Expressed Genes in the Lymphoid Organ of Broodstock Banana Prawn (Penaeus merguiensis) Using Suppression Subtractive Hybridization

Abstract

Most systemic viral infections in penaeid prawns are associated with the formation of lymphoid organ spheroid (LOS) cells in the lymphoid organ (LO). The development of spheroids is suggested to be a major defence mechanism against viral infection in penaeids. Spheroids were observed in a broodstock population of banana prawns (Penaeus merguiensis), while these changes were not identified in the wild population. This opportunity was taken to see how well suppression subtractive hybridization (SSH) would resolve a histological change with no known aetiology. A total of 316 sequenced clones were clustered into 141 contigs and 51.6% of the clones shared significant similarities to known peptide or nucleotide sequences in the NCBI GenBank database. These transcripts were assigned into 8 categories, including immune related genes (2.5%), synthesis, processing and regulation-related proteins (4.4%), ribosomal proteins (6.3%), proteases and inhibitors (7.0%), energy and metabolism factors (7.3%), structural and cytoskeletal related proteins (10.1%) and other sequences (13.9%). Many sequenced clones (48.4%) from the libraries had no significant similarity to amino acids/nucleotides in the public database revealing the ability of this method in disclosing new differentially expressed genes in the lymphoid organ of prawns. Despite the detection of differential gene expression in the SHH libraries, unfortunately there were no viral genomes identified which were associated with spheroid formation within the LO of penaeids. However, polymerase chain reaction (PCR) amplification with HPV140F and HPV140R primers suggested that the development of spheroid cells in the lymphoid organ of the broodstock population most likely due to Penaeus merguiensis hepandensovirus (PmeDV) which maybe the senior synonym of lymphoidal parvovirus (LPV).