Unique sequence characteristics of genes in the leftmost region of unique long region in duck enteritis virus.

Liu, Xiaoli; Liu, Shengwang; Li, Huixin; Han, Zongxi; Shao, Yuhao; Kong, Xiangang

OBJECTIVE Our objective was to further understand the evolutionary position of duck enteritis virus (DEV) in the family Herpesviridae and to determine the genomic structure in the leftmost region of the unique long region (UL) of DEV. METHODS 'Targeted gene walking PCR' was used to amplify the unknown gene of DEV clone-03 strain adjacent to known sequences in the UL region. Open reading frames (ORFs) were determined by Gene Runner and an online transcriptional element search engine. The phylogenetic tree was constructed by DNAStar based on the deduced amino acid sequences. RESULTS A fragment of 13,947 bp, containing 5 ORFs (designated ICP4, ORF1, ORF2, LORF2 and LORF3, respectively), was amplified from the DEV clone-03 strain genome. In addition, a tandem repeat region of alpha-type-like sequences was detected between ICP4 and LORF2. Phylogenetic analysis of ICP4 indicated that DEV ICP4 should be clustered into Varicellovirus. DEV ORF1 and ORF2 were unique among herpesviruses. Additionally, the existence and characteristics of LORF2 and LORF3 indicated a close relationship with Mardivirus members. CONCLUSION The characteristics and gene content in the leftmost end of the UL region of the DEV genome showed that the DEV genome is different from those of other herpesviruses.