Figure 2

Physical mapping of 45S rDNA in three Karenia species. DAPI-stained DNA (blue) and in situ hybridization of the digoxigenin-labeled pTa71 probe for the detection of 45S rDNA (green) in K. brevis (A–G), K. selliformis (H–J) and K. mikimotoi (K–Q) nuclei at different stages of the vegetative cell cycle. In E, the arrow points to a nucleolus at higher magnification to show the co-localization of rDNA in this less-intense DAPI-staining nuclear domain. M–Q provide an example of two-color FISH using the 45S rDNA (green) and (AG)10 probes (red) before ND-FISH using the telomeric probe. In M, the arrow indicates the AG-chromosome, and the boxes the nuclear areas amplified in N, O and in P, Q to show the precise co-localization of the 45S rDNA (arrows in N, P) with the telomeric signals (arrows in O, Q). Scale bar = 10 μm (A–D, F–M) or 2.5 μm (E, N–Q).