[B-BG01] Earth and Planetary Science Frontiers for Life and Global Environment

[BBG01-02] Unraveling the evolutionary history of photosynthesis through large-scale genome analysis

★Invited Papers

*Arisa Nishihara¹, Yusuke Tsukatani², Chihiro Azai³, Moriya Ohkuma¹, Masaru Konishi Nobu⁴ (1.RIKEN BioResource Research Center, 2.Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.Graduate School of Science and Engineering, Chuo University, 4.Institute for Extra-Cutting-Edge Science and Technology Avant-Garde Research (X-star))

Keywords:GOE, photosynthesis, cyanobacteria, Archean

The most primitive of photosynthetic organisms are thought to have emerged at least 3.5 billion years ago, as evidenced by geological records. The advent of the photosynthetic mechanism enabled organisms to obtain energy from light, which in turn promoted energy acquisition and carbon fixation on the primitive Earth, which was depleted of oxidative compounds (e.g. electron acceptors). Currently, photosynthetic bacteria have been identified in eight prokaryotic phyla; however, the evolutionary origins of photosynthesis remain topic of debate due to its prevalence across a wide range of phylogenetic groups. In this study, we performed a holistic phylogenetic comparison of bacteria and photosynthesis-related proteins (>10,000 genomes) to identify the correlation between the evolution of bacteria and photosynthesis. Our results reveal a date and forms of common ancestor, the Last Phototroph Common Ancestor (LPCA), which was an anoxygenic phototroph possessing carbon fixation mechanisms and two reaction centers – one similar to modern Type I and a primitive Type II. We also demonstrate that molecular evidence of photosynthesis originated before the LPCA. Approximately 2.5 billion years ago, a lineage from the LPCA acquired the ability to generate oxygen, leading to the Great Oxidation Event and subsequent diversification of life. Cyanobacteria emerged around 1.8 billion years ago as descendants of this lineage. Later, about 1.2 billion years ago, cyanobacteria were incorporated into eukaryotic cells, giving rise to plants. The present study provides not only a clarifying timeline for the evolution of photosynthesis but also a more profound comprehension of the coevolution of photosynthesis and bacterial lineages.