Apple stem pitting virus is a species in the genus Foveavirus in the family Betaflexiviridae. Apple stem pitting virus (ASPV) commonly infects apple and pear plants grown worldwide. In this study, by integrating bimolecular fluorescence complementation, split-ubiquitin-based membrane yeast two-hybrid, and Agrobacterium-mediated expression assays, the interaction relationships and the subcellular locations of ASPV proteins TGBp1–3 and CP in Nicotiana benthamiana leaf cells were determined. Proteins CP, TGBp1, TGBp2, and TGBp3 were self-interactable, and TGBp2 played a role in the formation of perinuclear viroplasm and enhanced the colocalization of TGBp3 with CP and TGBp1. We found that the plant microfilament and endoplasmic reticulum structures were involved in the production of TGBp3 and TGBp2 vesicles, and their disruption decreased the virus accumulation level in the systemic leaves. The TGBp3 motile vesicles functioned in delivering the viral ribonucleoprotein complexes to the plasma membrane. Two cysteine residues at sites 35 and 49 of the TGBp3 sorting signal were necessary for the diffusion of TGBp3-marked vesicles. Furthermore, our results revealed that TGBp1, TGBp2, and CP could increase plasmodesmal permeability and move to the adjacent cells. This study demonstrates an interaction network and a subcellular location map of four ASPV proteins and for the first time provides insight into the functions of these proteins in the movement of a foveavirus.

中文翻译：

---

苹果茎点蚀病毒三基因块蛋白和外壳蛋白在病毒细胞间运动中的功能

苹果茎点蚀病毒是Betaflexiviridae科Foveavirus属的一个物种。苹果茎点蚀病毒 (ASPV) 通常感染世界各地种植的苹果和梨植物。本研究通过整合双分子荧光互补、基于分裂泛素的膜酵母双杂交和农杆菌介导的表达测定，确定了本塞姆氏叶细胞中ASPV蛋白TGBp1-3和CP的相互作用关系和亚细胞位置。。蛋白质 CP、TGBp1、TGBp2 和 TGBp3 具有自相互作用性，TGBp2 在核周病毒质的形成中发挥作用，并增强 TGBp3 与 CP 和 TGBp1 的共定位。我们发现植物微丝和内质网结构参与了 TGBp3 和 TGBp2 囊泡的产生，它们的破坏降低了病毒在系统叶中的积累水平。TGBp3 运动囊泡的功能是将病毒核糖核蛋白复合物递送至质膜。TGBp3 分选信号位点 35 和 49 处的两个半胱氨酸残基对于 TGBp3 标记的囊泡的扩散是必需的。此外，我们的结果表明，TGBp1、TGBp2 和 CP 可以增加胞间连丝的通透性并移动到相邻细胞。这项研究展示了四种 ASPV 蛋白的相互作用网络和亚细胞位置图，并首次深入了解这些蛋白在中央凹病毒运动中的功能。