Nematodes are small, widespread roundworms that infect the roots of numerous plants, causing over $100 billion in crop harm all over the world on a yearly basis. A new study has discovered that plants manipulate these organisms’ pheromones to reject infestations, offering scientists clues on how farmers could address these pests.
The research was conducted by Boyce Thompson Institute faculty member Frank Schroeder and analyzes a set of chemicals known as ascarosides, which the worms generate and secrete to communicate with each other. As explained in the study, which was published in the journal Nature Communications on January 10th, the scientists have demonstrated that plants also ‘talk’ to nematodes by metabolizing ascarosides and producing the metabolites into the soil again.
“It’s not only that the plant can ‘sense’ or ‘smell’ a nematode,” Schroeder said. “It’s that the plant learns a foreign language, and then broadcasts something in that language to spread propaganda that ‘this is a bad place.’ Plants mess with nematodes’ communications system to drive them away.”
The research is a second phase on the team’s previous work depicting that plants respond to ascr#18, the main ascaroside generated by nematodes that infect plants, by backing their own immune defenses, hence protecting them against numerous kinds of pests and pathogens.
The lead author, Murli Manohar, a senior research associate at BTI, said: “We also saw that when ascr#18 was given to plants, the chemical disappears over time.”
That finding, together with published studies that implies plants could modify pest metabolites, had the team theorize that “plants and nematodes interact via small-molecule signaling and alter one another’s messages,” according to Schroeder.
To verify that idea, the team of researchers treated three different plant species, Arabidopsis, wheat, and tomato, with ascr#18 and compared elements discovered in treated and untreated plants. They found three ascr#18 metabolites, with ascr#19 being the most plentiful.
The paper also discovered Arabidopsis and tomato roots produced the three metabolites into the soil, and that combination of 90 percent ascr#9 and 10 percent ascr#18 brought to the soil guided the nematodes away from the plant’s roots, hence diminishing the infection.
An Unexpected Combination
The team theorized that nematodes in the soil interpret the combination as a signal generated by plants already infected, to vanish, and impede overpopulation of a plant.
“This is a dimension of their relationship that no one has seen before,” said Manohar. “And plants may have similar types of chemical communication with other pests.”
Even though the combination of ascr#9 and ascr#18 could work as a crop defender, Schroeder said there should exist no prejudice to use straight ascr#18 crops.
“Ascr#18 mainly primes the plant to respond more quickly and strongly to a pathogen, rather than fully inducing the defensive response itself,” he said. “So, there should be no cost to the plant in terms of reduced growth, yield, or other problems.”
The researchers also demonstrated that plants metabolize ascr#18 through the peroxisomal β-oxidation pathway, a structure preserved by numerous plant species.
“This paper uncovers an ancient interaction,” Schroeder said. “All nematodes make ascarosides, and plants have had millions of years to learn how to manipulate these molecules.”