Comparing Genes to Understand the Domestication of Corn

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 in Plant Science, detailing a new biotech tool that harnesses cutting-edge techniques to produce fertile transgenic teosinte plants for the first time.

Humans began domesticating teosinte, a wild grass native to Mexico, roughly 10,000 years ago. Each teosinte plant yields only up to a dozen kernels, which are tough and contain less nutrients than modern corn. So people selected individual teosinte plants for higher yields, eventually developing new varieties with their own unique traits.

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.