Amoebidium appalachense, a protist closely related to animals, harbors the remnants of ancient giant viruses woven into its own genetic code, according to new research led by Queen Mary University of London. The findings shed light on how complex organisms may have acquired some of their genes and highlights the dynamic interplay between viruses and their hosts.
Amoebidium appalachense is a unique model to understand the hybrid origins of eukaryotic DNA. Image credit: Alex de Mendoza.
In the current study, Dr. Alex de Mendoza Soler and colleagues sequenced and analyzed the genome of Amoebidium appalachense, a unicellular parasite originally isolated from the cuticle of freshwater arthropods.
They found a surprising abundance of genetic material originating from giant viruses — some of the largest viruses known to science.
These viral sequences were heavily methylated, a chemical tag that often silences genes.
“It’s like finding Trojan horses hiding inside Amoebidium appalachense’s DNA,” Dr. de Mendoza Soler said.
“These viral insertions are potentially harmful, but Amoebidium appalachense seems to be keeping them in check by chemically silencing them.”
The researchers then investigated how widespread this phenomenon might be.
They compared the genomes of several Amoebidium appalachense isolates and found significant variation in the viral content.
This suggests that the process of viral integration and silencing is ongoing and dynamic.
“These findings challenge our understanding of the relationship between viruses and their hosts,” Dr. de Mendoza Soler said.
“Traditionally, viruses are seen as invaders, but this study suggests a more complex story.”
“Viral insertions may have played a role in the evolution of complex organisms by providing them with new genes.”
“And this is allowed by the chemical taming of these intruders DNA.”
Furthermore, the findings in Amoebidium appalachense offer intriguing parallels to how our own genomes interact with viruses.
Similar to Amoebidium appalachense, humans and other mammals have remnants of ancient viruses, called endogenous retroviruses, integrated into their DNA.
While these remnants were previously thought to be inactive junk DNA, some might now be beneficial.
However, unlike the giant viruses found in Amoebidium appalachense, endogenous retroviruses are much smaller, and the human genome is significantly larger.
Future research can explore these similarities and differences to understand the complex interplay between viruses and complex life forms.
The team’s findings appear today in the journal Science Advances.
_____
Luke A. Sarre et al. 2024. DNA methylation enables recurrent endogenization of giant viruses in an animal relative. Science Advances 10 (28); doi: 10.1126/sciadv.ado6406
This article was adapted from an original release by Queen Mary University of London.
Source : Breaking Science News