A novel mechanism of herbicide action through disruption of pyrimidine biosynthesis

A combination of adverse events, particularly the proliferation of herbicide-resistant weeds, is limiting growers’ ability to achieve the crop yields necessary to satisfy the ever-increasing demand for food, feed, and fiber. One practice that can reverse this trend is to increase the number of molecular targets available to the grower to provide better solutions to combat weed resistance. Here, we describe a mechanism of weed control through disruption of plant de novo pyrimidine biosynthesis. The aryl pyrrolidinone anilide class of chemistry inhibits dihydroorotate dehydrogenase in the pathway, and crystal structures of the inhibitor bound to the enzyme define the nature of the interaction and the basis of herbicidal action.

A lead aryl pyrrolidinone anilide identified using high-throughput in vivo screening was optimized for efficacy, crop safety, and weed spectrum, resulting in tetflupyrolimet. Known modes of action were ruled out through in vitro enzyme and in vivo plant-based assays. Genomic sequencing of aryl pyrrolidinone anilide-resistant Arabidopsis thaliana progeny combined with nutrient reversal experiments and metabolomic analyses confirmed that the molecular target of the chemistry was dihydroorotate dehydrogenase (DHODH), the enzyme that catalyzes the fourth step in the de novo pyrimidine biosynthesis pathway. In vitro enzymatic and biophysical assays and a cocrystal structure with purified recombinant plant DHODH further confirmed this enzyme as the target site of this class of chemistry. Like known inhibitors of other DHODH orthologs, these molecules occupy the membrane-adjacent binding site of the electron acceptor ubiquinone. Identification of a new herbicidal chemical scaffold paired with a novel mode of action, the first such finding in over three decades, represents an important leap in combatting weed resistance and feeding a growing worldwide population.