Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218.
Applied BioSciences, Macquarie University, Sydney, NSW 2109, Australia.
Proc Natl Acad Sci U S A. 2023 Jun 13;120(24):e2216144120. doi: 10.1073/pnas.2216144120. Epub 2023 Jun 5.
Coral reefs are highly diverse ecosystems of immense ecological, economic, and aesthetic importance built on the calcium-carbonate-based skeletons of stony corals. The formation of these skeletons is threatened by increasing ocean temperatures and acidification, and a deeper understanding of the molecular mechanisms involved may assist efforts to mitigate the effects of such anthropogenic stressors. In this study, we focused on the role of the predicted bicarbonate transporter SLC4γ, which was suggested in previous studies to be a product of gene duplication and to have a role in coral-skeleton formation. Our comparative-genomics study using 30 coral species and 15 outgroups indicates that SLC4γ is present throughout the stony corals, but not in their non-skeleton-forming relatives, and apparently arose by gene duplication at the onset of stony-coral evolution. Our expression studies show that , but not the closely related and apparently ancestral , is highly upregulated during coral development coincident with the onset of skeleton deposition. Moreover, we show that juvenile coral polyps carrying CRISPR/Cas9-induced mutations in are defective in skeleton formation, with the severity of the defect in individual animals correlated with their frequencies of mutations. Taken together, the results suggest that the evolution of the stony corals involved the neofunctionalization of the newly arisen SLC4γ for a unique role in the provision of concentrated bicarbonate for calcium-carbonate deposition. The results also demonstrate the feasibility of reverse-genetic studies of ecologically important traits in adult corals.
珊瑚礁是高度多样化的生态系统，具有巨大的生态、经济和美学重要性，它们建立在石珊瑚基于碳酸钙的骨骼上。这些骨骼的形成受到海洋温度升高和酸化的威胁，对涉及的分子机制有更深入的了解可能有助于减轻人为胁迫的影响。在这项研究中，我们专注于预测的碳酸氢盐转运蛋白 SLC4γ 的作用，先前的研究表明它是基因复制的产物，并且在珊瑚骨骼形成中起作用。我们使用 30 种珊瑚物种和 15 种外群进行的比较基因组学研究表明，SLC4γ 存在于所有石珊瑚中，但不存在于它们非骨骼形成的亲属中，显然是在石珊瑚进化开始时通过基因复制产生的。我们的表达研究表明，而不是密切相关的、显然是祖先的 ，在珊瑚发育过程中高度上调，与骨骼沉积的开始同时发生。此外，我们表明，携带 CRISPR/Cas9 诱导的 突变的幼年珊瑚息肉在骨骼形成中存在缺陷，个体动物的缺陷严重程度与其 的突变频率相关。总之，结果表明，新出现的 SLC4γ 的石珊瑚的进化涉及新功能化，为碳酸钙沉积提供浓缩碳酸氢盐的独特作用。结果还证明了对成年珊瑚中具有生态重要性的性状进行反向遗传研究的可行性。
