QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 2 November 2004
doi: 10.1242/jcs.01504

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Loidl, J. Articles by Scherthan, H. Search for Related Content PubMed PubMed Citation Articles by Loidl, J. Articles by Scherthan, H.

Organization and pairing of meiotic chromosomes in the ciliate Tetrahymena thermophila

¹ Institute of Botany, University of Vienna, Rennweg 14, 1030 Vienna, Austria
² Institute for Radiation Biology Bw, Neuherbergstrasse 11, 80937 Munich, Germany

View larger version (62K): [in a new window]   Fig. 1. (a) Schematic diagram of MIC development according to Sugai and Hiwatashi (Sugai and Hiwatashi, 1974), and Martindale et al. (Martindale et al., 1982). (b) Changing morphology and divisions of the MIC throughout conjugation as visualized by DAPI staining. Bar, 10 µm.

View larger version (91K): [in a new window]   Fig. 2. (a-d) Immunostaining of Rad51 (green). No Rad51 (a) or very little (b) was detected in the early stage II MIC. (c) A large amount of Rad51 was detected in the somewhat later stage II MIC. (d) A stage IV MIC with granular staining of Rad51 (projection of a deconvolved Z stack of images). (e-l) Immunostaining of Rad51 (green) and phosphorylated histone H3 (phosH3) (red). phosH3 acts as a marker for chromatin condensation. (e) MACs and MICs in a conjugated pair of cells with slightly asynchronous meioses. In the smaller (earlier) MIC (left), the red phosH3 staining predominates because there is only a small amount of Rad51 present. In the later MIC (right) the strong Rad51 and the phosH3 staining mix to produce a yellow color. (f) In this stage III MIC, both phosH3 and Rad51 produce granular immunostaining patterns but the spots do not overlap. (g-l) Stages IV (g), V (h), metaphase I (i), anaphase I (j), anaphase II (k) and the tetrad stage (l). Some Rad51 remains on chromatin (overlapping with phosH3) until anaphase I, but much of it is shed from the chromosomes by metaphase I (note the green staining of the spindle in i), and it has virtually disappeared by anaphase II. Note that the MACs contain Rad51-positive spots (see text). The chromatin is stained with DAPI (blue). Bars, 5 µm (in f for a-f) and 10 µm (in l for g-l).

View larger version (71K): [in a new window]   Fig. 3. The substructure of meiotic MICs as seen by DAPI staining. (a) Stage IV crescents sometimes appear split into two longitudinal subunits that are separated by a gap (arrow) and have dark cross bands, which gives them the misleading appearance of being composed of tandemly arranged bipartite units (either replicated chromosomes or bivalents). (b) A broken stage IV crescent, which reveals its true composition of multiple strands (arrows). (c) A stage II MIC with a DNA-rich region (brightly stained with DAPI) near one pole, striated as if consisting of individual strands, and less dense chromatin towards the opposite pole. (d) In this stage II MIC the chromatin strands seem to form loops (arrow). Bar, 5 µm.

View larger version (105K): [in a new window]   Fig. 4. Chromosome painting by BrdU incorporation. BrdU-labeled chromosomes (red) extend along their entire length of the MICs in stage II (a,b), stage III (c) and stage IV (d). This observation is compatible both with a pole-to-pole and a narrow hairpin-loop arrangement, but not with a tandem arrangement of chromosomes within the crescents. In stage V (e,f) and stage VI (g,h) MICs, and also in diplotene-diakinesis (j), the chromosomes occupy an increasingly compact area. In d and e, some regions of the BrdU-positive threads appear double (arrows). The nuclei shown in f and i seem to contain two labeled chromosomes. (j,k) Conjugating cells, one of which has a labeled crescent. In addition both MACs in j carry labeled DNA. In a-d, the head pole is on the left. The chromatin is stained with DAPI (blue). Bars, 5 µm (in i for a-i) and 10 µm (in k for j,k).

View larger version (109K): [in a new window]   Fig. 5. FISH of meiotic MICs. (a-d) Telomere FISH (yellow) signals are most prevalent at the DAPI-bright, DNA-rich pole of stage II nuclei (a,b). The black and white image in (a) shows the DAPI distribution within the nucleus shown on the left. (c) In stage III nuclei, telomere FISH delineates the head region, which is separated from the trunk by the DAPI-dull neck (for designation see Fig. 1a). (d) The telomeres in stage IV MICs are clustered in the region corresponding to the former head as can be seen by the adjacent DAPI-dull area. (e-l) FISH with locus-specific probes. A pair of Teth2 loci (red) on homologous chromosomes appear mostly separate in stages I to III nuclei (e-h) and associated or fused as a single dot in stage IV (i). The position of the FISH signal in anaphase I (j) configurations confirms that the probed locus occupies a region in the distal third of a chromosome arm [arrows between C (centromere) and T (telomere)]. (k) A macronucleus (at half the magnification) shows multiple copies of the locus highlighted by the Teth2 probe. (l) A second locus (Teth1 – green) on the same chromosome and 167 kb away from Teth2 (red) is always located closer to the neck region (DAPI-dull to the left) of the crescents. All MICs are oriented with the head pole to the left. Bar, 5 µm.