A new tetra-segmented splipalmivirus with divided RdRP domains from Cryphonectria naterciae, a fungus found on chestnut and cork oak trees in Europe
A new tetra-segmented splipalmivirus with divided RdRP domains from Cryphonectria naterciae, a fungus found on chestnut and cork oak trees in Europe
复制标题
DOI：
10.1016/j.virusres.2021.198606
复制
发表时间：
2022-01-02
期刊：
影响因子：
5
通讯作者：
Suzuki, Nobuhiro
中科院分区：
文献类型：
--
作者：
Sato, Yukiyo;Shahi, Sabitree;Suzuki, Nobuhiro
自2020年以来，各种丝状子囊菌中报道了具有分裂RNA依赖RNA聚合酶（RdRP）结构域的阳性（+）单链RNA病毒。这些病毒被称为splipalmivirus或polynarnavirvirus，主要在序列水平上被描述，但在生物学上定义不清。白僵菌（Cryphonectria naterciae）是一种子囊真菌，对栗树和橡树具有潜在的植物致病性。我们采用超转录组学和常规双链RNA方法，对单一葡萄牙分离物（C0614）中的多种病毒进行了分子表征。其中包括一种新型splipalmivirus （Cryphonectria naterciae splipalmivirus 1, CnSpV1）和一种新型镰刀病毒（Cryphonectria naterciae fusagravirus 1, CnFGV1）。这项研究的重点是前一种病毒。CnSpV1具有四段（+）ssRNA基因组（RNA1至RNA4）。与2020年和2021年报道的其他裂唇病毒一样，RdRP结构域分别由RNA1（基序F、A和B）和RNA2（基序C和D）编码。由RNA3的5 '-近端开放阅读框编码的一种假设蛋白质与一些splipmivirus中保守的对应物相似。另一种rna3编码蛋白和rna4编码蛋白在胚泡搜索中显示与已知蛋白没有相似性。4个CnSpV1片段（RNA1 ~ RNA4）末端序列的保守性证实了它们的四片段性，并且在100多个单分生孢子分离株中100%共存。实验将CnSpV1和CnFGV1引入与C0614植物不相容的无病毒C0754株，结果没有发生表型改变，提示无症状感染。原生质体融合实验表明，CnSpV1的宿主范围相当狭窄，仅限于C. naterciae和C. carpinicola。这项研究有助于更好地了解这一独特病毒群的分子和生物学特性。
Positive-sense (+), single-stranded (ss) RNA viruses with divided RNA-dependent RNA polymerase (RdRP) domains have been reported from diverse filamentous ascomycetes since 2020. These viruses are termed splipalmiviruses or polynarnaviruses and have been characterized largely at the sequence level, but ill-defined biologically. Cryphonectria naterciae, from which only one virus has been reported, is an ascomycetous fungus potentially plant-pathogenic to chestnut and oak trees. We molecularly characterized multiple viruses in a single Portuguese isolate (C0614) of C. naterciae, taking a metatranscriptomic and conventional double-stranded RNA approach. Among them are a novel splipalmivirus (Cryphonectria naterciae splipalmivirus 1, CnSpV1) and a novel fusagravirus (Cryphonectria naterciae fusagravirus 1, CnFGV1). This study focused on the former virus. CnSpV1 has a tetra-segmented, (+)ssRNA genome (RNA1 to RNA4). As observed for other splipalmiviruses reported in 2020 and 2021, the RdRP domain is separately encoded by RNA1 (motifs F, A and B) and RNA2 (motifs C and D). A hypothetical protein encoded by the 5 '-proximal open reading frame of RNA3 shows similarity to a counterpart conserved in some splipalmiviruses. The other RNA3-encoded protein and RNA4-encoded protein show no similarity with known proteins in a blastp search. The tetra-segment nature was confirmed by the conserved terminal sequences of the four CnSpV1 segments (RNA1 to RNA4) and their 100% coexistence in over 100 single conidial isolates tested. The experimental introduction of CnSpV1 along with CnFGV1 into a virus free strain C0754 of C. naterciae vegetatively incompatible with C0614 resulted in no phenotypic alteration, suggesting asymptomatic infection. The protoplast fusion assay indicates a considerably narrow host range of CnSpV1, restricted to the species C. naterciae and C. carpinicola. This study contributes to better understanding of the molecular and biological properties of this unique group of viruses.