Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), H-12, Islamabad, 44000, Pakistan.
Institute of Plant Science and Resources, Okayama University, Kurashiki, 710-0046, Japan.
Arch Virol. 2022 Mar;167(3):923-929. doi: 10.1007/s00705-021-05304-7. Epub 2022 Feb 3.
Neofusicoccum parvum is an important plant-pathogenic ascomycetous fungus that causes trunk diseases in a variety of plants. A limited number of reports on mycoviruses from this fungus are available. Here, we report the characterization of a novel victorivirus, Neofusicoccum parvum victorivirus 3 (NpVV3). An agarose gel dsRNA profile of a Pakistani strain of N. parvum, NFN, showed a band of ~5 kbp that was not detectable in Japanese strains of N. parvum. Taking a high-throughput and Sanger sequencing approach, the complete genome sequence of NpVV3 was determined to be 5226 bp in length with two open reading frames (ORF1 and ORF2) that encode a capsid protein (CP) and an RNA-dependent RNA polymerase (RdRP). The RdRP appears to be translated by a stop/restart mechanism facilitated by the junction sequence AUGucUGA, as is found in some other victoriviruses. BLASTp searches showed that NpVV3 CP and RdRP share the highest amino acid sequence identity (80.5% and 72.4%, respectively) with the corresponding proteins of NpVV1 isolated from a French strain of N. parvum. However, NpVV3 was found to be different from NpVV1 in its terminal sequences and the stop/restart facilitator sequence. NpVV3 particles ~35 nm in diameter were partially purified and used to infect an antiviral-RNA-silencing-deficient strain (∆dcl2) of an experimental ascomycetous fungal host, Cryphonectria parasitica. NpVV3 showed symptomless infection in the new host strain.
细极毛壳菌（Neofusicoccum parvum）是一种重要的植物病原子囊菌，可引起多种植物的树干病害。目前有关该真菌病毒的报道较少。在这里，我们报告了一种新型的拟病毒——细极毛壳菌拟病毒 3（NpVV3）的特征。巴基斯坦细极毛壳菌 NFN 菌株琼脂糖凝胶 dsRNA 图谱显示，有一条约 5 kbp 的带在日本细极毛壳菌菌株中无法检测到。采用高通量和 Sanger 测序方法，确定 NpVV3 的全基因组序列长度为 5226 bp，包含两个开放阅读框（ORF1 和 ORF2），分别编码衣壳蛋白（CP）和 RNA 依赖性 RNA 聚合酶（RdRP）。RdRP 似乎通过 AUGucUGA 连接序列介导的停止/重新启动机制进行翻译，这在其他一些拟病毒中也有发现。BLASTp 搜索显示，NpVV3 CP 和 RdRP 与从法国细极毛壳菌菌株中分离得到的 NpVV1 相应蛋白的氨基酸序列相似性最高（分别为 80.5%和 72.4%）。然而，NpVV3 在其末端序列和停止/重新启动促进剂序列上与 NpVV1 不同。直径约 35nm 的 NpVV3 颗粒被部分纯化，并用于感染 Cryphonectria parasitica 实验子囊菌宿主的抗病毒 RNA 沉默缺陷株（∆dcl2）。NpVV3 在新宿主菌株中表现出无症状感染。
