Chen Xiaojiao, Luo Hengming, Zhang Jingyi, Ma Yan, Li Kehua, Xiong Feng, Yang Yahui, Yang Jiazhen, Lan Pingxiu, Wei Taiyun, Xu Yi, Chen Hairu, Li Fan
State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, China.
Key Laboratory of Agricultural Biotechnology of Yunnan Province, Institute of Biotechnology and Germplasm Resources, Yunnan Academy of Agricultural Sciences, Kunming, China.
Front Microbiol. 2022 Apr 4;13:846857. doi: 10.3389/fmicb.2022.846857. eCollection 2022.
Tobacco bushy top disease (TBTD), caused by multiple pathogens including tobacco bushy top virus (TBTV), tobacco vein distorting virus (TVDV), TBTV satellite RNA (TBTVsatRNA), and TVDV-associated RNA (TVDVaRNA), is a destructive disease in tobacco fields. To date, how these causal agents are co-transmitted by aphid vectors in field and their roles in disease symptom induction remain largely unknown, due mainly to the lack of purified causal agents. In this study, we have constructed four full-length infectious clones, representing the Yunnan Kunming isolates of TVDV, TBTV, TBTVsatRNA, and TVDVaRNA (TVDV-YK, TBTV-YK, TBTVsatRNA-YK, and TVDVaRNA-YK), respectively. Co-inoculation of these four causal agents to tobacco K326 plants caused typical TBTD symptoms, including smaller leaves, necrosis, and plant stunting. In addition, inoculation of tobacco K326 plants with TBTV alone caused necrosis in systemic leaves by 7 dpi. Tobacco K326 and plants infected by single virus or multiple viruses showed very different disease symptoms at various dpi. RT-PCR results indicated that co-infection of TVDVaRNA-YK could increase TVDV-YK or TBTV-YK accumulation in plants, suggesting that TVDVaRNA-YK can facilitate TVDV-YK and TBTV-YK replication and/or movement in the infected plants. Aphid transmission assays showed that the successful transmission of TBTV-YK, TBTVsatRNA-YK, and TVDVaRNA-YK by depended on the presence of TVDV-YK, while the presence of TBTVsatRNA-YK increased the aphid transmission efficiency of TBTV and TVDV. We consider that these four new infectious clones will allow us to further dissect the roles of these four causal agents in TBTD induction as well as aphid transmission.
烟草丛顶病（TBTD）由多种病原体引起，包括烟草丛顶病毒（TBTV）、烟草叶脉扭曲病毒（TVDV）、TBTV卫星RNA（TBTVsatRNA）和TVDV相关RNA（TVDVaRNA），是烟草田中的一种毁灭性病害。迄今为止，这些病原体如何在田间由蚜虫介体共同传播以及它们在病害症状诱导中的作用仍 largely未知，主要原因是缺乏纯化的病原体。在本研究中，我们构建了四个全长感染性克隆，分别代表TVDV、TBTV、TBTVsatRNA和TVDVaRNA的云南昆明分离株（TVDV-YK、TBTV-YK、TBTVsatRNA-YK和TVDVaRNA-YK）。将这四种病原体共同接种到烟草K326植株上会引起典型的TBTD症状，包括叶片变小、坏死和植株矮化。此外，单独用TBTV接种烟草K326植株在接种后7天会导致系统叶出现坏死。感染单一病毒或多种病毒的烟草K326植株在不同接种后天数表现出非常不同的病害症状。逆转录聚合酶链反应（RT-PCR）结果表明，TVDVaRNA-YK的共同感染可增加TVDV-YK或TBTV-YK在植株中的积累，这表明TVDVaRNA-YK可促进TVDV-YK和TBTV-YK在受感染植株中的复制和/或移动。蚜虫传播试验表明桃蚜成功传播TBTV-YK、TBTVsatRNA-YK和TVDVaRNA-YK取决于TVDV-YK的存在，而TBTVsatRNA-YK的存在提高了TBTV和TVDV的蚜虫传播效率。我们认为这四个新的感染性克隆将使我们能够进一步剖析这四种病原体在TBTD诱导以及蚜虫传播中的作用。
