Smirnova E A, Bajer A S
Biology Faculty, Department of Cytology and Histology, Moscow University, Russia.
Cell Motil Cytoskeleton. 1994;27(3):219-33. doi: 10.1002/cm.970270304.
We analyzed the distribution and orientation of transitory microtubule structures, microtubule converging centers, during interphase and mitosis in endosperm of the higher plant Haemanthus. In interphase the pointed tips of microtubule converging centers are associated with the nuclear envelope. Their orientation gradually reverses during prophase, and the tips tend to point away from the nucleus. From prometaphase through early telophase, microtubule converging centers are present predominantly in the cytoplasm at the polar region. They are either "free" or associated with chromosomes or microtubule bundles. In late telophase, pointed tips of microtubule converging centers are again associated with the reconstructed nuclear envelope and, additionally, they often appear in the phragmoplast area. The orientation of microtubule converging centers seems to be directly correlated to the previously determined microtubule polarity, with the converging tip being minus and the diverging one, plus. Elevated temperature (35 degrees-37 degrees C) enhances the number of microtubule converging centers in the cytoplasm and at the nuclear envelope. This is especially pronounced during the telophase-interphase transition and in some interphase cells, indicating temperature and stage dependence. Our data imply that microtubule converging centers bind together MT minus ends and, thus, control the predominant direction of elongation and shortening of microtubule arrays. We argue that these configurations are instrumental during the reorganization of interphase cytoskeleton and mitotic spindle in Haemanthus endosperm.
我们分析了高等植物海菖蒲胚乳在间期和有丝分裂过程中瞬时微管结构（微管汇聚中心）的分布和方向。在间期，微管汇聚中心的尖端与核膜相连。在前期，它们的方向逐渐反转，尖端倾向于远离细胞核。从前中期到末期早期，微管汇聚中心主要存在于极性区域的细胞质中。它们要么“游离”，要么与染色体或微管束相关联。在末期后期，微管汇聚中心的尖端再次与重建的核膜相连，此外，它们还经常出现在成膜体区域。微管汇聚中心的方向似乎与先前确定的微管极性直接相关，汇聚端为负端，发散端为正端。高温（35摄氏度至37摄氏度）会增加细胞质和核膜处微管汇聚中心的数量。这在末期 - 间期转变期间以及一些间期细胞中尤为明显，表明其对温度和阶段的依赖性。我们的数据表明，微管汇聚中心将微管负端结合在一起，从而控制微管阵列伸长和缩短的主要方向。我们认为这些结构在海菖蒲胚乳间期细胞骨架和有丝分裂纺锤体的重组过程中起作用。
