Mirror-imaged doublets of Tetmemena pustulata:: Implications for the development of left-right asymmetry
Mirror-imaged doublets of Tetmemena pustulata:: Implications for the development of left-right asymmetry
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DOI：
10.1016/j.ydbio.2007.11.020
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发表时间：
2008-02-01
影响因子：
2.7
通讯作者：
Grimes, Gary W.
中科院分区：
文献类型：
--
作者：
Bell, Aaron J.;Satir, Peter;Grimes, Gary W.
有纤毛的原生动物具有细胞轴，这反映在它们纤毛的排列上。在横向裂变时，子细胞发育出相同的纤毛模式，确保细胞表型的延续。实验操作的细胞可以被诱导形成非典型表型，能够在囊化后在克隆内繁殖和再生。一种这样的表型在纤毛虫Tetmemena pustulata（前身为Stylonychia pustulata）是镜像双重。这些细胞具有两组不同的纤毛，并以镜像对称的方式并列在表面上，具有共同的前后轴。我们已经检查了是否单独的纤毛组成的Tetmemena镜像双重镜像镜像。超微结构分析表明，尽管纤毛的整体镜像成像，但在镜像口腔器（OA）中，膜的详细组织是相反的，因此纤毛有效的中风推动食物远离OA。两种OA的复合纤毛结构的组装开始时是相同的，但随着与镜像OA相关的结构继续形成，相对于典型OA中的相同结构，新膜组在腹侧表面进行180度平面旋转。因此，OA的整体对称性似乎与单个基底体的更局部的组合是可分离的。膜的真正镜像将需要单个纤毛成分的新的对构形式，特别是基体，这是从未观察到的。这些观察结果提出了一种机制假说，它不仅对纤毛虫的左右不对称的发展有影响，而且可能对一般的左右不对称的发展也有影响。(C) 2007爱思唯尔公司版权所有。
Ciliated protozoa possess cellular axes reflected in the arrangement of their ciliature. Upon transverse fission, daughter cells develop an identical ciliary pattern, ensuring perpetuation of the cellular phenotype. Experimentally manipulated cells can be induced to form atypical phenotypes, capable of intraclonal propagation and regeneration after encystment. One such phenotype in the ciliate Tetmemena pustulata (formerly Stylonychia pustulata) is the mirror-imaged doublet. These cells possess two distinct sets of ciliature, juxtaposed on the surfaces in mirror image symmetry, with a common anterior-posterior axis. We have examined whether individual ciliary components of Tetmemena mirror-image doublets are mirror imaged. Ultrastructural analysis indicates that despite global mirror imaging of the ciliature, detailed organization of the membranelles is reversed in the mirror-image oral apparatus (OA), such that the ciliary effective stroke propels food away from the OA. Assembly of compound ciliary structures of both OAs starts out identically, but as the structures associated with the mirror-image OA continue to form, the new set of membranelles undergoes a 180 degrees planar rotation on the ventral surface relative to the same structures in the typical OA. The overall symmetry of the OA thus appears to be separable from the more localized assembly of individual basal bodies. True mirror imagery of the membranelles would require new enantiomorphic forms of the individual ciliary components, particularly the basal bodies, which is never observed. These observations suggest a mechanistic hypothesis with implications for the development of left-right asymmetry not only in ciliates, but perhaps also in development of left-right asymmetry in general. (C) 2007 Elsevier Inc. All rights reserved.