University of Maryland research shows fruit flies acquiring new DNA from bacterial infection
Researchers at the University of Maryland School of Medicine have published new research showing that a species of bacteria which infects fruit flies is capable of introducing parts of its genetic material into that of the fruit fly.
Researchers at the University of Maryland School of Medicine have published new research showing that a species of bacteria which infects fruit flies is capable of introducing parts of its own genetic material into that of the fruit fly.
The process, known as horizontal (or lateral) gene transfer, has been going on for some time, the scientists say, transferring genes from Wolbachia bacteria to the fruit flies.
Wolbachia are a common genus of intracellular bacteria that infect many types of insects, arthropods and nematode worms. In many cases the infection is thought to be endosymbiotic, or mutually beneficial, rather than parasitic. In some cases, the Wolbachia confer antiviral resistance to the host. Some host species cannot reproduce without the presence of Wolbachia in their cells.
Using a technique known as long-read DNA sequencing, the research established the presence of DNA segments from the Wolbachia in both the nuclear and mitochondrial DNA of the host fruit flies.
A report on the new work appeared in the open-access journal Current Biology on June 20.
Gene transfer controversy
Earlier work, dating to 2007, had established the transfer from the Wolbachia endosymbiont species known as wAna to the fruit fly species Drosophila ananassae as “extensive,” according to the authors. The site of the transferred DNA had been localized to chromosome four, contributing to an increase of size in this chromosome.
These arguments, however, were contested by some who asserted that the detected Wolbachia DNA sequences were merely contaminants in the mixture under examination and not a true part of the fruit fly genome.
The new research “revealed the integration of an entire [Wolbachia] bacterial genome at least once, with most portions present at least twice and smaller portions present in three to ten copies,” the authors say.
The researchers used a line of fruit flies that had been previously treated and cured of any infection. Long-read sequencing showed 4.9 mega-base pairs as Wolbachia DNA were transferred into the fruit fly nuclear DNA and 24 kilo-base pairs in the mitochondrial DNA.
The nuclear Wolbachia transfers (called “nuwts”) are less than 8,000 years old and found in at least two locations on chromosome 4, the researchers write. These contain “at least one whole-genome integration followed by rapid extensive duplication of most of the the genome with regions that have up to 10 copies.”
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Eric S. Tvedte et al. Accumulation of endosymbiont genomes in an insect autosome followed by endosymbiont replacement. Current Biology 32, 2786–2795( June 20, 2022)
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