University of Georgia researchers studying rice genomes under a National Science Foundation Plant Genome Research Program award have identified the species first active DNA transposons, or "jumping genes."
The research is published in the Jan. 9 edition of the journal Nature.
In collaboration with researchers from Cornell, Washington University and Japan, geneticist Susan Wessler also discovered the first active "miniature inverted-repeat transposable element," or "MITE," of any organism.
Rice (Oryza sativa), an important food crop worldwide, has the smallest genome size of all cereals at 430 million base pairs of DNA. About 40 percent of the rice genome comprises repetitive DNA that does not code for proteins and thus has no obvious function for the plant. Much of this repetitive sequence appears to be transposons similar to MITEs. But like most genomes studied to date, including the human genome, the function of this highly repeated so-called "junk DNA" has been a mystery. The discovery of active transposons in rice provides startling new insights into how genomes change and what role transposons may play in the process.
Active DNA transposons can move new copies of DNA to different places in the genome. To hunt for active DNA transposons, the researchers made use of the publicly available genome sequences for two subspecies of rice, japonica and indica. The researchers reasoned that in plants where such transposons move actively there would be multiple copies of an almost identical sequence. If they could find the conserved sequences in the two rice genomes, then they could test for transposon movement in cell cultures because the number of elements should have increased over time.
Using this approach, the researchers found a repeated sequence of 430 base pairs that was identified as a candidate for an active MITE because of the high degree of sequence conservation among the copies. Recognizing that it shared common size and other characteristics with MITEs, they named it "mPing" for "miniature Ping." They calculated that the entire genome of japonica rice contained about 70 copies of mPing, while indica rice had about 14 copies. When they looked in indica rice cell cultures, the number of mPing elements increased, suggesting that it was indeed actively transposing.
It was puzzling to understand how mPing could transpose, since MITEs do not code for any proteins and are thus unable to move on their own. The researchers reasoned that there must be another "autonomous" transposon that encodes proteins, enabling itself and other related elements to move. To find this autonomous element, the researchers compared the mPing sequence with the japonica and indica rice genome sequences to look for longer, related elements. They found two candidates: a long version called the "Ping" sequence and another shorter sequence they named "Pong." Ping lacked functional coding sequence and was also found only in japonica rice as a single copy. On the other hand, Pong was present in high copy numbers in all varieties, contained appropriate coding sequences, and also increased in number along with mPing during cell culture. This led the researchers to suspect that Pong, not Ping, is the autonomous element that causes mPing to transpose. It is also possible, the researchers speculate, that Ping and Pong may co-activate mPing in some cases.
Wessler and her collaborators have shed new light on the idea that transposons may be instrumental in promoting the diversity of plants during domestication. Their work meshes with an idea, raised almost 20 years ago by Nobel Prize-winning maize geneticist Barbara McClintock, that transposons are part of the dynamic forces shaping plant genomes.
The research findings will help researchers unravel the events leading to the origin, spread, and disappearance of miniature transposons. Remarkably, MITEs make up a large part of the non coding DNA in plant genomes. Through studies of transposons such as MITEs, researchers will begin to understand the impact of so called "junk DNA" on the dynamic structure and function of the genomes of all organisms.
Microscope measures muscle weakness
16.11.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg
Good preparation is half the digestion
16.11.2018 | Max-Planck-Institut für Stoffwechselforschung
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences