Mitogen-activated protein kinases (MAPKs) are a class of protein kinases that regulate various physiological processes, and play a crucial role in maintaining the osmotic equilibrium of fish. The objective of this study was to identify and characterize the family genes in cobia () and examine their expression profiles under different low salinity stress regimes (acute: from 30‰ to 10‰ in 1 h, sub-chronic: from 30‰ to 10‰ over 4 d). A total of 12 cobia genes () were identified and cloned, including six subfamily genes (), three subfamily genes () and three subfamily genes (). Domain analysis indicated that the RcMAPKs possessed the typical domains including S_TKc and PKc_like domain. Phylogenetic analysis revealed that the were most closely related to those of the turbot (). The tissue distribution of genes in adult cobia and the expression patterns of under different low salinity stress regimes were investigated using quantitative real-time PCR (qRT-PCR). The results revealed that exhibited a relatively broad expression distribution across 14 different tissues. For all these genes the highest expression level was in the brain, except for (highly expressed in the stomach, gill, and skin). The genes showed significantly higher expression in the testis. Under acute low salinity stress, expression of was significantly altered in the gill, intestine, and trunk kidney, however, the aforementioned genes exhibited very different expression patterns among the three tissues. In the gill, most of the genes from the () and subfamily () were significantly up-regulated at almost all the time points ( < 0.05); Similarly, the expression of genes were significantly increased in the trunk kidney; while in the intestine, most of the altered genes () were significantly down-regulated at 1 h. Following the sub-chronic low salinity stress, expression of genes were significantly altered in all three tissues. These findings provide important reference data for elucidating the roles of cobia family genes in response to low salinity stress.

中文翻译：

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军曹鱼 (Rachycentron canadum) 中 mapk 基因及其响应低盐胁迫的表达谱的鉴定

丝裂原激活蛋白激酶（MAPK）是一类调节多种生理过程的蛋白激酶，在维持鱼类渗透压平衡中发挥着至关重要的作用。本研究的目的是鉴定和表征军曹鱼 () 中的家族基因，并检查其在不同低盐度胁迫条件下的表达谱（急性：1 小时内从 30 ‰ 到 10 ‰，亚慢性：从 30 ‰ 到 10 ≥ 4 d)。共鉴定并克隆了12个军曹鱼基因()，其中包括6个亚科基因()、3个亚科基因()和3个亚科基因()。结构域分析表明RcMAPKs具有S_TKc和PKc_like结构域等典型结构域。系统发育分析表明，它们与大菱鲆的关系最为密切。采用实时定量PCR（qRT-PCR）研究了成年军曹鱼基因的组织分布以及不同低盐胁迫条件下的表达模式。结果显示，在 14 种不同组织中表现出相对广泛的表达分布。对于所有这些基因，最高表达水平在大脑中，除了（在胃、鳃和皮肤中高度表达）。这些基因在睾丸中表现出显着较高的表达。在急性低盐胁迫下，鳃、肠和躯干肾中的表达显着改变，然而，上述基因在三个组织中表现出非常不同的表达模式。在鳃中，来自()和亚家族()的大部分基因在几乎所有时间点均显着上调(<0.05)；同样，躯干肾脏中的基因表达显着增加；而在肠道中，大多数改变的基因()在1小时时显着下调。亚慢性低盐胁迫后，所有三种组织中的基因表达均发生显着改变。这些发现为阐明军曹鱼家族基因响应低盐胁迫的作用提供了重要的参考数据。