Photoperiodic time measurement is the ability of plants and animals to measure differences in day versus night length (photoperiod) and use that information to anticipate critical seasonal transformations, such as annual temperature cycles. This timekeeping phenomenon triggers adaptive responses in higher organisms, such as gonadal stimulation, flowering, and hibernation. Unexpectedly, we observed this capability in cyanobacteria—unicellular prokaryotes with generation times as short as 5 to 6 hours. Cyanobacteria exposed to short, winter-like days developed enhanced resistance to cold mediated by desaturation of membrane lipids and differential programs of gene transcription, including stress response pathways. As in eukaryotes, this photoperiodic timekeeping required an intact circadian clockwork and developed over multiple cycles of photoperiod. Therefore, photoperiodic timekeeping evolved in much simpler organisms than previously appreciated and enabled genetic responses to stresses that recur seasonally.

中文翻译：

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细菌可以预测季节：蓝细菌的光周期性


光周期时间测量是植物和动物测量昼夜长度（光周期）差异并使用该信息预测关键季节性变化（例如年度温度周期）的能力。这种计时现象会触发高等生物的适应性反应，例如性腺刺激、开花和冬眠。出乎意料的是，我们在蓝细菌（生成时间短至 5 至 6 小时的单细胞原核生物）中观察到了这种能力。暴露于短日、类似冬天的日子的蓝细菌对膜脂质的去饱和和基因转录的差异程序（包括应激反应途径）介导的耐寒性增强。与真核生物一样，这种光周期计时需要完整的昼夜节律时钟，并在多个光周期周期中发展。因此，光周期计时在比以前认识的要简单得多的生物体中进化出来，并能够对季节性重复出现的应激做出遗传反应。