Liu Zhaoqun, Zhou Zhi, Wang Lingling, Li Meijia, Wang Weilin, Yi Qilin, Huang Shu, Song Linsheng
Liaoning Key Laboratory of Marine Animal Immunology, Dalian Ocean University, Dalian, China.
Functional Laboratory of Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Front Physiol. 2018 Oct 10;9:1080. doi: 10.3389/fphys.2018.01080. eCollection 2018.
The Chinese mitten crab lives in saline or fresh water during different life stages and exhibits a complex life history, making it an ideal model to study the salinity adaptation of euryhaline animals. In this study, RNA-seq techniques, and determinations of free amino acids (FAAs), monoamine neurotransmitters, and Na/K pump activity, were employed to understand the osmoregulatory mechanism in Chinese mitten crab. A total of 15,138 differentially expressed genes were obtained from 12 transcriptome libraries. GO enrichment analysis revealed that the mRNA expression profiles were completely remodeled from 12 to 24 h after salinity stress. The neuroendocrine system was activated under stimulation, and the monoamine neurotransmitters including dopamine (DA) and serotonin (5-HT) were released to modulate osmoregulation. Furthermore, the Na/K pump in crab hemocytes was significantly inhibited post salinity stress, resulting in increased intracellular ion concentrations and osmotic pressure to sustain the osmotic balance. Moreover, six key FAAs, including alanine (Ala), proline (Pro), glycine (Gly), glutamate (Glu), arginine (Arg), and aspartate (Asp), were overexpressed to modulate the extracellular osmotic balance during salinity adaptation. Interestingly, the immune genes were not enriched in the GO analysis, implying that the immune system might not contribute fundamentally to the tolerance upon fluctuating ambient salinity in the Chinese mitten crab. These results collectively demonstrated that the Chinese mitten crab had evolved an efficient regulation mechanism by modulating the FAAs production and Na/K pump activity to sustain the osmotic balance independent of the immune system, in which the neuroendocrine modulation, especially generated by the monoamine neurotransmitter, played an indispensable role.
中华绒螯蟹在不同的生命阶段生活在咸水或淡水中，展现出复杂的生活史，这使其成为研究广盐性动物盐度适应性的理想模型。在本研究中，采用RNA测序技术以及游离氨基酸（FAA）、单胺神经递质和钠钾泵活性的测定，以了解中华绒螯蟹的渗透调节机制。从12个转录组文库中总共获得了15138个差异表达基因。基因本体（GO）富集分析表明，盐度胁迫后12至24小时，mRNA表达谱完全重塑。神经内分泌系统在刺激下被激活，包括多巴胺（DA）和5-羟色胺（5-HT）在内的单胺神经递质被释放以调节渗透调节。此外，盐度胁迫后蟹血细胞中的钠钾泵受到显著抑制，导致细胞内离子浓度和渗透压升高，以维持渗透平衡。此外，在盐度适应过程中，包括丙氨酸（Ala）、脯氨酸（Pro）、甘氨酸（Gly）、谷氨酸（Glu）、精氨酸（Arg）和天冬氨酸（Asp）在内的6种关键游离氨基酸过表达，以调节细胞外渗透平衡。有趣的是，免疫基因在GO分析中未被富集，这意味着免疫系统可能对中华绒螯蟹在环境盐度波动时的耐受性没有根本性贡献。这些结果共同表明，中华绒螯蟹通过调节游离氨基酸的产生和钠钾泵活性，进化出了一种有效的调节机制，以独立于免疫系统维持渗透平衡，其中神经内分泌调节，特别是由单胺神经递质产生的调节，发挥了不可或缺的作用。
