Genetically Reprogramming Crops and Rhizobacteria for Nutritional Iron Biofortification.

Iron is a critical micronutrient for both plants and humans, yet its declining availability across agricultural systems threatens global food security and health. Biofortification of food crops has emerged as a promising strategy to combat iron deficiency and anemia, leveraging both crop breeding and microbiome-based approaches to enhance iron mobilization and uptake. Advances in plant and bacterial synthetic biology could enable the precise programming of iron homeostasis and acquisition mechanisms, offering tailored solutions across diverse species and environments. Here, we outline key biomolecules, genes, and biosynthetic and transport pathways that represent underexplored synthetic biology targets for improving crop iron acquisition. We highlight opportunities to tune expression strength, tissue specificity, and cross-host pathway transfer to enhance chelation- and reduction-mediated solubilization of soil iron and augment plant uptake. Finally, we emphasize the broader importance of developing plant-microbe-metal actuators as modular components in genetic circuit design and discuss how their deployment across diverse plant and microbial chassis could accelerate agricultural biofortification and improve global nutrition.