Zhang Xiaoyan, Wen Haishen, Qi Xin, Zhang Kaiqiang, Liu Yang, Fan Hongying, Yu Peng, Tian Yuan, Li Yun
Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China.
Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China.
Comp Biochem Physiol A Mol Integr Physiol. 2019 Sep;235:69-81. doi: 10.1016/j.cbpa.2019.05.017. Epub 2019 May 23.
Euryhaline teleosts can survive in a wide salinity range via alteration of the molecular mechanisms to maintain internal ionic and osmotic balance in osmoregulatory organs such as gill，kidney and intestine. Na/K-ATPase (NKA), plays a crucial role in sustaining intracellular homeostasis and is characterized by association of multiple isoforms of α- and β-subunits. To gain insight into the potential function of nka genes in salinity adaptation, 5 nkaα genes (nkaα1a, nkaα1b, nkaα2, nkaα3a, nkaα3b) and 7 nkaβ genes (nkaβ1a, nkaβ1b, nkaβ2a, nkaβ2b, nkaβ3a, nkaβ3b and nkaβ4) were identified from transcriptomic and genomic databases of Lateolabrax maculatus. The annotation and evolutionary footprint of these nka genes was revealed via the analysis of phylogenetic tree, gene synteny, copy numbers, exon-intron structures and motif compositions. The expressions of 12 nka genes in spotted sea bass was tested in ten tissues (kidney, gonad, stomach, intestine, gill, muscle, heart, spleen, liver and brain) and 6 genes (nkaα1a, nkaα1b, nkaα3a, nkaα3b, nkaβ1b and nkaβ2a) showed high expression in osmoregulatory organs. Furthermore, the responses of NKA and potential salinity-sensitive nka genes were examined under different salinity treatment (0 ppt, 12 ppt, 30 ppt, 45 ppt). Results showed that the enzyme activity of NKA was highest in gill and exhibited salinity dependent variation, with the highest activity identified in 45 ppt. Different nkaα/β-isoforms showed their diverse responses to salinity changes and the expression of nka genes including nkaα1a, nkaα3b, nkaβ1b in gill, nkaα3a in kidney and nkaβ2a in intestine were transcriptionally regulated by altered salinity. Notably, the expression patterns of nkaα1a and nkaβ1b in gill showed similar variation trend with NKA activity, suggesting that nkaα1a/β1b could be the major function isoforms involved in primary ion transport during salinity adaptation. Our results provided insights into the roles of nkas in osmotic regulation and a theoretical basis for future studies that focus on detailed molecular mechanisms in salinity adaptation of euryhaline teleosts.
广盐性硬骨鱼可以通过改变分子机制，在很宽的盐度范围内生存，以维持鳃、肾脏和肠道等渗透调节器官内的离子和渗透平衡。钠钾ATP酶（NKA）在维持细胞内稳态中起关键作用，其特征是α和β亚基的多种同工型相互关联。为深入了解nka基因在盐度适应中的潜在功能，从斑尾鲈的转录组和基因组数据库中鉴定出5个nkaα基因（nkaα1a、nkaα1b、nkaα2、nkaα3a、nkaα3b）和7个nkaβ基因（nkaβ1a、nkaβ1b、nkaβ2a、nkaβ2b、nkaβ3a、nkaβ3b和nkaβ4）。通过系统发育树、基因共线性、拷贝数、外显子-内含子结构和基序组成分析，揭示了这些nka基因的注释和进化足迹。检测了12个nka基因在斑尾鲈10个组织（肾脏、性腺、胃、肠道、鳃、肌肉、心脏、脾脏、肝脏和大脑）中的表达，其中6个基因（nkaα1a、nkaα1b、nkaα3a、nkaα3b、nkaβ1b和nkaβ2a）在渗透调节器官中高表达。此外，还检测了不同盐度处理（0‰、12‰、30‰、45‰）下NKA和潜在盐度敏感nka基因的反应。结果表明，NKA的酶活性在鳃中最高，并呈现出盐度依赖性变化，在45‰时活性最高。不同的nkaα/β同工型对盐度变化表现出不同的反应，鳃中的nkaα1a、nkaα3b、nkaβ1b基因，肾脏中的nkaα3a基因和肠道中的nkaβ2a基因的表达受盐度变化的转录调控。值得注意的是，鳃中nkaα1a和nkaβ1b的表达模式与NKA活性呈现相似的变化趋势，表明nkaα1a/β1b可能是盐度适应过程中参与初级离子转运的主要功能同工型。我们的研究结果深入了解了nka在渗透调节中的作用，并为未来聚焦广盐性硬骨鱼盐度适应详细分子机制的研究提供了理论基础。
