Scientists studying ancient corncobs found at Antelope House, an Ancestral Puebloan ruin located at Canyon de Chelly National Monument, Arizona, have discovered a 1,000-year-old virus, the oldest plant virus ever reported. The discovery is described in a paper this week in the Journal of Virology.
Examining 1,000-year-old corncobs from an ancient ruin in Arizona, Peyambari et al found a previously unknown RNA virus. Image credit: Roossinck Laboratory, Pennsylvania State University.
Ancestral Puebloans who lived in Canyon de Chelly planted crops such as maize, beans and squash.
During the excavation of Antelope House by the National Park Service in the 1970s, more than two tons of plant refuse were recovered.
“It’s clear from these remains that maize was a major food source for the inhabitants,” said Professor Marilyn Roossinck, a researcher at Pennsylvania State University and the Samuel Roberts Noble Foundation.
“The maize remnants recovered at Antelope House consisted of cobs, ears with kernels, individual kernels, husks, leaves, shanks, stem portions and tassels.”
Using carbon 14 dating, Professor Roossinck and co-authors confirmed that the age of the ancient samples was about 1,000 years old.
While analyzing cobs, they isolated three nearly complete genomes of a previously unknown RNA virus.
This new virus, named Zea mays chrysovirus 1 (ZMCV1), is a member of Chrysoviridae, a family of double-stranded RNA viruses that infect plants and fungi.
“Chrysoviruses are persistent plant viruses that are transmitted from generation to generation through seeds and can remain in their hosts for very long time periods,” the scientists said.
“Persistent viruses typically do not cause disease and rarely are detected. ZMCV1 is the first chrysovirus described from maize,” Professor Roossinck added.
“When we analyzed modern corn samples, we found the same chrysovirus with only about 3% divergence from the ancient samples.”
“Most RNA viruses, with short generation times and error-prone replication, evolve rapidly. However, persistent viruses have very stable genomes.”
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Mahtab Peyambari et al. 2018. A 1,000-Year-Old RNA Virus. Journal of Virology 93: e01188-18; doi: 10.1128/JVI.01188-18
