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 Kernels of corn on the left contrast sharply with the grain produced by teosinte, pictured on the right. Humans began domesticating teosinte thousands of years ago as they developed modern corn. Image courtesy of Kan Wang. Larger image. AMES, Iowa – It’s almost like time travel. Iowa State University scientists are learning how to peer back through millennia of domestication to learn how a wild grassy plant known as teosinte developed into corn, the modern cash crop grown across the globe. The research allows scientists to compare genes in corn against its wild ancestor, which could help plant breeders identify advantageous traits that may have been bred out of teosinte over the centuries. The researchers published their findings recently in the academic journal Frontiers of Plant Science, detailing a new biotech tool that harnesses cutting-edge techniques to produce fertile transgenic teosinte plants for the first time. But some of the original genetic material from teosinte got lost along the way. Identifying this genetic material could help breed better corn today, or at least offer scientists clues about how to better harness the genetic diversity of corn, said Jacob Zobrist, a graduate student in agronomy and first author of the study. “We don’t know what we don’t know about those ancestor traits,” Zobrist said. “It’s our hope to identify traits in the wild ancestor that would be helpful for modern maize. Those traits could include disease resistance and stress resistance as well as nutrient content and maybe even improving growing and flowering times.” The new study details how the scientists discovered a robust callus induction and regeneration protocol using whorl segments of seedlings germinated from mature seeds. That means the researchers were able to produce callus tissue, which is similar to stem cells that are undifferentiated and haven’t yet developed into variant cells.These undifferentiated callus cells are amenable to the introduction of new DNA via transgenic technology. Using gene editing technology such as CRISPR, researchers can now target specific teosinte genes and switch them off, giving them a new level of understanding of how the wild plant was domesticated into a global staple crop. New biotech tool expands understandingIt's a little bit like reaching back through time to see what traits ancient plant breeders selected for, said Kan Wang, the Global Professor of Biotechnology in agronomy and corresponding author of the study. Wang’s laboratory began studying teosinte in 2010, and she said the new publication represents a major step forward in understanding teosinte and the origins of modern corn. “This is going to open up a lot of possibilities for many people who are interested in either basic research or agricultural applied research,” said Wang, who is currently a rotating program director for the National Science Foundation. Wang credited Zobrist’s contributions for making the overall study a success. Zobrist joined Wang’s lab in 2018 with support from the National Science Foundation’s Predictive Plant Phenomics Fellowship, which provides innovative data-enabled science and engineering training to students with experience in plant sciences. Zobrist’s contribution to the research was to make the transformation repeatable by optimizing the culture medium used to grow the teosinte plants. Zobrist found a new tissue-culture regimen that included plant hormones in the growth medium. “We’ve developed the tool, and without it, it’s very difficult to understand teosinte. One of the main players who made that happen was Jacob. He did critical work,” Wang said. Zobrist is a native of Spencer, Iowa. He completed his undergraduate studies at Iowa State before taking a job with Corteva for five years and then returning to Iowa State to begin graduate work in 2017. “I am fortunate to be a graduate student at a time when research and genome editing technologies are progressing at a rate that allowed me to put all of the pieces together into a functional and reproducible transformation method,” he said. Other co-authors of the study include Susana Martin-Ortigosa, Keunsub Lee, Qing Ji and Mercy Azanu, all current or former members of Wang’s lab. Indigenous farmers bred the plant for hardiness and better food quality
This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts. Researchers have identified corn genes that were preferentially selected by Native Americans during the course of the plant's domestication from its grassy relative, teosinte, (pronounced "tA-O-'sin-tE") to the single-stalked, large-eared plant we know today. The study revealed that of the 59,000 total genes in the corn genome, approximately 1,200 were preferentially targeted for selection during its domestication. The study, by University of California, Irvine's Brandon Gaut and his colleagues, appears in the May 27 issue of the journal, Science. Understandably, a primary goal of teosinte domestication was to improve the ear and its kernels. A teosinte ear is only 2 to 3 inches long with five to 12 kernels--compare that to corn's 12-inch ear that boasts 500 or more kernels! Teosinte kernels are also encased in a hard coating, allowing them to survive the digestive tracts of birds and grazing mammals for better dispersal in the wild. But, for humans, the tooth-cracking coating was undesirable so it was selectively reduced…and reduced…and reduced…until all that remains is the annoying bit of paper-thin, translucent tissue that sometimes sticks between the teeth when one munches corn on the cob. To analyze the genes of modern corn and its ancestral teosinte, Gaut and his coworkers used relatively new genomic techniques to determine the DNA sequence of 700 gene bits in the two plants and used "population genetics," the study of genetic variation, to compare them. "These results will provide important insights to modern corn breeders in their quest to establish hardier, higher-yielding corn plants," said Gaut. "The scientific approach will also be useful in the study of other domesticated organisms, plants and animals alike." This work generally confirms the idea that corn went through a "population bottleneck," or a period when a significant portion of corn’s genetic diversity was lost, which typically marks a domestication event. Calculations using these data reveal that fewer than 3,500 teosinte plants may have contributed to the genetic diversity in modern corn. Between 6,000 and 10,000 years ago, Native Americans living in what is now Mexico began domesticating teosinte, or the "grain of the gods," as the name has been interpreted to mean. Scientists cannot yet say how long this domestication process took, but they do know that around 4,500 years ago, a plant recognizable as today's corn was present across the Americas. So, thousands of years before Gregor Mendel postulated his theories on genetics and heredity, indigenous Americans were breeding corn to select for desirable traits. By selectively breeding each generation, ancient farmers drastically changed teosinte's appearance, yield, grain quality and survivability—culminating in today's "corn." In fact, teosinte is so unlike modern corn, 19th century botanists did not even consider the two to be related. "This is a very exciting finding," said Jane Silverthorne of the National Science Foundation's (NSF) biology directorate, which funded the project. "We are beginning to have a much clearer picture of what happened to the genes responsible for the structure of today’s corn plant." A broad understanding of the genes present in modern-day corn will provide a foundation for improving it as well as its cousin cereal crops. Target goals include yield increases, improved insect and pathogen resistance, enhanced environmental adaptability, and improved nutritional value. To that end, sequencing the entire genome of corn is also critical to improving the crop and its value in human subsistence. According to the U.S. Department of Agriculture (USDA), nearly 12 billion bushels of corn were harvested in the United States in 2004, which will be used for a diverse array of products including livestock feed, ethanol and plastic consumer items, as well as food. The National Corn Growers Association reported that 2003 corn exports were valued at $4.5 billion. Supported by NSF's Plant Genome Research Program, this collaborative project included Gaut and co-workers at the University of California, Irvine, together with scientists from the USDA-Agricultural Research Service, the University of Missouri and the University of Wisconsin. NSF is part of an interagency program along with the U.S. Department of Energy and the USDA that plans to support the sequencing of the corn genome over the next three years. -NSF- Media Contacts Program Contacts Principal Investigators The U.S. National Science Foundation propels the nation forward by advancing fundamental research in all fields of science and engineering. NSF supports research and people by providing facilities, instruments and funding to support their ingenuity and sustain the U.S. as a global leader in research and innovation. With a fiscal year 2022 budget of $8.8 billion, NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and institutions. Each year, NSF receives more than 40,000 competitive proposals and makes about 11,000 new awards. Those awards include support for cooperative research with industry, Arctic and Antarctic research and operations, and U.S. participation in international scientific efforts.
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What is the reason proposed by G Beadle why teosinte was eventually domesticated into modern corn?
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