Gonzales Eric E, van der Zee Maurijn, Dictus Wim J A G, van den Biggelaar Jo
Department of Developmental Biology, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
Evol Dev. 2007 Sep-Oct;9(5):416-31. doi: 10.1111/j.1525-142X.2007.00172.x.
The D quadrant organizer is a developmental signaling center that is localized to the vegetal D quadrant in different spiral-cleaving lophotrochozoan embryos and may be homologous to axial organizing regions in other metazoans. Patterning by this organizing center creates a secondary developmental axis and is required for the transition from spiral to bilateral cleavage and later establishment of the adult body plan. Organizer specification in equal-cleaving embryos is thought to involve inductive interactions between opposing animal and vegetal blastomeres. To date, experimental demonstration of this interaction has been limited to molluscs and nemerteans. Here, we examine three families of equal-cleaving polychaete annelids for evidence of animal-vegetal contact. We find that contact is present in the polynoid, Arctonoe vittata, but is absent in the serpulid, Serpula columbiana, and in the oweniid, Oweniia fusiformis. To interfere with cell signaling during the period predicted for organizer specification and patterning in A. vittata and S. columbiana, we use two general inhibitors of protein processing and secretion: Brefeldin A (BFA) and monensin. In A. vittata, we detail subsequent embryonic and larval adult development and show that treatment with either chemical results in radialization of the embryo and subsequent body plan. Radialized larvae differentiate many larval and adult structures despite the loss of bilateral symmetry but do so in either a radially symmetric or four-fold radially symmetric fashion. Our results suggest that the D quadrant organizer is functionally conserved in equal-cleaving polychaetes, but that details of its specification, induction, and patterning have diverged relative to other spiral-cleaving phyla.
D象限组织者是一个发育信号中心，定位于不同螺旋分裂的触手冠动物胚胎的植物性D象限，可能与其他后生动物的轴向组织区域同源。这个组织中心的模式形成会产生一条次级发育轴，是从螺旋分裂向两侧对称分裂转变以及随后建立成体身体模式所必需的。在均等分裂胚胎中，组织者的特化被认为涉及相对的动物性和植物性卵裂球之间的诱导相互作用。迄今为止，这种相互作用的实验证明仅限于软体动物和纽形动物。在这里，我们研究了三个均等分裂的多毛纲环节动物家族，以寻找动物性与植物性接触的证据。我们发现，多鳞虫属的Arctonoe vittata存在这种接触，但盘管虫属的Serpula columbiana和欧文蚓属的Oweniia fusiformis不存在。为了在预测的A. vittata和S. columbiana组织者特化和模式形成期间干扰细胞信号传导，我们使用了两种蛋白质加工和分泌的通用抑制剂：布雷菲德菌素A（BFA）和莫能菌素。在A. vittata中，我们详细描述了随后的胚胎和幼虫到成体的发育过程，并表明用这两种化学物质处理都会导致胚胎径向化以及随后的身体模式。尽管失去了双侧对称性，但径向化的幼虫仍能分化出许多幼虫和成体结构，不过是以径向对称或四重径向对称的方式进行。我们的结果表明，D象限组织者在均等分裂的多毛纲动物中功能保守，但其特化、诱导和模式形成的细节相对于其他螺旋分裂的门类已经发生了分化。
