Functional analysis on immune deficiency (IMD) homolog gene in Chinese shrimp Fenneropenaeus chinensis

IMD pathway is an important signaling pathway in regulating the innate immunity of invertebrate. IMD is regarded as a key adaptor to link the extracellular signals and intracellular signals. In the present study, a full-length cDNA encoding an IMD homolog (FcIMD) was isolated from Chinese shrimp Fenneropenaeus chinensis. It consists of 767 bp with a 483 bp open reading frame encoding 160 amino acids. A death domain was predicted which is crucial to the immune function of IMD. Tissue expression analysis showed that FcIMD mRNA had different expression level in different tissues. The transcriptional expression of FcIMD in shrimp was significantly induced at early stage (1 h) after stimulation by Vibrio or Micrococcus which suggested its important role in the immunity of shrimp to bacterium infection. The expressions of shrimp antimicrobial peptides (AMPs) were affected when FcIMD was silenced by dsRNA interference. Through analyzing the expression of FcRelish, FcDorsal and FcJNK in FcIMD silenced shrimp at 1 h post Vibrio injection, we deduced that IMD was involved in Relish regulated signaling pathway, not in Dorsal or JNK regulated signaling pathway.