Mitogen-activated protein kinase (MAPK) are a series of serine/threonine protein kinases showing evolutionary conservation, which can be activated by many stimulus signals and then transfer them from cell membrane to nucleus. MAPKs regulate a variety of biological processes, such as apoptosis, hormone signaling and immune response. In this study, 14 putative mapk genes in Japanese flounder were identified, and their basic physical and chemical properties were characterized. Phylogenetic analysis showed that mapk genes were divided into three main subfamilies, including ERK, JNK and the p38 MAPK. Selection pressure analysis revealed they were evolutionarily-constrained and undergone strong purifying selection. Gene structure and conserved protein motif comparison suggested high levels of conservation in members of mapk gene family. The expression patterns were further investigated in each embryonic and larval development stages and different tissues. In addition, RNA-seq analyses after bacteria and temperature stresses suggested mapk genes had different expression patterns. Three mapk genes showed significant differences in response to E. tarda challenge and five were induced significantly after temperature stress, indicating their potential functions. This systematic analysis provided valuable information for further understanding of the regulation mechanism of mapk gene family under different stresses in Japanese flounder.

丝裂原活化蛋白激酶（MAPK）是一系列显示进化保守性的丝氨酸/苏氨酸蛋白激酶，可以被许多刺激信号激活，然后从细胞膜转移到细胞核。MAPK 调节多种生物过程，例如细胞凋亡、激素信号传导和免疫反应。在这项研究中，鉴定了日本比目鱼中 14 个推定的 mapk 基因，并表征了它们的基本理化性质。系统发育分析表明，mapk基因分为三个主要亚家族，包括ERK、JNK和p38 MAPK。选择压力分析显示它们在进化上受到限制并经历了强烈的净化选择。基因结构和保守蛋白质基序比较表明 mapk 基因家族成员的高度保守。在每个胚胎和幼虫发育阶段和不同组织中进一步研究了表达模式。此外，细菌和温度胁迫后的 RNA-seq 分析表明 mapk 基因具有不同的表达模式。三个 mapk 基因在响应迟缓 E. tarda 时表现出显着差异，五个在温度胁迫后显着诱导，表明它们的潜在功能。该系统分析为进一步了解日本比目鱼不同胁迫下mapk基因家族的调控机制提供了有价值的信息。三个 mapk 基因在响应迟缓 E. tarda 时表现出显着差异，五个在温度胁迫后显着诱导，表明它们的潜在功能。该系统分析为进一步了解日本比目鱼不同胁迫下mapk基因家族的调控机制提供了有价值的信息。三个 mapk 基因在响应迟缓 E. tarda 时表现出显着差异，五个在温度胁迫后显着诱导，表明它们的潜在功能。该系统分析为进一步了解日本比目鱼不同胁迫下mapk基因家族的调控机制提供了有价值的信息。