Moreira Rebeca, Pereiro Patricia, Balseiro Pablo, Milan Massimo, Pauletto Marianna, Bargelloni Luca, Novoa Beatriz, Figueras Antonio
Instituto de Investigaciones Marinas, IIM - CSIC, Eduardo Cabello, 6, 36208 Vigo, Spain.
Instituto de Investigaciones Marinas, IIM - CSIC, Eduardo Cabello, 6, 36208 Vigo, Spain; Uni Research Environment, Uni Research AS, Nygårdsgaten 112, 5008 Bergen, Norway.
Dev Comp Immunol. 2018 Jul;84:292-306. doi: 10.1016/j.dci.2018.01.016. Epub 2018 Feb 23.
Mediterranean mussels are a worldwide spread bivalve species with extraordinary biological success. One of the reasons of this success could be the reproduction strategy of bivalves, characterized by the presence of trochophore larvae. Larval development in bivalves has been a topic of raising interest in the scientific community but it deserves much more attention. The principal objective of this work was to study the transcriptomic profile of the ontogeny of Mytilus galloprovincialis analyzing the gene expression in different developmental stages, from oocytes to juveniles. For this purpose, after conducting a 454 sequencing of the transcriptomes of mussel hemocytes, adult tissues and larvae, a new DNA microarray was designed and developed. The studied developmental stages: unfertilized oocytes, veliger, pediveliger, settled larvae and juveniles, showed very different transcriptomic profiles and clustered in groups defining their characteristic gene expression along ontogeny. Our results show that oocytes present a distinct and characteristic transcriptome. After metamorphosis, both settled larvae and juveniles showed a very similar transcriptome, with no enriched GO terms found between these two stages. This suggests: 1.- the progressive loss of RNA of maternal origin through larval development and 2.- the stabilization of the gene expression after settlement. On the other hand during metamorphosis a specific profile of differentially expressed genes was found. These genes were related to processes such as differentiation and biosynthesis. Processes related to the immune response were strongly down regulated. These suggest a development commitment at the expense of other non-essential functions, which are temporary set aside. Immune genes such as antimicrobial peptides suffer a decreased expression during metamorphosis. In fact, we found that the oocytes which express a higher quantity of genes such as myticins are more likely to reach success of the offspring, compared to oocytes poor in such mRNAs, whose progeny died before reaching metamorphosis.
地中海贻贝是一种在全球广泛分布的双壳类物种，具有非凡的生物学成功范例。这种成功的原因之一可能是双壳类的繁殖策略，其特点是存在担轮幼虫。双壳类幼虫的发育一直是科学界日益关注的话题，但它值得更多的关注。这项工作的主要目的是研究地中海贻贝个体发育的转录组概况，分析从卵母细胞到幼体不同发育阶段的基因表达。为此，在对贻贝血细胞、成体组织和幼虫的转录组进行454测序后，设计并开发了一种新的DNA微阵列。所研究的发育阶段：未受精卵母细胞、面盘幼虫、足面盘幼虫、附着幼虫和幼体，显示出非常不同的转录组概况，并聚类成组，定义了它们在个体发育过程中的特征性基因表达。我们的结果表明，卵母细胞呈现出独特且具有特征的转录组。变态后，附着幼虫和幼体都显示出非常相似的转录组，在这两个阶段之间未发现富集的基因本体（GO）术语。这表明：1. - 在幼虫发育过程中母源RNA的逐渐丢失；2. - 附着后基因表达的稳定。另一方面，在变态过程中发现了差异表达基因的特定概况。这些基因与分化和生物合成等过程相关。与免疫反应相关的过程被强烈下调。这表明以牺牲其他非必要功能为代价的发育承诺，这些功能被暂时搁置。抗菌肽等免疫基因在变态过程中表达下降。事实上，我们发现与表达此类mRNA较少的卵母细胞相比，表达较高数量诸如贻贝抗菌肽基因的卵母细胞更有可能使后代成功，后者的后代在达到变态之前就死亡了。
