Abstract

All animals are capable of undergoing gametogenesis. The ability of forming haploid cells from diploid cells through meiosis and recombination appeared early in eukaryotes, whereas further gamete differentiation is mostly a metazoan signature. Morphologically, the gametogenic process presents many similarities across animal taxa, but little is known about its conservation at the molecular level. Porifera are the earliest divergent animals and therefore are an ideal phylum to understand evolution of the gametogenic toolkits. Although sponge gametogenesis is well known at the histological level, the molecular toolkits for gamete production are largely unknown. Our goal was to identify the genes and their expression levels which regulate oogenesis and spermatogenesis in five gonochoristic and oviparous species of the genus Geodia, using both RNAseq and proteomic analyses. In the early stages of both female and male gametogenesis, genes involved in germ cell fate and cell-renewal were upregulated. Then, molecular signals involved in retinoic acid pathway could trigger the meiotic processes. During later stages of oogenesis, female sponges expressed genes involved in cell growth, vitellogenesis, and extracellular matrix reassembly, which are conserved elements of oocyte maturation in Metazoa. Likewise, in spermatogenesis, genes regulating the whole meiotic cycle, chromatin compaction, and flagellum axoneme formation, that are common across Metazoa were overexpressed in the sponges. Finally, molecular signals possibly related to sperm capacitation were identified during late stages of spermatogenesis for the first time in Porifera. In conclusion, the activated molecular toolkit during gametogenesis in sponges was remarkably similar to that deployed during gametogenesis in vertebrates.

中文翻译：

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Geodia Demosponges（Porifera）中配子发生的分子机制：跨动物保守工具箱的进化起源。

摘要

所有动物都能够进行配子发生。在真核生物中，通过减数分裂和重组从二倍体细胞形成单倍体细胞的能力出现在真核生物的早期，而进一步的配子分化则主要是后生动物的特征。从形态上讲，配子发生过程在动物类群中表现出许多相似之处，但对其分子水平上的保守性知之甚少。Porifera是最早分化的动物，因此是了解配子生成工具包演变的理想门。尽管海绵的配子发生在组织学水平上是众所周知的，但是用于配子生产的分子工具包在很大程度上是未知的。我们的目标是鉴定调节该属的五个生殖和卵生物种的卵子发生和精子发生的基因及其表达水平。Geodia，同时使用RNAseq和蛋白质组学分析。在雌性和雄性配子发生的早期，参与生殖细胞命运和细胞更新的基因均被上调。然后，参与视黄酸途径的分子信号可能触发减数分裂过程。在卵子发生的后期，雌性海绵体表达参与细胞生长，卵黄发生和细胞外基质重组的基因，这些基因是后生动物卵母细胞成熟的保守成分。同样，在精子发生过程中，在整个后生动物中常见的调控整个减数分裂周期，染色质紧实和鞭毛轴突形成的基因在海绵中过表达。最后，在Porifera中首次在精子发生的后期识别出可能与精子获能有关的分子信号。结论，