Above ground, plants grow toward the sun. Below ground, plants tunnel into the ground. As the roots absorb water and nutrients from the surrounding soil, they grow and spread to develop the distinct architecture of the root system. The architecture of the root system determines whether the roots remain in shallow soil layers or are more erect and reach deeper soil layers. Root systems are central to plant survival and production, determining the plant’s access to nutrients and water and, therefore, the plant’s ability to withstand extreme weather such as nutrient deficiencies and drought.

Now, Salk scientists have determined how a well-known plant hormone is important in controlling the angle of root growth. The study, published in Sales reports On February 13, 2024, for the first time, a hormone called ethylene has been shown to be involved in regulating the lateral root angles that make up the root system — findings that are a revelation to plant scientists who Improves the root system.

Researchers at Salk’s Harnessing Plants Initiative now plan to target the ethylene signaling pathway in their efforts to engineer plants and crops that can withstand the environmental stresses of climate change and drought, as well as carbon dioxide. The oxide can be extracted from the atmosphere and stored deep underground. climate change.

“Deeper roots lead to more durable storage of carbon in the soil and can make plants more resistant to drought, so the ability to control how deep roots grow is important to scientists.” for those looking to engineer better root systems is really exciting,” says senior author Wolfgang Bosch, Prof. , executive director of the Harnessing Plants Initiative, and Hayes Chair in Plant Science at Salk. “We are particularly excited that the pathway we found is conserved in many plant species, meaning that our findings can be used to improve root architecture in all land plants, including food, feed and fuel crops. can be widely applied to.”

Environmental factors—such as average rainfall or the abundance of certain nutrients—can affect the shape of a plant’s root system. The angle at which the roots grow produces different results in the overall root architecture, with horizontal root angles creating a shallow root system and vertical root angles creating a deep root system. But scientists do not clearly understand how these root angles are determined at the molecular level.

Plant hormones such as auxin and cytokinin have been linked to root growth angle in the past, but the mechanisms of this relationship are not well understood. In search of molecules and pathways involved in regulating root growth angle, the team examined genetics. Arabidopsis thaliana — a small flowering weed in the mustard family — changes in the root system in response to thousands of molecules.

“We found that this molecule, mebendazole, was causing the roots to grow more horizontally,” says first author Wenrong He, a former postdoctoral researcher in Bosch’s lab. “When we looked at which target protein or pathway mebendazole was interacting with to have this effect, we discovered that it was ethylene signaling — and that ethylene was thus involved in the architecture of the root system. playing an important role, was really interesting.”

The team observed that genes throughout the ethylene signaling pathway were activated in response to mebendazole, and that this pathway was causing changes in root development. Biochemical studies of this relationship revealed that mebendazole inhibits the activity of a protein kinase called CTR1. This enzyme negatively regulates ethylene signaling, which in turn promotes a shallow root system.

“Since ethylene signaling is a widely conserved process in land plants, targeting the ethylene pathway is a very promising technique for root system engineering,” Bush says. “Hopefully, we will now be able to use this tool to make crop species more resilient and create ideal salicy plants.® That sequesters more carbon underground to help fight climate change.”

The new implication of ethylene in root system architecture prompts new questions, including whether there is another molecule that — unlike mebendazole — deepens the root system, or if it is already well established. The variously cataloged ethylene signaling pathways contain specific genes that can be largely targeted. Effectively promote deep rooting in crops and succulent plants.

Other authors include Hai An Truong, Ling Zhang, Min Cao, and Kaizhen Zhong of Salk. Neil Arakawa of UC San Diego; Yao Xiao of Scripps Research Institute; and Yingnan Hou of UC Riverside and Shanghai Jiaotong University in China.

This work was supported by Salk’s Harnessing Plants Initiative, a Salk Women and Science Special Award, a Pioneer Fund Postdoctoral Scholar Award, National Institutes of Health (NIH-NCI CCSG: P30 CA01495, NIH-NIA San Diego Nathan Shock Center P30 AG06865 ) was supported by , the Chapman Foundation, and the Helmsley Charitable Trust.