Teosinte Today, Maize Tomorrow

Fig.1. This photo, published in 1919, shows the stages between a simple spike of Euchlaena mexicana and an ear of maize. (Credit: Journal of Agriculture)

Jeffrey Ross-Ibarra, associate professor and section chair of the Department of Plant Sciences at the University of California at Davis, and his team study maize and teosinte evolution. Researchers and post-docs - with backgrounds in plant biology and population biology and integrated genetics and genomics - focus on various research areas, such as genetics and genomics, how human and environmental factors have affected the adaptation and domestication of crops and more.

“Domestication (of the crop) has always struck me as a really exciting story because it’s a case where the evolution of the plant was directed by, or affected by, humans,” Ross-Ibarra said about how he became interested in maize and teosinte research.

Ross-Ibarra’s background in evolutionary biology seemed like a natural fit for engagement in this research area. 

“That adaptability struck me as exciting from an evolutionary standpoint, and interaction between maize and humans was also appealing. And then as a geneticist, there are lots of exciting crops, but there are very few crops ... that have the genetic tools that are available in maize,” he said.

And through a collaboration with Dolores Piperno, senior scientist and curator of South American Archaeology Emerita at the Smithsonian’s National Museum of Natural History, Ross-Ibarra was able to mix the study of genetics with evolution of the crop over time.

“Dolores has this really exciting project that she’s been (working on), growing teosinte in ancient climate conditions,” Ross-Ibarra said, “and the teosinte grown in those conditions starts to look more like maize in some important characteristics.”

The two study how the genes of maize and teosinte plants compare in past and current climate conditions. Looking at atmospheric and climatic data from 12,000 to 10,000 years ago, Piperno began growing teosinte, or “maize’s wild ancestor,” in those same conditions.

“So the question was, did wild corn look like it did today under what were pretty different environmental conditions of atmospheric (carbon dioxide) and temperature and precipitation,” Piperno said. 

Not only were Piperno and Ross-Ibarra able to note the morphological changes they saw, but through a mechanism called gene expression, they log genetic changes in response to the varied CO2 levels.

The work, however, is not only done through newer genetic methods or the study of phenotypic changes. Piperno and Ross-Ibarra’s research relies heavily on the use of scientific collections. Beyond using historical records and climate data to determine what conditions to cultivate the crops in, Piperno utilizes phytolith, starch grain and other modern-reference collections. Additionally, Ross-Ibarra and colleagues in his lab employ various maize collections from germplasm banks at the U.S. Department of Agriculture and the International Maize and Wheat Improvement Center. They even collect some of the maize and teosinte themselves. 

“It’s one of the advantages of maize because it’s been widely collected. It allows us access to a broader array of samples across geography and even time than we could possibly do ourselves,” Ross-Ibarra said.

He added, “In terms of collecting, while we have collected maize and teosinte in the field, it is  thanks to germplasm collections that we have more than 1,000 (samples) of diverse maize and teosinte.”

Through their current projects, Ross-Ibarra and Piperno are collecting even more. Ongoing collection work involves gathering maize and teosinte grown in past climate conditions. 

Ross-Ibarra and Piperno are currently writing up their research results for publication, and they hope to have a paper about their gene expression studies out within the coming months. Future research includes growing the crops in predicted future environmental conditions, according to Piperno.

Glossary

gene expression
The process by which instructions encoded in genes are used to synthesize gene products, such as proteins
phytolith
Microscopic structures made of silica, formed in plant cell walls, which are used to identify plant remains