摘要Modern agricultural practices rely on herbicides to reduce yield losses.Herbicide-resistant weeds threaten herbicide utility and,hence,food security.New herbicide modes of action and integrated pest-manage-ment practices are vital to mitigate this threat.As the antimalarials that target the bifunctional enzyme di-hydrofolate reductase-thymidylate synthase(DHFR-TS)have been shown to be herbicidal,DHFR-TS might represent a mode-of-action target for the development of herbicides.Here,we present the crystal structure of a DHFR-TS(AtDHFR-TS1)from the model dicot Arabidopsis thaliana.It shows a divergent DHFR active site and a linker domain that challenges previous classifications of bifunctional DHFR-TS proteins.This plant-conserved architecture enabled us to develop highly selective herbicidal inhibitors of AtDHFR-TS1 over human DHFR and identify inhibitors with unique scaffolds via a large-library virtual screen.These re-sults suggest that DHFR-TS is a viable herbicide target.