Non-canonical functions of hunchback in segment patterning of the intermediate germ cricket Gryllus bimaculatus
Non-canonical functions of hunchback in segment patterning of the intermediate germ cricket Gryllus bimaculatus
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DOI：
10.1242/dev.01784
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发表时间：
2005-05-01
期刊：
影响因子：
4.6
通讯作者：
Noji, S
中科院分区：
文献类型：
--
作者：
Mito, T;Sarashina, I;Noji, S
在短胚和中间胚昆虫中，只有前节在胚盘阶段被指定，留下后节在胚胎发生期间被指定，这与果蝇（一种长胚昆虫）中的分割过程不同。为了阐明短胚和中间胚昆虫的分节机制，我们研究了果蝇分节基因在一种遗传基础的中间胚昆虫Gryllus bimaculatus（Gb）中的直系同源物。在这里，我们集中在它的hunchback直系同源物（Gb'hb），因为果蝇hb的功能作为一个缺口基因在前面的分割，被称为一个典型的功能。Gb'hb在胚胎发生的早期阶段以间隙模式表达，随后在后生长区表达。通过对Gb'hb的胚胎和亲本RNA干扰，我们发现：（1）Gb'hb调控Hox基因的表达，以确定前区的区域同一性，如在果蝇和Oncopeltus中所观察到的：（2）Gb'hb控制胚带的形态发生和前区的分割，可能是通过配对规则基因，甚至至少是跳过的;（3）Gb'hb可能在前胸节后部和中胸节前部之间的有限区域内作为间隙基因发挥作用;（4）Gb'hb可能通过在后生长区表达而参与至少7个腹节的形成，这在果蝇中是不保守的。这些发现表明，Gb'Hb功能在一个非典型的方式在节段图案。我们的结果与其他衍生物种的结果的比较表明，典型的血红蛋白功能可能已经从非典型的血红蛋白功能在进化过程中演变。
In short and intermediate germ insects, only the anterior segments are specified during the blastoderm stage, leaving the posterior segments to be specified later, during embryogenesis, which differs from the segmentation process in Drosophila, a long germ insect. To elucidate the segmentation mechanisms of short and intermediate germ insects, we have investigated the orthologs of the Drosophila segmentation genes in a phylogenetically basal, intermediate germ insect, Gryllus bimaculatus (Gb). Here, we have focused on its hunchback ortholog (Gb'hb), because Drosophila hb functions as a gap gene during anterior segmentation, referred as a canonical function. Gb'hb is expressed in a gap pattern during the early stages of embryogenesis, and later in the posterior growth zone. By means of embryonic and parental RNA interference for Gb'hb, we found the following: (1) Gb'hb regulates Hox gene expression to specify regional identity in the anterior region, as observed in Drosophila and Oncopeltus; (2) Gb'hb controls germband morphogenesis and segmentation of the anterior region, probably through the pair-rule gene, even-skipped at least; (3) Gb'hb may act as a gap gene in a limited region between the posterior of the prothoracic segment and the anterior of the mesothoracic segment; and (4) Gb'hb is involved in the formation of at least seven abdominal segments, probably through its expression in the posterior growth zone, which is not conserved in Drosophila. These findings suggest that Gb'hb functions in a non-canonical manner in segment patterning. A comparison of our results with the results for other derived species revealed that the canonical hb function may have evolved from the non-canonical hb functions during evolution.