by Dan Charles
October 4, 2011
NPR - The Food Blog
Scientists unlock another piece of the puzzle about the evolution of corn
Ever wonder where your food came from? No, I mean where it really came from — as in, where did humans first find the plants that we now depend on for survival, like potatoes or wheat or corn, and what made those plants such generous providers of food, anyway?
Last week, the world's leading experts on the origins of corn at the University of Wisconson-Madison, added a new twist to King Corn's still-evolving story. They pinpointed a particular mutation that happened 23,000 years ago in corn's nearest relative — a short, bushy plant called teosinte, which grows wild in Central America.
It was caused by a "jumping gene" — a little piece of DNA that's able, as its name suggests, to jump from one place to another on a plant's chromosomes. Now usually, jumping genes cause a bad or neutral effect. "But occasionally, they do something good," like in this case, says UWM plant geneticist John Doebley, who led the research team.
When this particular jumper, aptly named "Hopscotch," landed where it did, it rejiggered the plant's genetic machinery so that the plant no longer grew as a bush with lots of branches, but with one strong central stalk.
The plant also produced bigger ears with more kernels. In other words, it started to look more like the corn we count on.
The researchers published this bit of detective work on the web site of the journal Nature Genetics. The paper is tough going for non-specialists, but the University's News Service also put together a nice explanation for the rest of us.
Other mutations in teosinte, thousands of years later, made those kernels much easier to harvest and eat.
Central American farmers knew a good thing when they saw it. They saved those mutants, replanted them, selected the best offspring, and modern corn was born: A remarkable botanical food factory, with an unparallelled ability to turn sunlight, water, and soil nutrients into tall stalks and starchy grain.
Now, with corn dominating vast areas of the American Midwest, feeding ethanol factories and industrial-scale chicken and pork operations, the problem may be that we've become too good at growing it.
This is very interesting. especially in light of the fact that jumping genes, also called transposons, were first described in corn, by Barbara McClintock, who got a Nobel Prize for her discovery. She is the only woman to have ever received an unshared Nobel Prize in Medicine or Physiology.