Nucleolar clustering of rDNA determines preferential association of rDNA-carrying chromosome ends. (A) Two-color DNA FISH of telomeric clusters (rep20, green) and 18S rDNA (red). The 18S rDNA FISH probe simultaneously detects the five rDNA units, which are clustered at one pole of the nucleus opposing the telomere clusters. White arrow points to the potential nucleolus-associated telomeric cluster. (B) Table presenting relative nuclear position of chromosome-ends (all genes encode PfEMP1) used in C determined by immuno-FISH using PfNop1 antibodies. (C) Two-color DNA FISH analysis of chromosome end pairs. Chromosome end 1 is labeled in green, and chromosome ends 5, 11, 13, 6, and 12 are shown in red. In all images, the parasites are in ring-stage, and nuclei are shown by DAPI staining (blue). (Scale bar, 1 μm).

Mancio-Silva L, Zhang Q, Scheidig-Benatar C, Scherf A. Clustering of dispersed ribosomal DNA and its role in gene regulation and chromosome-end associations in malaria parasites. Proc Natl Acad Sci U S A. 2010 107:15117-22.