The intracellular Arabidopsis COPT5 transport protein is required for photosynthetic electron transport under severe copper deficiency

Abstract

Summary Copper is an essential micronutrient that functions as a redox cofactor in multiple plant processes, including photosynthesis. Arabidopsis thaliana possesses a conserved family of CTR‐like high‐affinity copper transport proteins denoted as COPT1‐5. COPT1, the only family member that is functionally characterized, participates in plant copper acquisition. However, little is known about the function of the other Arabidopsis COPT proteins in the transport and distribution of copper. Here, we show that a functional fusion of COPT5 to the green fluorescent protein localizes in Arabidopsis cells to the prevacuolar compartment. Plants defective in COPT5 do not exhibit any significant phenotype under copper‐sufficient conditions, but their growth is compromised under copper limitation. Under extreme copper deficiency, two independent copt5 knockout mutant lines exhibit severe defects in vegetative growth and root elongation, low chlorophyll content, and impairment in the photosynthetic electron transfer. All these phenotypes are rescued when the wild‐type copy of the COPT5 gene is retransformed into a copt5 knockout line or when copper, but not other metals, are added to the medium. COPT5 is expressed in vascular tissues, with elevated levels in roots. Taken together, these results suggest that COPT5 plays an important role in the plant response to environmental copper scarcity, probably by remobilizing copper from prevacuolar vesicles, which could act as internal stores or recycling vesicles to provide the metal cofactor to key copper‐dependent processes such as photosynthesis.

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…The rice mitochondrial Fe transporter (MIT) also appears to regulate the influx of Cu, although more studies are needed to confirm this (Bashir et al, 2011). The tonoplastlocalized AtCOPT5 is important for Cu export from the vacuole and is involved in the remobilization of Cu ions (Garcia-Molina et al, 2011;Klaumann et al, 2011). Until now, none of the eight identified FRO present in Arabidopsis have been expected to play a role in the reduction process of Cu on the vacuolar membrane, raising the possibility that other reductase enzymes may function as ferric reductases in plants (Jeong and Connolly, 2009).…”

Comparison of global responses to mild deficiency and excess copper levels in Arabidopsis seedlings

“…15 Moreover, COPT5 is involved in the mobilisation of Cu from the lumen of the vacuole or prevacuolar compartments towards the cytosol in response to extreme Cu-deficient conditions. 16,17 Other components in the Cu homeostasis network are soluble cytosolic cuprochaperones, 18 one of their tasks is to provide Cu to cytosolic targets, such as the CCS cuprochaperone, which delivers Cu to the Cu and zinc (Zn) superoxide dismutase (Cu/ ZnSOD). ATX1 is another cuprochaperone that delivers Cu to the P-type ATPases of Cu + (Cu + -ATPases) at the endoplasmic reticulum to pump Cu into the lumen, where it is loaded into cuproproteins in the secretory pathway.…”

Spatiotemporal Analysis of Copper Homeostasis in Populus trichocarpa Reveals an Integrated Molecular Remodeling for a Preferential Allocation of Copper to Plastocyanin in the Chloroplasts of Developing Leaves

“…Cu enters the cytoplasm via members of the COPT (for Cu transporter) family (Kampfenkel et al, 1995;Sancenó n et al, 2003Sancenó n et al, , 2004Andrés-Colás et al, 2010;Garcia-Molina et al, 2011). In the cytosol, three Cu chaperones have been described.…”