Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China.
University of Chinese Academy of Sciences, Beijing, China.
BMC Genomics. 2024 Aug 27;25(1):807. doi: 10.1186/s12864-024-10727-y.
Hagfishes are fascinating creatures that typically inhabit the deep sea. The deep sea is characterized by its lack of sunlight, primary productivity, and diminishing biomass with increasing ocean depth. Therefore, hagfishes living in this environment must develop effective survival strategies to adapt to the limited food supply. Deep-sea hagfishes have been observed to survive without food intake for up to one year. In this study, we have assembled a high-quality somatic genome of the deep-sea hagfish (Eptatretus okinoseanus) captured below 1,000 m. We compared the genome of E. okinoseanus with the genomes of inshore hagfish, lampreys, and other related species to investigate the genetic factors underlying the deep-sea hagfish adaptations to the environment.
The E. okinoseanus somatic genome was estimated to be 1.89 Gb and assembled into 17 pseudochromosomes. Phylogenetic analysis showed that shallow-sea and deep-sea hagfishes diverged approximately 58.8 million years ago. We found Perilipin gene family was significantly expanded in deep sea E. okinoseanus, which promotes triacylglycerol storage. Furthermore, a series of genes involved in fatty acid synthesis and metabolism, blood glucose regulation, and metabolic rate regulation were also expanded, rapid evolution or positive selection, and these changes contribute to their efficiency in energy utilization. Among these genes, the positively selected gene JNK may play an important role in energy metabolism. In addition, the olfactory receptors of the deep-sea hagfish were significantly expanded to 86, and three conserved motifs present only in hagfishes olfactory receptors were identified, which may facilitate the rapid localization of carrion.
This study provides valuable genomic resources for insights into the survival strategies of deep-sea hagfishes in oligotrophic environments.
盲鳗是一种生活在深海中的迷人生物。深海的特点是缺乏阳光、初级生产力，并且随着海洋深度的增加，生物量逐渐减少。因此，生活在这种环境中的盲鳗必须发展出有效的生存策略来适应有限的食物供应。人们观察到深海盲鳗可以在不进食的情况下存活长达一年。在这项研究中，我们组装了一条生活在 1000 米以下深海盲鳗（Eptatretus okinoseanus）的高质量体细胞基因组。我们将 E. okinoseanus 的基因组与近岸盲鳗、七鳃鳗和其他相关物种的基因组进行比较，以研究深海盲鳗适应环境的遗传因素。
E. okinoseanus 体细胞基因组估计为 1.89Gb，组装成 17 条假染色体。系统发育分析表明，浅海和深海盲鳗大约在 5880 万年前分化。我们发现深海盲鳗的 Perilipin 基因家族显著扩张，促进了三酰甘油的储存。此外，一系列与脂肪酸合成和代谢、血糖调节和代谢率调节相关的基因也得到了扩张，这些基因的快速进化或正选择，有助于它们高效地利用能量。在这些基因中，正选择的 JNK 基因可能在能量代谢中发挥重要作用。此外，深海盲鳗的嗅觉受体显著扩张到 86 个，并且鉴定出了仅存在于盲鳗嗅觉受体中的三个保守基序，这可能有助于盲鳗快速定位腐肉。
本研究为深入了解深海盲鳗在贫营养环境中的生存策略提供了有价值的基因组资源。
