The full length cDNA cloning and expression profile of prophenoloxidase of Fenneropenaeus chinensis

Chinese shrimp (Fenneropenaeus chinensis) is one of the most economically valuable and widely cultured species in China. During the last decade its development has been seriously affected on a regular basis by the outbreak of viral and bacterial diseases. To analyze the immune defense mechanisms of shrimp F. chinensis, a prophenoloxidase gene (FCproPO) was cloned from haemocytes of Chinese shrimp by Rapid Amplification Complementary DNA Ends (RACE) method. The full length cDNA of FCproPO consisted of 2 311 bp with a 2 061 bp Open Reading Frame(ORF)，which encoded 687 amino acids，and the predicted molecular mass was 78.71 ku. It showed 84% and 71% homology with those of Litopenaeus vannamei and Marsupenaeus japonicas. The Realtime-PCR results showed that the expression level of FCproPO in haemoeytes was highest among seven studied tissues．Sequence analysis showed FCproPO contained two conserved copper-binding sites. Phylogenetic analysis revealed that FCproPO and prophenoloxidase from L. vannamei, M. japonicus and P. monodon were in the same phylogenetic branches. Realtime-PCR analysis showed that the expression of FCproPO was up-regulated distinctly in the hepatopanereas of shrimp when they were challenged by Vibrio anguillarum and white spot syndrome virus (WSSV). FCproPO showed different expression profiles in the hepatopancreas during V. anguillarum or WSSV virus infection．The result implied that FCproPO might play an important role in the shrimp immune system．