This discovery contributes to understanding that evolution is not strictly conducted from parent to offspring

A fruit fly genome is not just made up of fruit fly DNA – at least for a fruit fly species. New research from the Institute for Genome Sciences (IGS) at the University of Maryland School of Medicine (UMSOM) shows that a species of fruit fly contains entire genomes of a type of bacteria, this making it the largest transfer of genetic material from bacteria to animal ever. discovered. The new research also sheds light on how this happens.

IGS researchers, led by Julie Dunning Hotopp, PhD, Professor of Microbiology and Immunology at UMSOM and IGS, used new long-read gene sequencing technology to show how genes from the bacterium Wolbachia incorporated into the fly genome until recently. is 8 000 years old.

Researchers say their findings show that, unlike Darwin’s finches or Mendel’s peas, genetic variation is not always small, incremental and predictable.

Scientist Barbara McClintock has first identified “jumping genes ” in years 1940, such as those that can move or transfer into the genomes of other species. However, researchers continue to discover their value in evolution and health.

“We did not previously have the technology to unequivocally demonstrate these genomes within genomes showing such extensive lateral gene transfer from bacteria to fly,” explained Dr. Dunning Hotopp. “We used state-of-the-art long-read gene sequencing to make this important discovery.”

The new research was published in the June issue of Existing Biology.

In the past, researchers had to break DNA into small pieces in order to sequence it. Then they had to put them together, like a puzzle, to examine a gene or a segment of DNA. Long-read sequencing, however, allows sequences of more than 100 000 DNA letters, turning a million piece puzzle into a puzzle designed for toddlers.

In addition to the long reads, the researchers validated the junctions between the integrated bacteria genes and the host fruit fly genome. To determine if the bacteria’s genes were functional and not just DNA fossils, the researchers sequenced RNA from fruit flies looking specifically for RNA copies created from templates of the inserted bacterial DNA. They showed that the bacteria’s genes were encoded in RNA and were edited and rearranged into newly modified sequences indicating that the genetic material is functional.

An analysis of these unique sequences revealed that the bacteria’s DNA integrated into the fruit fly genome within the past 8 000 years – exclusively in chromosome 4 – increasing the size of the chromosome by constituting approximately 20% of chromosome 4. Integration of the complete bacterial genome supports a DNA-based rather than an RNA-based integration mechanism.

Dr. Dunning Hotopp and colleagues have discovered a complete bacterial genome of the common bacterium Wolbachia transferred into the genome of the fruit fly Drosophila ananassae. They also found almost a second complete genome and much more with nearly 10 copies of certain regions of the bacterial genome.

“There have always been skeptics about lateral gene transfer, but our research clearly demonstrates for the first time the mechanism of integration of Wolbachia DNA into the genome of this fruit fly. ,” said Dr. Dunning Hotopp.

“This new research shows basic science at its best,” said Dean E. Albert Reece, MD, PhD, MBA, who is also executive vice president of medical affairs, UM Baltimore, John Z. and Akiko K. Bowers Professor Emeritus, and dean of the University of Maryland School of Medicine. “This will contribute to our understanding of evolution and may even help us understand how microbes contribute to human health.”

Wolbachia is an intracellular bacterium that infects many styles of insects. Wolbachia transmits its genes maternally through female eggs. Some research has shown that these infections are more mutualistic than parasitic, conferring benefits on insects, such as resistance to certain viruses.

Sequenced just three years before the human genome, fruit flies have long been used in genomic research due to the abundance of common fly-human genetic similarities. In fact, 75% of the genes responsible for human diseases are also found in the fruit fly.

Authors from the Institute of Genome Sciences, University of Maryland Faculty of Medicine, second in writing, include Eric S. Tvedte Mark Gasser Xuechu Zhao, Laboratory Research Specialist Luke J. Tallon, Executive Scientific Director, Maryland Genomics Lisa Sadzewicz, Executive Director, Maryland Genomics Administration Robin E. Bromley, Laboratory Research Supervisor Matthieu Chung John Mattick, PostDoc, and Benjamin C. Sparklin.

Eric S. Tvedte is currently NCBI affiliate at the National Institutes of Wellness, Bethesda, MD Mark Gasser is currently affiliated with the Applied Physics Laboratory, Johns Hopkins University, Laurel, MD Matthew Chung is currently affiliated with the National Institute of Allergy Symptoms and Infectious Diseases of the Countrywide Institutes of Overall health, Bethesda, MD and Benjamin C. Sparkin is currently affiliated with AstraZeneca, Rockville, MD.

This work was supported by the U grant19AI110820 from the Nationwide Institute of Allergy and Infectious Illnesses and the R75 grant CA206188 of the Countrywide Institutes of Well being.

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