Heat shock proteins (hsps) are cellular chaperones that are involved in developmental stages and stress responses. Hsp40 is the major subfamily of hsps, but has not been fully characterized in Japanese flounder (Paralichthys olivaceus), especially their roles in immune response. In this study, a comprehensive identification and analysis of hsp40 in flounder is presented, including gene structures, evolutionary relationships, conserved domains, molecular evolution analysis, and expression patterns. Sequence features and phylogenetic analysis revealed that hsp40 genes could be grouped into 40 distinct subfamilies and most of them (96%) in Japanese flounder possessed no less than two introns. Molecular evolution analysis indicated that the hsp40 genes were conservative during evolution and were functional-constrained. Meanwhile, hsp40 genes were found to express in different embryonic and larval stages and might play the role of sentinel in healthy organisms. Furthermore, hsp40 genes’ expression profiles after Edwardsiella tarda injection were determined in Japanese flounder without precedent, and 88% (44/50) of hsp40 genes showed differential expression patterns after bacterial challenge. Our findings provide basic and useful resources for understanding the immune responsibilities of hsp40 genes in flatfish.

中文翻译：

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日本比目鱼中的 hsp40 基因家族：鉴定、系统发育关系、分子进化分析和表达模式

热休克蛋白 (hsps) 是参与发育阶段和应激反应的细胞伴侣。Hsp40 是 hsps 的主要亚科，但尚未在日本比目鱼 (Paralichthys olivaceus) 中得到充分表征，尤其是它们在免疫反应中的作用。本研究对比目鱼中的 hsp40 进行了全面的鉴定和分析，包括基因结构、进化关系、保守域、分子进化分析和表达模式。序列特征和系统发育分析表明，hsp40 基因可分为40 个不同的亚科，其中大多数（96%）在日本比目鱼中拥有不少于两个内含子。分子进化分析表明，hsp40 基因在进化过程中是保守的，并且是功能受限的。同时，hsp40 基因被发现在不同的胚胎和幼虫阶段表达，并可能在健康生物中发挥哨兵的作用。此外，在日本比目鱼中测定了迟发性爱德华氏菌注射后 hsp40 基因的表达谱，这是史无前例的，88% (44/50) 的 hsp40 基因在细菌攻击后表现出差异表达模式。我们的研究结果为了解比目鱼中 hsp40 基因的免疫责任提供了基本和有用的资源。