Scientists Pinpoint Exact Mutation That Turned Corn Into A Power Crop


10,000 years ago, the teosinte plant went through a mutation that would eventually change the world. The husks that surrounded its golden grains disappeared and the plant gradually evolved into one of the planet's top agricultural commodities.

Now researchers from the University of Wisconsin-Madison revealed that it only took a change in a single letter in the DNA of the corn's ancestor that made the corn the power crop that it is today.

For their study published in the journal Genetics on May 4, John Doebley, from the UW-Madison, and colleagues reported that during the domestication of corn, one single change in the nucleotide of the teosinte glume architectural gene (tga1) removed the hard and inedible casing of the wild grass exposing its edible golden kernel.

Doebley, who has been studying how maize evolved, said that a large chunk of the world economically depends on corn showing how important the genetic change was.

Maize, the plant where the corn grows, and teosinte may not look as if they belong to the same family tree. Maize is tall and stalked with massive ears that contain hundreds of kernels. Teosinte, on the other hand, is bushy and branched. It also has miniscule ear with stronger resemblance to wheat and only contain between 10 and 12 kernels.

Research, however revealed that the roots of the maize can be traced to the weedy form of teosinte in a Mexican valley. The researchers investigated six potential mutations in the gene that could be attributed to the change by studying large numbers of teosinte and corn genomes. They learned that there was only one mutation that was consistently different between the plants.

Doebley and colleagues found out that the single letter change paved way to a difference in the protein produced by tga1. The small change in the DNA led to a big change in the plant's form and a change to the function of one protein that controls the action of the genes caused the dramatic effect.

"Genetic mapping and phenotypic data show that tga1, without a contribution from not1, controls the difference in covered vs. naked kernels. No trait differences could be associated with the maize vs. teosinte alleles of not1," the researchers wrote in their study. "Our results document how morphological evolution can be driven by a simple nucleotide change that alters protein function." 

Photo: Erfan A. Setiawan | Flickr

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