RNA transport and localization represent important post‐transcriptional mechanisms to determine the subcellular localization of protein synthesis. Plants have the capacity to transport messenger (m)RNA molecules beyond the cell boundaries through plasmodesmata and over long distances in the phloem. RNA viruses exploit these transport pathways to disseminate their infections and represent important model systems to investigate RNA transport in plants. Here, we present an in vivo plant RNA‐labeling system based on the Escherichia coli RNA‐binding protein BglG. Using the detection of RNA in mobile RNA particles formed by viral movement protein (MP) as a model, we demonstrate the efficiency and specificity of mRNA detection by the BglG system as compared with MS2 and λN systems. Our observations show that MP mRNA is specifically associated with MP in mobile MP particles but hardly with MP localized at plasmodesmata. MP mRNA is clearly absent from MP accumulating along microtubules. We show that the in vivo BglG labeling of the MP particles depends on the presence of the BglG‐binding stem–loop aptamers within the MP mRNA and that the aptamers enhance the coprecipitation of BglG by MP, thus demonstrating the presence of an MP:MP mRNA complex. The BglG system also allowed us to monitor the cell‐to‐cell transport of the MP mRNA, thus linking the observation of mobile MP mRNA granules with intercellular MP mRNA transport. Given its specificity demonstrated here, the BglG system may be widely applicable for studying mRNA transport and localization in plants.

中文翻译：

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使用细菌转录抗终止剂BglG对植物组织中标记的mRNA进行体内成像

RNA的运输和定位代表了重要的转录后机制，以确定蛋白质合成的亚细胞定位。植物具有将信使（m）RNA分子转运通过胞膜胞质并在韧皮部中长距离运输的能力。RNA病毒利用这些运输途径来传播其感染，并代表了重要的模型系统来研究植物中RNA的运输。在这里，我们介绍了一种基于大肠杆菌的体内植物RNA标记系统RNA结合蛋白BglG。使用病毒运动蛋白（MP）形成的移动RNA颗粒中的RNA检测作为模型，我们证明了与MS2和λN系统相比，BglG系统检测mRNA的效率和特异性。我们的观察结果表明，MP mRNA与可移动MP颗粒中的MP特异性相关，但几乎与定位在胞浆内的MP无关。沿着微管积累的MP中显然不存在MP mRNA。我们表明，MP颗粒的体内BglG标记取决于MP mRNA中BglG结合的茎环适体的存在，并且适体增强了MP对BglG的共沉淀，从而证明了MP的存在：MPmRNA复合物。BglG系统还使我们能够监测MP mRNA的细胞间运输，从而将移动MP mRNA颗粒的观察与细胞间MP mRNA的运输联系起来。鉴于此处显示的特异性，BglG系统可广泛应用于研究植物中的mRNA转运和定位。