Researchers discover natural product that could lead to new class of commercial herbicide
A garden can be a competitive environment. Plants and microorganisms invisible in the soil all need valuable space to grow. And to gain this space, a microbe can produce and use chemicals that kill its plant competitors. But the germ also needs immunity from its own poisons.
By searching for this protective shield in microorganisms, especially the genes that can make it, a team of UCLA engineers and scientists discovered a new type of potentially highly effective weed killer. This discovery could lead to the creation of the first new class of commercial herbicides in more than 30 years, an important result as weeds continue to develop resistance to current herbicide regimes.
Using a technique that combines data science and genomics, the team discovered the new herbicide by looking for the genes of thousands of fungi to find one that could provide immunity against fungal poisons. This approach is known as "genome extraction driven by resistance genes".
The study, which was published in Nature, also highlights the potential of this genomics-based approach for medicine, with applications ranging from new antibiotics to advanced cancer drugs.
"Microorganisms are very smart to protect themselves from the powerful molecules they make to kill their enemies," said Yi Tang, co-principal investigator of the study and professor of chemical and biomolecular engineering, chemistry and biochemistry at UCLA. "The presence of these resistance genes provides a window on the functions of molecules and can allow us to discover these molecules and apply them to various applications in human health and agriculture.
For example, if a resistance gene that protects a microorganism from an antibacterial product is discovered, it is possible that the microorganism also has genes to produce the same antibacterial compound. This discovery could lead to the development of new antibacterial drugs.
The new herbicide acts by inhibiting the function of an enzyme necessary for plant survival. The enzyme is a key catalyst in an important metabolic pathway that produces essential amino acids. When this pathway is disrupted, plants die.
This pathway is not present in mammals, including humans, and has therefore been a common target in herbicide research and development. The new herbicide acts on a different part of the pathway than current herbicides. A commercial product that uses it would require more research and regulatory approval.
"An exciting aspect of the work is that we have not only discovered a new herbicide, but also its exact target in the plant, opening up the possibility of modifying crops to be resistant to a commercial product based on this herbicide," said Steven Jacobsen, assistant principal investigator in the study, professor of molecular, cellular and developmental biology at UCLA College and researcher at the Howard Hughes Medical Institute. "We are looking to work with major agrochemical companies to develop this promising avenue."
To confirm the efficacy of the new herbicide, the UCLA team tested the fungal product on a common plant used in laboratory studies, Arabidopsis. In the experiments, the product killed the plants after they were sprayed. The researchers also implanted the fungus' resistance gene into Arabidopsis genomes. Plants that carried the implanted resistance gene were immune to the herbicide.
"The emergence of herbicide-resistant weeds thwarts all classes of herbicides used; in fact, no new types have been commercialized in the last 30 years," said Yan Yan Yan, a UCLA graduate student in chemical engineering who was the main author of the paper. "We believe that this powerful new herbicide, combined with immune crops, will complement urgent efforts to overcome weed resistance."
