New research shows how gene function drives natural selection in important class of geneti...( Athens Ga. Transposons are the Clar...)

Athens, Ga. Transposons are the Clark Kents of a genome. Apparently mild-mannered and inconsequential but with sudden bursts of activity, these free-floating bits of genetic material have for millions of years been sneaking into the genetic maps of plants and animals, dramatically increasing a genome's size.

For years, researchers thought that most of this DNA was passive "junk" and knew little about it. New findings, however, are peeling back the odd and baffling world of transposons. Now, researchers at the University of Georgia have just found that natural selection on gene function is driving the evolution of one kind of transposable element called the LTR retrotransposon. (LTR refers to the "long terminal repeat"a repetition of a recognizable sequence of nucleotides, the chemical bases that make up strands of DNA.)

"The lab of Professor Jeff Bennetzen at UGA discovered that this class of mobile DNA comprises more than half of most plant genomes and has led the way in determining the extraordinary rates of both amplification and removal of this type of repetitive element," said Regina Baucom, a genetics post-doctoral research assistant at UGA and lead author of the research.

Understanding the evolutionary pressures between host genome and transposable element will in the future be of interest to those studying retroviruses, which evolved from retrotransposons. There are a number of animal and human diseases caused by retroviruses including HIV/AIDS, avian leukosis and feline leukemia.

"Because LTR retrotransposons are abundant and impact host genomes, we wanted to determine the influence of natural selection on their evolution," said Baucom. "We find that the genes involved in their replication are subject to Darwinian evolutionthe same evolutionary processes that affect species."

Other authors of the paper just published in the online version of the journal Genome Research, were Jeff Bennetzen, in wh
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