Expression of immune-related genes in embryos and larvae of sea cucumber Apostichopus japonicus.

The echinoderm immunity system has been extensively investigated in adults in several classes such as echinoid and holothuroidea. However, the defense mechanism in embryos and larvae remains largely unexplored. To profile the immune-related genes expression in embryos and larvae and to monitor the stimulation of the innate immune response by lipopolysaccharides (LPS) challenge, we investigated the expression patterns of nine immune-related genes in embryos and larvae of sea cucumber (Apostichopus japonicus) at eleven developmental stages using quantitative real-time PCR (qRT-PCR). The expression of six encoding proteins including heat shock protein70 (Hsp70), Hsp90, Hsp gp96, thymosin-beta, ferritin and DD104 protein was detected at all eleven development stages according to mRNA expression data. However, the expression of mannan-binding C-type lectin (MBCL) was detected at early auricularia to juvenile stages, while lysozyme and serine proteinase inhibitor (SPI) were detected only at juvenile stage. Out of these nine genes, three (MBCL, lysozyme and SPI) were found to be up-regulated in mRNA expression upon LPS challenge, whereas the other six showed no significant change. Our study presents a first preliminary view into the expression patterns of immune-related genes at different developmental stages of sea cucumber, which increases the available information on echinoderm immunity.