Callaini G, Dallai R, Riparbelli M G
Department of Evolutionary Biology, University of Siena, Italy.
J Cell Sci. 1997 Jan;110 ( Pt 2):271-80. doi: 10.1242/jcs.110.2.271.
The behavior of parental chromosomes during the first mitosis of Drosophila simulans zygotes obtained from unidirectional incompatible crosses is described and it is demonstrated that the condensation of parental chromatin complements was asynchronous. The timing of paternal chromatin condensation appeared to be delayed in these embryos, so that condensed maternal chromosomes and entangled prophase-like paternal fibers congressed in the equatorial plane of the first metaphase spindle. At anaphase the maternal chromosomes migrated to opposite poles of the spindle, whereas the paternal chromatin lagged in the midzone of the spindle. This resulted in dramatic errors in paternal chromatin inheritance leading to the formation of embryos with aneuploid or haploid nuclei. These observations suggest that the anaphase onset of maternal chromosomes is unaffected by the improper alignment of the paternal complement. Since the first metaphase spindle of the Drosophila zygote consists of twin bundles of microtubules each holding one parental complement, we suspect that each half spindle regulates the timing of anaphase onset of its own chromosome set. In normal developing embryos, the fidelity of chromosome transmission is presumably ensured by the relative timing required to prepare parental complements for the orderly segregation that occurs during the metaphase-anaphase transition.
描述了从单向不亲和杂交获得的拟暗果蝇合子第一次有丝分裂期间亲代染色体的行为，并证明亲代染色质互补体的凝聚是不同步的。在这些胚胎中，父本染色质凝聚的时间似乎延迟了，因此凝聚的母本染色体和纠缠的前期样父本纤维在第一次中期纺锤体的赤道平面上聚集。在后期，母本染色体迁移到纺锤体的相对两极，而父本染色质则滞留在纺锤体的中区。这导致了父本染色质遗传中的严重错误，导致形成具有非整倍体或单倍体核的胚胎。这些观察结果表明，母本染色体的后期开始不受父本互补体排列不当的影响。由于果蝇合子的第一次中期纺锤体由双束微管组成，每束微管容纳一个亲代互补体，我们怀疑每个半纺锤体调节其自身染色体组后期开始的时间。在正常发育的胚胎中，染色体传递的保真度大概是通过为中期 - 后期转变期间发生的有序分离准备亲代互补体所需的相对时间来确保的。
