Shandong Provincial Key Laboratory of Agricultural Microbiology, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong, China.
Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland.
Mol Plant Pathol. 2021 Feb;22(2):189-203. doi: 10.1111/mpp.13017. Epub 2020 Nov 27.
Coat proteins (CPs) play critical roles in potyvirus cell-to-cell movement. However, the underlying mechanism controlling them remains unclear. Here, we show that substitutions of alanine, glutamic acid, or lysine for the conserved residue tryptophan at position 122 (W ) in tobacco vein banding mosaic virus (TVBMV) CP abolished virus cell-to-cell movement in Nicotiana benthamiana plants. In agroinfiltrated N. benthamiana leaf patches, both the CP and RNA accumulation levels of three W mutant viruses were significantly reduced compared with those of wild-type TVBMV, and CP accumulated to a low level similar to that of a replication-deficient mutant. The results of polyprotein transient expression experiments indicated that CP instability was responsible for the significantly low CP accumulation levels of the three W mutant viruses. The substitution of W did not affect CP plasmodesmata localization or virus particle formation; however, the substitution significantly reduced the number of virus particles. The wild-type TVBMV CP could complement the reduced replication and abolished cell-to-cell movement of the mutant viruses. When the codon for W was mutated to that for a different aromatic residue, phenylalanine or tyrosine, the resultant mutant viruses moved systemically and accumulated up to 80% of the wild-type TVBMV level. Similar results were obtained for the corresponding amino acids of W in the watermelon mosaic virus and potato virus Y CPs. Therefore, we conclude that the aromatic ring in W in the core domain of the potyviral CP is critical for cell-to-cell movement through the effects on CP stability and viral replication.
外壳蛋白 (CP) 在马铃薯 Y 病毒属病毒的细胞间运动中起着关键作用。然而，控制它们的潜在机制仍不清楚。在这里，我们表明，在烟草叶脉镶嵌病毒（TVBMV）CP 中，位置 122（W）处的保守色氨酸突变为丙氨酸、谷氨酸或赖氨酸，会导致病毒在 Nicotiana benthamiana 植物中的细胞间运动能力丧失。在农杆菌浸润的 N. benthamiana 叶片斑中，与野生型 TVBMV 相比，三种 W 突变病毒的 CP 和 RNA 积累水平均显著降低，CP 积累水平低至类似于复制缺陷型突变体的水平。瞬时表达实验结果表明，CP 不稳定性是导致三种 W 突变病毒 CP 积累水平显著降低的原因。W 的取代不影响 CP 胞间连丝定位或病毒粒子形成；然而，它显著减少了病毒粒子的数量。野生型 TVBMV CP 可以补充突变病毒复制减少和丧失的细胞间运动能力。当 W 的密码子突变为不同的芳香族残基苯丙氨酸或酪氨酸时，所得突变病毒可以系统性地运动，并积累高达野生型 TVBMV 水平的 80%。在西瓜花叶病毒和马铃薯病毒 Y CP 中，W 的相应氨基酸也得到了类似的结果。因此，我们得出结论，核心结构域中 CP 的 W 的芳香环通过影响 CP 稳定性和病毒复制，对细胞间运动至关重要。
