Complete Genome Sequence of the Shrimp White Spot Bacilliform Virus

Abstract

We report the first complete genome sequence of a marine invertebrate virus. White spot bacilliform virus (WSBV; or white spot syndrome virus) is a major shrimp pathogen with a high mortality rate and a wide host range. Its double-stranded circular DNA genome of 305,107 bp contains 181 open reading frames (ORFs). Nine homologous regions containing 47 repeated minifragments that include direct repeats, atypical inverted repeat sequences, and imperfect palindromes were identified. This is the largest animal virus that has been completely sequenced. Although WSBV is morphologically similar to insect baculovirus, the two viruses are not detectably related at the amino acid level. Rather, some WSBV genes are more homologous to eukaryotic genes than viral genes. In fact, sequence analysis indicates that WSBV differs from all known viruses, although a few genes display a weak homology to herpesvirus genes. Most of the ORFs encode proteins that bear no homology to any known proteins, either suggesting that WSBV represents a novel class of viruses or perhaps implying a significant evolutionary distance between marine and terrestrial viruses. The most unique feature of WSBV is the presence of an intact collagen gene, a gene encoding an extracellular matrix protein of animal cells that has never been found in any viruses. Determination of the genome of WSBV will facilitate a better understanding of the molecular mechanism underlying the pathogenesis of the WSBV virus and will also provide useful information concerning the evolution and divergence of marine and terrestrial animal viruses at the molecular level.White spot bacilliform virus (WSBV) or white spot syndrome virus (WSSV) is a major shrimp pathogen that is highly virulent in penaeid shrimp, the most important species used in aquaculture, and can also infect most species of crustacean (15, 32). Infection of penaeid shrimp by WSBV can result in mortality of up to 90 to 100% within 3 to 7 days (57). A major outbreak of WSBV infection in 1993 resulted in a 70% reduction in shrimp production in China (14, 57) and has raised major concerns in aquaculture around the world. Prevention and inhibition of infection by this virus can be difficult due largely to the ability of WSBV to survive for a long time in the environment (2 years in a shrimp pond) and also due to a poor understanding of this virus at the molecular level.WSBV was originally classified as an unassigned member of the Baculoviridae because of its rod-shaped, enveloped morphology (20). However, it was recently excluded from the baculovirus family and is temporarily unclassified due to the lack of molecular information (53). The virus is known generally as white spot syndrome virus (WSSV) (31), and a new genus name, Whispovirus, was proposed by Vlak et al. (48). Sequence analysis of individual genes and proteins later showed that most WSBV proteins bear poor sequence homology to baculovirus proteins but have repeated regions similar to those of some baculoviruses. To understand the molecular basis of viral repl...

Molecular basis and genetic improvement of economically important traits in aquaculture animals

“…Especially in infectious virus diseases, a lot of pathogenic viruses were identified from freshwater and marine culture animals [103], and the complete genomes of several viruses, such as grass carp hemorrhage virus (GCHV) [104], shrimp white spot syndrome virus (WSSV) [105], mandarin fish infectious spleen and kidney necrosis iridovirus (ISKNV) [106], and flounder lymphocystis disease virus isolated in China (LCDV-C) [107], were sequenced in China. Moreover, their structure proteins were characterized [108][109][110][111], and some of them were functionally analyzed [112,113].…”

Molecular characterization of a crustin-like antimicrobial peptide in the giant tiger shrimp, Penaeus monodon, and its expression profile in response to various immunostimulants and challenge with WSSV

“…1995). WSSV is an enveloped virus with a large, double-stranded, circular DNA genome (∼300 kb) containing approximately 180 putative open reading frames (ORFs), most of which have no homology with any known genes or proteins in public databases Wongteerasupaya et al 1995;Wang et al 1995;Chang et al 1996;Chen et al 1997;Yang et al 2001). Proper husbandry and management of farms with the application of immunostimulants, probiotics and bioremediators can save the industry from the onslaught of diseases to a certain extent.…”

Molecular epidemiology of white spot syndrome virus within Vietnam

“…Preliminary studies indicated that there is also little difference in virulence between various WSSV isolates, although direct comparisons were not made (Wang et al, 1999;Lan et al, 2002). After the complete sequencing of three different WSSV isolates originating from Taiwan (WSSV-TW; Wang et al, 1995), China (WSSV-CN; Yang et al, 2001) and Thailand (WSSV-TH;van Hulten et al, 2001), the major variable loci in the WSSV genome were mapped by alignment of these sequences (Marks et al, 2004). Roughly, the variable loci can be divided into deletions, variable numbers of tandem repeats (VNTRs), single nucleotide indels and single nucleotide polymorphisms (SNPs).…”

“…The circular dsDNA genome of WSSV has a size of around 300 kb and is one of the largest animal virus genomes that has been entirely sequenced (van Hulten et al, 2001;Yang et al, 2001). Only 6 % of the putative 184 ORFs encoded by the viral genome have homologues in public databases, mainly representing genes encoding enzymes for nucleotide metabolism, DNA replication and protein modification (van Hulten et al, 2001).…”