Copper connections: coordinating transport, sensing and systemic signalling in plants

Copper is an essential micronutrient that plays critical roles in plant metabolism, development and stress responses through its unique redox properties. While tightly regulated to prevent toxicity, labile copper also functions as a dynamic signalling molecule mediating developmental and environmental cues. Copper bioavailability in soils is influenced by complex physicochemical factors, posing challenges for plant acquisition and homeostasis. Plants have evolved sophisticated mechanisms to regulate copper uptake, long-distance transport, intracellular trafficking and storage, balancing its essentiality with potential toxicity. This review summarizes current knowledge on copper homeostasis in plants, discusses uptake strategies in dicots and non-grass monocots, the coordination of internal copper transport and tissue distribution, and the emerging evidence for systemic copper signalling. Understanding these processes is important for improving crop nutrient use efficiency and resilience in mineral-deficient soils.