Despite the ecological significance of the mutualistic relationship between Symbiodiniaceae and reef‐building corals, the molecular interactions during establishment of this relationship are not well understood. This is particularly true of the transcriptional changes that occur in the symbiont. In the current study, a dual RNA‐sequencing approach was used to better understand transcriptional changes on both sides of the coral–symbiont interaction during the colonization of Acropora tenuis by a compatible Symbiodiniaceae strain (Cladocopium goreaui; ITS2 type C1). Comparison of transcript levels of the in hospite symbiont 3, 12, 48 and 72 hr after exposure to those of the same strain in culture revealed that extensive and generalized down‐regulation of symbiont gene expression occurred during the infection process. Included in this “symbiosis‐derived transcriptional repression” were a range of stress response and immune‐related genes. In contrast, a suite of symbiont genes implicated in metabolism was upregulated in the symbiotic state. The coral data support the hypothesis that immune‐suppression and arrest of phagosome maturation play important roles during the establishment of compatible symbioses, and additionally imply the involvement of some SCRiP family members in the colonization process. Consistent with previous ecological studies, the transcriptomic data suggest that active translocation of metabolites to the host may begin early in the colonization process, and thus that the mutualistic relationship can be established at the larval stage. This dual RNA‐sequencing study provides insights into the transcriptomic remodelling that occurs in C. goreaui during transition to a symbiotic lifestyle and the novel coral genes implicated in symbiosis.

中文翻译：

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共生建立过程中对珊瑚及其原生共生体的双重RNA测序分析。

尽管共生菌科与造礁珊瑚之间的相互关系具有生态学意义，但这种关系建立期间的分子相互作用尚不十分清楚。对于共生体中发生的转录变化尤其如此。在当前的研究中，使用双重RNA测序方法更好地了解了在兼容的Symbiodiniaceae菌株（Cladocopium goreaui ; ITS2类型C1）的Acropora tenuis定殖过程中，珊瑚-共生体相互作用的两侧的转录变化。医院成绩单水平的比较在暴露于培养的同一菌株的共生菌第3、12、48和72小时后，发现在感染过程中发生了广泛而普遍的共生菌基因表达下调。这种“共生衍生的转录抑制”包括一系列应激反应和免疫相关基因。相反，一组参与代谢的共生基因在共生状态下被上调。珊瑚的数据支持了这样的假说，即在相容性共生的建立过程中，免疫抑制和吞噬体成熟的抑制起着重要作用，并且还暗示了一些SCRiP家族成员参与了定植过程。与先前的生态学研究一致，转录组数据表明，代谢物向宿主的主动转运可能在定植过程的早期开始，因此可以在幼体阶段建立相互关系。这项双重RNA测序研究可深入了解发生在C. goreaui在过渡到一种共生的生活方式和与共生有关的新的珊瑚基因。