Characterization of a dual-strand D. virilis piRNA cluster uniquely expressed in strain 160. (A) Example of in situ hybridization with cluster DNA. Arrows indicate hybridization at the telomere of chromosome 2 and at the 7C region of the X-chromosome of strain 9. Virtually all probes hybridized with variable efficiency to the heterochromatic chromocenter but also to other discrete genomic locations, which agreed with sequence-based assignments. The consistent hybridization with the 7C region on the X-chromosome of strain 9 was absent in strain 160. (B) Uniquely mapped piRNAs were plotted over cluster 1 (see Supplemental Table S1), which contains TART elements and protein-coding regions. These are differentially processed into piRNAs in strains 160 (red) and 9 (green).
