Molecular evolutionary study on the phylogeny and body plan of chaetognath.

毛颚类的系统发育位置一直存在争议。最近的分子证据表明，它们不是后口动物，而是原口动物。毛颚类发育的分子生物学研究是解决进化关系的重要手段。胚粒的存在是毛颚类发育的特征之一。本研究对高等后生动物生殖系中与输精管相关的基因进行了研究，为比较系统发育关系提供了分子标记。从箭虫Paraspadella gotoi中克隆了vasa相关基因。系统发育分析表明，Pgvas1与真涡虫vasa相关基因Plvas1同源性较高。结果表明，毛颚类是一个非常古老的分类群在双边。Pgvas1在PGCs中表达，表明vasa相关基因参与生殖细胞。我们也一直试图分离与背腹轴形成有关的dpp和sog的同源物。

Phylogenetical position of the chaetognaths are always debated. Recent molecular evidence has suggested that they are not deuterostomes but protostomes. Molecular investigations of chaetognath development are much needed to resolve evolutionary relationship. Existence of germ granules is one of the characteristic in chaetognath development. In the present study we examined the vasa-related genes which are involved in germ line in higher metazoans and would be a molecular marker to compare phylogenetic relationship. We cloned the vasa-related gene from the arrow worm Paraspadella gotoi A vasa-related gene (Pgvas1) was isolated and the whole length of Pgvas1 was obtained. The phylogenetic analysis suggested that Pgvas1 was close to a vasa-related gene from the planarian (Plvas1). The result indicates that chaetognath is a very ancient taxon in bilateralians. Pgvas1 was expressed in the PGCs, indicatings the vasa-related gene is involved in germline cells. We have also been trying to isolate homologs of dpp and sog which are involved in the formation of the dorso-ventral axis.