The Study Of A C-type Lectin (EsLecB) With Antibacterial Activity In Eriocheir Sinensis

Chinese mitten crab, Eriocheir sinensis, is widely distributed in the north and south along the coast around the lake, and an important economic species of crabs in China, also as a traditional savory food in China. With economic development, the demand for E. sinensis is gradually increasing, leading to its large-scale aquaculture development, and often suffer pathogenic bacteria or viruses large-scale outbreak of disease, and have result in direct economic loss. Therefore, the study on E. sinensis immune defense mechanisms, especially study the complex identification mechanism of the breeding environment of bacteria and other pathogens is particularly important.The immune system is usually divided into two branches:innate or natural immunity, and adaptive or acquired immunity. Invertebrates do not have a typical adaptive immunity, which comprises various immunocytes and induced immunelogical memory, but have inate immunity. Invertebrates rely solely on a series of germ-line encoded pattern recognition receptors (PRRs) that mediate immune recognition and binding pathogen-associated molecular patterns (PAMPs) activating signaling pathway and defense against various pathogens. As a pattern recognition receptor (PRR), C-type lectins (CTLs) as an important gene involved innate immunity.Based on the initial expressed sequence tags (EST) of a hepatopancreatic cDNA library, a novel CTL, designated as EsLecB, including a signal peptide of 19 amino acid residues, with a 470 bp open reading frame (ORF) encodes a polypeptide of 156 amino acids, and one carbohydrate-recognition domain of 131 aa residues, was cloned from E. sinensis. By qRT-PCR analysis, EsLecB was detected in all tested tissues, and showed highest expression in hemocytes, hepatopancreas and heart. The expression of EsLecB up-regulated following injections of PAMPs or bacteria. Moreover, the recombinant EsLecB protein (rEsLecB) had microbial-binding and microbial-agglutinating activities which calcium-independent but carbohydrate-depen -dent, microorganism growth inhibitory, hem-encapsulation and could stimulate the activation of prophenoloxidase activities.Our study not only enrich the C-type lectin (CTLs) immune function studies, also provides a reference for other studies of pattern recognition receptors (PRRs) immune regulation mechanism, but will also contribute to a better understanding of the E. sinensis as well as other innate immune response mechanism of crustaceans.