Tissue distribution of prophenoloxidase transcript in the Pacific white shrimp Litopenaeus vannamei

The expression of prophenoloxidase (proPO) transcript in the tissues of the Pacific white shrimp Litopenaeus vannamei was studied by Northern blot, RT-PCR and in situ hybridisation. Northern blot analysis reveals that proPO was constitutive mainly in shrimp haemocytes. Its transcripts, when detected with RT-PCR, were widely distributed in haemocytes, gill, heart, lymphoid organ, stomach, midgut, anterior midgut caecum and ganglion. A lower expression was found in hepatopancreas, muscle and cuticular epidermis. The results of in situ hybridisations showed that gill, heart, muscle, haematopoitic tissue and hepatopancreas that were infiltrated by haemocytes also presented positive signals. ProPO transcripts, however, were detected in non-haemocyte cells, including F and E cells of the hepatopancreas, epithelium in stomach, anterior midgut caecum, glia cell in nervous cord and neurosecretory cells in ganglions.