Harada Keigo, Komasaka Yukariko, Yamada Keisuke, Iizuka Takumi, Otani Minato, Murayama Yoshihiro
Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
Department of Biomedical Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
PNAS Nexus. 2024 Oct 4;3(10):pgae444. doi: 10.1093/pnasnexus/pgae444. eCollection 2024 Oct.
A spherical green alga, , achieves phototaxis via a simple on/off switch of flagellar beating in response to changes in light intensity, without the need for complex signal transduction between cells. Moreover, the alga can change its susceptibility to light in order to adapt to its environment. To identify the mechanisms of susceptibility regulation, experiments were conducted at three different levels: population, individual, and cellular. The light intensity dependence of the average velocity at the population level and that of the change in flow speed obtained at the individual level were consistent, indicating that susceptibility regulation occurred in each colony. Furthermore, by measuring the probability of stopping flagellar beating when the light intensity was changed, susceptibility regulation was found to result from the properties of somatic cells as differential and adaptive photosensors. These photosensing properties deteriorated from the anterior to the posterior regions of the colony. Considering the mechanical motion of a colony, the position-dependent ability of somatic cells indicates that the anterior cells play the role of a rudder, whereas the posterior cells play the role of a rower. The position-dependent properties of somatic cells imply an early stage of cell differentiation that allows for an efficient response to changes in the circumstances.
一种球形绿藻，通过鞭毛摆动的简单开/关开关来实现趋光性，以响应光强度的变化，无需细胞间复杂的信号转导。此外，这种藻类可以改变其对光的敏感性以适应环境。为了确定敏感性调节的机制，在群体、个体和细胞三个不同层面进行了实验。群体水平上平均速度的光强度依赖性与个体水平上获得的流速变化的光强度依赖性是一致的，这表明每个群体中都发生了敏感性调节。此外，通过测量光强度改变时停止鞭毛摆动的概率，发现敏感性调节是由体细胞作为差异和适应性光传感器的特性导致的。这些光传感特性从群体的前部到后部逐渐变差。考虑到群体的机械运动，体细胞的位置依赖性能力表明前部细胞起到舵的作用，而后部细胞起到桨手的作用。体细胞的位置依赖性特性意味着细胞分化的早期阶段，这使得能够对环境变化做出有效反应。
