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The pl0 gene of Spodoptera exigua multiple nuclear polyhedrosis virus (SeMNPV) was localized on the XbaI fragment H (5.1 kb) of the physical map of the viral genome. The coding sequence of the SeMNPV pl0 gene is 264 nucleotides (nt) long corresponding to a predicted protein of 88 amino acids with an MuF of 9607. The SeMNPV pl0 protein showed only limited amino acid identity (39 % and 26 %, respectively) to those of Orgyia pseudotsugata MNPV (OpMNPV) and Autographa californica MNPV (AcMNPV) and thus appears less conserved than other viral proteins. The SeMNPV pl0 gene was expressed by a transcript of approximately 450 nt, which started in the conserved baculovirus late gene promoter motifTAAG. The leader of the SeMNPV pl0 transcript was AT-rich (92 %) and at 36 nt was the shortest leader of all baculovirus major late genes reported so far. The SeMPNV pl 0 transcript terminated 6nt downstream from a putative poly(A) signal sequence (AATAAA); the latter was 61 nt downstream of the translational stop codon TAA. Upstream and downstream of the p 10 gene, partial putative ORFs were found that showed significant amino acid sequence identity to the baculovirus p26 and p74 proteins. It is concluded that the region of SeMNPV DNA containing the p 10 gene is collinear with the corresponding regions in the AcMNPV and OpMNPV genomes.

In the genomes of two baculoviruses, Spodoptera exigua and S. littoralis multicapsid nucleopolyhedroviruses (SeMNPV and SpliMNPV, respectively), an open reading frame (ORF) encoding the large subunit of ribonucleotide reductase (RR1) was identified. The predicted amino acid sequences of SeMNPV and SpliMNPV RR1 showed high homology to RR1 proteins from eukaryotes (ca. 70 % and 80 % similarity, respectively). The amino acid residues thought to be involved in catalytic function were conserved in the baculoviral RR1 ORFs. The RR1 ORFs in SeMNPV and SpliMNPV were located in different genomic positions. In SeMNPV, the RR1 ORF was located upstream of the polyhedrin gene, in an anti-genomic orientation. In SpliMNPV, the RR1 ORF preceded the p74 gene. By searching databanks, sequences homologous to the N ter-

The nucleotide sequence of a 1.1 kbp fragment of the multiple nucleocapsid nuclear polyhedrosis virus (MNPV) of Spodoptera exigua (Se) containing the polyhedrin gene was determined. An open reading frame (ORF) of 738 nucleotides (nt) was detected. This ORF encoded a protein of 246 amino acids with a predicted Mr of 29K. The nucleotide and amino acid sequences were compared with the sequences of eight other NPV polyhedrins. The SeMNPV polyhedrin protein was most closely related to S. frugiperda MNPV polyhedrin with differences in only five amino acids, and most distantly related to the Lymantria dispar MNPV polyhedrin. The size of the mRNA was approximately 1000 nt, as determined by Northern blot analysis. Using primer extension assays and S1 nuclease mapping the transcriptional start and stop sites of the polyhedrin mRNA were located. The 5' regulatory sequence appeared to be 44 nt in length with the mRNA start site predominantly at the first A of the TAAG consensus start sequence. Two degenerate poly(A) signals were found immediately downstream of the translational stop signal. The transcriptional stop was located approximately 230 nt downstream from the translational stop signal, in an AT-rich sequence that appears to be common to all baculovirus polyhedrin genes. The SeMNPV polyhedrin mRNA does not appear to be polyadenylated.

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