Molecular characterization of the herpes simplex virus 1 (HSV-1) homologues, UL25 to UL30, in duck enteritis virus (DEV) Shengwang Liu 1 , Shuhong Chen 1 , Huixin Li, Xiangang Kong ⁎ Division of Avian Infectious Diseases, National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China Received 28 March 2007; received in revised form 27 June 2007; accepted 27 June 2007 Received by M. Di Giulio Available online 17 July 2007 Abstract A 16.6-kilo-base pair (kb) sequence was amplified from the duck enteritis virus (DEV) clone-03 strain genome using ‘targeted gene walking polymerase chain reaction (PCR)’. Seven complete open reading frames (ORFs) were predicted, and designated herpes simplex virus 1 (HSV-1) homologues, unique long (UL) 25, UL26, UL26.5, UL27, UL28, UL29, and UL30. Sequence analysis revealed that the arrangement of seven genes in DEV clone-03 strain was collinear to that from HSV-1. In addition, mRNA transcription orientation was identical to the HSV-1 genes. While UL25, UL26, and UL26.5 shared the same poly A signal, the UL27 and UL28 genes overlapped by 211bp nucleotides and shared the same 3′ transcription terminus. UL26.5, an in-frame ORF of UL26, was co-terminal with UL26 at its 3′-end. We predicted that the gene arrangement in the unique long segment of the DEV clone-03 was identical to that in HSV-1, particularly in the region from UL25 to UL30 gene. Phylogenetic trees of the putative proteins encoded by these seven genes showed that UL27, UL28, and UL30 had a close evolutionary relationship with the Mardivirus, however, the other four proteins exhibited close relationships with the Simplexvirus or Varicellovirus, indicating that the DEV clone- 03 should be placed into a single cluster within the subfamily Alphaherpesvirinae. © 2007 Elsevier B.V. All rights reserved. Keywords: Duck enteritis virus (DEV); Gene arrangement; UL25, UL26, UL26.5, UL27, UL28, UL29 and UL30 gene; Molecular characteristics 1. Introduction Duck viral enteritis (DVE), or duck plague, is an acute and contagious disease that is highly lethal in all ages of birds from the order Anseriformes (ducks, geese, and swans) (Davison et al., 1993). Duck enteritis virus (DEV) or anatid herpesvirus 1 (AnHV-1), a member of the family Herpesviridae, is the causative agent for DVE. DVE was first recorded in domestic ducks in Holland as early as 1923 (Baudet, 1923). In 1957, China had its first outbreak of DVE (Huang, 1959). Several studies indicate that DVE survivors may carry the virus for up to 4 years. This makes the disease difficult to monitor and control since DEV establishes an asymptomatic carrier state in water- fowl that is only detectable during the intermittent shedding period of the virus (Burgess et al., 1979). DEV is composed of a linear, double stranded DNA genome with 64.3% G + C content, higher than any other reported avian herpesvirus in the subfamily Alphaherpesvirinae (Gardner et al., 1993). DEV was classified as unassigned virus in the family Herpesviridae according to the Eighth International Committee on Taxonomy of Viruses (ICTV) (Fauquet et al., 2005) although it was previously grouped in the subfamily Al- phaherpesvirinae (Kaleta, 1990; Shawky and Schat, 2002). While some DEV gene fragments have been published, the genomic organization of this virus remains unknown. The Gene 401 (2007) 88 – 96 www.elsevier.com/locate/gene Abbreviations: HSV-1, herpes simplex virus 1; HSV-2, herpes simplex virus 2; VZV, varicella-zoster virus; BHV-1, bovine herpesvirus 1; BHV-2, bovine herpesvirus 2; EHV-1, equine herpesvirus 1; EHV-4, equine herpesvirus 4; PRV, pseudorabies virus; MDV-1, Marek's disease virus 1; MDV-2, Marek's disease virus 2; HVT, turkey herpesvirus; ILTV, infectious laryngotracheitis virus; DEV, duck enteritis virus; DVE, Duck viral enteritis; PCR, polymerase chain reaction; ORF, open reading frame; CEF, chicken embryo fibroblasts; NLS, nuclear localization signal. ⁎ Corresponding author. Tel.: +86 451 85935000; fax: +86 451 82733132. E-mail address: xgkong@hvri.ac.cn (X. Kong). 1 These two authors contributed equally to the work. 0378-1119/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gene.2007.06.022