The light–dark cycle is the primarily environmental stimulus responsible for entraining the major circadian clock located within the suprachiasmatic nucleus (SCN), which in turn coordinates various physiological processes in fish, including those in non‐SCN regions of the brain. To better understand differences in gene expression due to the light–dark cycle, we compared the transcriptomes of Pelteobagrus vachellii in non‐SCN regions of the brain in the daytime (12:00) and nighttime (24:00). The two cDNA libraries yielded 217,575,058 and 350,784,004 paired‐end clean reads, and 311,143 unique transcript fragments (unigenes) averaging 600.94 base pairs were assembled. It was possible to annotate ~7,426 (2.39%) unigenes based on homology with all database sequences. Gene expression analysis revealed that 2,406 and 1,665 annotated unigenes were up‐ and downregulated, respectively, with ≥twofold differences between daytime and nighttime. Enrichment analysis of differentially expressed genes predicted the pathways in which they operate, including development, endocrine function, adaptation to environmental changes and immunity. In summary, characterization of daytime and nighttime gene expression patterns in P. vachellii showed that the light–dark cycle coordinates gene expression in non‐SCN regions of the brain.

中文翻译：

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黄颡鱼白天和夜间大脑转录组的比较分析

明暗循环是主要的环境刺激，负责夹带位于视交叉上核 (SCN) 内的主要生物钟，后者又协调鱼的各种生理过程，包括大脑非 SCN 区域的生理过程。为了更好地了解由于明暗循环而导致的基因表达差异，我们比较了白天 (12:00) 和夜间 (24:00) 大脑非 SCN 区域中黄颡鱼的转录组。这两个 cDNA 文库产生了 217,575,058 和 350,784,004 个双端清洁读数，并且组装了 311,143 个独特的转录片段（unigenes），平均 600.94 个碱基对。基于与所有数据库序列的同源性，可以注释 ~7,426 (2.39%) unigenes。基因表达分析显示，2,406 和 1，665 个带注释的 unigenes 分别被上调和下调，白天和夜间的差异≥两倍。差异表达基因的富集分析预测了它们运行的​​途径，包括发育、内分泌功能、对环境变化的适应和免疫。总之，P. vachellii 白天和夜间基因表达模式的特征表明，明暗循环协调了大脑非 SCN 区域的基因表达。