Molecular cloning and expression analysis of Relish gene from the ridgetail white prawn Exopalaemon carinicauda

Rel/NF-kappa B transcription factors play critical roles in induction and regulation of innate immune response in organisms. In this study, the full length of a Relish homolog cDNA from Exopalaemon carinicauda named EcRelish was 2141 bp encoding a 660 amino-acid polypeptide. EcRelish cDNA contained a conserved Rel homology domain and two nucleus localization signals. Sequence analysis indicated that the deduced amino acid sequence of the EcRelish showed high similarities to that of other crustaceans. Real time RT-PCR analysis showed that EcRelish mRNA expressed with different levels in tested tissues, and the highest expression was observed in the hemocytes. With longer infection time, the cumulative mortality rates increased gradually followed by the proliferation of Vibrio anguillarum and WSSV. The expression profiles of EcRelish gene were analyzed after V. a nguillarum, white spot syndrome virus (WSSV) challenge, and ammonia-N stress. The results showed that the expression levels of EcRelish mRNA in the hemocytes were up-regulated at 1-24 h after V. a nguillarum challenge. Meanwhile, the expression levels of EcRelish mRNA were up-regulated at 3 h after WSSV challenge. The expression of EcRelish in hemocytes was down-regulated significantly under ammonia-N stress during the experimental time. The results indicated that EcRelish might be involved in immune defense against pathogens and ammonia-N stress in E. c arinicauda.