Molecular evolution of Cu transporters and transcription factors in plant response to copper stress

Copper (Cu) is an essential micronutrient for plants, playing a crucial role in various physiological and molecular processes. Excess Cu induces oxidative stress and disrupts cellular functions, while Cu deficiency causes chlorosis and poor pollen development, thereby reducing crop yields. However, the molecular and evolutionary mechanisms of Cu tolerance and homeostasis remain unclear in the plant kingdom. In this review, we discuss the uptake, transport, and detoxification of Cu through high-affinity Cu transporters (COPTs). Additionally, we update recent studies on maintaining Cu balance by mediating the root exudation of organic acids (e.g., citrate and proline), xylem/phloem loading, cell wall binding, vacuolar sequestration, redistribution, and the activity of antioxidant enzymes (e.g., SOD, CAT, and APX). Furthermore, tissue-specific expression analyses reveal that COPT genes exhibit distinct spatial regulation in the roots and leaves, which are the primary sites of Cu transport and detoxification. Overall, our review highlights the critical roles of COPT gene families and detoxification pathways in maintaining Cu homeostasis in plants. Future research should focus on genetic engineering approaches to enhance Cu tolerance, optimize Cu distribution in grains, and mitigate soil contamination risks. By clarifying these mechanisms, we can develop strategies to sustain crop production under increasing Cu stress, thereby ensuring food security and human health.