Do you like corn? Thanks intersection | Popular science

The story of corn is anything but corny. It’s a story about resilience and survival, all because corn was selfish (genetically). Corn and his numerous varieties have rapidly adapted to different types of climates over thousands of years while feeding countless generations in the Americas. Now a team of scientists believe that a genetic process called selfish inheritance may be responsible for this rapid evolution. The findings are described in a study published Aug. 7 in the journal Nature, and could have applications beyond agriculture.

The corn maze

About 9,000 years agocorn was first domesticated by indigenous peoples in the Mexican lowlands. About 5,000 years later, corn was crossed with another type from the Mexican highlands called corn teosinte mexicana. The mixing resulted in an adaptability to cold, and the crop quickly spread across the continent. Scientists are still not entirely sure how it managed to achieve all this so quickly.

[Related: The bizarre botany that makes corn a fruit, a grain, and also (kind of) a vegetable.]

“Civilizations depend on the domestication of key crops such as corn, and like humans, crops often undergo multiple rounds of evolution. For example, modern humans have interbred with Neanderthals in Europe and Denisovans in Asia,” study co-author and geneticist from Cold Spring Harbor Laboratory (CSHL). Rob Martienssen tells Popular science. “Modern maize was only crossed with teosinte mexicana 4,000 years ago and acquired several useful genes in a very short time.”

Martienssen is studying RNA interferencethe process by which small RNAs silence genes and can do so manipulate how the genes are expressed. Geneticist from the University of Wisconsin Jerry Kermicle offered Martienssen with a curious observation. When crossing semi-sterile teosinte hybrids with traditional corn, he noticed that their offspring behaved unusually. With normal inheritance, the offspring should eventually become completely infertile or fertile. Instead, every time Kermicle crossed the hybrids with corn, all the resulting offspring were semi-sterile. The answer may be a bit selfish.

Selfish inheritance

Previously, scientists thought that selfish genetic systems – or gene drives– were quite rare in nature.

‘Finding a specimen in corn suggested that [gene drives] could have played an important role in the mysterious origin of corn,” says Martienssen.

In the new studyMartienssen and CSHL graduate student Ben Berube sequenced the genomes of hundreds of pollen grains from the semi-sterile offspring. They found that the same pieces of the teosinte genome were present in each piece: one on chromosome 5 and one on chromosome 6. These were always inherited, so the genes responsible for this outcome must be located somewhere around those chromosomes.

They looked more closely at chromosome 5 and found a gene called Dicer-like 2. This gene makes a group of small RNAs that are always present in the semi-sterile hybrids, but not in traditional corn. This data allowed the team to identify a ‘selfish’ genetic system which they call the ‘selfish’ genetic system Teosinte Pollen Drive. The greedy system eliminates the competing pollen grains who lack this gene drive. The maize-teosinte hybrids then pass on certain traits more often to men than to women.

“The most surprising finding was that modern maize had become ‘immune’ to selfish inheritance, through mutation of a single gene in pollen that could be traced from wild grasses, through tropical maize and popcorn, all the way to modern maize,” says Martienssen . “This suggests that the selfish genetic system has been active for a long period of time.”

‘The Neanderthal of corn’

The findings could have broader implications for the agricultural sector, as well as reveal more about the process of domestication of all living things. If teosinte mexicana is what Martinssen calls ‘the Neanderthal of maize’, then it is ability to crosswe may have found a missing link in this selfish gene drive that could explain how corn was able to thrive across America. It could also explain why some small RNAs are so common in sperm cells of plants and animals, including humans.

[Related: Mummified poop reveals a diverse ancient Caribbean diet.]

“Basic discoveries in plant biology can have implications far beyond agriculture. The small RNAs we describe in corn pollen are powerful agents of inheritance and evolution, and similar small RNAs are found in sperm cells of animals, including ours,” says Martienssen. “It is possible that they played a similar role in animal domestication, and perhaps even in human evolution.”