Routing resilience: Engineering metabolite transport for combined drought and heavy-metal tolerance in plants

Plants can experience individual stresses such as drought or heavy-metal exposure, yet in many environments these factors co-occur, imposing conflicting demands on water conservation, ion homeostasis, and metabolic detoxification. While biosynthetic pathways for stress-responsive metabolites are well studied, the regulation and engineering of metabolite transport remain largely overlooked. Transporters such as ABC, MATE, NPF, SWEET, and ALMT determine how osmolytes, antioxidants, and chelators are distributed across tissues and the rhizosphere, shaping physiological outcomes under stress. This Opinion highlights metabolite transport as a missing regulatory layer linking drought physiology and metal detoxification networks. I propose a Cross-stress Metabolite-Transport Engineering (CoMET) framework that treats these transporters as programmable valves to optimize metabolite fluxes under combined stress. CoMET integrates flux diagnostics, synthetic promoter logic, transporter editing, and field-based learning loops. Recognizing and engineering metabolite transport as a dynamic control system could redefine how crops maintain both water relations and detoxification capacity in increasingly contaminated and drought-prone soils.