Hydra vulgaris exhibits day-night variation in behavior and gene expression levels
Hydra vulgaris exhibits day-night variation in behavior and gene expression levels
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DOI：
10.1186/s40851-019-0127-1
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发表时间：
2019-03-08
影响因子：
2.7
通讯作者：
Itoh, Taichi Q.
中科院分区：
文献类型：
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作者：
Kanaya, Hiroyuki J.;Kobayakawa, Yoshitaka;Itoh, Taichi Q.
背景：在大多数生物体中观察到昼夜行为变化，并且通常受昼夜生物钟和/或与环境线索的同步控制。九头蛇属淡水爬行动物，被认为缺乏在时钟系统中形成转录-翻译反馈环路的核心时钟基因。在这项研究中，我们研究了在没有典型时钟基因的情况下，九头蛇的行为和基因表达水平是否表现出昼夜节律。结果：我们发现，在12h的光暗周期下，九头蛇的总行为在白天上升，在夜间下降。息肉收缩频率是行为的一个组成部分，表现出明显的昼夜节律。然而，在恒定的光照和恒定的黑暗条件下，总行为和息肉收缩频率都没有表现出节律性的变化。为了确定潜伏在潜伏行为的基因，我们进行了全基因组转录组分析的水蛇在光-暗周期。使用三种不同的分析算法，我们发现380个基因在表达上表现出强劲的昼夜振荡。这些基因中的一些基因与其他具有内源性时钟系统的蛇类物种的昼夜周期基因具有共同的特征。结论：尽管没有典型的核心时钟基因，但九头蛇在明暗周期下表现出昼夜行为节律。考虑到水蛇类中显示昼夜振荡的基因的功能，以及这些基因与其他具有昼夜节律的蛇类物种的昼夜周期基因的相似性，无论在明暗周期下是否存在核心时钟基因，昼夜周期基因可能在蛇行动物物种中发挥重要作用。
Background: Day-night behavioral variation is observed in most organisms, and is generally controlled by circadian clocks and/or synchronization to environmental cues. Hydra species, which are freshwater cnidarians, are thought to lack the core clock genes that form transcription-translation feedback loops in clock systems. In this study, we examined whether hydras exhibit diel rhythms in terms of behavior and gene expression levels without typical clock genes.Results: We found that the total behavior of hydras was elevated during the day and decreased at night under a 12-h light-dark cycle. Polyp contraction frequency, one component of behavior, exhibited a clear diel rhythm. However, neither total behavior nor polyp contraction frequency showed rhythmic changes under constant light and constant dark conditions. To identify the genes underlying diel behavior, we performed genome-wide transcriptome analysis of hydras under light-dark cycles. Using three different analytic algorithms, we found that 380 genes showed robust diel oscillations in expression. Some of these genes shared common features with diel cycle genes of other cnidarian species with endogenous clock systems.Conclusion: Hydras show diel behavioral rhythms under light-dark cycles despite the absence of canonical core clock genes. Given the functions of the genes showing diel oscillations in hydras and the similarities of those genes with the diel cycle genes of other cnidarian species with circadian clocks, it is possible that diel cycle genes play an important role across cnidarian species regardless of the presence or absence of core clock genes under light-dark cycles.