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.感染鳞翅目昆虫的杆状病毒是害虫生物防治领域最具潜力的替代方案之一。其中，草地贪夜蛾颗粒体病毒（Spodoptera frugiperda granulovirus, SfGV）可侵染草地贪夜蛾（Spodoptera frugiperda）——这是一种在全球范围内对玉米及其他作物危害日益严重的重要农业害虫。学界对SfGV的研究兴趣源于两点：其一，其具备增强其他杆状病毒侵染能力的特性；其二，其本身可作为生物农药加以应用。尽管SfGV包涵体（occlusion bodies, OB）的蛋白质组与其侵染特性息息相关，但目前学界对其蛋白组分的详细解析，以及与其他杆状病毒的组分差异仍缺乏深入认知。为填补这一研究空白，本研究对从感染幼虫中分离得到的SfGV包涵体开展了基于质谱的蛋白质组学分析，最终成功鉴定出SfGV包涵体中的72种蛋白质，并确认了两种增效蛋白的存在。基于EmPAI的半定量分析结果显示，ORF101与ORF141这两种颗粒体病毒蛋白在其他颗粒体病毒蛋白质组学研究中也被共同检出。ORF101的序列与结构特征与研究较为透彻的苜蓿银纹夜蛾多核型多角体病毒（Autographa californica multiple nucleopolyhedrovirus, AcMNPV）P10蛋白高度相似，二者均包含卷曲螺旋结构域与磷酸化位点；本研究通过在昆虫细胞中进行绿色荧光蛋白（Green Fluorescent Protein, GFP）标记的ORF101表达实验，证实其可在细胞质中聚集，这提示该蛋白可能在病毒粒子的组装或释放过程中发挥潜在作用。通过对包涵体蛋白结构的预测与比较分析，本研究在PEP-1、PEP-2、PEP-P10、ORF007、ORF025与Bro-f这6种蛋白中检测到了共同的结构折叠模体。最后，通过对四项已发表的不同颗粒体病毒的包涵体来源病毒（occlusion-derived virus, ODV）蛋白质组学研究进行比较，本研究发现ORF040、ORF101、ORF141与Bro-f是颗粒体病毒包涵体的常见组分。