Scientists Weaponize Plant Hormones to Trick Parasitic Weeds Into Early Death

In the harsh farmlands of sub-Saharan Africa, where every harvest can mean the difference between sustenance and hunger, a silent battle rages beneath the soil. Parasitic weeds—nature’s ruthless freeloaders—have long devastated critical food crops by draining them of nutrients before they can properly grow. Now, researchers at UC Riverside have discovered a deceptively simple strategy that could give farmers a fighting chance: tricking these agricultural vampires into committing “suicide.”

The technique, detailed in a January 17 publication in the journal Science, exploits a unique class of plant hormones called strigolactones that exhibit an unusual behavior most plant hormones don’t share.

“Most of the time, plant hormones do not radiate externally — they aren’t exuded. But these do,” explained UCR plant biologist and paper co-author David Nelson. “Plants use strigolactones to attract fungi in the soil that have a beneficial relationship with plant roots.”

This external signaling has been hijacked by invasive parasitic weeds, which use strigolactones as a chemical beacon indicating a potential host is nearby. The weeds’ seeds can lie dormant in soil for years, waiting for this signal before germinating and attaching to crop roots.

The UCR team’s insight was elegantly brutal in its simplicity: use the weeds’ own biology against them.

“These weeds are waiting for a signal to wake up. We can give them that signal at the wrong time — when there’s no food for them — so they sprout and die,” Nelson said. “It’s like flipping their own switch against them, essentially encouraging them to commit suicide.”

Across food-insecure regions in Africa and parts of Asia, farmers have watched helplessly as entire fields of staples like rice and sorghum are consumed by these parasites. Traditional methods to combat these weeds have proven largely ineffective, as the parasites establish themselves underground before farmers even realize they’ve been invaded.

To better understand strigolactone production, the research team, led by Yanran Li (formerly at UCR and now at UC San Diego), developed an innovative system that turns ordinary microorganisms into hormone factories. By engineering E. coli and yeast cells to produce these chemicals, they recreated the biological pathways necessary for hormone synthesis in a controlled environment.

This approach didn’t just help researchers understand how the hormones work—it could potentially lead to cost-effective methods for producing large quantities of these valuable chemicals for field application.

The team also made progress in understanding the enzymes responsible for producing strigolactones, identifying a key metabolic branch point that appears to have been crucial in the evolution of these hormones from internal plant regulators to external signaling molecules.

“This is a powerful system for investigating plant enzymes,” Nelson noted. “It enables us to characterize genes that have never been studied before and manipulate them to see how they affect the type of strigolactones being made.”

While the primary focus is on agricultural applications, the findings could have broader implications. Some studies suggest strigolactones might have potential as anti-cancer or anti-viral agents. There’s also interest in their possible role in combating citrus greening disease—a condition currently devastating Florida’s citrus industry.

The work comes amid growing concerns about global food security, with climate change expected to exacerbate challenges in agricultural production worldwide. Student researcher Annalise Kane, who served as co-first author on the study, represents the next generation of scientists tackling these problems.

The research was supported by the NSF-funded Plants3D traineeship program at UCR, which is led by distinguished professor and geneticist Julia Bailey-Serres.

“The program is so exciting because it helps students learn to use the most cutting-edge technologies to increase crop yields and nutritional value, while also helping themselves professionally,” Bailey-Serres said.

Real-world application of the “weed suicide” strategy remains an open question. The team is continuing to refine their approach before field testing.

“We’re testing whether we can fine-tune the chemical signal to be even more effective,” Nelson said. “If we can, this could be a game-changer for farmers battling these weeds.”

For struggling farmers across the developing world, such innovations can’t come soon enough. As global populations continue to rise and arable land becomes scarcer, finding sustainable ways to combat agricultural pests has never been more urgent. By turning parasitic plants’ own signaling systems against them, these researchers may have found an elegant solution hidden in plain sight—within the very biology of the plants themselves.