Experimental verification of a hypothesis of early evolution of complexity using a primitive life-like system

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K23763
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0703:Biology at organismal to population levels and anthropology, and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Mizuuchi Ryo 東京大学, 大学院総合文化研究科, 特任助教 (60845535)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: 生命の起源 / 生命の初期進化 / 複雑化 / RNA / 実験進化 / 翻訳システム / 再構成 / 人工細胞

Outline of Final Research Achievements

In this study, we (1) theoretically investigated how primitive RNA replicators could be integrated into a long genome through Darwinian evolution, and (2) developed necessary molecules for examining the validity of a theoretical prediction. In the theoretical part, we simulated the long-term replication of cooperative RNA replicators, during which mutations may integrate the cooperators. We found that a critical factor for the evolution of such an RNA assembly is the appearance of unfunctional RNAs that replicate by exploiting the cooperative RNAs, which has been considered a major problem in the early evolution of life. In the experimental part, by combining genetic engineering and directed evolution, we obtained a long replicable RNA derived from two RNA replicators encoding different proteins. The study not only revealed likely conditions where primitive molecular replicators could have been integrated but also established the necessary basis for experimental verification.

Free Research Field

生命の起源

Academic Significance and Societal Importance of the Research Achievements

原始地球において生命がどのように誕生し、進化してきたのかを理解することは、科学の大きな問の一つである。一般に原始生命はRNAなどの情報分子の自己複製体として誕生した後、進化によって徐々に遺伝情報を拡張して複雑化したと考えられているが、この複雑化を引き起こす要因は謎に包まれていた。本研究では、原始複製体や原始区画で考えられる特徴が複雑化の一側面、すなわち複数の複製体がもつ遺伝情報の統合を促進する可能性を見出した。この結果は単純な分子複製体が複雑な生命システムへと進化していく一つのシナリオを提示し、例えば生命の起源の必要条件を絞り込むことに繋がる。