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

毛类动物的系统发育地位一直备受争议。最近的分子证据表明，它们不是后口动物，而是原口动物。为了解决进化关系，迫切需要对毛喉类发育进行分子研究。生殖粒的存在是毛囊动物发育的特征之一。在本研究中，我们研究了高等后生动物胚系中与VasA相关的基因，并将其作为比较系统发育关系的分子标记。本研究克隆了戈托氏副甲虫VasA相关基因，获得了PgVas1的全长序列。系统发育分析表明，该基因与原脊椎动物的VasA相关基因(Plvas1)很接近。这一结果表明，毛藻是一个非常古老的分类单元。PGCs中有PgVas1的表达，表明VasA相关基因参与了生殖细胞的发育。我们也一直在努力分离参与背腹轴形成的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.