Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany.
BMC Genomics. 2013 Dec 27;14:923. doi: 10.1186/1471-2164-14-923.
The genetics of development in the nematode Caenorhabditis elegans has been described in exquisite detail. The phylum Nematoda has two classes: Chromadorea (which includes C. elegans) and the Enoplea. While the development of many chromadorean species resembles closely that of C. elegans, enoplean nematodes show markedly different patterns of early cell division and cell fate assignment. Embryogenesis of the enoplean Romanomermis culicivorax has been studied in detail, but the genetic circuitry underpinning development in this species has not been explored.
We generated a draft genome for R. culicivorax and compared its gene content with that of C. elegans, a second enoplean, the vertebrate parasite Trichinella spiralis, and a representative arthropod, Tribolium castaneum. This comparison revealed that R. culicivorax has retained components of the conserved ecdysozoan developmental gene toolkit lost in C. elegans. T. spiralis has independently lost even more of this toolkit than has C. elegans. However, the C. elegans toolkit is not simply depauperate, as many novel genes essential for embryogenesis in C. elegans are not found in, or have only extremely divergent homologues in R. culicivorax and T. spiralis. Our data imply fundamental differences in the genetic programmes not only for early cell specification but also others such as vulva formation and sex determination.
Despite the apparent morphological conservatism, major differences in the molecular logic of development have evolved within the phylum Nematoda. R. culicivorax serves as a tractable system to contrast C. elegans and understand how divergent genomic and thus regulatory backgrounds nevertheless generate a conserved phenotype. The R. culicivorax draft genome will promote use of this species as a research model.
秀丽隐杆线虫的发育遗传学已被详细描述。线虫门有两个纲：色线纲（包括秀丽隐杆线虫）和动吻纲。虽然许多色线纲物种的发育与秀丽隐杆线虫非常相似，但动吻纲线虫表现出明显不同的早期细胞分裂和细胞命运分配模式。动吻纲的 Romanomermis culicivorax 的胚胎发生已被详细研究，但该物种发育的遗传机制尚未被探索。
我们生成了 Romanomermis culicivorax 的基因组草图，并将其基因组成与秀丽隐杆线虫、另一种动吻纲线虫、脊椎动物寄生虫旋毛虫和代表性节肢动物赤拟谷盗进行了比较。这一比较表明，Romanomermis culicivorax 保留了秀丽隐杆线虫丢失的保守节肢动物发育基因工具包的组成部分。旋毛虫比秀丽隐杆线虫丢失了更多的这个工具包。然而，秀丽隐杆线虫的工具包并不是简单的退化，因为许多对秀丽隐杆线虫胚胎发生至关重要的新基因在 Romanomermis culicivorax 和旋毛虫中都没有发现，或者只有极其分化的同源物。我们的数据表明，不仅在早期细胞特化方面，而且在其他方面，如生殖腔形成和性别决定方面，遗传程序存在根本差异。
尽管形态上存在保守性，但线虫门内部已经进化出了发育分子逻辑的重大差异。Romanomermis culicivorax 作为一个可行的系统，可以与秀丽隐杆线虫进行对比，以了解不同的基因组和因此不同的调控背景如何产生保守的表型。Romanomermis culicivorax 的基因组草图将促进该物种作为研究模型的使用。
