Cloning And Expression Analysis Of Toll-like Receptor Homologue Gene In Chinese Shrimp Fenneropenaeus Chinensis

Chinese shrimp Fenneropenaeus chinensis, mainly distributed along inshore coastal areas of China, has rapidly developed into an integral component of the country's aquaculture industry. Nevertheless, the outbreak of diseases has significantly compromised shrimp aquaculture worldwide since 1993, and shrimp farmings in China also suffered severely from the catastrophic epidemics. With the improvement of the cultivating marine environment, enhancing the disease resistance of shrimp is commonly believed to be a powerful tool to control the disease. Better understanding of the innate immune system of shrimp will undoubtedly help us to develop strategies in disease control and sustainable shrimp-farming.Toll-like receptors(TLRs) are an evolutionarily ancient family of pattern recognition receptors(PRRs), playing a crucial role in innate immune responses that eradicate invading pathogens. Here we present a Toll homolog from Chinese shrimp Fenneropenaeus chinensis, designated FcToll. The full-length cDNA of FcToll is 4115 bp including a poly A-tail of 16 bp, encoding a putative protein of 931 amino acids. The predicted protein consists of an extracellular domain with a potential signal peptide, sixteen leucine-rich repeats(LRR), two LRR-C-termina(lLRR-CT) motifs, and two LRR-N-terminal(LRR-NT) motifs, followed by a transmembrane segment of 23 amino acids, and a cytoplasmic Toll/Interleukin-1R(TIR) domain of 139 residues. Genomic structure of FcToll gene contains five exons and four introns. Phylogenetic analysis revealed that it belongs to insect-type invertebrate Toll family. Transcripts of FcToll gene were constitutively expressed in various tissues, with predominant level in lymphoid organ. Real-time PCR assays demonstrated that expression patterns of FcToll were distinctly modulated after bacterial or viral stimulation, with significant enhancement after five hours post-Vibrio anguillarum challenge but markedly reduced level immediately after white spot syndrome virus(WSSV) exposure. These results suggest that FcToll may be involved in innate host defense, especially against pathogen Vibrio anguillarum.