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Homologous genetic recombination in the yellow head complex of nidoviruses infecting Penaeus monodon shrimp.

ABSTRACT: Yellow head virus (YHV) is a highly virulent pathogen of Penaeus monodon shrimp. It is one of six known genotypes in the yellow head complex of nidoviruses which also includes mildly pathogenic gill-associated virus (GAV, genotype 2) and four other genotypes (genotypes 3-6) that have been detected only in healthy shrimp. In this study, comparative phylogenetic analyses conducted on replicase- (ORF1b) and glycoprotein- (ORF3) gene amplicons identified 10 putative natural recombinants amongst 28 viruses representing all six genotypes from across the Indo-Pacific region. The approximately 4.6 kb genomic region spanning the two amplicons was sequenced for three putative recombinant viruses from Vietnam (genotype 3/5), the Philippines (genotype 5/2) and Indonesia (genotype 3/2). SimPlot analysis using these and representative parental virus sequences confirmed that each was a recombinant genotype and identified a recombination hotspot in a region just upstream of the ORF1b C-terminus. Maximum-likelihood breakpoint analysis predicted identical crossover positions in the Vietnamese and Indonesian recombinants, and a crossover position 12 nt upstream in the Philippine recombinant. Homologous genetic recombination in the same genome region was also demonstrated in recombinants generated experimentally in shrimp co-infected with YHV and GAV. The high frequency with which natural recombinants were identified indicates that genetic exchange amongst genotypes is occurring commonly in Asia and playing a significant role in expanding the genetic diversity in the yellow head complex. This is the first evidence of genetic recombination in viruses infecting crustaceans and has significant implications for the pathogenesis of infection and diagnosis of these newly emerging invertebrate pathogens.

SUBMITTER: Wijegoonawardane PK

PROVIDER: S-EPMC7127526 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Homologous genetic recombination in the yellow head complex of nidoviruses infecting Penaeus monodon shrimp.

Wijegoonawardane Priyanjalie K M PK Sittidilokratna Nusra N Petchampai Natthida N Cowley Jeff A JA Gudkovs Nicholas N Walker Peter J PJ

Virology 20090531 1

Yellow head virus (YHV) is a highly virulent pathogen of Penaeus monodon shrimp. It is one of six known genotypes in the yellow head complex of nidoviruses which also includes mildly pathogenic gill-associated virus (GAV, genotype 2) and four other genotypes (genotypes 3-6) that have been detected only in healthy shrimp. In this study, comparative phylogenetic analyses conducted on replicase- (ORF1b) and glycoprotein- (ORF3) gene amplicons identified 10 putative natural recombinants amongst 28 v ...[more]

PMID: 19487006

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Project description:Among the emerging diseases in shrimp aquaculture, monodon slow growth syndrome (MSGS) is a major concern in South and Southeast Asia. Shrimp farming in Thailand was severely affected during 2000-2002 due to MSGS, which caused an economic loss, of about US$ 300 million. MSGS is characterized by abnormally slow growth with coefficients of size variation of >35 %, that has impacted P. monodon production in Thailand. A new shrimp virus, Laem-Singh virus (LSNV) was identified to be associated in MSGS affected shrimp. LSNV a RNA virus of about 25 nm diameter is phylogenetically related to the insect-borne viruses in the families Barnaviridae, Tymoviridae and Sobemoviridae an important histopathological observation is exclusively noticed in growth-retarded shrimp. The LSNV infections have been confirmed in various organs of infected shrimp such as lymphoid organ, gills and nervous tissues by various diagnostic techniques such as reverse transcription polymerase chain reaction (RT-PCR), in situ hybridization, quantitative real-time RT-PCR and reverse transcription loop-mediated isothermal amplification combined with a lateral flow dipstick (RT-LAMP-LFD) and these tools are available for the diagnosis of LSNV. Recently, an integrase containing element has been identified in absolute association with LSNV in stunted growth shrimp. The transmission of LSNV through horizontal and vertical routes has been experimentally demonstrated. The known natural host-range of LSNV includes P. monodon and other penaeid shrimp. The putative RdRp gene involved in replication of LSNV was targeted for dsRNA-mediated gene silencing and appeared to be effective in a dose-dependent manner. Since the discovery of LSNV in 2006 in Thailand, it has been added to the list of viruses to be excluded from domesticated specific pathogen-free stocks of P. monodon and it has been recommended that shrimp farmers avoid stocking post larvae positive for LSNV to prevent MSGS in their farms.

Project description:BACKGROUND: The black tiger shrimp (Penaeus monodon) is one of the most important aquaculture species in the world, representing the crustacean lineage which possesses the greatest species diversity among marine invertebrates. Yet, we barely know anything about their genomic structure. To understand the organization and evolution of the P. monodon genome, a fosmid library consisting of 288,000 colonies and was constructed, equivalent to 5.3-fold coverage of the 2.17 Gb genome. Approximately 11.1 Mb of fosmid end sequences (FESs) from 20,926 non-redundant reads representing 0.45% of the P. monodon genome were obtained for repetitive and protein-coding sequence analyses. RESULTS: We found that microsatellite sequences were highly abundant in the P. monodon genome, comprising 8.3% of the total length. The density and the average length of microsatellites were evidently higher in comparison to those of other taxa. AT-rich microsatellite motifs, especially poly (AT) and poly (AAT), were the most abundant. High abundance of microsatellite sequences were also found in the transcribed regions. Furthermore, via self-BlastN analysis we identified 103 novel repetitive element families which were categorized into four groups, i.e., 33 WSSV-like repeats, 14 retrotransposons, 5 gene-like repeats, and 51 unannotated repeats. Overall, various types of repeats comprise 51.18% of the P. monodon genome in length. Approximately 7.4% of the FESs contained protein-coding sequences, and the Inhibitor of Apoptosis Protein (IAP) gene and the Innexin 3 gene homologues appear to be present in high abundance in the P. monodon genome. CONCLUSIONS: The redundancy of various repeat types in the P. monodon genome illustrates its highly repetitive nature. In particular, long and dense microsatellite sequences as well as abundant WSSV-like sequences highlight the uniqueness of genome organization of penaeid shrimp from those of other taxa. These results provide substantial improvement to our current knowledge not only for shrimp but also for marine crustaceans of large genome size.

Dataset Information

Homologous genetic recombination in the yellow head complex of nidoviruses infecting Penaeus monodon shrimp.

Publications

Homologous genetic recombination in the yellow head complex of nidoviruses infecting Penaeus monodon shrimp.

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