A HIGHLY CONSERVED GENOMIC REGION IN BACULOVIRUSES - SEQUENCE-ANALYSIS OF AN 11.3 KBP DNA FRAGMENT (46.5-55.1 MU) OF THE SPODOPTERA-EXIGUA MULTICAPSID NUCLEOPOLYHEDROVIRUS

A DNA fragment of 11.3 kilobase pairs (kbp) in size of the baculovirus Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV) genome (4 6.5 to 55.1 m.u.) was completely sequenced. Analysis of the sequence r evealed eleven potential open reading frames (ORF). Tell of these ORFs showed significant amino acid identity to Autographa californica MNPV (AcMNPV) and Orgyia pseudotsugata MNPV (OpMNPV) genes p6.9, lef5, 38K , p19, p143, p25, p18: vp33, lef4, and vp39. One ORF (XC12) has no hom o:og in other baculoviruses and may be unique to SeMNPV. All but three of these putative genes are preceeded by the consensus baculovirus la te promoter element (5'-ATAAG-3'). The genetic organization and the pu tative map of transcripts of this fragment suggested that this region is highly similar to a region in AcMNPV fragment EcoRI-D. Comparison o f the genetic organization of this 11.3 kbp Fragment with the genomes of AcMNPV, OpMNPV, Bombyx,mori NPV (BmNPV) and SeMNPV revealed that th is region is highly conserved among baculovirus genomes. This is in co ntrast to the genetic organization of the polyhedrin-p10 region, which is much more diverged, but has been taken as point of reference to or ient baculovirus physical maps. Through its diversity the latter legio n, however, would be an excellent candidate to determine baculovirus r elatedness and phylogeny. The presence of conserved and diverged regio ns in baculovirus genomes with respect to gene order is reminiscent to the situation in other large DNA viruses, such as herpes- and poxviru ses, where conserved central and diverged terminal parts are common ch aracteristics. The role of this feature in the genomic organization of large DNA viruses is discussed with particular emphasis on virus repl ication and evolution. (C) 1998 Published by Elsevier Science B.V. All rights reserved.