Up-regulation of ribophorin I after yellow head virus (YHV) challenge in black tiger shrimp Penaeus monodon.

This work constitutes the second report from a continuing investigation of shrimp genes that may be involved in apoptosis associated death resulting from yellow head virus (YHV) infection. Here, we describe from the black tiger shrimp Penaeus monodon, a ribophorin I-like gene that is probably a subunit of the oligosaccharyltransferase complex (OST), a key enzyme in N-linked glycosylation that occurs in the endoplasmic reticulum. The OST complex also contains DAD1 (defender against apoptotic death 1) that has been reported to control apoptosis and that we have previously reported from P. monodon. The full length ribophorin I of P. monodon comprised 2157 bp with the ORF of 1806 bp corresponding to 601 deduced amino acids and three putative N-linked glycosylation sites. Analysis revealed hydrophobic properties implying that it could be a membrane protein. Tissue distribution analysis using real-time RT-PCR with SYBR Green revealed that ribophorin I was endogenously expressed in all examined tissues of normal shrimp. However, unlike DAD1 that was down-regulated after YHV challenge, ribophorin I expression was up-regulated and remained high until the moribund stage.

Down-regulation of defender against apoptotic death (DAD1) after yellow head virus (YHV) challenge in black tiger shrimp Penaeus monodon.

Here we describe the highly conserved gene, defender against apoptotic death (DAD1) identified from an EST library of the black tiger shrimp Penaeus monodon. The full-length cDNA of DAD1 of P. monodon comprised 638bp with an ORF of 345bp corresponding to 114 deduced amino acids. The deduced amino acid sequence was compared to known DAD1 sequences in the GenBank and in other databases. Phylogenetic analysis revealed that P. monodon DAD1 clustered with DAD1 from other invertebrates. Real-time RT-PCR with RNA extracts from normal P. monodon revealed DAD1 expression in several tissues including those of digestive and defense organs such as the hepatopancreas and hemocytes, respectively. If death from YHV infection was related to increased levels of apoptosis, we reasoned that the level of DAD1 should decrease as YHV infections progressed, especially in hemocytes (HC), one of its main targets. Real-time RT-PCR with RNA extracts from HC of P. monodon challenged with YHV revealed that the transcriptional level of DAD1 declined dramatically (approximately 50%) after YHV challenge. Although this suggests that DAD1 plays a role in mortality caused by YHV, control of apoptosis is complex and involves the interaction of many proteins, few of which have been characterized for shrimp. Thus, firm conclusions regarding the role of DAD1 must await the description and characterization of other proteins.

Hepatopancreatic nuclease of black tiger shrimp Penaeus monodon unlikely to be involved in viral triggered apoptosis.

Nucleases are phosphodiesterases that hydrolyze DNA and/or RNA. In a search for shrimp nucleases involved in apoptosis, we discovered a nuclease from hepatopancreatic cDNA of the black tiger shrimp Penaeus monodon. The full-length nuclease gene was amplified and revealed to contain 1668bp corresponding to 381 deduced amino acid residues in the mature enzyme. Sequence analysis indicated 83% nucleic acid identity and 89% amino acid identity to a nuclease from the Kuruma shrimp Penaeus japonicus (also called Marsupenaeus japonicus). Comparative analysis of sequences, conserved motifs and phylogenetic trees indicated that P. monodon nuclease (PMN) belonged to the family of DNA/RNA non-specific endonucleases (DRNSN). RT-PCR analysis using primers specific for PMN mRNA with seven different shrimp tissues revealed that expression in normal shrimp was restricted to the hepatopancreas. Semiquantitative RT-PCR analysis of PMN using hepatopancreatic mRNA from normal shrimp and from shrimp challenged with white spot syndrome virus (WSSV) indicated significant up-regulation of PMN in the hepatopancreas (P<0.05) at the early stage of viral infection but a return to baseline levels as gross signs of disease developed. At the same time, expression was always confined to the hepatopancreas and never seen in other tissues, including those reported to be prime targets for WSSV and subject to increased levels of apoptosis after infection. The results suggested that PMN is probably a digestive enzyme that is unlikely to be involved in hallmark DNA digestion associated with apoptosis.

Characterization and function of kuruma shrimp lysozyme possessing lytic activity against Vibrio species.

Lysozyme cDNA was isolated from a kuruma shrimp, Marsupenaeus japonicus, hemocyte cDNA library. The cDNA consists of 1055 base pairs (bp) and encodes a chicken-type (c-type) lysozyme with a deduced amino acid sequence of 156 residues. The kuruma shrimp lysozyme has a high identity (79.7%) with pacific white shrimp lysozyme, and low to moderate identities (33.3-43.0%) with lysozymes of insects and vertebrates. Comparisons with other c-type lysozymes from invertebrates and vertebrates showed that the two catalytic residues (Glu58 and Asp75) and the eight cysteine residue motif were completely conserved. Two novel insertion sequences were also observed in the kuruma and pacific white shrimp lysozyme amino acid sequences. Interestingly, phylogenetic analysis revealed that the kuruma shrimp lysozyme was more closely related to vertebrate c-type lysozymes. Expression of the cDNA in insect cells, using a baculovirus expression system, yielded a recombinant lysozyme with optimum activity at pH 7.5 and 50 degrees C, as evaluated by a lysoplate assay. The kuruma shrimp lysozyme displayed lytic activities against several Vibrio species and fish pathogens, including Vibrio penaeicida (a pathogenic bacteria to the kuruma shrimp) and suggested that shrimp lysozyme affects a greater variety of pathogens.

Gene expression in haemocytes of kuruma prawn, Penaeus japonicus, in response to infection with WSSV by EST approach.

Gene expression in haemocytes of the kuruma prawn (Penaeus japonicus) was investigated using an expressed sequence tag (EST) approach. Partial nucleotide sequences of cDNA library clones constructed from normal and white spot syndrome virus (WSSV)--infected P. japonicus haemocytes were determined. Of 635 clones obtained from the normal library, 284 (44.7%) significantly matched sequences in GenBank, and of 370 clones obtained from WSSV-infected library, 174 (47.0%) significantly matched sequences in the database. One hundred fifty-two deduced proteins were newly identified. Of these, 28 types were involved in biodefence. For the prophenoloxidase system, there are prophenoloxidase, coagulation factor G-beta chain precursor, factor D, Masquarade-like protease, transglutaminase (TGase), clottable protein and eight types of protease inhibitors (two types of antileukoproteinase, alpha-2-macroglobulin, chelonianin, elastase inhibitor, two types of Kazal inhibitor and Kunitz-type inhibitor). For antibacterial peptides, there are bactinecin 11, penaeidin-2 precursor and lysozyme c type. The others defence-related proteins are basophil leukocyte interleukin-3-regulated protein, natural killer enhancing factor (NK-EF), integral membrane protein (CD34+), ESM-1, Notch homologue and Drac homologue. For the adhesion proteins, there are beta-integrin, cell adhesion molecule (CAM) and three types of collagens. All ESTs representing protease inhibitors and tumour-related proteins were found only in the WSSV-infected library. Those encoding for apoptotic peptides were expressed at high levels in infected library. The putative defence proteins accounted for 2.7% of total ESTs in a normal shrimp library and 15.7% of the total ESTs in an infected library.