Tissue expressions of nine genes important to immune defence of the Pacific white shrimp Litopenaeus vannamei.

The tissue expressions of nine immune related genes in apparently healthy Pacific white shrimp Litopenaeus vannamei were analyzed by conventional RT-PCR, quantitative real time PCR (qPCR) and in situ hybridisation. The nine genes were beta-glucan binding protein-high density lipoprotein (BGBP-HDL), lipopolysaccharide-beta-glucan binding protein (LGBP), haemocyanin, prophenoloxidase (proPO), transglutaminase (TGase), crustins, penaeidins (PEN), cytosolic manganese superoxide dismutase (cMnSOD), and lysozyme. Transcripts of all nine genes were detected in all tissues with differential expression levels when examined by RT-PCR and qPCR. BGBP-HDL, LGBP and haemocyanin were mainly expressed in the hepatopancreas and their expressions levels were about 1/10-1/3 those of beta-actin. Their expressions in other tissues were relatively limited. ProPO, TGase, crustins, PEN-3, and lysozyme showed the highest levels of expression in haemocytes and the lowest in hepatopancreas. Their expression levels in the haemocytes were 3 (PEN-3) to 10(-2) (proPO) times those of beta-actin. In contrast to the other genes, cMnSOD showed higher expression levels in haemolymph related organ, stomach and muscle; and lower expression levels in haemocyte, migut, neural ganglion and hepatopancreas. When examined by in situ hybridisation, hepatopancreatic F cells were found to be the major cell type that produced transcripts of BGBP-HDL, LGBP and haemocyanin. On the other hand, circulatory haemocytes and haemocytes infiltrated in various tissues contributed to the expressions of proPO, TGase, crustins, PEN-3 and lysozyme. Both hepatopancreatic F cell and haemocyte generated cMnSOD transcripts. Using in situ hybridisation, the present study is the first to show the tissue distributions of BGBP-HDL, LGBP, haemocyanin, TGase, crustins and cMnSOD in healthy white shrimp. The present results provide a baseline data of physiological expressions for the genes that are important in immune activation and modulation in Pacific white shrimp and a guideline of tissue or organ sampling for effective gene expression analyses for future immunological studies.