Jiang Yanliang, Feng Shuaisheng, Xu Jian, Zhang Songhao, Li Shangqi, Sun Xiaoqing, Xu Peng
CAFS Key Laboratory of Aquatic Genomics, Beijing Key Laboratory of Fishery Biotechnology, Centre for Applied Aquatic Genomics, Chinese Academy of Fishery Sciences, Beijing 100141, China.
CAFS Key Laboratory of Aquatic Genomics, Beijing Key Laboratory of Fishery Biotechnology, Centre for Applied Aquatic Genomics, Chinese Academy of Fishery Sciences, Beijing 100141, China; College of Life Sciences, Shanghai Ocean University, Shanghai 201306, China.
Mar Genomics. 2016 Oct;29:89-96. doi: 10.1016/j.margen.2016.06.002. Epub 2016 Jun 16.
Aerial breathing in fish was an important adaption for successful survival in hypoxic water. All aerial breathing fish are bimodal breathers. It is intriguing that they can obtain oxygen from both air and water. However, the genetic basis underlying bimodal breathing has not been extensively studied. In this study, we performed next-generation sequencing on a bimodal breathing fish, the Northern snakehead, Channa argus, and generated a transcriptome profiling of C. argus. A total of 53,591 microsatellites and 26,378 SNPs were identified and classified. A Ka/Ks analysis of the unigenes indicated that 63 genes were under strong positive selection. Furthermore, the transcriptomes from the aquatic breathing organ (gill) and the aerial breathing organ (suprabranchial chamber) were sequenced and compared, and the results showed 1,966 genes up-regulated in the gill and 2,727 genes up-regulated in the suprabranchial chamber. A gene pathway analysis concluded that four functional categories were significant, of which angiogenesis and elastic fibre formation were up-regulated in the suprabranchial chamber, indicating that the aerial breathing organ may be more efficient for gas exchange due to its highly vascularized and elastic structure. In contrast, ion uptake and transport and acid-base balance were up-regulated in the gill, indicating that the aquatic breathing organ functions in ion homeostasis and acid-base balance, in addition to breathing. Understanding the genetic mechanism underlying bimodal breathing will shed light on the initiation and importance of aerial breathing in the evolution of vertebrates.
鱼类的空气呼吸是其在缺氧水体中成功生存的一项重要适应性特征。所有具有空气呼吸能力的鱼类都是双重呼吸者。有趣的是，它们能够从空气和水中获取氧气。然而，双重呼吸背后的遗传基础尚未得到广泛研究。在本研究中，我们对一种双重呼吸鱼类——乌鳢（Channa argus）进行了二代测序，并生成了乌鳢的转录组图谱。共鉴定并分类了53,591个微卫星和26,378个单核苷酸多态性（SNP）。对单基因的Ka/Ks分析表明，有63个基因受到强烈的正选择。此外，对水生呼吸器官（鳃）和空气呼吸器官（鳃上腔）的转录组进行了测序和比较，结果显示鳃中有1,966个基因上调，鳃上腔中有2,727个基因上调。基因通路分析得出结论，四个功能类别具有显著性，其中血管生成和弹性纤维形成在鳃上腔中上调，这表明空气呼吸器官因其高度血管化和有弹性的结构可能在气体交换方面更高效。相比之下，离子摄取、运输和酸碱平衡在鳃中上调，这表明水生呼吸器官除了呼吸外，还在离子稳态和酸碱平衡方面发挥作用。了解双重呼吸背后的遗传机制将有助于揭示脊椎动物进化过程中空气呼吸的起源和重要性。
