Fungal negative-stranded RNA virus that is related to bornaviruses and nyaviruses

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 33; pp. 12205 - 12210
• Main Authors: Liu, Lijiang, Xie, Jiatao, Cheng, Jiasen, Fu, Yanping, Li, Guoqing, Yi, Xianhong, Jiang, Daohong
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 19.08.2014; National Acad Sciences
• Subjects: Amino Acid Sequence; Biological Sciences; Bornaviridae; Bornaviridae - classification; Bornaviridae - genetics; Bornaviridae - isolation & purification; Bunyaviridae - classification; Bunyaviridae - genetics; Bunyaviridae - isolation & purification; China; complementary DNA; double-stranded RNA; ecology; Electrophoresis, Polyacrylamide Gel; Filoviridae; Fungi; Fungi - virology; genes; Genomes; hyphae; Microbiology; Molecular Sequence Data; molecular weight; Morphology; Mycoviruses; Nucleocapsid; nucleoproteins; Nyamiviridae; Open reading frames; Phylogeny; polyacrylamide gel electrophoresis; rapid amplification of cDNA ends; Rhabdoviridae; Ribonucleic acid; RNA; RNA Viruses - classification; RNA Viruses - genetics; RNA Viruses - isolation & purification; RNA-directed RNA polymerase; Sclerotinia sclerotiorum; sequence analysis; Sequence Homology, Amino Acid; Viral morphology; Viral Proteins - chemistry; virion; Virions; virulence; Viruses; China; biological control; mononegavirus; rapeseed stem rot; fungal plant pathogen
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1401786111

Mycoviruses are widespread in nature and often occur with dsRNA and positive-stranded RNA genomes. Recently, strong evidence from RNA sequencing analysis suggested that negative-stranded (-)ssRNA viruses could infect fungi. Here we describe a (-)ssRNA virus, Sclerotinia sclerotiorum negative-stranded RNA virus 1 (SsNSRV-1), isolated from a hypovirulent strain of Sclerotinia sclerotiorum. The complete genome of SsNSRV-1 is 10,002 nt with six ORFs that are nonoverlapping and linearly arranged. Conserved gene-junction sequences that occur widely in mononegaviruses, (A/U)(U/A/C)UAUU (U/A)AA(U/G)AAAACUUAGG(A/U)(G/U), were identified between these ORFs. The analyses 5' and 3' rapid amplification of cDNA ends showed that all genes can be transcribed independently. ORFs. encodes the largest protein that contains a conserved mononegaviral RNA-dependent RNA polymerase (RdRp) domain. Putative enveloped virion-like structures with filamentous morphology similar to members of Filoviridae were observed both in virion preparation samples and in ultrathin hyphal sections. The nucleocapsids are long, flexible, and helical; and are 22 nm in diameter and 200-2,000 nm in length. SDS/PAGE showed that the nucleocapsid possibly contains two nucleoproteins with different molecular masses, ~43 kDa (p43) and ~41 kDa (p41), and both are translated from ORF II. Purified SsNSRV-1 virions successfully transfected a virus-free strain of S. sclerotiorum and conferred hypovirulence. Phylogenetic analysis based on RdRp showed that SsNSRV-1 is clustered with viruses of Nyamiviridae and Bornaviridae. Moreover, SsNSRV-1 is widely distributed, as it has been detected in different regions of China. Our findings demonstrate that a (-)ssRNA virus can occur naturally in fungi and enhance our understanding of the ecology and evolution of (-)ssRNA viruses.