Distinct satellite DNA composition between core and germline restricted chromosomes in Bradysia (Sciara) coprophila

Programmed DNA elimination (PDE), a phenomenon wherein cells eliminate a subset of genetic material during certain stages of development, is observed in a broad range of organisms. The fungus gnat Bradysia (formerly Sciara ) coprophila undergoes a series of PDE events during their development, including elimination of germline-restricted chromosomes (called L chromosomes) in soma and elimination of paternal chromosomes during male meiosis. However, the underlying mechanisms of this phenomenon are poorly understood. Highly repetitive satellite DNA, which often shows chromosome specific distribution, is a possible candidate for sequences involved in PDE. In this study, we utilized recent genomic data and genome assemblies to identify new satellite DNA sequences of B. coprophila . Through characterization of satellite DNA distribution on chromosomes, we found that the X and autosomes do not share centromeric satellite DNA sequence with the L chromosomes. We further provide the cytological evidence that confirms a recent finding based on the genome assembly that there are two distinct L chromosomes that were not previously distinguished cytologically. Together, our work lays a foundation for future studies to explore the possible connection between satellite DNA and the mechanism of PDE in B. coprophila .