The functional role of photosynthesis-related genes in non-photosynthetic symbionts of corals

• Project/Area Number: 22KF0361
• Project/Area Number (Other): 21F21081 (2021-2022)
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Multi-year Fund (2023); Single-year Grants (2021-2022)
• Section: 外国
• Review Section: Basic Section 43050:Genome biology-related
• Research Institution: Okinawa Institute of Science and Technology Graduate University
• Principal Investigator: ALVES・DOS・SANTOS Maria・Eduarda (2023) 沖縄科学技術大学院大学, 進化・細胞・共生の生物学ユニット, 客員研究員 (30854674); HUSNIK Filip (2021) 沖縄科学技術大学院大学, 進化・細胞・共生の生物学ユニット, 准教授 (30886130)
• Co-Investigator(Kenkyū-buntansha): ALVES DOS SANTOS MARIA 沖縄科学技術大学院大学, 進化・細胞・共生の生物学ユニット, 外国人特別研究員
• Host Researcher: HUSNIK Filip (2022) 沖縄科学技術大学院大学, 進化・細胞・共生の生物学ユニット, 准教授 (30886130)
• Foreign Research Fellow: ALVES DOS SANTOS MARIA 沖縄科学技術大学院大学, 進化・細胞・共生の生物学ユニット, 外国人特別研究員
• Project Period (FY): 2023-03-08 – 2024-03-31
• Project Status: Completed (Fiscal Year 2023)
• Budget Amount: ¥2,200,000 (Direct Cost: ¥2,200,000); Fiscal Year 2023: ¥600,000 (Direct Cost: ¥600,000); Fiscal Year 2022: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2021: ¥500,000 (Direct Cost: ¥500,000)
• Keywords: evolution / symbiosis / corals / Symbiosis / Microbiome / Evolution / Genomics / Ecology / Apicomplexa / Dinoflagellate / Coral

Outline of Research at the Start

My research will shed light on the interaction between corallicolids and zooxanthellae, the two most common protists associated with corals. This will also help to improve the management of coral reefs, for example, in relation to the monitoring and forecast of coral ‘bleaching’ events with zooxanthellae expulsion. These results will have a substantial impact on the knowledge of the scientific community on the evolutionary transition from free-living autotrophs to parasites. Several peer-reviewed manuscripts will be published in international journals with open-access.

Outline of Annual Research Achievements

I sequenced and analyzed the symbionts of over 100 coral samples from Okinawa and 16 regions worldwide. Our results clarified their global distribution, as well as their localization in the coral tissues. For instance, Sanger sequencing of the 18S-rRNA gene region of corallicolids showed that coral species from Japan are associated with the same lineage, and this same corallicolid clade is also symbiotic with coral species from different Hawai’i and the Caribbean Sea.

Additionally, our results with amplicon sequencing (16S, 18S, and ITS2) indicated global patterns of coral-symbiont diversity. The predominant bacteria phylum associated with coral samples worldwide was Proteobacteria, such as the mutualistic Endozoicomonas and the pathogenic Vibrios. As expected, the most abundant eukaryote associated with coral colonies was Dinoflagellate, especially zooxanthellae of Cladocopium, followed by Durisdinium. A few samples were also associated with lineages of Symbiodinium, mostly restricted to the Atlantic Ocean. Other common microeukaryotes were apicomplexans of corallicolids, chromerids, and Fungi. Furthermore, our results indicated that corallicolids were more abundant in samples from the Atlantic Ocean compared to the Indo-Pacific Ocean, including Okinawa.

Our metagenomic and genomic results confirmed the high diversity of coral microbes. Moreover, we reported a potentially undescribed bacteria species of the genus Spiroplasma, and its genes indicated that this might be a mutualistic symbiont.

Research Products

• [Presentation] A new Spiroplasma species with a highly reduced genome discovered from a coral metagenome in Okinawa (2023)
  • Author(s): Yumiko M, Choi J, Santos MEA, Husnik F
  • Organizer: XXIV Biennial Congress of the International Organization for Mycoplasmology
  • Int'l Joint Research
• [Presentation] Global connectivity and symbiosis of Palythoa hexacorals (2023)
  • Author(s): Santos MEA, Reimer JD, Mizuyama M, Kise H, Boo WH, Iguchi A, Dudoi A, Toonen R, Kitahara MV, Husnik F
  • Organizer: SHINKA Evolutionary Society of Japan
• [Presentation] Global diversity of Symbiodiniaceae and Corallicolida associated with corals. (2022)
  • Author(s): Santos MEA, Reimer JD, Mizuyama M, Kise H, Boo WH, Iguchi A, Dudoi A, Toonen R, Kitahara MV, Husnik F
  • Organizer: Conferences Jacques Monod 4 - From parasites to plankton and back: comparative biology and ecology of apicomplexans and dinoflagellates
  • Int'l Joint Research
• [Presentation] Global diversity of coral symbionts (2022)
  • Author(s): Santos MEA, Reimer JD, Mizuyama M, Kise H, Boo WH, Iguchi A, Dudoi A, Toonen R, Kitahara MV, Husnik F
  • Organizer: 3rd OIST-Tohoku University Joint Workshop “Biodiversity: From genes and species to ecosystem services and resilience”
• [Presentation] Global diversity of coral endosymbionts (2022)
  • Author(s): Maria E. A. Santos, James D. Reimer, Masaru Mizuyama, Hiroki Kise, Wee H. Boo, Akira Iguchi, ‘Ale’alani Dudoit, Robert Toonen, Marcelo V. Kitahara, Filip Husnik
  • Organizer: “Oceans - and the impact of humans and climate change” - OIST-Tohoku U. 2nd Joint Workshop on Marine Science