise to a population of heterogeneous MAC chromosomes. Indeed, imprecise elimination of repeated DNA is associated with alternative rearrangements: (I) chromosome fragmentation is observed and telomeres (blue squares) are added to new MAC chromosome ends; (II) the two chromosome arms that flank the eliminated germline region can be joined in an imprecise manner to generate internal deletions of heterogeneous sizes.