Abstract
The complete genomic sequence of a new Muscovy duck-origin reovirus (N-MDRV), strain J18 from China, was determined. The virus has a tricistronic S1 genome segment that is distinct from the originally described MDRV, which possesses a bicistronic S4 genome segment. Pairwise comparisons and phylogenetic analyses suggest that N-MDRV J18 is a new isolate within the species Avian orthoreovirus.
GENOME ANNOUNCEMENT
Avian orthoreovirus (ARV) is a member of the genus Orthoreovirus in the family Reoviridae, and numerous isolates have been identified from poultry flocks, including chickens, Muscovy ducks, turkeys, and geese (1). ARV isolates from Muscovy ducks (ARV-Md), formerly known as Muscovy duck reovirus (MDRV), can cause a severe disease, with mortality ranging from 10 to 50%, and it is therefore of significant economic importance in regions with intensive Muscovy duck production (7, 8). In 2005, a new type (or pathotype) of Muscovy duck-origin MDRV (N-MDRV) emerged in Muscovy duck populations in China (4, 5). Several notable differences exist between N-MDRV and ARV-Md, including different antigenicities, laboratory host ranges, pathogenic properties, and a double-stranded electropherotype (4). To date, the complete sequence has not been reported for ARV-Md or N-MDRV.
Here we report the complete genomic sequence of N-MDRV strain J18, which was isolated from a dead Muscovy duckling that exhibited lesions of hemorrhagic-necrotic hepatitis from Fujian Province, China, in 2008. Sequences of the genome segments (except S1) were amplified by reverse transcription-PCR by using primers designed based on the available sequences of ARV and ARV-Md. The termini of the genome segments were determined by using a 5′ rapid amplification of cDNA ends protocol. The sequence of segment S1 was obtained using sequence-independent amplification strategies described previously (2).
The genome of J18 comprises 23,419 bp, and the sizes of the 10 segments are as follows: L1, 3,959 bp; L2, 3,830 bp; L3, 3,907 bp; M1, 2,284 bp; M2, 2,158 bp; M3, 1,996 bp; S1, 1,568 bp; S2, 1,324 bp; S3, 1,202 bp; S4, 1,191bp. The sizes of the deduced proteins are as follows: λA, 1,293 amino acids (aa); λB, 1,259 aa; λC, 1,285 aa; μA, 732 aa; μB, 675 aa; μNS, 635 aa; p10, 97 aa; p18, 162 aa; σC, 321 aa; σA, 416 aa; σB, 367 aa; σNS, 367aa. J18 has a tricistronic S1 genome segment that encodes p10, p18, and σC, similar to chicken-origin ARV but distinct from ARV-Md, which possesses a bicistronic S4 genome segment that encodes p10 and σC (3, 6).
Sequence diversity (48 to 74% identity in the L3, M1, M3, S1, and S3 segments, 78 to 79% identity in the λC protein, and only 26 to 30% identity in the σC protein) between J18 and chicken-origin ARVs was demonstrated by using ClustalW 1.83, which hindered our ability to achieve the classification based on the sequence identity score criteria proposed by the International Committee on Taxonomy of Viruses (1). Phylogenetic analyses using the nucleotide and amino acid sequences of the σC-encoding region indicated that J18 forms an individual cluster, clearly distinguished from chicken-origin ARV and ARV-Md clusters. In view of the similarity of the conserved terminal genome segment sequences and the organization of the polycistronic S1 genome segment between J18 and ARVs, N-MDRV J18 is considered a new isolate within the species Avian orthoreovirus.
Nucleotide sequence accession numbers.
The sequences of the 10 segments of N-MDRV strain J18 have been deposited with GenBank under accession numbers JX478260 (segment L1) to JX478269 (segment S4).
ACKNOWLEDGMENTS
This work was supported by the China Agriculture Research System (CARS-43) and the Special Fund for Agro-scientific Research in the Public Interest (201003012).
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