Ciliated protists rearrange their genomes dramatically during nuclear development via chromosome fragmentation and DNA deletion to produce a trimmer and highly reorganized somatic genome. The deleted portion of the genome includes potentially active transposons or transposon-like sequences that reside in the germline. Three independent studies recently showed that transposase proteins of the DDE/DDD superfamily are indispensible for DNA processing in three distantly related ciliates. In the spirotrich Oxytricha trifallax, high copy-number germline-limited transposons mediate their own excision from the somatic genome but also contribute to programmed genome rearrangement through a remarkable transposon mutualism with the host. By contrast, the genomes of two oligohymenophorean ciliates, Tetrahymena thermophila and Paramecium tetraurelia, encode homologous PiggyBac-like transposases as single-copy genes in both their germline and somatic genomes. These domesticated transposases are essential for deletion of thousands of different internal sequences in these species. This review contrasts the events underlying somatic genome reduction in three different ciliates and considers their evolutionary origins and the relationships among their distinct mechanisms for genome remodeling.

+More

fragmentation piggybaclike somatic genome reduction transposons or transposonlike singlecopy transposase proteins deletion ddeddd

Laura F Landweber,Aaron David Goldman,Alexander Vogt,Kazufumi Mochizuki,.Transposon domestication versus mutualism in ciliate genome rearrangements.. 9 (8),.

Laura F Landweber,Aaron David Goldman,Alexander Vogt,Kazufumi Mochizuki,"Transposon domestication versus mutualism in ciliate genome rearrangements." 9

Laura F Landweber,Aaron David Goldman,Alexander Vogt,Kazufumi Mochizuki,"Transposon domestication versus mutualism in ciliate genome rearrangements."