Identification and characterization of a major early-transcribed gene of Trichoplusia ni single nucleocapsid nucleopolyhedrovirus using the baculovirus expression system.

An early transcribed gene (me-53) of a South Africa strain of Trichoplusia ni single nucleocapsid nucleopolyhedrovirus (TnSNPV) was sequenced and identified. It has an open reading frame of 1146 nucleotides that encodes a protein of 382 amino acids with a molecular mass of 45.2 kDa. The deduced protein sequence alignment of 13 baculovirus ME-53s indicated that the TnSNPV ME-53 shares the highest homologies with NPV subgroup II-A Spodoptera exigua multiple and Mamestra configurata (Maco) nucleopolyhedrovirus ME-53s. The zinc finger-like motifs at the C-termini of ME-53s are highly conserved with similar patterns of cysteine positions. Upon introduction of the gene and a green fluorescent protein reporter gene into the baculovirus expression vector system, the transcriptional analysis of me-53 in two cell lines infected with the Autographa californica nucleopolyhedrovirus (AcMNPV) recombinant revealed that an early TnSNPV me-53 transcript can be detected by 1 h postinfection (hpi) until 12 hpi and a late one from 18 hpi up to 48 hpi, while early and late transcripts of the AcMNPV me-53 of the recombinant can be detected at 3 and 24 hpi, respectively. This suggested that the early and late promoters of both AcMNPV and TnSNPV me-53s were recognized in recombinant virus-infected cells. The regulatory elements of the TnSNPV me-53 promoter were also analyzed.