Proteomic Characterization of Spodoptera frugiperda granulovirus Occlusion Bodies

Lepidopteran-infecting baculoviruses represent one of
the most
promising alternatives for pest biocontrol. In particular, Spodoptera
frugiperda granulovirus (SfGV) infects the fall armyworm Spodoptera frugiperda, an increasingly important
pest for maize and other crops around the world. SfGV has been investigated
due to its capacity to enhance other baculovirus infectivity and as
a biopesticide itself. Although the proteome of SfGV occlusion bodies
(OB) is fundamental for their infectivity properties, we still lack
a detailed understanding of its protein components and how they compare
with other baculoviruses. To tackle this problem, we performed mass
spectrometry-based proteomics analysis on SfGV OB obtained from infected
larvae. We could detect 72 proteins included in SfGV OB and confirm
the presence of two enhancins. EmPAI-based semiquantification highlighted
the presence of two granulovirus proteins, ORF101 and ORF141, shared
with other GV proteomic studies. ORF101 exhibits sequence and structural
features reminiscent of the well-characterized AcMNPV P10 protein,
including a coiled-coil domain and phosphorylation sites, and we confirmed
its cytoplasmic aggregation through GFP-tagged expression in insect
cells, suggesting a potential role in virion assembly or release.
Prediction and comparison of OB protein structures allowed the detection
of a common structural fold among 6 proteins PEP-1, PEP-2, PEP-P10,
ORF007, ORF025, and Bro-f. Finally, comparison of four reported ODV
proteomic studies of different GVs indicated that ORF040, ORF101,
ORF141, and Bro-f are common components in GV OBs.