Copper homeostasis

Abstract

Contents Summary 799 Introduction 800 The origins of Cu homeostasis 800 Copper homeostasis in unicellular photosynthetic model organisms 801 Functions of Cu in plants 802 Typical levels of Cu in plants, deficiency and toxicity 802 Copper abundance in soils and appropriate Cu concentrations in media 804 Uptake in the root and distribution to aerial tissues 804 Uptake in the shoot symplast, redistribution of Cu during flowering, seed set and senescence 806 Cu delivery inside the cell 806 Regulation of Cu homeostasis 809 Conclusions and outlook 811 Acknowledgements 811 References 811 Summary Copper (Cu) is a cofactor in proteins that are involved in electron transfer reactions and is an essential micronutrient for plants. Copper delivery is accomplished by the concerted action of a set of evolutionarily conserved transporters and metallochaperones. As a result of regulation of transporters in the root and the rarity of natural soils with high Cu levels, very few plants in nature will experience Cu in toxic excess in their tissues. However, low Cu bioavailability can limit plant productivity and plants have an interesting response to impending Cu deficiency, which is regulated by an evolutionarily conserved master switch. When Cu supply is insufficient, systems to increase uptake are activated and the available Cu is utilized with economy. A number of Cu‐regulated small RNA molecules, the Cu‐microRNAs, are used to downregulate Cu proteins that are seemingly not essential. On low Cu, the Cu‐microRNAs are upregulated by the master Cu‐responsive transcription factor SPL7, which also activates expression of genes involved in Cu assimilation. This regulation allows the most important proteins, which are required for photo‐autotrophic growth, to remain active over a wide range of Cu concentrations and this should broaden the range where plants can thrive.

A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

“…These results provided direct evidence of Cu transport mediated by OsHMA5 protein in yeast. Guerinot, 2006; Argüello et al, 2007;Burkhead et al, 2009). The functional characterization of OsHMA5 in this study showed that it transports Cu and is involved in the xylem loading of Cu at the both vegetative and reproductive growth stages (Figs.…”

“…A number of different transporters, such as Cation Diffusion Facilitator, Natural resistance-associated macrophage protein, ATPBinding Cassette, Zinc-and Iron-regulated-like Protein, and P-type ATPase, have been reported to be involved in the uptake, translocation, distribution, and homeostasis of nutrients (Hall and Williams, 2003;Krämer et al, 2007;Palmer and Guerinot, 2009). Among them, heavy metal-transporting P-type ATPase (HMA), the P 1B subfamily of the P-type ATPase superfamily, has been implicated in heavy metal transport (Williams and Mills, 2005;Grotz and Guerinot, 2006;Argüello et al, 2007;Burkhead et al, 2009). There are eight and nine members of P 1B -ATPase in Arabidopsis thaliana and rice (Oryza sativa), respectively (Williams and Mills, 2005).…”

Optimal copper supply is required for normal plant iron deficiency responses

“…These metals form the active sites in numerous enzymes involved in disparate processes, such as mitochondrial respiration, photosynthesis, oxidative stress protection, and various metabolic pathways. [1][2][3][4] Low metal concentration leads to deficiency and inefficiencies in metabolism, while too much causes metal toxicity. Consequences of metal toxicity are oxidative damage to cellular components, 5 or displacement of the correct metal from active sites in proteins.…”

Deregulated Copper Transport Affects Arabidopsis Development Especially in the Absence of Environmental Cycles

“…The heterologous expression in yeast indicates that the COPT1 transporter is highly specific for Cu + (Sancenon et al, 2003), similar to the Cu transporters of the CTR family from other eukaryotic organisms, and that it functions in transporting Cu + toward the cytosolic compartment. After transport through the membrane, Cu is delivered to target subcellular compartments and cuproproteins by specific and conserved cytosolic metallochaperones (for review, see Puig et al, 2007;Burkhead et al, 2009;Puig and Peñ arrubia, 2009).…”