Cell shape changes and the mechanism of inversion in Volvox.
Cell shape changes and the mechanism of inversion in Volvox.
复制标题
DOI：
10.1083/jcb.75.3.719
复制
发表时间：
1977-12
期刊：
影响因子：
--
通讯作者：
Kirk DL
中科院分区：
文献类型：
--
作者：
Viamontes GI;Kirk DL
反转是团藻形态发生的主要方面。在这个过程中，中空的球形团藻胚胎通过一个叫做瓶孔的小开口从内向外翻转，将鞭毛从内部带到外部表面。通过光镜、扫描电子显微镜和透射电子显微镜对完整的、切片的和碎片化的胚胎进行分析，表明预先编程到细胞中的形状变化引起倒位。首先，整个胚胎的细胞从梨形变成纺锤形，这导致胚胎收缩，瓶梗打开。然后，与瓶梗动物相邻的细胞变成烧瓶状，在它们的外端有细长的柄。同时，连接所有相邻细胞的细胞质桥从细胞的中点迁移到茎尖。这些变化共同导致瓶梗目边缘细胞的唇向外卷曲。现在，离瓶梗较远的细胞逐渐变成烧瓶状，而离瓶梗较近的细胞变成柱状，导致唇在胚胎表面上逐渐卷曲，直到胚胎完全由内而外。精细结构分析揭示了微管的外周细胞骨架，显然参与细胞伸长。反转前分离的细胞团经历了类似的形状变化程序;这表明细胞形状的变化是反转过程的原因而不是结果。
Inversion is a dominant aspect of morphogenesis in Volvox. In this process, the hollow, spheroidal Volvox embryo turns inside-out through a small opening called the phialopore to bring flagella from its inner to its outer surface. Analyses of intact, sectioned, and fragmented embryos by light, scanning electron, and transmission electron microscopy, suggest that shape changes preprogrammed into the cells cause inversion. First, cells throughout the embryo change from pear to spindle shape, which causes the embryo to contract and the phialopore to open. Then cells adjacent to the phialopore become flask-shaped, with long, thin stalks at their outer ends. Simultaneously, the cytoplasmic bridges joining all adjacent cells migrate from the midpoint of the cells to the stalk tips. Together, these changes cause the lips of cells at the phialopore margin to curl outward. Now cells progressively more distal to the phialopore become flask-shaped while the more proximal cells become columnar, causing the lips to curl progressively further over the surface of the embryo until the latter has turned completely inside-out. Fine structural analysis reveals a peripheral cytoskeleton of microtubules that is apparently involved in cellular elongation. Cell clusters isolated before inversion undergo a similar program of shape changes; this suggests that the changes in cellular shape are the cause rather than an effect of the inversion process.