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Kim K.I.,Pukyong National University | Nam J.H.,Fisheries Research and Development Institute | Jeong J.B.,Jeju National University | Jin J.W.,Pukyong National University | And 4 more authors.
Aquaculture | Year: 2011

We examined the multi-length amplicons by PCR with a single set of primers to a putative open reading frame, the ORF-2 genomic region of megalocytivirus isolates obtained from freshwater ornamental fish. From sequence analysis of the multi-amplicons, we demonstrated the presence of distinct genomic polymorphisms in the ORF-2 region with differing numbers of repetitive element (RE) of 32 aa and 17 aa. SMPV (single major amplicon-producing megalocytiviruses) and MMPV (multiple major amplicon-producing megalocytiviruses) after challenge experiments in two different host species, the pearl gourami (Trichogaster leeri), the original ornamental species, and rock bream (Oplegnathus fasciatus), a cross-infective marine species, displayed the same feature of polymorphism in the ORF-2 region as those in the original sample. No significant difference in pathogenicity was found between SMPV and MMPV. Additionally, viral DNA extracted from the infected tissue homogenates incubated even for two days can produce distinct polymorphism in ORF-2 region is implying that each RE-subtype corresponding to each different amplicon is present in the capsid of viral particles rather than in the form of a naked nucleic acid. This is the first report elucidating the presence of various RE subtypes of megalocytivirus and possible simultaneous infection with different RE subtypes of virus in freshwater ornamental fish. © 2011 Elsevier B.V.

Choi D.-L.,Fisheries Research and Development Institute | Lee N.-S.,Fisheries Research and Development Institute | Kim M.S.,Fisheries Research and Development Institute | Seo J.S.,Fisheries Research and Development Institute | And 3 more authors.
Aquaculture | Year: 2010

The mortality of the tunicate Halocynthia roretzi due to softness syndrome, which exhibits tunic thinning as well as loss of muscle elasticity, has caused serious problems for the aquaculture industry in Korea. The effects of softness syndrome can be better understood by studying the defense mechanisms of Halocynthia roretzi. This study used flow cytometry to assess hemocyte parameters in H. roretzi. Flow cytometry provided a means to rapidly quantify tunicate defense mechanisms by measuring temperature and zymosan-dependent effects on phagocytosis activity.Also, immune parameters, such as morphology of cell sub-populations (size and granularity), total hemocyte counts (THC), hemocyte viability, and phagocytosis activity using flow cytometry analysis, of normal tunicates and softness syndrome tunicates were compared. The results showed that, in normal tunicates, the phagocytic rate and hemocyte viability are higher than those of tunicates with softness syndrome. Total hemocyte numbers in softness syndrome tunicates were 4 times higher than that of normal tunicates.It is suggested that the tunicate immune system is associated with softness syndrome and that flow cytometry is a powerful tool for characterizing immune response. © 2010 Elsevier B.V.

Umasuthan N.,Jeju National University | Bathige S.D.N.K.,Jeju National University | Revathy K.S.,Jeju National University | Nam B.-H.,Fisheries Research and Development Institute | And 2 more authors.
Fish and Shellfish Immunology | Year: 2015

Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) is a crucial docking molecule for TNFR superfamily and Interleukin-1 receptor/Toll-like receptor (IL-1R/TLR) superfamily. As an adaptor protein in pathogen-induced signaling cascades, TRAF6 modulates both adaptive- and innate-immunity. In order to understand the immune responses of teleost TRAF6, Oplegnathus fasciatus TRAF6-like gene (. OfTRAF6) was identified and characterized. Genomic length of OfTRAF6 (4kb), obtained by means of a genomic BAC library, spanned seven exons which represented a putative coding sequence of 1716bp and encoded 571 amino acids (aa) with an estimated molecular weight of 64kDa. This putative protein demonstrated the classical tetra-domain architecture composed of a zinc finger RING-type profile, two zinc finger TRAF-type profiles, a coiled-coil region and a MATH domain. While the sequence similarity with human TRAF6 was 66.5%, OfTRAF6 shared a higher overall similarity with teleost homologs (~75-92%). Phylogeny of TRAF-family was examined and TRAF6-subfamily appeared to be the precursor of other subfamilies. In addition, the clustering pattern confirmed that OfTRAF6 is a novel member of TRAF6subfamily. Based on comparative genomic analysis, we found that vertebrate TRAF6 exhibits two distinct structures in teleost and tetrapod lineages. An intron-loss event has probably occurred in TRAF6 gene during the evolution of tetrapods from teleosts. Inspection of putative OfTRAF6 promoter revealed the presence of several immune responsive transcription factor binding sites. Real-time qPCR assay detected OfTRAF6 transcripts in eleven juvenile fish tissues with higher levels in peripheral blood cells followed by liver. Putative role of OfTRAF6 in response to flagellin, LPS, poly I:C, pathogenic bacteria (. Edwardsiella tarda and Streptococcus iniae) and rock bream iridovirus (RBIV) was profiled in different tissues and OfTRAF6 revealed up-regulated transcript levels. Altogether, these findings implicate that OfTRAF6 is not only involved in flagellin-induced signaling cascade, but also contributes to the antibacterial- and antiviral-responses. © 2014 Elsevier Ltd.

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