A recent study has uncovered important genetic pathways in corn that enable its roots to branch out and search for water in the soil. The research indicates that corn varieties adapted to temperate climates, like those in the U.S. corn belt, demonstrate significant differences in their ability to grow roots towards water sources. This discovery could lead to the creation of corn types that are more resistant to drought.
Corn plants possess the ability to seek out moisture in the soil using their root tips; however, some varieties, particularly those bred for high yields in the U.S., seem to have lost some of this capability, as highlighted by a study led by Stanford University. Given that climate change is resulting in more frequent droughts, these findings offer valuable insights for breeding more resilient corn varieties.
The research, published in the journal Science, reveals the genetic factors influencing a process called root “hydropatterning,” which is how roots navigate towards water and steer clear of dry soil areas. The team discovered that ethylene, a hormone commonly known for aiding banana ripening, is also a crucial player in directing root growth towards moisture sources.
According to José Dinneny, the senior author of the study and a biology professor at Stanford, “Plants have an intricate ability to perceive where water resides in the soil, and the genes associated with this capability are vital for forming root systems that maximize efficient water absorption.”
Dinneny explained that corn plants utilize the ethylene gas produced by their roots to detect air spaces within the soil, enabling them to adjust their root branching in response to this hormone.
Roots that find water
The Dinneny lab had previously highlighted the remarkable sensitivity of corn roots in detecting water; however, the effectiveness of this capability relied significantly on the specific corn variety in question.
In this study, the researchers devised a new, streamlined method to investigate root water sensitivity, allowing them to examine the responses of 250 different corn varieties that represent the genetic diversity found in contemporary corn breeding. They observed that corn varieties adapted to tropical or subtropical regions, such as Mexico, excelled at forming new root branches in search of water and avoiding dry spots. In contrast, varieties from temperate regions in North America tended to grow roots erratically without differentiating between moist and dry soil. This research benefited from an international collaboration among various groups specializing in quantitative genetics, evolutionary biology, and root development.
The scientists suggested that the evolution of modern corn cropping in the U.S., typically grown in rich agricultural land, may have diminished these plants’ ability to effectively respond to water through root branching. They also noted that their findings correlate with field studies linking enhanced hydropatterning to deeper root systems.
Lead author Johannes Scharwies, a postdoctoral researcher in Dinneny’s lab, said, “Interestingly, the varieties that are more adept at locating water also develop deeper root structures. One possible explanation could be that by not wasting energy on root branches in areas devoid of water and nutrients, plants can focus more on growing deeper where water is likely to be found.”
Enhancing drought resistance
The researchers identified through genetic analyses that two hormones, auxin and ethylene, significantly influence how corn roots adapt to water availability. While auxin’s role in this process was already recognized, the involvement of ethylene emerged as a new finding. In experiments using thale cress (Arabidopsis thaliana), a common model plant in research, it was found that the signaling pathways of these two hormones work together: Auxin signaling encourages root branch growth towards water, while ethylene inhibits branching when the root encounters air.
Further investigation is required to fully understand the interactions within these genetic pathways before breeding corn varieties with more resilient root systems can be pursued. However, Scharwies emphasized the significance of examining localized responses at root tips.
“Each root tip functions as a sensor within the soil, foraging for water and nutrients and determining the direction for new root branches,” he stated. “We need to dedicate more time to studying these localized root reactions to grasp the overall plant behavior, and from this, we can work on developing crops that can better withstand drought conditions.”
Additional co-authors on the study include life sciences technician Taylor Clarke, lab manager Andrea Dinneny, and postdoctoral researcher Héctor Torres-MartÃnez from Stanford, along with collaborators from institutions such as the Howard Hughes Medical Institute, Iowa State University, Norwegian University of Life Sciences, University of Oslo (Norway), University of Nottingham (U.K.), and the University of North Carolina, Chapel Hill.
This research was supported by the Howard Hughes Medical Institute, U.S. Department of Energy, National Science Foundation, UKRI Frontiers Research, Biotechnology and Biological Sciences Research Council, European Research Council, Horizon Europe, and the Evotree project.
