Graduate School of Science, Chiba University, Chiba, 263-8522, Japan.
Heredity (Edinb). 2024 May;132(5):267-274. doi: 10.1038/s41437-024-00680-7. Epub 2024 Mar 27.
Organisms have diverse biological clocks synchronised with environmental cycles depending on their habitats. Anticipation of tidal changes has driven the evolution of circatidal rhythms in some marine species. In the freshwater snail, Semisulcospira reiniana, individuals in nontidal areas exhibit circadian rhythms, whereas those in tidal areas exhibit both circadian and circatidal rhythms. We investigated whether the circatidal rhythms are genetically determined or induced by environmental cycles. The exposure to a simulated tidal cycle did not change the intensity of circatidal rhythm in individuals in the nontidal population. However, snails in the tidal population showed different activity rhythms depending on the presence or absence of the exposure. Transcriptome analysis revealed that genes with circatidal oscillation increased due to entrainment to the tidal cycle in both populations and dominant rhythmicity was consistent with the environmental cycle. These results suggest plasticity in the endogenous rhythm in the gene expression in both populations. Note that circatidal oscillating genes were more abundant in the tidal population than in the nontidal population, suggesting that a greater number of genes are associated with circatidal clocks in the tidal population compared to the nontidal population. This increase of circatidal clock-controlled genes in the tidal population could be caused by genetic changes in the biological clock or the experience of tidal cycle in the early life stage. Our findings suggest that the plasticity of biological rhythms may have contributed to the adaptation to the tidal environment in S. reiniana.
生物具有与环境周期同步的各种生物钟，这取决于它们的栖息地。对潮汐变化的预测推动了一些海洋物种的潮汐节律的进化。在淡水蜗牛 Semisulcospira reiniana 中，非潮汐区的个体表现出昼夜节律，而潮汐区的个体则表现出昼夜和潮汐节律。我们研究了这些潮汐节律是由遗传决定的还是由环境周期诱导的。暴露于模拟潮汐周期不会改变非潮汐种群个体的潮汐节律强度。然而，潮汐种群的蜗牛表现出不同的活动节律，这取决于暴露的存在与否。转录组分析表明，由于在两个种群中都与潮汐周期同步，具有潮汐振荡的基因的表达增加，并且主导节律与环境周期一致。这些结果表明，两个种群的内源性节律在基因表达上具有可塑性。值得注意的是，与非潮汐种群相比，潮汐种群中具有潮汐振荡的基因更为丰富，这表明与潮汐时钟相关的基因数量在潮汐种群中比在非潮汐种群中更多。这种潮汐时钟控制基因在潮汐种群中的增加可能是由于生物钟的遗传变化或早期生活阶段经历潮汐周期引起的。我们的研究结果表明，生物节律的可塑性可能有助于 S. reiniana 适应潮汐环境。
