Challenge to elucidating calcite aragonite problem by using scleractinian corals

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H05034
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Aquatic life science
• Research Institution: The University of Tokyo
• Principal Investigator: Higuchi Tomihiko 東京大学, 大気海洋研究所, 特任研究員 (40570510)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: アラゴナイト / カルサイト / 造礁サンゴ / バイオミネラリゼーション

Outline of Final Research Achievements

Although coral skeletons generally comprise aragonite crystals, changes in the molar Mg/Ca ratio (mMg/Ca) in seawater result in the incorporation of calcite crystals. Previous studies suggested that aragonitic scleractinian corals controlled skeletal formation biologically under low mMg/Ca conditions at higher temperature. The mechanism of formation of aragonite and calcite crystals in coral skeletons was therefore investigated by RNA-seq analysis, using early growth stage calcite and aragonite-based corals. As a result, 1287 genes were up-regulated and 748 down-regulated in calcite-based corals. In particular, 68 skeletogenesis-related genes were detected as up-regulated, and 6 genes down-regulated in low-Mg/Ca conditions. It is thought that corals actively cause the skeletal organic matrix to construct an aragonite skeleton in low-Mg/Ca conditions. These results suggest that the composition of these proteins could be a key factor in the selective formation of aragonite or calcite.

Free Research Field

生物地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究により、サンゴの骨格中のカルサイトやアラゴナイト形成の遺伝学的制御に関与する物質の候補がリストアップできたことで、様々な生物における炭酸カルシウム骨格形成のメカニズムの解明に貢献しうる成果が得られた。
また、白亜紀におけるサンゴのアラゴナイト形成は、高水温と、生物による積極的な骨格タンパク形成に起因しているということを結論付けることができ、長年の謎であったカルサイトーアラゴナイト問題解決への一助となった。