The early development stages of fish are a highly ordered and tightly regulated, involving many circadian rhythm-related gene and protein processes. Nonetheless, there are few reports on the effects of circadian clock genes on the early development stages of fish. We studied Pelteobagrus fulvidraco Period 2 (Pf-Per 2) gene structures and expression patterns during the early life stages of development, including the fertilized embryo, yolk absorption, preliminary food, rotifer breeding, and mixed food stages. cDNA of Pf-Per 2 is 4593 bp in length, with 357 bp 5ʹ-untranslated region (5ʹUTR), 216 bp 3ʹUTR. The 4020 bp open reading frame consists of 1339 encoded amino acids. By multiple sequence alignment and phylogenetic analysis, the sequence was found to demonstrate high similarity to humans, rodents, microorganisms, and other fish species. Expression patterns of mRNA transcripts showed existence of rhythmic oscillations in the yellow catfish during the early development phase. The higher expression level of Per 2 is obviously present in the early embryonic development stage; the continuous downward trend of Per 2 was observed in the embryonic development and yolk nutrition absorption stages; additionally, the expression of Per 2 mRNA was significantly increased during individual development, rotifer breeding, and mixed food stages. Moreover, immunohistochemistry studies revealed strongest immune-labeled positive signals of Per 2 proteins mainly located in the cytoplasm of the olfactory bulb cell. Our findings reveal Pf-Per 2 serves important functions and may be useful as an indicator of P. fulvidraco early life development and initial food intake process stages.

鱼的早期发育阶段是高度有序的且受到严格调控的，涉及许多与生物节律有关的基因和蛋白质过程。但是，关于昼夜节律基因对鱼类早期发育的影响的报道很少。我们研究了Pelteobagrus fulvidraco时期2（Pf-Per 2）在发育的早期生命阶段的基因结构和表达模式，包括受精的胚胎，卵黄吸收，初级食物，轮虫繁殖和混合食物阶段。Pf-Per 2的cDNA长度为4593 bp，具有357 bp的5′-非翻译区（5ʹUTR），216 bp的3ʹUTR。4020 bp的开放阅读框由1339个编码的氨基酸组成。通过多重序列比对和系统发育分析，发现该序列与人类，啮齿动物，微生物和其他鱼类具有高度相似性。mRNA转录物的表达模式表明，黄development鱼在早期发育阶段存在节律性振荡。Per 2的较高表达水平显然存在于胚胎早期发育阶段。在胚胎发育和蛋黄营养吸收阶段观察到Per 2的持续下降趋势。另外，Per 2的表达式在个体发育，轮虫繁殖和混合食物阶段，mRNA显着增加。此外，免疫组化研究显示，Per 2蛋白的免疫标记阳性信号最强，主要位于嗅球细胞的细胞质中。我们的研究结果表明，Pf-Per 2发挥着重要的功能，并且可以作为指示黄腐体育早期生活发展和食物摄入初期阶段的指标。