Cloning and sequencing of Epinotia aporema Granulovirus (EpapGV) gp37-like protein gene

RICARDO SALVADOR, LETICIA FERRELLI, MARINA BIEDMA, ALEJANDRO PAROLA, VÍCTOR ROMANOWSKI AND ALICIA SCIOCCO-CAP

Wuhan, China

Congreso; IX International Colloquium on Invertebrate Pathology and Microbial Control (ICIPMC), XXXIX Annual Meeting of the SIP and VIII International Conference on Bacillus thuringiensis (ICBt); 2006

Society for Invertebrate Pathology

Epinotia aporema (Lep. Tortricidae) and Anticarsia gemmatalis (Lep. Noctuidae) are major soybean pests in Argentina. Studies conducted to evaluate the effect of the interaction between the baculoviruses EpapGV and AgMNPV, on A. gemmatalis larvae, showed that the addition of EpapGV occlusion bodies enhanced the virulence of AgMNPV preparations.  At present, certain baculovirus encoded proteins have been indentified as infectivity enhancers: e.g. VEFs (virus enhancing factor, also known as enhancin) and GP37-like proteins. Enhancin is a metalloproteinase, which digests components of the insect peritrophic membrane facilitating the initiation of infection. GP37 (spindolin) is related to the fusolins of entomopoxviruses. A gp37 gene was localized in the genome of EpapGV, whereas attempts to find vef homologous were unsuccessful.  In this work, we cloned the entire EpapGV- p37 gene. Sequence analysis indicated that the gene is 669 bp long (the smallest gp37 sequenced at present) and encodes a predicted 222 amino acid long protein. A late promoter element was found upstream the ORF. Characteristic N-glycosylation sites, five chitin-binding domains and six cystein residues were present. The pairwise comparison of EpapGV gp37 gene product with all the baculovirus sequences in GenBank yielded high similarity values, ranging from 45 to 63%, CpGV-gp37 being the most closely related gene. Interestingly, the phylogenetic analysis grouped the GVs in a cluster more closely related to entomopoxviruses than to NPVs. This result, could be interpreted a priori as indicating independent events of gene acquisition by different baculovirus lineages. The precise biological function of GP37 has not been elucidated yet. Consequently, further studies are conducted in this direction. We are also aiming to evaluate the capacity EpapGV GP37 to enhance the infection of heterologous baculoviruses, such as AgMNPV. Since no spindle-like crystals were detected in larval tissues or viral preparations, an antiserum against EpapGV gp37 will be raised to characterize its subcellular and structural localization.