Mitochondrion is an organelle responding to providing cell energy by oxidative phosphorylation (OXPHOS) reaction. In the mitochondrial genome of animals, 13 important protein-coding genes (ND1, ND2, ND3, ND4, ND4L, ND5, ND6, CTYB, COX1, COX2, COX3 ATP6, ATP8) play important roles on mediating the OXPHOS reaction. The study is to compare the expressional level of 13 mitochondrial PCGs among muscle of diverse fish species to ask whether the 13 PCGs expressional level is correlated to fish living habitat or phylogenetic position. We used a metatranscriptomic approach to explore the expression level of 13 PCGs among diverse fish species (24 bony fish and one cartilaginous fish) by downloading the raw next-generation data from the NCBI SRA database and using two commercial software of Geneious and CLCBio to perform gene mapping and gene expression profiling. Principal component analysis (PCA) and hierarchy clustering were utilized to study the gene or species relationship based on 13 PCGs’ expression pattern. Based on the results, we discovered the expression pattern of PCG genes derived from the same OXPHOS complex is closer to each other showing co-expression or co-regulation relationship. The 13 PCGs expression profile was not co-related to fish living habitats but instead, well correlated to their phylogenetic position. The clustering results for 13 PCGs’ expressional patterns showed bony fish and cartilaginous fish were grouped into two distinct clades. For bony fish clades, all COX genes displayed high expression patterns while for the cartilaginous clade, the CYTB gene was highly expressed with the low expression level of COX3. In conclusion, by using the metatranscriptomic approach, we were able to explore and compare the gene expression profiles of 13 PCGs from diverse fish species for the first time. The co-expression pattern of 13 PCGs discovered in fish was well consistent with previous observations done in plants or mammals. However, one has to keep in mind that the current finding results were based only on one example of a cartilaginous fish that was accessible in the SRA database. Thus, future studies are needed by constructing more additional cartilaginous fish muscle transcriptomes.

线粒体是一种细胞器，通过氧化磷酸化（OXPHOS）反应来响应提供细胞能量。在动物的线粒体基因组中，13个重要的蛋白质编码基因（ND1，ND2，ND3，ND4，ND4L，ND5，ND6，CTYB，COX1，COX2，COX3 ATP6，ATP8）在介导OXPHOS反应中起重要作用。该研究旨在比较多种鱼类肌肉中13种线粒体PCG的表达水平，以询问13种PCG的表达水平是否与鱼类的栖息地或系统发育位置相关。通过从NCBI SRA数据库下载原始的下一代数据，并使用Geneious和CLCBio的两个商业软件来进行转录，我们使用一种超转录组学的方法探索了13种PCG在不同鱼类（24种骨鱼和一种软骨鱼）中的表达水平。基因定位和基因表达谱分析。利用主成分分析（PCA）和层次聚类，基于13种PCG的表达模式研究基因或物种之间的关系。根据结果​​，我们发现源自同一OXPHOS复合物的PCG基因的表达模式彼此更接近，表现出共表达或共调控关系。13种PCG的表达谱与鱼类的栖息地并不相关，而是与其系统发育位置密切相关。13种PCGs表达模式的聚类结果表明，骨鱼和软骨鱼被分为两个不同的进化枝。对于骨鱼类进化枝，所有COX基因均表现出高表达模式，而对于软骨进化枝，CYTB基因则高表达而COX3表达水平低。总之，通过使用超转录组学方法，我们能够首次探索和比较来自不同鱼类的13种PCG的基因表达谱。在鱼类中发现的13种PCG的共表达模式与以前在植物或哺乳动物中观察到的现象非常吻合。但是，必须记住，当前的发现结果仅基于SRA数据库中可访问的一个软骨鱼类的示例。从而，