Transcriptional analysis and promoter activity of the Spodoptera littoralis multicapsid nucleopolyhedrovirus ecdysteroid UDP-glucosyltransferase gene.

The ecdysteroid UDP-glucosyltransferase gene (egt) of Spodoptera littoralis multicapsid nucleopolyhedrovirus (SpliMNPV) is a homologue of the Autographa californica MNPV (AcMNPV) egt gene, which has been found to block insect moulting. Infection of larvae with an egt-deleted AcMNPV resulted in enhanced mortality as compared to infection with the wild-type virus. Consequently, deletion of an egt gene has been proposed as a tempting approach for enhancing the insecticidal properties of baculoviruses. In a previous report we described the mapping and sequencing of the SpliMNPV egt gene. Here we use time-course Northern blot and biochemical analyses to show the production of egt transcripts and protein. The SpliMNPV egt transcription start sites were mapped to 22 and 25 nucleotides downstream of the TATA box by primer extension. Transient expression assays of chimeric egt promoter-chloramphenicol acetyltransferase (cat) reporter gene constructs revealed low promoter activity that was transactivated by AcMNPV immediate-early viral protein IE-1.