Summary auto-generated
This study identifies and characterizes the p10 gene from Buzura suppressaria single-nucleocapsid nucleopolyhedrovirus (BusuNPV), an insect pest pathogen. The researchers located the p10 gene by its conserved position downstream of the p26 gene, a strategy used successfully in multiple-nucleocapsid baculoviruses. The BusuNPV p10 gene encodes a 94-amino acid protein with characteristic P10 domains: an N-terminal coiled-coil region, a proline-rich motif, and a positively charged C-terminus. The protein showed highest sequence similarity to P10 proteins from other Spodoptera species. When expressed in insect cells using an Autographa californica MNPV vector, BusuNPV P10 formed fibrillar structures in the cytoplasm and unusual amorphous structures in the nucleus. However, unlike native AcMNPV P10, the BusuNPV protein failed to efficiently release polyhedra from infected cell nuclei. The findings suggest that while P10 sequence conservation is low across baculoviruses, the protein's structural domains are evolutionarily preserved, indicating this gene exists in all nucleopolyhedroviruses, including single-nucleocapsid types.
Key findings
- BusuNPV encodes a 94-amino acid P10 protein with conserved structural domains characteristic of baculovirus P10 proteins, despite low sequence homology to other NPVs
- BusuNPV P10 successfully forms fibrillar cytoplasmic and nuclear structures when expressed in insect cells, confirming its identity as a functional P10 homologue
- BusuNPV P10 cannot fully replace AcMNPV P10 in nuclear disintegration function, as polyhedra were not efficiently released from infected cell nuclei
- The p10 gene is located downstream of p26 in BusuNPV, consistent with other baculoviruses, suggesting this gene arrangement is conserved across all nucleopolyhedroviruses including SNPVs
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Abstract
The p10 gene of Buzura suppressaria single-nucleocapsid nucleopolyhedrovirus (BusuNPV) was identified by virtue of its localization downstream from the Autographa californica (Ac) MNPV p26 homologue. The BusuNPV p10 gene encodes a protein of 94 amino acids. The amino acid sequence contains domains characteristic of baculovirus P10 proteins, e.g. a coiled-coil domain, a proline-rich motif and a positively charged C terminus. The highest amino acid homologies were found with the Spodoptera littoralis (Spli) NPV and Spodoptera exigua (Se) MNPV P10 proteins. An AcMNPV recombinant expressing the BusuNPV P10 formed fibrillar structures in the cytoplasm of Spodoptera frugiperda cells. BusuNPV P10 could not fully replace AcMNPV P10 in its nuclear disintegration function, since polyhedra were not efficiently liberated from infected cells late in infection. The BusuNPV p26 gene encodes a protein of 263 amino acid residues with 70% amino acid similarity with SeMNPV P26. Downstream of the BusuNPV p10 gene, the gene for the occlusion-derived virus protein ODVP-6e is located. This is unlike the situation in many other NPVs, including SeMNPV, where the p10 gene neighbours the p74 gene. The data presented here suggest that although the p10 gene is not conserved in sequence, evolutionary pressure preserves the structure of P10 and hence its function. These data also indicate that all NPVs, MNPVs as well as SNPVs, contain this gene.