Caloric restriction (CR) produces clear phenotypic effects within and between generations of the model crustacean Daphnia magna. We have previously established that micro‐RNAs and cytosine methylation change in response to CR in this organism, and we demonstrate here that CR has a dramatic effect on gene expression. Over 6,000 genes were differentially expressed between CR and well‐fed D. magna, with a bias towards up‐regulation of genes under caloric restriction. We identified a highly expressed haemoglobin gene that responds to CR by changing isoform proportions. Specifically, a transcript containing three haem‐binding erythrocruorin domains was strongly down‐regulated under CR in favour of transcripts containing fewer or no such domains. This change in the haemoglobin mix is similar to the response to hypoxia in Daphnia, which is mediated through the transcription factor hypoxia‐inducible factor 1, and ultimately the mTOR signalling pathway. This is the first report of a role for haemoglobin in the response to CR. We also observed high absolute expression of superoxide dismutase (SOD) in normally fed individuals, which contrasts with observations of high SOD levels under CR in other taxa. However, key differentially expressed genes, like SOD, were not targeted by differentially expressed micro‐RNAs. Whether the link between haemoglobin and CR occurs in other organisms, or is related to the aquatic lifestyle, remains to be tested. It suggests that one response to CR may be to simply transport less oxygen and lower respiration.

中文翻译：

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大型蚤（Daphnia magna）响应热量限制而广泛修饰其基因表达，揭示了对血红蛋白同工型偏好的新影响。

热量限制（CR）在甲壳纲水蚤（Daphnia magna）模型的各代之间以及各代之间产生明显的表型效应。我们先前已经确定，在这种生物体中，微RNA和胞嘧啶甲基化会响应CR而变化，并且我们在此处证明了CR对基因表达具有显着影响。CR和饲喂的D. magna之间有超过6,000个基因差异表达，偏向于热量限制下基因的上调。我们确定了高表达的血红蛋白基因，可通过改变同工型比例来响应CR。具体而言，在CR下，含有三个与血红素结合的赤藓红素结构域的转录本被强烈下调，从而有利于含有较少或没有此类结构域的转录本。血红蛋白混合物的这种变化类似于水蚤对缺氧的反应，它通过转录因子低氧诱导因子1介导，并最终通过mTOR信号传导途径介导。这是血红蛋白在CR反应中作用的首次报道。我们还观察到正常喂养的个体中超氧化物歧化酶（SOD）的绝对表达高，这与其他类群在CR下高SOD水平的观察结果形成对比。但是，关键差异表达基因（如SOD）并未被差异表达的micro-RNA靶向。血红蛋白和CR之间的联系是否发生在其他生物中，还是与水生生活方式有关，尚待检验。这表明对CR的一种反应可能是简单地运输较少的氧气和降低呼吸。