Mechanism and evolution of inorganic nitrogen assimilation in kleptoplastic dinoflagellates

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15853
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 45020:Evolutionary biology-related
• Research Institution: Kobe University (2021-2022); National Institute of Genetics (2020)
• Principal Investigator: Onuma Ryo 神戸大学, 内海域環境教育研究センター, 講師 (80756825)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 渦鞭毛虫 / クリプト藻 / 盗葉緑体 / 細胞内共生 / 窒素同化

Outline of Final Research Achievements

Algae are known to have evolved via endosymbiosis. However, the evolutionary process of the endosymbiosis is still unclear. The present study focused on kleptoplastic dinoflagellates Nusuttodinium spp. aimed to elucidate the mechanism by which they temporarily maintain the kleptoplast. N. poecilochroum, which exhibits a “predator-like” kleptoplasty, does not express nitrate transporter and nitrate reductase genes, whereas these genes are upregulated in N. aeruginosum, which exhibits a “advanced” kleptoplasty, in the light phase. Nitrate reductase in N. aeruginosum was acquired by horizontal gene transfer from cryptophytes, and its expression is changed depending on the extracellular nitrogen source. Furthermore, the expression of genes related to nitrogen assimilation in N. aeruginosum shares some similarities with gene expression patterns found in algae and plants.

Free Research Field

藻類学

Academic Significance and Societal Importance of the Research Achievements

一時的に共生体を維持する生物を用いたこれまでの研究では、宿主と共生体の系統解析、宿主への遺伝子の水平転移などに焦点を当てられてきた。対して本研究では、植物・藻類と類似した硝酸同化機構を盗葉緑体性の段階でも進化させうることを示し、細胞内共生の成立には光合成能の維持とその制御だけではなく、無機栄養塩の同化能も重要である可能性を示した。