CORVALLIS, Ore. A new study of the genetic basis of circadian rhythms the biological responses related to daily light exposure has found that a few minutes of light exposure in a fungus directly affects a huge range of its biological functions, everything from reproduction to coloring and DNA repair.
Prior to this, five "DNA binding sites" in this fungus were known to be responsible for gene activation by light exposure. Through advanced "high throughput" DNA sequencing, researchers discovered that light actually affects not just a few but more than 300 binding sites, ultimately controlling 2,500 of the 10,000 genes in the fungus Neurospora crassa.
The research, done by four universities in the U.S. and Germany, has revealed for the first time how specific metabolic pathways can be directly activated by light in this fungus, which has long served as a model to understand gene regulation by light, and circadian rhythms in animals and humans.
"You have one factor, light exposure, to start with," said Michael Freitag, an assistant professor of biochemistry and biophysics at Oregon State University. "In just a few minutes, this turns on genetic mechanisms that influence everything from spore development to stress response, pigmentation, carbon metabolism, the cell cycle, nitrogen regulation, DNA repair and many other functions."
This new research shows that light exposure affects 24 "transcription factors" that function as master genetic regulators, which in turn activate dozens of other genes that control everything from behavior to physiology in this fungus. For instance, if the fungus is grown in the dark, it will be white but with just two minutes of exposure to light, it turns orange and stays that way permanently, its gene for pigmentation having been activated.
Although not all of the genes involved are identical, many genes perform similar functions in humans, Freitag said, and the effect of light exposure
|Contact: Michael Freitag|
Oregon State University