| Iridoviruses are relatively large,icosahedral,cytoplasmic deoxyriboviruses that can infect invertebrates and poikilothermic vertebrates. Iridoviruses are well-known causative agents of many serious systemic diseases occurred in economically important freshwater and marinefish worldwide. TRBIV(turbot reddish body iridovirus)was the causative agent of serious systemic diseases with high mortality in the cultured turbot, Scophthalmus maximus cultured in Korea and China.Here a few primer pairs baseing on the conserved genes of ISKNV, OSGIV, RBIV were designed to amplify TRBIV genome. The author reported the complete genome sequence of TRBIV. The genome was a linear double-stranded DNA of 110,104 basepairs in length with a base composition of 54.99% G+C. About 115 open reading frames (ORFs) were identified with coding capacities for polypeptides ranging from 40 to 1168 amino acids. The 115 predicted ORFs accounted for 92% of the genetic information in the TRBIV genome, and these ORFs were present on both strands (42% forward, 58% reverse). The analysis of the amino acid sequences deduced from the individual ORFs revealed that 39 of the 115 potential gene products of TRBIV showed significant homology to other iridovirus genes, such as ISKNV (infectious spleen and kidney necrosis virus) (76-99%), OSGIV (orange-spotted grouper iridovirus) (75-99%), RBIV (rock bream iridovirus) (87-99%). These proteins included structural proteins and enzymes involved in virus replication, transcription, protein modification, and virus–host interaction. The TRBIV genome also contained numerous short direct, inverted and palindromic repetitive sequences which was alse found in ISKNV, OSGIV, RSIV (red sea bream iridovirus). Phylogenetic analysis of a few conserved genes, such as MCP, ATPase, DdDP, DMet, RNRS indicated that TRBIV was closely related to ISKNV, RBIV and OSGIV. The results from this study indicated that TRBIV belongs to the genus Megalocystivirus of the family Iridoviridae. The determination of the genome of TRBIV may provide useful information to develop diagnosis methods and strategies to control outbreak of TRBIV.The author compared the TRBIV genome with ISKNV, RBIV, OSGIV to find the differences with ISKNV, RBIV, OSGIV and supposed these differences as potential variable regions. four TRBIV geographical isolates are used in this study. Five pair of special primers for five variable regions were set for PCR amplification. The conclusion showed that there was no sequence variability among these isolates.A nested-polymerase chain reaction was optimized to simultaneously detect TRBIV in this study. The author evaluated the effect of the nested-PCR with detecting TRBIV using pMD18-TRBIV ATPase with different dilutions, the results showed that the sensitivity of nested-PCR was 104 times higher than that of PCR test. Nested-PCR analysis was performed on six marine fishes for the purpose of the molecular epidemic investigation of TRBIV. Broad tonguefish (Cynoglossus robustus), half-smooth tongue-sole (Cynoglossus semilaevis), red nigger hamlet (Alphestes afer), black rockfish (Sebastodes fuscescerns) which showed negative by PCR, but specific fragment with the length of 471 bp was amplified with nested-PCR assay from the extraction of spleen. The amplified product was sequenced. The sequence was compared with NCBI-Blast in GenBank and found to have the homogenicity of 100% with the fragment of TRBIV (coded as AY608684.1). The result showed that these four marine culture fish can also be asymptomatic infected naturally by TRBIV.
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