Interactions Between Copper Homeostasis and Metabolism in Plants

Vascular plants require the micronutrient copper (Cu) at merely 6–8 μg g−1 leaf dry biomass. Yet insufficient bioavailable soil Cu is an immediate threat for growth, stress resistance and reproduction, because the flux through major metabolic pathways depends critically on Cu-containing metalloproteins, for example in the electron transport chains of both photosynthesis and respiration, in cell wall biosynthesis and in secondary metabolism. A first understanding is emerging of how a tightly knit Cu homeostasis network orchestrates Cu uptake, distribution, storage and remobilisation to meet a plant’s nutritional demands while mitigating the unsurpassed toxicity potential of this nutrient element. In order to manage environmental, developmental and metabolic transitions, a plant must efficiently coordinate its metabolism with Cu homeostasis. In this review, we focus on interactions between Cu homeostasis and metabolism in plants, drawing also from insights obtained through the study of other biological systems. We describe evidence for possible roles of CuZn superoxide dismutases, convergence between Cu and sugar signalling, as well as the transcriptional remodelling predominantly of cell wall and secondary metabolism in response to Cu deficiency. The biological functions of most Cu-dependent proteins, which are often members of large protein families, remain to be demonstrated. Finally, we pinpoint future research needs towards an improved understanding of the interactions between Cu homeostasis and metabolism, which will provide avenues for improving not only crop quality, but importantly also crop resilience and yields.