Abstract

The genus Acropora comprises the most diverse and abundant scleractinian corals (Anthozoa, Cnidaria) in coral reefs, the most diverse marine ecosystems on Earth. However, the genetic basis for the success and wide distribution of Acropora are unknown. Here, we sequenced complete genomes of 15 Acropora species and 3 other acroporid taxa belonging to the genera Montipora and Astreopora to examine genomic novelties that explain their evolutionary success. We successfully obtained reasonable draft genomes of all 18 species. Molecular dating indicates that the Acropora ancestor survived warm periods without sea ice from the mid or late Cretaceous to the Early Eocene and that diversification of Acropora may have been enhanced by subsequent cooling periods. In general, the scleractinian gene repertoire is highly conserved; however, coral- or cnidarian-specific possible stress response genes are tandemly duplicated in Acropora. Enzymes that cleave dimethlysulfonioproprionate into dimethyl sulfide, which promotes cloud formation and combats greenhouse gasses, are the most duplicated genes in the Acropora ancestor. These may have been acquired by horizontal gene transfer from algal symbionts belonging to the family Symbiodiniaceae, or from coccolithophores, suggesting that although functions of this enzyme in Acropora are unclear, Acropora may have survived warmer marine environments in the past by enhancing cloud formation. In addition, possible antimicrobial peptides and symbiosis-related genes are under positive selection in Acropora, perhaps enabling adaptation to diverse environments. Our results suggest unique Acropora adaptations to ancient, warm marine environments and provide insights into its capacity to adjust to rising seawater temperatures.

中文翻译：

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十八个珊瑚基因组揭示了鹿角珊瑚适应环境变化的策略的进化起源。

摘要

属鹿角包括珊瑚礁最多样化的和丰富的礁石珊瑚（珊瑚虫，刺胞动物门），地球上最多样化的海洋生态系统。然而，鹿角珊瑚成功和广泛分布的遗传基础尚不清楚。在这里，我们对 15种鹿角珊瑚属物种和 3 种其他属于Montipora和Astreopora属的顶峰动物分类群的完整基因组进行了测序，以检查解释它们进化成功的基因组新颖性。我们成功获得了所有 18 个物种的合理基因组草图。分子测年表明，鹿角祖先从白垩纪中期或晚期到始新世早期没有海冰的温暖时期幸存下来，并且随后的冷却时期可能增强了鹿角珊瑚的多样化。一般来说，巩膜蛋白基因库是高度保守的；然而，珊瑚或刺胞动物特定的可能应激反应基因在Acropora中串联复制。将二甲基磺基丙酸盐裂解成二甲硫醚的酶是鹿角珊瑚祖先中复制最多的基因，它促进云的形成和对抗温室气体。这些可能是通过从属于共生科的藻类共生体或从球石藻中的水平基因转移获得的，这表明尽管这种酶在鹿角目尚不清楚，鹿角目可能在过去通过增强云形成而在温暖的海洋环境中幸存下来。此外，可能的抗菌肽和与共生相关的基因在Acropora中处于正选择状态，这可能能够适应不同的环境。我们的研究结果表明，鹿角珊瑚对古老温暖的海洋环境具有独特的适应性，并提供了对其适应海水温度上升的能力的见解。