Fig. 1. Chromatin rearrangement and bouquet formation in meiotic prophase of maize. Images of each nucleus were acquired using a DeltaVision Microscopy system (Applied Precision) followed by computational deconvolution (Golubovskaya et al., 2002). This results in a 3D data stack. Shown here are 2D projections from whole or partial 3D data stacks. We encourage you to view the movies of rotating 3D images of these same nuclei in the supplemental material (http://jcs.biologists.org/supplemental/). Chromatin (stained with DAPI) is shown in red; telomeres (FITC) are shown in green; centromeres (Cy3 or Cy5) are shown in blue in A, B and G; and the single 5SrRNA (Cy3 or Cy5) locus is shown in blue in C, D, E, F and H. (A) Leptotene. Telomeres and centromeres are distributed throughout the nuclear volume. Chromosomes can be seen as thin threads almost like beads on a string, and heterochromatin knobs appear spherical. (B) Late leptotene. Telomeres are attached to the inner surface of the nuclear envelope (NE). Centromeres are distributed throughout the nuclear volume. Chromosomes are still completely unsynapsed but appear more condensed. (C) Early zygotene. Telomeres are gathered in a narrow patch on the NE, but are not yet completely clustered. Chromatin is more condensed, and some regions are beginning to synapse. This can be seen more easily in the supplemental material as thicker and apparently paired regions of the chromosomes. Some knobs are round, and some are elongated. The two 5SrRNA foci, seen here as blue dots, one on each homolog, are obviously not paired. (D,E) Classic zygotene. Telomeres are clustered in the bouquet. These cells are very typical of the maize bouquet. Chromatin structure has not changed from earlier zygotene, except that more chromosome regions are paired. This is readily apparent in the supplemental material. The 5SrRNA foci are still not paired, but we imagine that they are in the process of pairing in E (compare distances between two foci in C, D and E). (F) Pachytene. All chromosomes are completely paired and synapsed. This can be seen as a doubled chromatin width (compare E and F), and there is only one 5SrRNA focus. All telomeres are still on the NE, but they are beginning to disperse from the bouquet. (G,H) Late pachytene. All chromosomes are still completely paired and synapsed, but telomeres are being released from the NE. Centromeres (G) are dispersed throughout the nucleus, and the 5SrRNA foci is paired (H). The chromatin appears thinner in G owing to a different fixation.