Changes in anterior head patterning underlie the evolution of long germ embryogenesis
Changes in anterior head patterning underlie the evolution of long germ embryogenesis
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DOI：
10.1016/j.ydbio.2012.11.026
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发表时间：
2013-02-01
影响因子：
2.7
通讯作者：
Bucher, Gregor
中科院分区：
文献类型：
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作者：
Kittelmann, Sebastian;Ulrich, Julia;Bucher, Gregor
早期胚胎阶段在相关动物类群之间存在显着差异，而随后的发育在再次分化之前在保守的单型阶段收敛。虽然这种现象已经被观察到很久了，但其潜在的遗传机制仍然是个谜。双翅目果蝇（Drosophilamelanogaster）发育为一个长形胚，其头部原基在胚盘的前极形成一个帽。因此，前和终端母体系统提供了至关重要的输入头部图案。然而，在短胚芽甲虫赤拟谷盗，在大多数昆虫，头原基位于腹侧位置远离前极的胚盘。根据这些不同的胚胎原基，已经发现昆虫之间的轴形成的几个差异。我们现在问到什么程度的图案和形态发生的前正中区（AMR）的头部，包括唇腭裂和stomodeal原基，这些昆虫之间的不同。出乎意料的是，我们发现，Tc-huckebein是不是一个终端的差距基因，不像它的果蝇直系同源物，是不参与赤拟谷盗头部的发展。相反，Tc-six 3作用于Tc-crocodile和Tc-cap 'n'collar的上游，分别对AMR的后部和前部进行图案化。我们进一步发现，而不是huckebein，Tc-鳄鱼是需要通过激活Tc-叉头的口道发育。最后，一种在果蝇中没有发现的形态发生运动塑造了赤拟谷盗的胚胎头部。显然，随着果蝇在长时间的生殖进化过程中头部原基的向前移位，由两侧前部控制基因six 3进行的祖先调控被前部和末端母系系统所取代，并通过添加bicoid，tailless和huckebein作为前部区域化基因而进一步阐述。(c)2012 Elsevier Inc. All rights reserved.
Early embryonic stages differ significantly among related animal taxa while subsequent development converges at the conserved phylotypic stage before again diverging. Although this phenomenon has long been observed, its underlying genetic mechanisms remain enigmatic. The dipteran Drosophila melanogaster develops as a long germ embryo where the head anlagen form a cap at the anterior pole of the blastoderm. Consequently, the anterior and terminal maternal systems give crucial input for head patterning. However, in the short germ beetle Tribolium castaneum, as in most insects, the head anlagen is located at a ventral position distant from the anterior pole of the blastoderm. In line with these divergent embryonic anlagen, several differences in the axis formation between the insects have been discovered. We now ask to what extent patterning and morphogenesis of the anterior median region (AMR) of the head, including clypeolabral and stomodeal anlagen, differ among these insects. Unexpectedly, we find that Tc-huckebein is not a terminal gap gene and, unlike its Drosophila ortholog, is not involved in Tribolium head development. Instead, Tc-six3 acts upstream of Tc-crocodile and Tc-cap'n'collar to pattern posterior and anterior parts of the AMR, respectively. We further find that instead of huckebein, Tc-crocodile is required for stomodeum development by activating Tc-forkhead. Finally, a morphogenetic movement not found in Drosophila shapes the embryonic head of Tribolium. Apparently, with anterior displacement of the head anlagen during long germ evolution of Drosophila, the ancestral regulation by the bilaterian anterior control gene six3 was replaced by the anterior and terminal maternal systems, which were further elaborated by adding bicoid, tailless and huckebein as anterior regionalization genes. (c) 2012 Elsevier Inc. All rights reserved.