Jones J C, Tucker J B
J Cell Sci. 1981 Aug;50:259-80. doi: 10.1242/jcs.50.1.259.
The double-spiral microtubule pattern is established by a self-linkage procedure when axopodial axonemes reassemble after cold treatment in multinucleate Echinosphaerium nucleofilum and mononucleate Actinophrys sol. Nuclei are related spatially to axoneme morphogenesis in both organisms but in rather different ways. Microtubules grow out in all directions from discrete clumps of dense material situated close to nuclei in E. nucleofilum as axonemal assembly begins. Each clump acts as a microtubule-organizing centre (MTOC) in so far as it is associated spatially with the assembly of microtubules for a single axoneme. The dense material spreads along the sides of a developing axoneme for several micrometers, where it probably promotes further microtubule assembly as the double-spiral pattern is established. Pattern is generated as microtubules that are randomly oriented to begin with become more closely juxtaposed and aligned with each other. There are indications that juxtaposition is brought about by the contractile action of a filamentous meshwork that interconnects the microtubules. Final positioning and alignment appears to be accomplished by a 'zippering' together of adjacent portions of microtubules that proceeds in both directions along the lengths of developing axonemes as self-linkage is effected. Considerable numbers of more or less radially oriented microtubules remain and project from the surface membrane of the single central nucleus during cold treatment of A. sol. Additional tubules assemble and become associated similarly with the nuclear envelope immediately after cold treatment. Initially these microtubules are not arranged in a double-spiral pattern, which is subsequently generated by procedures similar to those outlined above for E. nucleofilum. It is suggested that the surface of the nuclear envelope may act as an MTOC.
在多核的核丝棘球虫和单核的太阳放射虫中，当轴伪足轴丝在冷处理后重新组装时，双螺旋微管模式通过一种自连接过程形成。在这两种生物中，细胞核在空间上都与轴丝形态发生相关，但方式截然不同。在核丝棘球虫中，随着轴丝组装开始，微管从靠近细胞核的离散致密物质团块向各个方向生长。每个团块在空间上与单个轴丝的微管组装相关联，因此起到微管组织中心（MTOC）的作用。致密物质沿着发育中的轴丝侧面延伸数微米，在那里，随着双螺旋模式的建立，它可能促进进一步的微管组装。模式的产生是因为最初随机取向的微管彼此靠得更近并排列整齐。有迹象表明，并列是由连接微管的丝状网络的收缩作用引起的。最终的定位和排列似乎是通过相邻微管部分的“拉链”作用完成的，随着自连接的实现，这种作用沿着发育中的轴丝长度双向进行。在太阳放射虫冷处理期间，相当数量的或多或少呈放射状排列的微管保留并从单个中央细胞核的表面膜伸出。冷处理后，额外的微管立即组装并以类似方式与核膜相关联。最初，这些微管不是以双螺旋模式排列的，随后通过与上述核丝棘球虫类似的过程产生这种模式。有人认为核膜表面可能起到微管组织中心的作用。
