Study of late expression factors of Spodoptera frugiperda nucleopolyhedrovirus in the permissive insect cell line Sf-9

BERRETTA MF, LÓPEZ MG, SCIOCCO A, ROMANOWSKI V.

Halifax

Congreso; 2011 International Congress on Invertebrate Pathology and Microbial Control & 44th Annual Meeting of the Society for Invertebrate Pathology; 2011

SIP

Baculovirus expression of late genes depends on the activity of a group of genes, collectively known as late expression factors (lefs), that includes components of the DNA replication machinery and the viral RNA polymerase complex. Lefs have been more extensively studied in the model virus AcMNPV, a group I alphabaculovirus. Nineteen AcMNPV lefs were required to achieve optimal expression from a late promoter in a transient expression assay in Sf-21 cells, although other genes may also influence late expression in the context of the viral infection. Since homologs were not identified for all AcMNPV lefs in other baculovirus lineages it is possible that functional homologs occur in other species. We are interested in studying lefs of SfMNPV, a group II alphabaculovirus. SfMNPV infects productively Sf-21 and Sf-9 cell lines, as AcMNPV does. However, SfMNPV lacks homologs of AcMNPV lefs ie-2, lef-12 and p35. We constructed a SfMNPV lef library and tested the ability of this set of 16 genes to activate a late promoter in a reporter plasmid cotransfected in Sf-9 cells. These SfMNPV lefs were not functional in this assay; therefore, in order to identify putative genes able to complement the SfMNPV lef library, we initiated a genome-wide screening.In a preliminary survey DNA fragments that account for approximately one third of the genome and do not encompass any previously known lefs supported a significant increase of reporter activity. This result warrants further dissection of these regions to ultimately identify genes putatively involved in late expression in this virus-host system.