How do plants respond to copper deficiency?

The transition metal copper is essential for all organisms yet excess copper is toxic because of production of free radicals via its free form. Therefore, the levels of copper are precisely regulated in a cell. Under copper depleted conditions, the expression of Cu/Zn superoxide dismutase (SOD) is downregulated and its function is compensated by Fe SOD in chloroplasts of higher plants. We presented evidence that a microRNA, miR398, is involved in this downregulation of Cu/Zn SOD genes in Arabidopsis thaliana when grown at low copper levels, corresponding to less than 1 microM Cu in tissue culture media. However, a green alga, Chlamydomonas reinhardtii, adjusts to copper depletion by modifying the photosynthetic apparatus from copper containing plastocyanin to iron containing cytochrome c(6). During evolution plants modified one of the main strategies to respond to copper deficiency probably to adapt to different metal environments.