Kaczanowska J, Joachimiak E, Buzanska L, Krawczynska W, Wheatley D N, Kaczanowski A
Institute of Zoology, Warsaw University, Warsaw, 00-927/1, Poland.
Dev Biol. 1999 Aug 1;212(1):150-64. doi: 10.1006/dbio.1999.9362.
In contrast to a mitotic-spindle-associated bipolar cytokinesis, the cytokinesis of polarized ciliates is preceded by a reorganization of the cortex into dual metameric patterns for prospective daughter cells and then separated by a transverse fission line. This study concerns relations between the generation of cortical metamery and the formation of the fission line in an amicronuclear (i.e., without mitotic spindle) ciliate, Tetrahymena pyriformis. The fission line appears in the division of T. pyriformis as a transverse line formed by equatorial gaps in the meridional ciliary rows, with the second oral structure (OA2) formed posterior to it. It was found that the metamery of cortical morphogenesis is expressed by the appearance of increased MPM2 antibody binding in dividing cells in an apical area and posterior to the fission line gaps, including patterned changes of this binding in both oral apparatuses (OA1 and OA2), and by a reciprocal decrease of binding of an anti-epiplasm antibody. These tested antigens are localized to different cortical structures, but in predividing cells both uniformly show formation of the fission line contrast of labeling. A serine/threonine kinase inhibitor, 6-dimethylaminopurine (6-DMAP), was applied to dividing T. pyriformis at specific stages: (1) if 6-DMAP was added to early dividing cells, it prevented cells from initiating cytokinesis. (2) If 6-DMAP was added to cells at stages close to the physiological transition point of cell division, it yielded either (i) a partial formation of the fission line on the ventral side, combined with modified growth of undivided cortex adjacent to the fission line, with abnormal cytokinesis, or (ii) variable anterior displacement of the complete fission line, which contracted slowly but uniformly. (3) If 6-DMAP was applied during cytokinesis, it did not delay cell division, but daughter cells become abnormal and underwent an incomplete oral reorganization. These results suggest that the generation of metamerism in the cortex of T. pyriformis involves differentiation of the asymmetric fission zone. At least four stage-dependent 6-DMAP-sensitive effects jointly control the progress of cell division and the mutual spatial relations between the generation of metamery and the appearance, completeness, and position of the fission zone in the cortex of polarized T. pyriformis.
与有丝分裂纺锤体相关的双极胞质分裂不同，极化纤毛虫的胞质分裂之前，皮层会重新组织成预期子细胞的双节段模式，然后由一条横向分裂线分开。本研究关注无小核（即没有有丝分裂纺锤体）的纤毛虫梨形四膜虫中皮层节段化的产生与分裂线形成之间的关系。在梨形四膜虫的分裂过程中，分裂线表现为纵向纤毛排中的赤道间隙形成的一条横向线，其后方会形成第二个口器结构（OA2）。研究发现，皮层形态发生的节段化表现为在分裂细胞的顶端区域以及分裂线间隙后方，MPM2抗体结合增加，包括两个口器（OA1和OA2）中这种结合的模式变化，以及抗表质抗体结合的相应减少。这些被检测的抗原定位于不同的皮层结构，但在即将分裂的细胞中，两者均显示出分裂线标记的对比形成。一种丝氨酸/苏氨酸激酶抑制剂6-二甲基氨基嘌呤（6-DMAP）在特定阶段应用于分裂的梨形四膜虫：（1）如果在早期分裂细胞中添加6-DMAP，它会阻止细胞启动胞质分裂。（2）如果在接近细胞分裂生理转变点的阶段向细胞中添加6-DMAP，它会产生以下两种情况之一：（i）腹侧分裂线部分形成，同时与分裂线相邻的未分裂皮层生长发生改变，胞质分裂异常；（ii）完整分裂线出现可变的向前移位，分裂线缓慢但均匀地收缩。（3）如果在胞质分裂期间应用6-DMAP，它不会延迟细胞分裂，但子细胞会变得异常并经历不完全的口器重组。这些结果表明，梨形四膜虫皮层中节段化的产生涉及不对称分裂区的分化。至少四种阶段依赖性的6-DMAP敏感效应共同控制细胞分裂的进程以及极化的梨形四膜虫皮层中节段化产生与分裂区的出现、完整性和位置之间的相互空间关系。
