Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2014
Publication Date: 6/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59353
Citation: Bekel, S., Domier, L.L., Gonfa, B., McCoppin, N.K., Lambert, K.N., Bhalerao, K. 2014. A novel flavivirus in the soybean cyst nematode. Journal of General Virology. 95(6):1272-1280. Interpretive Summary: Soybean cyst nematode (SCN) is a subterranean root pathogen that causes the most damaging disease of soybean in the United States. One potential method to reduce yield losses caused by SCN is the use of biological control agents that infect and reduce the virulence of the nematodes. In this study a novel nematode-infecting virus, soybean cyst nematode virus 5 (SbCNV5), was identified in SCN eggs and juveniles. The new virus was related to arthropod-borne viruses that infect mammals and viruses that infect invertebrates and plants. SbCNV5 was detected in all nematode developmental stages indicating that the virus is transmitted from infected females to their offspring. Virus particles were visualized in infected nematodes by electron microscopy. If field and greenhouse bioassays determine that SbCNV-5 perturbs SCN growth, then this virus may be an effective biological control agent for SCN. In addition, because of its genome structure, it may also be amenable to conversion to a viral vector to study and alter nematode gene expression. These data will be useful to scientists interested in SCN biological control, SCN gene expression and invertebrate-infecting viruses.
Technical Abstract: Heterodera glycines, the soybean cyst nematode (SCN) is a subterranean root pathogen that causes the most damaging disease of soybean in the United States. A novel nematode virus genome, soybean cyst nematode virus 5 (SbCNV5), was identified in RNASeq data from SCN eggs and second-stage juveniles. The SbCNV5 RNA dependent RNA polymerase and RNA helicase domains have homology to pestiviruses in the Flaviviridae, suggesting SbCNV5 is a positive-polarity single-stranded RNA virus. SbCNV5 RNA was present in all nematode developmental stages indicating a transovarial mode of transmission, but it is also potentially sexually transmitted via the male. SbCNV5 was common in SCN laboratory cultures and in nematode populations isolated from the field. Transmission electron microscopy of sections from a female SCN shows virus particles budding from the endoplasmic reticulum and in endosomes. The size of the viral genome is 19,191 nucleotides, which makes it much larger than known pestiviruses. Additionally, the presence of a methyltransferase in the SbCNV5 genome is atypical for a pestivirus. When cDNA sequences were mapped to the genome of SbCNV5, a disproportionate number aligned to the 3’ non-translated region, suggesting that SbCNV5 produces a subgenomic RNA. Since subgenomic RNAs and methyltransferases do not occur in pestiviruses, we conclude that SbCNV5 is a new flavivirus infecting the soybean cyst nematode.