Interferon regulatory factors (IRFs) are a family of transcription factors involved in regulating interferon (IFN) responses and immune cell development. A total of 11 IRFs have been identified in teleost fish. Here, a complete repertoire of 11 IRFs (LcIRFs) in the large yellow croaker (Larimichthys crocea) was characterized with the addition of five newly identified members, LcIRF2, LcIRF5, LcIRF6, LcIRF10, and LcIRF11. These five LcIRFs possess a DNA-binding domain (DBD) at the N-terminal that contains five to six conserved tryptophan residues and an IRF-association domain (IAD) or IAD2 at the C-terminal that is responsible for interaction with other IRFs or co-modulators. Phylogenetic analysis showed that the 11 LcIRFs were divided into four clades including the IRF1 subfamily, IRF3 subfamily, IRF4 subfamily, and IRF5 subfamily. These are evolutionarily related to their respective counterparts in other fish species. The 11 LcIRFs were constitutively expressed in all examined tissues, although at different expression levels. Upon polyinosinic: polycytidylic acid (poly (I:C)) stimulation, the expression of all 11 LcIRFs was significantly induced in the head kidney and reached the highest levels at 6 h post-stimulation (except LcIRF4). LcIRF1, LcIRF3, LcIRF7, LcIRF8, and LcIRF10 were more strongly induced by poly (I:C) than the other LcIRFs. Significant induction of all LcIRFs was observed in the spleen, with LcIRF2, LcIRF5, LcIRF6, LcIRF7, LcIRF9, and LcIRF11 reaching their highest levels at 48 h LcIRF3 and LcIRF11 showed a stronger response to poly (I:C) in the spleen than the other LcIRFs. In addition, LcIRF1, LcIRF3, LcIRF7, LcIRF9, LcIRF10, and LcIRF11 were significantly induced by Vibro alginolyticus in both the spleen and the head kidney, with LcIRF1 strongly induced. Thus, LcIRFs exhibited differential inducible expression patterns in response to different stimuli in different tissues, suggesting that LcIRFs have different functions in the regulation of immune responses. Furthermore, overexpression of LcIRF11 activated the promoters of LcIFNc, LcIFNd, and LcIFNh, and differentially induced the expression levels of LcIFNs and IFN-stimulated genes (ISGs). Overexpression of LcIRF11 in epithelioma papulosum cyprinid (EPC) cells inhibited the replication of viral genes after infection of spring viremia of carp virus (SVCV). These data suggested that LcIRF11 may function as a positive regulator in regulating the cellular antiviral response through induction of type I IFN expression. Taken together, the present study reported molecular characterization and expression analysis of 11 IRFs in the large yellow croaker, and investigated the role of LcIRF11 in the antiviral response, which laid a good foundation for further study on the evolution and functional characterization of fish IRFs.

干扰素调节因子（IRF）是涉及调节干扰素（IFN）反应和免疫细胞发育的转录因子家族。在硬骨鱼中共鉴定出11种IRF。在这里，通过添加五个新识别的成员Lc IRF2，Lc IRF5，Lc IRF6，Lc IRF10和Lc IRF11来表征大型黄鱼（Larimichthys crocea）中11个IRF（Lc IRF）的完整库。这五个LCIRF在N端具有一个DNA结合结构域（DBD），其中包含5至6个保守的色氨酸残基，在C端具有一个IRF关联结构域（IAD）或IAD2，负责与其他IRF或co-调制器。系统发育分析表明，将11个Lc IRFs分为IRF1亚家族，IRF3亚家族，IRF4亚家族和IRF5亚家族四个分支。这些在进化上与其他鱼类中的对应物种有关。11 Lc IRF在所有检查的组织中组成性表达，尽管表达水平不同。在聚肌苷酸：聚胞苷酸（poly（I：C））刺激下，所有11 Lc的表达IRF在头肾中被明显诱导，并在刺激后6小时达到最高水平（Lc IRF4除外）。Lc IRF1 ，Lc IRF3，Lc IRF7，Lc IRF8和Lc IRF10比其他Lc IRF更受聚（I：C）诱导。所有的显著诱导LC在脾中观察到IRF，这与LC IRF2，LC IRF5，LC IRF6，LC IRF7，LC IRF9，和LC IRF11达到在48小时的最高水平LC IRF3和LC与其他Lc IRF相比，IRF11对脾脏中的poly（I：C）的反应更强。此外，LC IRF1，LC IRF3，LC IRF7，LC IRF9，LC IRF10，和LC IRF11均显著致振冲溶藻弧菌在脾脏和头肾都与LC IRF1强烈诱导。因此，Lc IRF对不同组织中的不同刺激表现出不同的诱导型表达模式，表明Lc IRF在调节免疫应答中具有不同的功能。此外，Lc的过表达IRF11激活Lc IFNc，Lc IFNd和Lc IFNh的启动子，并差异性诱导Lc IFN和IFN刺激基因（ISG）的表达水平。鲤鱼上皮细胞瘤（EPC）细胞中Lc IRF11的过表达抑制了鲤鱼春季病毒血症（SVCV）感染后病毒基因的复制。这些数据表明，Lc IRF11可能通过诱导I型IFN表达而在调节细胞抗病毒应答中起积极的调节作用。综上所述，本研究报道了大黄鱼中11种IRF的分子表征和表达分析，并研究了Lc的作用IRF11的抗病毒反应，为进一步研究鱼类IRF的进化和功能特性奠定了良好的基础。