Progressive activation of Delta-Notch signaling from around the blastopore is required to set up a functional caudal lobe in the spider Achaearanea tepidariorum
Progressive activation of Delta-Notch signaling from around the blastopore is required to set up a functional caudal lobe in the spider Achaearanea tepidariorum
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DOI：
10.1242/dev.004598
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发表时间：
2007-06-15
期刊：
影响因子：
4.6
通讯作者：
Akiyama-Oda, Yasuko
中科院分区：
文献类型：
--
作者：
Oda, Hiroki;Nishimura, Osamu;Akiyama-Oda, Yasuko
在大多数节肢动物的发育过程中，伸长胚带的尾部区域(生长带)会依次产生新的节段。之前对蜘蛛Cupiennius Salei的研究表明，Delta-Notch信号参与了片段的形成。在这里，我们报告，在蜘蛛Achaearanea tepidariorum中，相同的信号通路在开始分段之前的假定尾部区域发挥不同的功能。在发育中的蜘蛛胚胎中，生长区在形态上变得明显，就像封闭的胚孔周围的尾叶。我们发现，在尾叶形成之前，Delta同源基因at-Delta的转录本在覆盖关闭的胚孔的小区域内均匀分布的细胞中表达，然后在生殖盘上皮的逐渐扩大的区域中表达。具有高at-Delta表达的细胞可能是预期的中胚层细胞，后者随后表达扭曲同源、at-twist，并单独内化。保留在表面的细胞开始表达尾部同源基因，即尾部，以分化为尾部外胚层。通过亲本RNA干扰敲除at-Delta导致表达at-twist的中胚层细胞的过量生产，而以表达at-尾部的外胚层细胞为代价。这种情况导致尾部区域杂乱无章，不能形成鱼尾状突起。此外，敲除Notch和抑制无毛同系物会产生类似的表型。我们认为，在蜘蛛中，胚孔周围Delta-Notch信号的逐渐激活导致了中胚层和尾部外胚层之间的随机细胞命运决定，通过一个侧向抑制过程建立了一个功能性的尾叶。
In the development of most arthropods, the caudal region of the elongating germ band ( the growth zone) sequentially produces new segments. Previous work with the spider Cupiennius salei suggested involvement of Delta-Notch signaling in segmentation. Here, we report that, in the spider Achaearanea tepidariorum, the same signaling pathway exerts a different function in the presumptive caudal region before initiation of segmentation. In the developing spider embryo, the growth zone becomes morphologically apparent as a caudal lobe around the closed blastopore. We found that, preceding caudal lobe formation, transcripts of a Delta homolog, At-Delta, are expressed in evenly spaced cells in a small area covering the closing blastopore and then in a progressively wider area of the germ disc epithelium. Cells with high At-Delta expression are likely to be prospective mesoderm cells, which later express a twist homolog, At-twist, and individually internalize. Cells remaining at the surface begin to express a caudal homolog, At-caudal, to differentiate as caudal ectoderm. Knockdown of At-Delta by parental RNA interference results in overproduction of At-twist-expressing mesoderm cells at the expense of At-caudal-expressing ectoderm cells. This condition gives rise to a disorganized caudal region that fails to pattern the opisthosoma. In addition, knockdown of Notch and Suppressor of Hairless homologs produces similar phenotypes. We suggest that, in the spider, progressive activation of Delta-Notch signaling from around the blastopore leads to stochastic cell fate decisions between mesoderm and caudal ectoderm through a process of lateral inhibition to set up a functional caudal lobe.