Huang Ying-Ping, Zhang Jun-Wei, Huang Ching-Ing, Chen I-Hsuan, Huang Ying-Wen, Cheng Chi-Ping, Tsai Ching-Hsiu
Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan.
Advanced Plant and Food Crop Biotechnology Center, National Chung Hsing University, Taichung, Taiwan.
Mol Plant Pathol. 2025 Jul;26(7):e70120. doi: 10.1111/mpp.70120.
The transcription factor NbTFIISL, a TFIIS-like protein in Nicotiana benthamiana, plays a critical role in facilitating bamboo mosaic virus (BaMV) infection. BaMV infections significantly downregulate NbTFIISL expression, with transcript levels reduced to 38% by 7 days post-inoculation. Virus-induced gene silencing of NbTFIISL impaired BaMV accumulation, reducing coat protein levels to 45% and leading to smaller GFP-labelled infection foci. Protoplast-based assays further confirmed its involvement in viral replication, with BaMV RNA levels dropping to 12% in NbTFIISL-silenced cells. Subcellular localisation analysis revealed that NbTFIISL is primarily nuclear, directed by a classical nuclear localisation signal (NLS) and an LW motif. Mutant constructs lacking these signals-NbTFIISL/ΔNLS and NbTFIISL/ΔNLS/ΔLW-lost nuclear targeting and instead localised to mitochondria, with the double mutant forming distinct speckle-like aggregates. Overexpression experiments uncovered a dual role for NbTFIISL: nuclear-localised wild-type protein induced necrosis, whereas mitochondria-localised NbTFIISL/ΔNLS significantly enhanced BaMV accumulation (148%). In contrast, protein aggregation in the NbTFIISL/ΔNLS/ΔLW mutant partially impaired this enhancement. Yeast two-hybrid assays revealed specific interactions between NbTFIISL and BaMV proteins, including the replicase RdRp domain and movement protein TGBp1. These findings suggest that NbTFIISL promotes BaMV replication through mitochondrial relocalisation and interaction with viral proteins, whereas its nuclear presence may trigger necrosis, potentially limiting viral spread. This study highlights the multifunctional roles of NbTFIISL and advances our understanding of host factors in plant-virus interactions and viral pathogenesis.
转录因子NbTFIISL是本氏烟草中一种类TFIIS蛋白，在促进竹花叶病毒（BaMV）感染中起关键作用。BaMV感染显著下调NbTFIISL的表达，接种后7天转录水平降至38%。NbTFIISL的病毒诱导基因沉默损害了BaMV的积累，使外壳蛋白水平降至约45%，并导致绿色荧光蛋白标记的感染灶变小。基于原生质体的分析进一步证实其参与病毒复制，在NbTFIISL沉默的细胞中BaMV RNA水平降至12%。亚细胞定位分析表明，NbTFIISL主要定位于细胞核，由一个经典的核定位信号（NLS）和一个LW基序引导。缺乏这些信号的突变体构建体——NbTFIISL/ΔNLS和NbTFIISL/ΔNLS/ΔLW失去了核靶向性，转而定位于线粒体，双突变体形成明显的斑点状聚集体。过表达实验揭示了NbTFIISL的双重作用：核定位的野生型蛋白诱导坏死，而线粒体定位的NbTFIISL/ΔNLS显著增强BaMV的积累（约148%）。相比之下，NbTFIISL/ΔNLS/ΔLW突变体中的蛋白质聚集部分损害了这种增强作用。酵母双杂交分析揭示了NbTFIISL与BaMV蛋白之间的特异性相互作用，包括复制酶RdRp结构域和运动蛋白TGBp1。这些发现表明，NbTFIISL通过线粒体重新定位和与病毒蛋白相互作用促进BaMV复制，而其在细胞核中的存在可能触发坏死，潜在地限制病毒传播。这项研究突出了NbTFIISL的多功能作用，并推进了我们对植物-病毒相互作用和病毒发病机制中宿主因子的理解。
