1+1=1: deciphering how two different organisms became one by comparative genomics

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H03282
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 45030:Biodiversity and systematics-related
• Research Institution: University of Tsukuba
• Principal Investigator: Ishida Ken-ichiro 筑波大学, 生命環境系, 教授 (30282198)
• Co-Investigator(Kenkyū-buntansha): 白鳥 峻志 筑波大学, 生命環境系, 助教 (70800621)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 二次共生 / 細胞進化 / 葉緑体 / クロララクニオン藻 / ケルコゾア / アオサ藻 / ゲノム

Outline of Final Research Achievements

To understand the cellular evolution in the process of chloroplast acquisition by secondary endosymbiosis in chlorarachniophytes, we squenced the complete genomes of two species of cercozoan that are the most closely related to the chlorarachniophyte’s host compartment and one species of ulvophyte green alga that is closely related to the chloroplasts, and performed comparative genome analysis with chlorarachniophyte genome. The results suggest that there was a large-scale increase in gene families in the ancestor of the host compartment before the chloroplast acquisition by the chlorarachniophytes, which indicates that the cellular evolution allowing the chloroplast acquisition had already occurred in ancestral lineage. In addition, about 8% of genes in the chlorarachniophyte genome were found to be derived from organisms other than the host and endosymbiont of the secondary endosymbiosis, and some of the chloroplast protein genes were also found to be derived from the host.

Free Research Field

系統分類学、細胞進化学

Academic Significance and Societal Importance of the Research Achievements

本研究によって、二次共生の際の細胞進化を、個々の遺伝子ベースにこれまでにない精度で、解析することができた。これは二次共生による葉緑体獲得を理解する上で非常に大きな進展をもたらすものである。また、ゲノムデータの少ないケルコゾアとアオサ藻についてそれぞれ２種と１種の全ゲノム解読に成功したことは、クロララクニオン藻の進化だけでなく、真核生物の様々な研究の進展において有意義な貢献となった。