Marine Core Research Institute, Kochi University, Kōchi, Japan.
Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan.
Sci Adv. 2023 Jun 23;9(25):eadd3584. doi: 10.1126/sciadv.add3584. Epub 2023 Jun 21.
Foraminifera, the most ancient known calcium carbonate-producing eukaryotes, are crucial players in global biogeochemical cycles and well-used environmental indicators in biogeosciences. However, little is known about their calcification mechanisms. This impedes understanding the organismal responses to ocean acidification, which alters marine calcium carbonate production, potentially leading to biogeochemical cycle changes. We conducted comparative single-cell transcriptomics and fluorescent microscopy and identified calcium ion (Ca) transport/secretion genes and α-carbonic anhydrases that control calcification in a foraminifer. They actively take up Ca to boost mitochondrial adenosine triphosphate synthesis during calcification but need to pump excess intracellular Ca to the calcification site to prevent cell death. Unique α-carbonic anhydrase genes induce the generation of bicarbonate and proton from multiple CO sources. These control mechanisms have evolved independently since the Precambrian to enable the development of large cells and calcification despite decreasing Ca concentrations and pH in seawater. The present findings provide previously unknown insights into the calcification mechanisms and their subsequent function in enduring ocean acidification.
有孔虫是已知最古老的产碳酸钙真核生物，它们是全球生物地球化学循环的重要参与者，也是生物地球科学中广泛应用的环境指标。然而，人们对它们的钙化机制知之甚少。这阻碍了我们理解生物对海洋酸化的反应，海洋酸化改变了海洋碳酸钙的产生，可能导致生物地球化学循环的变化。我们进行了比较单细胞转录组学和荧光显微镜研究，鉴定了钙离子（Ca）运输/分泌基因和α-碳酸酐酶，这些基因控制有孔虫的钙化过程。在钙化过程中，它们会主动摄取 Ca 以促进线粒体三磷酸腺苷的合成，但需要将过多的细胞内 Ca 泵到钙化部位，以防止细胞死亡。独特的α-碳酸酐酶基因可从多种 CO 来源中产生碳酸氢根和质子。这些控制机制自前寒武纪以来就已经独立进化，使它们能够在海水中 Ca 浓度和 pH 值下降的情况下，发展出大型细胞并进行钙化。本研究结果为理解钙化机制及其在持续海洋酸化中的后续功能提供了以前未知的见解。
