Identification of the VP92R gene from infectious spleen and kidney necrosis virus

Megalocytiviruses, which belong to the family Iridoviridae, are among the most harmful viruses to cultured fishes. Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the Megalocytivirus genus. The genome of ISKNV was sequenced and annotated by He et al. (Virology 291:126–139, 2001) in 2001 and re-annotated by Eaton et al. (Virol. J. 4:11, 2007) in 2007. The ORF092R of ISKNV was identified in the annotations of He et al. but was not reported by Eaton et al. In this study, by using Northern-blot and RACE assays, we identified the ORF092R transcript, indicating that ORF092R was indeed transcribed in the ISKNV-infected cells. Immunofluorescence and Western-blot showed that VP92R protein was expressed in the ISKNV-infected cells, and the molecular mass of VP92R is consistent with the theoretical one. Sequence comparison demonstrated that the VP92R orthologous protein is present in large yellow croaker iridovirus (LYCIV), but not in rock bream iridovirus (RBIV) or orange-spotted grouper iridovirus (OSGIV). Therefore, VP92R may have specific functions during ISKNV pathogenesis and could be a subject for studying the differences between megalocytiviruses.