Behavior of sex chromosomes, autosomes, and the spindle during nonrandom segregation in a flea beetle

Kupfer, Holly; Wise, Dwayne

doi:10.1139/g00-006

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…It is especially interesting in this light, that all the chromosomes begin meiosis in the central area of the forming spindle and the sex chromosomes are separated to the peripheral spindle area. Further, as we have shown elsewhere, the sex chromosomes accomplish segregation mostly by reorientation and little by kinetochore-to-pole movement (Kupfer and Wise 2000). It is possible that the motor properties of the two spindle domains are different.…”

Section: Discussionmentioning

confidence: 71%

Orientation of nonrandomly segregating sex chromosomes in spermatocytes of the flea beetle, Alagoasa bicolor L.

et al. 2001

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In males of the flea beetle, Alagoasa bicolor L., spermatocytes have two achiasmate sex chromosomes, X and Y, each of which is approximately five times larger than the ten pairs of chiasmate autosomes. At metaphase I, these univalent sex chromosomes are located on a spindle domain separated from the autosomal spindle domain by a sheath of mitochondria. A single centriole pair is located at each pole of the spindle. In prometaphase I, each sex chromosome appears to maintain an attachment to both spindle poles via kinetochore microtubules (i.e., amphitelic orientation). Before anaphase I, this orientation changes to the syntelic orientation (both sister kinetochores connected to the same pole), perhaps by the release of microtubule attachments from the more distant pole by each of the chromosomes. The syntelic orientation just prior to anaphase I leaves each sex chromosome attached to the nearest pole via kinetochore microtubules, ensuring nonrandom segregation. As the sex chromosomes reorient, the autosomes follow in a sequential manner, starting with the bivalent closest to the sex spindle domain. We report here data that shed new light on the mechanism of this exceptional meiotic chromosome behavior.

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Section: Discussionmentioning

confidence: 71%

Orientation of nonrandomly segregating sex chromosomes in spermatocytes of the flea beetle, Alagoasa bicolor L.

et al. 2001

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Microtubule distribution during meiosis I in flea-beetle[Alagoasa(Oedionychus)] spermatocytes: evidence for direct connections between unpaired sex chromosomes

Wilson

Forer

Wise

2003

Journal of Cell Science

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The meiosis-I spindle in flea-beetle spermatocytes is unusual in that the autosomes and univalent sex chromosomes are separated by a mitochondrial sheath and move polewards at different times. To help understand the basis for this interesting chromosome behaviour, and to gather more detailed information about it, we studied microtubule distributions throughout meiosis I using immunofluorescence and confocal microscopy, and took careful measurements of pole and kinetochore positions at all stages of division. Our results show that, by late prophase, there is a spindle-shaped cytoplasmic array of microtubules in the central part of the cell, with the nucleus at the periphery. Following nuclear envelope breakdown, both autosomes and sex chromosomes become associated with cytoplasmic microtubules, although only the autosomes move centrally to the `cytoplasmic spindle'. The two unpaired sex chromosomes remain at the cell periphery and appear to be connected to each other by a microtubule bundle extending between their kinetochores. These bundles often persist into anaphase. Analysis of measurements taken from fixed/stained cells supports previous observations that sex chromosomes move part way to the pole in early prometaphase and then stop. The measurements also suggest that during autosomal anaphase, spindle elongation precedes autosome movement to the poles and polewards movement of sex chromosomes is limited or absent when autosomes are moving polewards.

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Two Desynaptic Mutants of Rhoeo spathacea (Commelinaceae).

García-Velázquez¹

2001

CYTOLOGIA

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Two desynaptic plants causing dissociation of pairing chromosomes were found among plants collected in wild populations of Rhoeo spathacea.One of those plants is of the spathacea variety and was identified as GAVA YT-1, while the other was found to be of the concolor variety and was identified as GAVA C-2. Both plants were found to be diploids with 2n=12 and displayed 2 cytotypes: 9m +3sm and 4m +8sm, respectively.GAVA C-2 is the first desynaptic plant observed of the concolor variety. The mutant plants formed univalents in all PMC at MI. GAVA YT-1 formed 12 univalents in 84.9% of PMC and 89.7% in PMC of GAVA C-2. Microspores from GAVA YT-1 had chromosome from n=5 to n=12, and microspores produced by GAVA C-2 showed n=8 to n=18.The GAVA C-2 plant produced 21.3% unreduced microspores. There were large differences in pollen stainability between the 2 desynaptics: GAVA YT-1 with 17.2% and GAVA C-2 with 55.5%.

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Behavior of sex chromosomes, autosomes, and the spindle during nonrandom segregation in a flea beetle

Cited by 3 publications

References 18 publications

Orientation of nonrandomly segregating sex chromosomes in spermatocytes of the flea beetle, Alagoasa bicolor L.

Orientation of nonrandomly segregating sex chromosomes in spermatocytes of the flea beetle, Alagoasa bicolor L.

Microtubule distribution during meiosis I in flea-beetle[Alagoasa(Oedionychus)] spermatocytes: evidence for direct connections between unpaired sex chromosomes

Two Desynaptic Mutants of Rhoeo spathacea (Commelinaceae).

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