Isoda Minako, Ito Shogo, Oyama Tokitaka
Department of Botany, Graduate School of Science, Kyoto University, Kyoto, Japan.
Plant Cell Environ. 2022 Jun;45(6):1942-1953. doi: 10.1111/pce.14297. Epub 2022 Mar 8.
The circadian clock system is widely conserved in plants; however, divergence in circadian rhythm properties is poorly understood. We conducted a comparative analysis of the circadian properties of closely related duckweed species. Using a particle bombardment method, a circadian bioluminescent reporter was introduced into duckweed plants. We measured bioluminescence circadian rhythms of eight species of the genus Lemna and seven species of the genus Wolffiella at various temperatures (20, 25, and 30°C) and light conditions (constant light or constant dark). Wolffiella species inhabit relatively warm areas and lack some tissues/organs found in Lemna species. Lemna species tended to show robust bioluminescence circadian rhythms under all conditions, while Wolffiella species showed lower rhythm stability, especially at higher temperatures. For Lemna, two species (L. valdiviana and L. minuta) forming a clade showed relatively lower circadian stability. For Wolffiella, two species (W. hyalina and W. repanda) forming a clade showed extremely long period lengths. These analyses reveal that the circadian properties of species primarily reflect their phylogenetic positions. The relationships between geographical and morphological factors and circadian properties are also suggested.
生物钟系统在植物中广泛存在；然而，昼夜节律特性的差异却鲜为人知。我们对近缘浮萍物种的昼夜节律特性进行了比较分析。采用粒子轰击法，将昼夜生物发光报告基因导入浮萍植株。我们在不同温度（20、25和30°C）和光照条件（持续光照或持续黑暗）下，测量了8种浮萍属植物和7种无根萍属植物的生物发光昼夜节律。无根萍属物种栖息在相对温暖的地区，并且缺乏一些浮萍属物种中存在的组织/器官。浮萍属物种在所有条件下往往都表现出较强的生物发光昼夜节律，而无根萍属物种的节律稳定性较低，尤其是在较高温度下。对于浮萍属，形成一个分支的两个物种（瓦尔迪维亚浮萍和微小浮萍）表现出相对较低的昼夜节律稳定性。对于无根萍属，形成一个分支的两个物种（透明无根萍和匍匐无根萍）表现出极长的周期长度。这些分析表明，物种的昼夜节律特性主要反映了它们的系统发育位置。同时也揭示了地理和形态因素与昼夜节律特性之间的关系。
