DNA of 'Evolution Canyon' fruit flies reveals drivers of evolutionary change

July 07, 2014

Scientists have long puzzled over the genetic differences between fruit flies that live hardly a puddle jump apart in a natural environment known as "Evolution Canyon" in Mount Carmel, Israel.

Now, an international team of researchers led by scientists with the Virginia Bioinformatics Institute at Virginia Tech has peered into the DNA of these closely related flies to discover how these animals have been able to adapt and survive in such close, but extremely different, ecologies.

One reason lies in a startling abundance of repetitive DNA elements that, until recently, were considered little more than unused letters in a word game. The explanation will be published this week in the Proceedings of the National Academy of Sciences.

"We've come to understand that not all repeat sequences are junk DNA," said Pawel Michalak, an associate professor at the Virginia Bioinformatics Institute. "These repetitive sequences are increasingly being recognized as agents of adaptive change. We discovered a larger than expected amount of genetic variation in these repeating sequences between the fly populations and saw that the variation resulted in potentially functional differences in important biological processes, such as stress resistance and mating."

Even with migration, cross-breeding, and near-extinction of whole populations, the environment is the driving force in the fruit-fly gene pool in Evolution Canyon.

The two slopes of the canyon are about two football fields apart at their bases -- between 100 meters and 400 meters -- but the south-facing slope is tropical and may receive eight times as much sun, while the north-facing slope is darker, more like a European forest.

Animals genetically adapt depending on whether they live on the drier, hotter side of the canyon, or the more humid, cooler side.

Researchers extracted DNA from flies collected in the canyon, then identified and mapped repeating patterns of what genomics researchers call "transposable elements" -- DNA sequences capable of spontaneously changing position within the genome.

The scientists discovered flies taken from the opposing sides of the canyon displayed a significant difference in the contents and distribution of mobile elements.

The biological roles of these place-jumping, repetitive elements are mysterious.

They are largely viewed as "genomic parasites," but in this study, researchers found the mobile DNA can provide genetic novelties recruited as certain population-unique, functional enrichments that are nonrandom and purposeful.

"The first shocker was the sheer volume of genetic variation due to the dynamics of mobile elements, including coding and regulatory genomic regions, and the second was amount of population-specific insertions of transposable DNA elements," Michalak said. "Roughly 50 percent of the insertions were population unique."

More than 65 percent of disease-causing genes in humans are believed to have functional counterparts in the fly, including many genes involved in certain cancers, Alzheimer's and Parkinson's diseases, heart disease, and other medical conditions.

The discovery adds to current understanding of the biodiversity and ability of a species to adapt to rapidly changing climates and other environmental conditions.
The research was conducted by scientists with the Virginia Bioinformatics Institute, the departments of Biological Sciences and of Fish and Wildlife Conservation at Virginia Tech, Memorial Sloan-Kettering Cancer Center, and the Institute of Evolution at Haifa University, Israel.

Support was provided by the United States-Israel Binational Science Foundation and the Ancell Teicher Research Foundation for Genetics and Molecular Evolution.

Virginia Tech

Related DNA Articles from Brightsurf:

A new twist on DNA origami
A team* of scientists from ASU and Shanghai Jiao Tong University (SJTU) led by Hao Yan, ASU's Milton Glick Professor in the School of Molecular Sciences, and director of the ASU Biodesign Institute's Center for Molecular Design and Biomimetics, has just announced the creation of a new type of meta-DNA structures that will open up the fields of optoelectronics (including information storage and encryption) as well as synthetic biology.

Solving a DNA mystery
''A watched pot never boils,'' as the saying goes, but that was not the case for UC Santa Barbara researchers watching a ''pot'' of liquids formed from DNA.

Junk DNA might be really, really useful for biocomputing
When you don't understand how things work, it's not unusual to think of them as just plain old junk.

Designing DNA from scratch: Engineering the functions of micrometer-sized DNA droplets
Scientists at Tokyo Institute of Technology (Tokyo Tech) have constructed ''DNA droplets'' comprising designed DNA nanostructures.

Does DNA in the water tell us how many fish are there?
Researchers have developed a new non-invasive method to count individual fish by measuring the concentration of environmental DNA in the water, which could be applied for quantitative monitoring of aquatic ecosystems.

Zigzag DNA
How the cell organizes DNA into tightly packed chromosomes. Nature publication by Delft University of Technology and EMBL Heidelberg.

Scientists now know what DNA's chaperone looks like
Researchers have discovered the structure of the FACT protein -- a mysterious protein central to the functioning of DNA.

DNA is like everything else: it's not what you have, but how you use it
A new paradigm for reading out genetic information in DNA is described by Dr.

A new spin on DNA
For decades, researchers have chased ways to study biological machines.

From face to DNA: New method aims to improve match between DNA sample and face database
Predicting what someone's face looks like based on a DNA sample remains a hard nut to crack for science.

Read More: DNA News and DNA Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.