斑点叉尾TICAM在细菌和病毒感染后的基因表达特征

Gene expression profiling of TIR-domain-containing adaptor molecule (TICAM) in channel catfish Ictalurus punctatus challenged with different pathogens including bacteria and virus

采用实时定量RT-PCR方法研究斑点叉尾在不同病原(链球菌、嗜水气单胞菌、迟钝爱德华菌、斑点叉尾病毒)感染后TICAM基因在mRNA水平的组织和时空表达特征。感染嗜水气单胞菌可引起TICAM基因在肝脏和脾脏中的上调表达,在注射后24h和12h后上调最大分别为2.3倍和1.9倍;而在头肾和后肠中的表达则下调到感染后48h的0.15倍和24h的0.53倍;感染链球菌后则导致在肝脏、脾脏、后肠和头肾中TICAM基因表达的强烈上调,最大上调幅度为感染后7d肝脏中表达提高了23倍,其次,在脾脏和头肾中基因表达最大可上调到感染前的10倍左右;在感染迟钝爱德华菌后,TICAM基因在肝脏、脾脏、后肠和头肾中表达上调。其中,感染后7d脾脏中的表达提高到感染前的23.1倍。而感染叉尾病毒后,TICAM基因在肝脏、头肾和后肠的表达上调但幅度不大,基因表达在4种组织内表达变化量在1.5～3.7倍范围内波动,而在脾脏中TICAM表达下调,在感染24h后达到最低为感染前的0.13倍。以上实验结果显示,斑点叉尾TICAM基因表达变化与病原感染密切相关,暗示TICAM基因在斑点叉尾天然免疫中起重要作用。

In mammals, Toll-IL-1 receptor （TIR） domain-containing adaptor molecule 1（TICAM-1） is a signaling adaptor for TLR3 and TLR4 that activates the transcription factors IRF-3, NF-КB, and AP-1, leading to the induction of type I interferon and cytokines. TICAM is also identified in some fish species, however, the gene expression profiling of TICAM is largely unknown in teleosts. Because bacteria such as Aeromonas hydrophila, Streptococcus spp. and Edwardsiella tarda and viruses such as channel catfish virus cause a multisystemic disease responsible for severe losses in channel catfish aquaculture in China. In this study, gene expression profiling of TICAM in different immune tissues（liver, headkidney, spleen, and intestine） after infection with these pathogens assayed by quantitative RT-PCR was described. After infection with A. hydrophila, TICAM was up-regulated approximately 2.3-fold at 24 h in liver and 1.9-fold at 12 h in spleen, while expression of this gene was down-regulated in headkidney and intestine, with the lowest expression as 0.15-fold at 48 h in headkidney, 0.53-fold at 24 h in intestine, respectively. TICAM was up-regulated drastically in liver, spleen, headkidney and intestine after infection with Streptococcus spp. It reached the highest level with 23-fold in liver at 7 d post infection, and it increased about 10 times in headkidney and spleen after infection. The expression of TICAM increased in all tested tissues after infection with E. tarda, especially it was up-regulated to the highest （23.1-fold） at 7d in spleen. After infection with channel cat- fish virus, the gene TICAM expression was up-regulated in liver, headkidney and intestine moderately, with the highest expression of 3.7-fold in liver at 72 h, 2.8-fold in headkidney at 7 d, 1.5-fold at 24 h in intestine. However, it was down-regulated in spleen,and its lowest expression was 0. 13-fold at 24 h. In conclusion, the results of this study suggest that the TICAM gene may play crucial roles in innate immunity in channel catfish.