Functional consequences of rapid evolution at Drosophila centromeres

Abstract

Centromeres are loci on chromosomes that are essential for faithful inheritance of genomic information at every cell division in eukaryotic organisms. Centromeric chromatin is the foundation for one of the largest macromolecular structures in the cell - the kinetochore, which facilitates tension between the chromosome and the spindle pole during the act of chromosome segregation. Despite this vital function, centromeric DNA and genes that encode essential centromeric proteins evolve rapidly in plants and animals. However, the selective forces driving the rapid evolution of centromeres and the functional consequences of such rapid change are not well understood. I aimed to gain insight into the functional consequences of centromere evolution, using Drosophila as a model system. I discovered that rapid evolution has resulted in species-specific function of the centromeric histone variant CENP-A/Cid. Furthermore, I found rapid evolution had not only affected the primary sequence of kinetochore proteins in Drosophila, but also the composition of the kinetochore itself, since the young gene Umbrea gained essential centromere function after duplication. Finally, I found that divergence at Drosophila centromeres may have broad consequences for species, since some genes involved in speciation encode rapidly evolving centromeric proteins.