The molecular mechanisms underlying development of the pentameral body of adult echinoderms are poorly understood but are important to solve with respect to evolution of a unique body plan that contrasts with the bilateral body plan of other deuterostomes. As Nodal and BMP2/4 signalling is involved in axis formation in larvae and development of the echinoderm body plan, we used the developmental transcriptome generated for the asterinid seastar Parvulastra exigua to investigate the temporal expression patterns of Nodal and BMP2/4 genes from the embryo and across metamorphosis to the juvenile. For echinoderms, the Asteroidea represents the basal-type body architecture with a distinct (separated) ray structure. Parvulastra exigua has lecithotrophic development forming the juvenile soon after gastrulation providing ready access to the developing adult stage. We identified 39 genes associated with the Nodal and BMP2/4 network in the P. exigua developmental transcriptome. Clustering analysis of these genes resulted in 6 clusters with similar temporal expression patterns across development. A co-expression analysis revealed genes that have similar expression profiles as Nodal and BMP2/4. These results indicated genes that may have a regulatory relationship in patterning morphogenesis of the juvenile seastar. Developmental RNA-seq analyses of Parvulastra exigua show changes in Nodal and BMP2/4 signalling genes across the metamorphic transition. We provide the foundation for detailed analyses of this cascade in the evolution of the unusual pentameral echinoderm body and its deuterostome affinities.

成年棘皮动物五角体发育的分子机制知之甚少，但对于与其他后口动物的双侧身体计划形成对比的独特身体计划的进化，解决这一问题很重要。由于 Nodal 和 BMP2/4 信号传导参与幼虫的轴形成和棘皮动物体计划的发育，我们使用为 asterinid seastar Parvulastra exigua生成的发育转录组来研究来自胚胎的 Nodal 和 BMP2/4 基因的时间表达模式并跨越变态到少年。对于棘皮动物，Asteroidea 代表具有独特（分离）射线结构的基底型身体结构。Parvulastra exgua在原肠胚形成后不久就具有形成幼体的促卵泡发育，从而为进入发育中的成年阶段提供了方便的途径。我们在P. exgua发育转录组中鉴定了 39 个与Nodal和BMP2/4网络相关的基因。这些基因的聚类分析产生了 6 个在整个发育过程中具有相似时间表达模式的聚类。共表达分析揭示了与Nodal和BMP2/4具有相似表达谱的基因。这些结果表明基因可能在幼年海星的形态发生中具有调节关系。Parvulastra exigua的发育 RNA-seq 分析显示Nodal的变化和BMP2/4信号基因跨越变质转变。我们为这种级联在不寻常的五角棘皮动物体及其后口亲缘关系的进化中的详细分析提供了基础。