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Abstract：
Mycoviruses can infect many of the major taxa of fungi including yeasts. Mycoviruses in the yeast fungus Geotrichum candidum are not well studied with only three G. candidum-associated viral species characterized to date, all of which belong to the Totiviridae genus Totivirus. In this study, we report the molecular characteristics of another two totiviruses co-infecting isolate Gc6 of G. candidum. The two totiviruses were tentatively named Geotrichum candidum totivirus 2 isolate Gc6 (GcTV2-Gc6) and Geotrichum candidum totivirus 4 isolate Gc6 (GcTV4-Gc6). Both viruses have the typical genome organization of totiviruses comprising two ORFs encoding capsid protein (CP) and RNA-dependent RNA polymerase (RdRp) at the N and C termini, respectively. The genomes of GcTV2-Gc6 and GcTV4-Gc6 are 4592 and 4530 bp long, respectively. Both viruses contain the-frameshifting elements and their proteins could be expressed as a single fusion protein. GcTV2-Gc6 is closely related to a totivirus isolated from the same host whereas GcTV4-Gc6 is related to insect-associated totiviruses. The phylogenetic analysis indicated that GcTV2-Gc6 and GcTV4-Gc6 belong to two different sister clades, I-A and I-B, respectively. It is interesting that all viruses identified from G. candidum belong to the genus Totivirus; however, this might be due to the lack of research reporting the characterization of mycoviruses from this fungal host. It is possible that the RNA interference (RNAi) mechanism cannot actively suppress totivirus accumulation in G. candidum Gc6.
摘要：
分枝杆菌病毒可以感染真菌的许多主要分类群，包括酵母。酵母真菌念珠菌中的分枝杆菌病毒尚未得到很好的研究，迄今为止只有三种与念珠菌相关的病毒种类。所有这些都属于Totiviridae属Totivirus。在这项研究中,我们报道了另外两种共同感染G.cc6分离株Gc6的病毒的分子特征。这两种病毒暂定名为念珠菌毒素2分离株Gc6（GcTV2-Gc6）和念珠菌毒素4分离株Gc6（GcTV4-Gc6）。两种病毒都具有典型的基因组组织，包括在N和C末端编码衣壳蛋白（CP）和RNA依赖性RNA聚合酶（RdRp）的两个ORF，分别。GcTV2-Gc6和GcTV4-Gc6的基因组长4592和4530bp，分别。两种病毒都含有移码元件，它们的蛋白质可以作为单个融合蛋白表达。GcTV2-Gc6与从同一宿主分离的转录病毒密切相关,而GcTV4-Gc6与昆虫相关转录病毒相关。系统发育分析表明，GcTV2-Gc6和GcTV4-Gc6属于两个不同的姐妹进化枝，I-A和I-B,分别。有趣的是，从G.candidum鉴定的所有病毒都属于Totivirus属；然而，这可能是由于缺乏报道该真菌宿主的分枝杆菌病毒特征的研究。RNA干扰（RNAi）机制可能无法主动抑制念珠菌Gc6中的转录病毒积累。
