Ancient Plant Viruses Took Root in Eurasia Before the Last Ice Age
As our ancient human ancestors were evolving and branching out across Eurasia and into the Americas, so too were the ancestors of a common plant virus genus.
Using genome sequencing, researchers in an international study published in Plant Disease have traced the ancestry of tymoviruses back to before the last Ice Age in Eurasia, and they likely arrived in the Americas around 15,000 years ago.
These new findings are reshaping what science knows about the history of plant disease and the role humanity plays in its spread. The results could also reveal new ways to mitigate risks and help keep crops healthy in the future.
Read More: How Plant ‘Vaccines’ Could Save Us From a World Without Fruit
What are Tymoviruses?
According to the study, tymoviruses are a genus of viruses that mostly attack dicot plants — plants that begin life with two embryonic leaves in their seed. Dicot plants can include flowering plants and crops.
These viruses are usually spread by leaf-eating beetles and through infected seeds or plant-to-plant contact. In the Americas and parts of Eurasia, tymoviruses can infect both wild and commercial plants, including those cultivated for food.
Possible crops impacted include those in the brassica family, such as cabbage, as well as seed oils, and produce like tomatoes, potatoes, eggplants, and even tobacco. In parts of Southeast Asia, Africa, and Australia, these viruses can also infect legumes.
Because these viruses can jump from wild plants to cultivated crops, they can be difficult to mitigate and manage, and greatly damage both natural and agricultural ecosystems. However, researchers may be getting closer to understanding more about these viruses.
Tracing Plant Virus Lineages
For the study, the research team, led by Adrian J. Gibbs, Emeritus Faculty at the Australian National University, performed genomic sequencing and phylogenetic analysis of 109 tymoviruses to reconstruct their evolutionary relationships and determine when they first evolved.
Based on the results, the team believes that the most recent common ancestor of all the tymoviruses in the genus existed before the last Ice Age (about 120,000 years to 11,500 years ago) and began by infecting Brassica species in Eurasia.
Further results found that some of the tymovirus lineages eventually reached the Americas about 15,000 years ago, suggesting the viruses predated human agriculture.
However, the team also noted that the tymoviruses that spread across more than one continent did so more recently, likely within the last 200 years or so, coinciding with the growth of agricultural trade and international exchange.
Protecting Future Crops
Beyond tracing lineages, the research team also filled in the gaps on how these viruses adapted over time. Based on the analysis, the team noted that the virus’s genes offered some flexibility. The gene associated with replication and protective structures showed signs of stabilizing selection, while the gene associated with movement between plant cells evolved more rapidly.
This flexibility, according to the study, may have been what helped these viruses adapt to new plants.
The results could help open more doors to plant virus research in the future. Based on what the research team has learned so far, experts may be able to anticipate and mitigate future risks of these viruses spreading and damaging or killing essential food sources.
Overall, the study found that although these viruses spread around the globe through more natural means, it was more recent human activity that really drove their spread.
Read More: Did Viruses Help Build Complex Life? A New Discovery Rekindles the Question
Article Sources
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