Location: Floral and Nursery Plants ResearchTitle: Characterization of the Taura syndrome virus isolate originating from the 2004 Texas Epizootic in cultured shrimp Author
Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2010
Publication Date: 4/8/2010
Publication URL: http://hdl.handle.net/10113/42489
Citation: Dhar, A.K., Lakshman, D.K., Amundsen, K., Robles-Sikisaka, R., Kaiser, K., Roy, S., Hasson, K.W., Allnutt, F.C.T. 2010. Characterization of the Taura Syndrome virus isolate originating from the 2004 Texas epizoonatic in cultured shrimps. Archives of Virology. 155:315-327. Interpretive Summary: Eukaryotic viruses are generally explored as sources of stronger, constitutive, organ or tissue non-specific transcription promoters, enhancer elements, and translational regulators. Earlier, we reported the isolation and characterization of two pantropic promoters from a shrimp virus, infectious hypodermal and hematopoietic necrosis virus (IHHNV) that are functional in vertebrates and invertebrates. In this communication, we have cloned and characterized an RNA virus of shrimp, Taura syndrome virus (TSV) isolate that caused epizootics in Texas in 2004. Analysis of the viral genome revealed that it contains two open reading frames (ORF) that are separated by an intergenic region (IGR) with putative internal ribosomal entry site (IRES) properties. The IHHNV promoters have been used to construct IRES-based vector for the expression of reporter genes in fungi, plants, invertebrates and vertebrates. In future, the feasibility of the above IHHNV-promoters and TSV-IRES elements will be tested in the gene expression experiments on plants and fungi to elucidate roles of specific genes in plant disease development.
Technical Abstract: Taura syndrome virus (TSV) is a major viral pathogen of penaeid shrimp worldwide. A comprehensive investigation of the Texas isolate of TSV that caused epizootics in shrimp farms in Texas in 2004 (Us04Pv1) revealed that the virus was highly virulent in laboratory bioassays causing severe symptom development and rapid mortality. Histopathology of moribund animals demonstrated epithelial necrosis within the stomach, appendages, general body cuticle and gills. Animals that survived lethal infection demonstrated moderate to numerous lymphoid organ spheroids (LOS), suggestive of chronic phase TSV infection. In situ hybridization with a TSV-specific probe detected the virus in the LOS. Transmission electron microscopy of the virus purified from infected shrimp showed that the virions are 31 nm in diameter with icosahedral symmetry. The genome of the Us04Pv1 isolate was cloned, sequenced in its entirety and compared to five other geographically distinct TSV isolates for which complete genome sequences are available in the GenBank database. Comparative genome analysis at the nucleotide and amino acid levels showed that the Us04Pv1 isolate is more closely related to TSV isolates from Thailand and China and only distantly related to the Venezuelan TSV isolate. Computational prediction indicated that the tertiary structures of the inhibitor of apoptosis (IAP) and protease domains of all six TSV isolates were very similar. However, the data from our 3-D modeling showed that the RNA-dependent RNA polymerase (RdRp) of Us94Pv1 has significant structural differences from the respective domains of five other TSV isolates. It remains to be determined if the structural differences of TSV RdRps play a significant role in virulence or ecological adaptability of this isolate.