Takahashi-Nakaguchi Azusa, Shishido Erika, Yahara Misa, Urayama Syun-Ichi, Sakai Kanae, Chibana Hiroji, Kamei Katsuhiko, Moriyama Hiromitsu, Gonoi Tohru
Medical Mycology Research Center, Chiba University, Chiba, Japan.
Front Microbiol. 2020 Jan 17;10:3045. doi: 10.3389/fmicb.2019.03045. eCollection 2019.
is an airborne fungal pathogen that causes severe infections with invasive growth in immunocompromised patients. Several mycoviruses have recently been isolated from strains, but there are presently no reports of mycoviral-mediated reduction or elimination of fungal pathogenicity in vertebrate models. Here, we report the biological features of a novel mycovirus, chrysovirus 41362 (AfuCV41362), isolated from the hypovirulent strain IFM 41362. The AfuCV41362 genome is comprised of four dsRNAs, each of which contains a single ORF (ORF1-4). ORF1 encodes a protein with sequence similarity to RNA-dependent RNA polymerases of viruses in the family Chrysoviridae, while ORF3 encodes a putative capsid protein. Viral RNAs are expressed primarily during the germination stage, and RNA-seq analysis of virus-infected at the germination stage suggested that the virus suppressed expression of several pathogenicity-associated host genes, including hypoxia adaptation and nitric oxide detoxification genes. functional analysis revealed that the virus-infected strain had reduced tolerance to environmental stressors. Virus-infected strain IFM 41362 had reduced virulence compared to the virus-free strain in a mouse infection model. Furthermore, introduction of the mycovirus to a natively virus-free KU strain induced virus-infected phenotypes. To identify mycovirus genes responsible for the reduced virulence of , each viral ORF was ectopically expressed in the virus-free KU strain. Ectopic expression of the individual ORFs only nominally reduced virulence of the host fungus in a mouse infection model. However, we found that ORF3 and ORF4 reduced tolerance to environmental stresses in analysis. Based on these results, we suggest that the AfuCV41362 mycovirus ORF3 and ORF4 reduce fungal virulence by suppressing stress tolerance together with other viral genes, rather than alone.
是一种空气传播的真菌病原体，可在免疫功能低下的患者中引起严重感染并具有侵袭性生长。最近从菌株中分离出了几种真菌病毒，但目前尚无关于真菌病毒介导的在脊椎动物模型中降低或消除真菌致病性的报道。在此，我们报告了从低毒力菌株IFM 41362中分离出的一种新型真菌病毒——金黄病毒41362（AfuCV41362）的生物学特性。AfuCV41362基因组由四条双链RNA组成，每条双链RNA都包含一个单一的开放阅读框（ORF1 - 4）。ORF1编码一种与金黄病毒科病毒的RNA依赖性RNA聚合酶具有序列相似性的蛋白质，而ORF3编码一种假定的衣壳蛋白。病毒RNA主要在萌发阶段表达，对萌发阶段病毒感染的进行RNA测序分析表明，该病毒抑制了几种与致病性相关的宿主基因的表达，包括缺氧适应和一氧化氮解毒基因。功能分析表明，病毒感染的菌株对环境应激源的耐受性降低。在小鼠感染模型中，与无病毒菌株相比，病毒感染的菌株IFM 41362的毒力降低。此外，将该真菌病毒引入天然无病毒的KU菌株会诱导出病毒感染的表型。为了鉴定导致毒力降低的真菌病毒基因，每个病毒ORF在无病毒的KU菌株中异位表达。在小鼠感染模型中，单个ORF的异位表达仅名义上降低了宿主真菌的毒力。然而，我们发现在分析中ORF3和ORF4降低了对环境应激的耐受性。基于这些结果，我们认为AfuCV41362真菌病毒的ORF3和ORF4通过与其他病毒基因一起抑制应激耐受性来降低真菌毒力，而不是单独作用。
