Caspases are highly conserved cysteine-dependent aspartyl-specific proteases that play an important role in regulating cell death and inflammation. However, the caspase genes have not been systematically studied in rainbow trout (Oncorhynchus mykiss). Rainbow trout experienced 4 rounds (4R) of genome duplication in the evolutionary history. Thereby an increased numbers of paralogs are observed in trout, probably with more complicated gene functions. We identified 18 caspase genes in rainbow trout, including two inflammatory caspases (casp1a, casp1b), six apoptosis executioner caspases (casp3, casp3a1, casp3a2, casp3b, casp6, and casp7), nine apoptosis initiator caspases (casp2a, casp2b, casp8, casp9a, casp9b, casp10a, casp10b, casp20a, and casp20b) and one uncategorized caspase gene (casp17). To investigate the potentially physiological functions of caspase genes, we challenged the rainbow trout with Aeromonas salmonicida (A. salmonicida) and Vibrio anguillarum (V. anguillarum). Results showed that the CASP3-regulated intrinsic apoptosis was activated after A. salmonicida infection, while the CASP8 and CASP6-regulated extrinsic apoptosis exerted the greatest effect on trout challenged with V. anguillarum. In response to V. anguillarum infection, the data of RNA-Seq further showed the casp8 was tightly integrated with the significantly enriched Gene Ontology terms and functional pathways, including apoptosis regulation, pathogen detection and immunomodulation. Our study provides a foundation for the physiological functions and regulatory network of the caspase genes in teleosts.

半胱天冬酶是高度保守的半胱氨酸依赖性天冬氨酰特异性蛋白酶，在调节细胞死亡和炎症中起重要作用。然而，尚未对虹鳟鱼（Oncorhynchus mykiss）中的半胱天冬酶基因进行系统研究。虹鳟鱼在进化史上经历了 4 轮 (4R) 的基因组复制。因此，在鳟鱼中观察到的旁系同源物数量增加，可能具有更复杂的基因功能。我们在虹鳟鱼中鉴定出 18 个 caspase 基因，包括 2 个炎性 caspase（casp1a、casp1b）、6 个凋亡执行 caspase（casp3、casp3a1、casp3a2、casp3b、casp6和casp7），9 个凋亡起始 caspase（casp2a、 casp2b、 casp8、 casp9a、 casp9b、 casp10a、 casp10b、 casp20a和casp20b ) 和一个未分类的 caspase 基因 ( casp17 )。为了研究半胱天冬酶基因的潜在生理功能，我们用杀鲑气单胞菌（A.salmonicida）和鳗弧菌（V. anguillarum ）对虹鳟鱼进行了挑战。结果表明， CASP3调控的内在细胞凋亡在杀鲑鱼感染后被激活，而 CASP8 和 CASP6 调控的外在细胞凋亡对受到V. anguillarum攻击的鳟鱼发挥最大的作用。响应V. anguillarum感染后，RNA-Seq 的数据进一步显示casp8与显着丰富的 Gene Ontology 术语和功能通路紧密结合，包括细胞凋亡调节、病原体检测和免疫调节。我们的研究为硬骨鱼中 caspase 基因的生理功能和调控网络提供了基础。