The genome of bipartite geminiviruses in the genus Begomovirus comprises two circular DNAs: DNA-A and DNA-B. The DNA-B component encodes a nuclear shuttle protein (NSP) and a movement protein (MP), which cooperate for systemic spread of infectious nucleic acids within host plants and affect pathogenicity. MP mediates multiple functions during intra- and intercellular trafficking, such as binding of viral nucleoprotein complexes, targeting to and modification of plasmodesmata, and release of the cargo after cell-to-cell transfer. For Abutilon mosaic virus (AbMV), phosphorylation of MP expressed in bacteria, yeast, and Nicotiana benthamiana plants, respectively, has been demonstrated in previous studies. Three phosphorylation sites (T221, S223, and S250) were identified in its C-terminal oligomerization domain by mass spectrometry, suggesting a regulation of MP by posttranslational modification. To examine the influence of the three sites on the self-interaction in more detail, MP mutants were tested for their interaction in yeast by two-hybrid assays, or by Förster resonance energy transfer (FRET) techniques in planta. Expression constructs with point mutations leading to simultaneous (triple) exchange of T221, S223, and S250 to either uncharged alanine (MP^AAA), or phosphorylation charge-mimicking aspartate residues (MP^DDD) were compared. MP^DDD interfered with MP-MP binding in contrast to MP^AAA. The roles of the phosphorylation sites for the viral life cycle were studied further, using plant-infectious AbMV DNA-B variants with the same triple mutants each. When co-inoculated with wild-type DNA-A, both mutants infected N. benthamiana plants systemically, but were unable to do so for some other plant species of the families Solanaceae or Malvaceae. Systemically infected plants developed symptoms and viral DNA levels different from those of wild-type AbMV for most virus-plant combinations. The results indicate a regulation of diverse MP functions by posttranslational modifications and underscore their biological relevance for a complex host plant-geminivirus interaction.

双性双生子病毒属的基因组 乙状病毒包含两个环状DNA：DNA-A和DNA-B。DNA-B组分编码核穿梭蛋白（NSP）和运动蛋白（MP），它们协同作用，使感染性核酸在宿主植物中全身扩散并影响致病性。MP在细胞内和细胞间运输过程中介导多种功能，例如结合病毒核蛋白复合物，靶向并修饰纤毛虫，以及在细胞间转移后释放货物。对于Abutilon花叶病毒（AbMV），在细菌，酵母和烟草以前的研究已经证明了植物。通过质谱法在其C端低聚结构域中发现了三个磷酸化位点（T221，S223和S250），表明通过翻译后修饰调节MP。为了更详细地检查这三个位点对自我相互作用的影响，通过两种杂交测定法或Förster共振能量转移（FRET）技术测试了MP突变体在酵母中的相互作用。在植物。比较了具有点突变的表达构建体，这些点突变导致T221，S223和S250同时（三重）交换为不带电荷的丙氨酸（MP ^AAA）或模拟磷酸化电荷的天冬氨酸残基（MP ^DDD）。与MP ^AAA相比，MP ^DDD会干扰MP-MP绑定。进一步研究了磷酸化位点在病毒生命周期中的作用，使用了具有植物感染力的AbMV DNA-B变体，每个变体都具有相同的三重突变体。与野生型DNA-A一起接种时，两个突变体均被感染本萨姆猪笼草属植物，但对茄科或锦葵科的其他一些植物却没有。对于大多数病毒-植物组合，系统感染的植物出现的症状和病毒DNA水平不同于野生型AbMV。结果表明通过翻译后修饰来调节多种MP功能，并强调了它们与复杂宿主植物-双子病毒相互作用的生物学相关性。