Mukaiyama Atsushi, Furuike Yoshihiko, Ito-Miwa Kumiko, Onoue Yasuhiro, Horiuchi Kota, Kondo Kanta, Yamashita Eiki, Akiyama Shuji
Department of Bioscience and Biotechnology, Fukui Prefectural University, Eiheiji, 910-1195, Japan.
Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, 444-8585, Japan.
Nat Commun. 2025 May 15;16(1):4541. doi: 10.1038/s41467-025-59908-7.
Light-dark cycles affect photosynthetic efficiency in autotrophic cyanobacteria; therefore, determining whether ancient cyanobacteria possessed a self-sustained circadian clock when oxygenic photosynthetic systems were established is an important issue in chronobiology. Here we examine the oscillation of the clock protein KaiC in modern cyanobacteria, as well as the function and structure of ancestral Kai proteins, to determine the evolutionary origin of the self-sustained Kai-protein oscillators. The results show that the oldest double-domain KaiC in ancestral bacteria lacks the factors functionally and structurally essential for rhythmicity. The ancestral Kai proteins have acquired these factors through molecular evolution that occurred around Global Oxidation and Snowball Earth events, and are eventually inherited as a self-sustained circadian oscillator by the most recent common ancestor of cyanobacteria capable of oxygenic photosynthesis. This autonomous Kai protein oscillator is further inherited by most freshwater and marine cyanobacteria present today as an autotrophic basis for time-optimal acquisition and consumption of energy from oxygenic photosynthesis.
光暗循环会影响自养蓝细菌的光合效率；因此，确定在有氧光合系统建立时，古代蓝细菌是否拥有自我维持的生物钟是时间生物学中的一个重要问题。在这里，我们研究了现代蓝细菌中生物钟蛋白KaiC的振荡，以及祖先Kai蛋白的功能和结构，以确定自我维持的Kai蛋白振荡器的进化起源。结果表明，祖先细菌中最古老的双结构域KaiC缺乏对节律性在功能和结构上至关重要的因子。祖先Kai蛋白通过在全球氧化和雪球地球事件期间发生的分子进化获得了这些因子，并最终被能够进行有氧光合作用的蓝细菌的最近共同祖先作为自我维持的生物钟继承下来。这种自主的Kai蛋白振荡器作为从有氧光合作用中最佳获取和消耗能量的自养基础，被当今大多数淡水和海洋蓝细菌进一步继承。
