Researchers have brought an ancient viral genome back to life. The reconstituted viral genome came from 700-year-old caribou feces frozen within an ice patch in the subarctic. It showed that the virus displayed the ability to infect laboratory plants, according to the study in PNAS.
Resurrecting viruses from caribou droppings isn’t just Halloween fodder, such ancient viral genetic material can illuminate viral evolution. Intact samples are rarely isolated from the environment. Eric Delwart and colleagues analyzed the viral genetic material contained in a core drilled through layers of accumulated caribou feces up to 4,000 years old in an ice patch in Canada’s Selwyn Mountains. Caribou congregate on ice patches to escape insects and summer heat, and deposit feces containing partially digested plant material.
The authors isolated the complete genome of a DNA virus from a 700-year-old ice core layer that was distantly related to plant and fungi-infecting viruses, and a partial viral RNA genome that was related to an insect-infecting cripavirus. The appearance of the viral material in the fecal samples suggests that the viruses may have originated in plants eaten by the caribou or flying insects attracted to the material.
Using a reverse genetics approach, the authors reconstituted the genome of the DNA virus to confirm whether the virus might infect plants. Nicotiana benthamiana plants inoculated with the ancient viral DNA displayed evidence of infection including replication of viral DNA in inoculated and newly emerging leaves. According to the authors, cryogenically preserved environmental samples may preserve ancient viral genetic material for present day study.
Article: “Preservation of viral genomes in 700-y-old caribou feces from a subarctic ice patch,” by Terry Fei Fan Ng et al.
