Copper homeostasis

Authors


Author for correspondence:
Marinus Pilon
Tel: +1 970 491 0803
Email: pilon@lamar.colostate.edu

Abstract

Contents

  • Summary  799

  • I. Introduction  800
  • II.  The origins of Cu homeostasis  800
  • III. Copper homeostasis in unicellular photosynthetic model organisms  801
  • IV. Functions of Cu in plants  802
  • V. Typical levels of Cu in plants, deficiency and toxicity  802
  • VI. Copper abundance in soils and appropriate Cu concentrations in media  804
  • VII. Uptake in the root and distribution to aerial tissues  804
  • VIII. Uptake in the shoot symplast, redistribution of Cu during flowering, seed set and senescence  806
  • IX. Cu delivery inside the cell  806
  • X. Regulation of Cu homeostasis  809
  • XI. 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.

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