Abstract
S. frugiperda (Lepidoptera) is both a major pest of cultivated plants and the source of the Sf9 cell line, widely used for the production of recombinant proteins in the baculovirus expression system. In the first part of this work, we studied the transcriptional events occuring during the early steps of the viral infection. We first show that homologous regions (hrs) of the AcMNPV baculovirus contain a large number of binding sites for AP1/CREB transcription factors, that specifically bind proteins of the Sf9 host cell. Furthermore, in the infected context these sites are required for the transactivation mediated by the immediate-early viral factor IE1, that also binds hr sequences. This study shows for the first time the involvement of cellular factors in this mechanism of viral transactivation. However, this work has been impaired by the fact that little is known about the genes expressed in the Sf9 cell line. We thus decided to construct a cDNA library, that was used for different purposes: screening of the library using a probe previously identified in the lab allowed us to obtain the complete hsp90 gene sequence and to determine its main features. Besides this work, large-scale sequencing of the library led to the construction of an EST library, from which we identified almost all the ribosomal protein genes. Sequence analysis revealed several features that seemed to be restricted to insect or lepidoptera species, an unexpected result given the large conservation of these genes througout the evolution.