Flavivirus in Soybean Cyst Nematode

Viruses of the family Flaviviridae have been well documented as the cause of major vector-borne and hepatic diseases in humans. The family currently comprises four genera: Flavivirus, Hepacivirus (Hepatitis B Viruses), Pestivirus and a newly proposed genus Pegivirus.

Viruses of the Flaviviridae have a wide host range that includes both vertebrates and invertebrates. Until recently, the only invertebrate hosts for the flaviviruses were mosquitoes and ticks, which contained viruses exclusively found within the genus Flavivirus. The remaining genera in the family—Hepacivirus, Pegivirus and Pestivirus—are exclusively found in mammals and their diversity has greatly expanded with recent virus discoveries in various mammalian species including bats, dogs, horses, pigs, ruminants and rodents.

Yet, nature always has some surprises in store.
Recently, a flavi-like virus, Soybean Cyst Nematode Virus 5 (SbCNV-5), was discovered from the soybean cyst nematode (Heterodera glycines)[1]. The soybean cyst nematode is a subterranean root pathogen that causes the most damaging disease of soybean in the US.

This novel nematode virus genome was identified in RNA sequencing data from both soybean cyst nematode eggs and second-stage juveniles. Some features of the Soybean Cyst Nematode Virus 5 had homology to pestiviruses in the family Flaviviridae.

The size of the viral genome was exceptionally long (23kb and 19kb, respectively) genomes making it larger than other known pestiviruses. Additionally, the presence of a methyltransferase in the Soybean Cyst Nematode Virus 5 genome is atypical for a pestivirus.

The scientists conclude that Soybean Cyst Nematode Virus 5 is a new flavivirus infecting soybean cyst nematodes.

[1] Bekal et al: A novel flavivirus in the soybean cyst nematode in Journal of General Virology – 2014

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