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首页> 外文期刊>Molecular biology of the cell >Maloriented bivalents have metaphase positions at the spindle equator with more kinetochore microtubules to one pole than to the other
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Maloriented bivalents have metaphase positions at the spindle equator with more kinetochore microtubules to one pole than to the other

机译：方向错误的二价在纺锤状赤道的中期位置，一根极的动球微管比另一极多。

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摘要

To test the "traction fiber" model for metaphase positioning of bivalents during meiosis, kinetochore fibers of maloriented bivalents, induced during recovery from cold arrest, were analyzed with a liquid crystal polarizing microscope. The measured birefringence retardation of kinetochore fibers is proportional to the number of microtubules in a fiber. Five of the 11 maloriented bivalents analyzed exhibited bipolar malorientations that had at least four times more kinetochore microtubules to one pole than to the other pole, and two had microtubules directed to only one pole. Yet all maloriented bivalents had positions at or near the spindle equator. The traction fiber model predicts such maloriented bivalents should be positioned closer to the pole with more kinetochore microtubules. A metaphase position at the spindle equator, according to the model, requires equal numbers of kinetochore microtubules to both poles. Data from polarizing microscope images were not in accord with those predictions, leading to the conclusion that other factors, in addition to traction forces, must be involved in metaphase positioning in crane-fly spermatocytes. Although the identity of additional factors has not been established, one possibility is that polar ejection forces operate to exert away-from-the-pole forces that could counteract pole-directed traction forces. Another is that kinetochores are "smart," meaning they embody a position-sensitive mechanism that controls their activity.
机译：为了测试减数分裂过程中二价分子中期定位的“牵引纤维”模型，用液晶偏振显微镜分析了从冷阻恢复过程中诱导的取向错误的二价体的动线粒纤维。线粒体纤维的双折射延迟量与纤维中微管的数量成正比。在分析的11个取向错误的二价化合物中，有5个显示出双极性错误取向，其中一个极的动球微管至少是另一极的四倍，而两个只有一个极的微管。然而，所有取向错误的二价分子都位于或接近主轴赤道。牵引纤维模型预测，这种方向不正确的二价化合物应通过更多的动粒微管定位在更靠近杆的位置。根据模型，在主轴赤道的中期位置需要两个极都具有相等数量的动粒微管。来自偏光显微镜图像的数据与那些预测不符，从而得出结论，除牵引力外，其他因素也必须参与鹤蝇精细胞的中期定位。尽管尚未确定其他因素的确定性，但一种可能性是极地弹射力的作用是施加极杆力，该极杆力会抵消极杆牵引力。另一个是动植物很“聪明”，这意味着它们体现了控制其活动的位置敏感机制。

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