DataSheet1_High-throughput sequencing detected a virus–viroid complex in a single pokeweed plant.pdf

In this study, total RNA high-throughput sequencing (HTS) of a single symptomatic Phytolacca americana plant enabled the obtention of a nearly complete genome of two new isolates of turnip yellows virus (TuYV), named TuYV-ITA1 and TuYV-ITA2, and revealed a mixed infection with a new variant of citrus exocortis viroid (CEVd), named CEVd-ITA1. The TuYV-ITA2 isolate diverged from the known virus isolates of TuYV and showed variability in the P0 and P5 readthrough domain. Recombination analysis revealed its recombinant nature between TuYV and an unidentified polerovirus. The putative recombination event was identified in the P5 readthrough domain of the TuYMV-ITA2 isolate. Our results thus represent the first report of TuYV in Italy and some molecular evidence for the possible natural co-existence of TuYV and CEVd in a new natural host for both infectious entities. This study is adding further knowledge about the role of weed plants as virus reservoirs, and thus additional biological and impact studies would be desirable to determine in particular the role of P. americana in the spread of TuYV and if this virus should be considered a new threat for the susceptible Italian crops.

本研究通过对1株表现症状的美洲商陆（*Phytolacca americana*）开展总RNA高通量测序（high-throughput sequencing, HTS），获得了2株新的芜菁黄化病毒（turnip yellows virus, TuYV）分离物的近乎完整基因组，分别命名为TuYV-ITA1与TuYV-ITA2；同时发现该样本与1株新的柑橘裂皮类病毒（citrus exocortis viroid, CEVd）变异株存在混合感染，该变异株被命名为CEVd-ITA1。TuYV-ITA2分离物与已报道的TuYV病毒分离物存在进化分歧，其P0与P5通读结构域存在序列变异。重组分析显示，该分离物属于TuYV与1株未鉴定黄症病毒属（Polerovirus）病毒的重组体，推测的重组位点被定位在TuYV-ITA2分离物的P5通读结构域中。综上，本研究结果为TuYV在意大利的首次报道，同时为两种侵染性实体（TuYV与CEVd）在全新自然寄主中共存的现象提供了分子生物学证据。本研究进一步明确了杂草作为病毒自然贮存宿主的作用，因此未来亟需开展更多生物学与风险性研究，尤其是明确美洲商陆在TuYV传播过程中所扮演的角色，并评估该病毒是否会对意大利易感农作物构成新的威胁。