Meiotic telomere clustering is inhibited by colchicine but does not require cytoplasmic microtubules

Abstract

Telomere clustering, the defining feature of the bouquet, is an almost universal feature of meiotic prophase, yet its mechanism remains unknown. The microtubule-depolymerizing agent colchicine was found to inhibit bouquet formation. Telomeres in colchicine-treated cells remained scattered in the nuclear periphery, whereas untreated cells exhibited a prominent telomere cluster. Colchicine administered after the bouquet had formed did not affect telomere dispersal. The effect of colchicine on bouquet formation appeared to be separable from its effect on cytoplasmic microtubules; amiprophos methyl, a highly effective plant microtubule-depolymerizing drug, did not affect telomere clustering. Inhibition of bouquet formation was limited to colchicine and the related drug podophyllotoxin out of the variety of microtubule-depolymerizing drugs tested, suggesting that the target involved in bouquet formation has a structural specificity.

Live imaging of rapid chromosome movements in meiotic prophase I in maize

“…These results suggest that chromosome motility in maize meiocytes requires both actin and tubulin. It is worth noting that Cowan and Cande (17) demonstrated that, in rye, the telomere clustering at the onset of zygonema is sensitive to colchicine, but does not require cytoplasmic microtubules, and suggested that membrane-associated tubulin or tubulins other than ␤-tubulin may be the colchicine target in this case. We used colchicine concentrations that were higher than those found by Cowan and Cande (17) to specifically disrupt the telomere clustering and that would also disrupt the cytoplasmic microtubules.…”

“…It is worth noting that Cowan and Cande (17) demonstrated that, in rye, the telomere clustering at the onset of zygonema is sensitive to colchicine, but does not require cytoplasmic microtubules, and suggested that membrane-associated tubulin or tubulins other than ␤-tubulin may be the colchicine target in this case. We used colchicine concentrations that were higher than those found by Cowan and Cande (17) to specifically disrupt the telomere clustering and that would also disrupt the cytoplasmic microtubules. However, if colchicine has the same effect on chromosome motility in zygonema and pachynema as it does on the prezygotene telomere clustering, it is possible that the nuclear movement cessation after colchicine treatment in our experiments was a result of colchicine disruption of these other tubulins rather than disruption of cytoplasmic microtubules.…”

“…Latrunculin B (Sigma-Aldrich) (35) was used at concentrations of 500 nM and 1 M in the APW medium. Colchicine (SigmaAldrich) (17) was used at concentrations of 1 and 5 mM. In the drug treatment experiments, anthers were incubated in the APW medium containing DAPI, DMSO, and colchicine or latrunculin B for 1 h. After DAPI staining, this solution was replaced with a wash solution comprised of APW medium supplemented with the same concentration of colchicine or latrunculin B as used during the 1-h DAPI incubation.…”

“…To examine whether components of the cytoskeleton are required for chromosome movements in meiotic prophase in maize, we tested the effects of an actin-depolymerizing drug latrunculin B and a tubulin-depolymerizing drug colchicine (9,17). An hour-long incubation of anthers in latrunculin B (at concentrations 0.5 or 1 M) or colchicine (1 or 5 mM) resulted in cessation of all chromosome movements as well as NE deformations in both zygonema and pachynema (Movies S29 and S30).…”

“…Although metaphase I and later meiocytes develop properly in culture (15), attempts to culture isolated meiocytes in early stages of meiotic prophase have failed (16). To circumvent this problem, we developed a system to observe meiotic prophase in meiocytes inside intact live anthers, which, in contrast to isolated meiocytes, can be cultured in grasses during prophase I (17). Maize meiocytes develop in the center of the anther locule, which lies Ϸ70 to 100 m from the outside surface of the anther (Fig.…”