Fig. 3. Alterations in rDNA structure in meiocytes of ask1-1 plants. FISH using an rDNA probe on meiotic chromosomes in wild-type (A-D,I-L) and ask1-1 (E-H,M-P) plants. Merged photos of biotin-labeled rDNA signals (green) on chromosomes counterstained with DAPI (red) are shown. (A,E) Early leptotene; (B,F) zygotene; (C,G) pachytene; (D,H) diakinesis; (I,M) premetaphase; (J,N) metaphase I/early anaphase I; (K,O) telophase I; (L,P) metaphase II. Arrow shows the single rDNA region. Eleven chromosomes are observed suggesting the breakage of rDNA from chromosomes II and IV. Assignment of meiotic stages in ask1-1 is based on chromosome morphology and the stage of the surrounding tapetal cells (Wang et al., 2004). Bar, 10 µm.