Muscovy duck reovirus sigmaC protein is atypically encoded by the smallest genome segment.
Although muscovy duck reovirus (DRV) shares properties with the reovirus isolated from chicken, commonly named avian reovirus (ARV), the two virus species are antigenically different. Similar to the DRV sigmaB-encoded gene (1201 bp long) previously identified, the three other double-stranded RNA small genome segments of DRV have been cloned and sequenced. They were 1325, 1191 and 1124 bp long, respectively, and contained conserved terminal sequences common to ARVs. They coded for single expression products, except the smallest (S4), which contained two overlapping open reading frames (ORF1 and ORF2). BLAST analyses revealed that the proteins encoded by the 1325 and 1191 bp genes shared high identity levels with ARV sigmaA and sigmaNS, respectively, and to a lesser extent with other orthoreovirus counterparts. No homology was found for the S4 ORF1-encoded p10 protein. The 29.4 kDa product encoded by S4 ORF2 appeared to be 25% identical to ARV S1 ORF3-encoded sigmaC, a cell-attachment oligomer inducing type-specific neutralizing antibodies. Introduction of large gaps in the N-terminal part of the DRV protein was necessary to improve DRV and ARV sigmaC amino acid sequence alignments. However, a leucine zipper motif was conserved and secondary structure analyses predicted a three-stranded alpha-helical coiled-coil feature at this amino portion. Thus, despite extensive sequence divergence, DRV sigmaC was suggested to be structurally and probably functionally related to ARV sigmaC. This work provides evidence for the diversity of the polycistronic S class genes of reoviruses isolated from birds and raises the question of the relative classification of DRV in the Orthoreovirus genus.
Kuntz-Simon
Gaëlle
G
French Agency for Food Safety (AFSSA), Poultry and Swine Research Laboratory, Avian and Rabbit Virology, Immunology and Parasitology Unit1 and Viral Genetics and Biosafety Unit2, Zoopôle Les Croix, BP 53, 22440 Ploufragan, France.
Le Gall-Reculé
Ghislaine
G
French Agency for Food Safety (AFSSA), Poultry and Swine Research Laboratory, Avian and Rabbit Virology, Immunology and Parasitology Unit1 and Viral Genetics and Biosafety Unit2, Zoopôle Les Croix, BP 53, 22440 Ploufragan, France.
de Boisséson
Claire
C
French Agency for Food Safety (AFSSA), Poultry and Swine Research Laboratory, Avian and Rabbit Virology, Immunology and Parasitology Unit1 and Viral Genetics and Biosafety Unit2, Zoopôle Les Croix, BP 53, 22440 Ploufragan, France.
Jestin
Véronique
V
French Agency for Food Safety (AFSSA), Poultry and Swine Research Laboratory, Avian and Rabbit Virology, Immunology and Parasitology Unit1 and Viral Genetics and Biosafety Unit2, Zoopôle Les Croix, BP 53, 22440 Ploufragan, France.
D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins; D004372:Ducks / Q000821:virology*; D004586:Electrophoresis; D016679:Genome, Viral; D008969:Molecular Sequence Data; D030101:Orthoreovirus, Avian / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D012367:RNA, Viral / Q000032:analysis; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics*
D036022:Capsid Proteins; D012367:RNA, Viral; D014764:Viral Proteins; C031728:sigma 1 protein, reovirus