title: Copper and iron homeostasis in plants: the challenges of oxidative stress.
abstract: CONCLUSIONS
  Photosynthesis, the process that drives life on earth, relies on transition metal (e.g., Fe and Cu) containing proteins that participate in electron transfer in the chloroplast. However, the light reactions also generate high levels of reactive oxygen species (ROS), which makes metal use in plants a challenge.
  
  
  BACKGROUND
  Sophisticated regulatory networks govern Fe and Cu homeostasis in response to metal ion availability according to cellular needs and priorities. Molecular remodeling in response to Fe or Cu limitation leads to its economy to benefit photosynthesis. Fe toxicity is prevented by ferritin, a chloroplastic Fe-storage protein in plants. Recent studies on ferritin function and regulation revealed the interplay between iron homeostasis and the redox balance in the chloroplast.
  
  
  RESULTS
  Although the connections between metal excess and ROS in the chloroplast are established at the molecular level, the mechanistic details and physiological significance remain to be defined. The causality/effect relationship between transition metals, redox signals, and responses is difficult to establish.
  
  
  CONCLUSIONS
  Integrated approaches have led to a comprehensive understanding of Cu homeostasis in plants. However, the biological functions of several major families of Cu proteins remain unclear. The cellular priorities for Fe use under deficiency remain largely to be determined. A number of transcription factors that function to regulate Cu and Fe homeostasis under deficiency have been characterized, but we have not identified regulators that mediate responses to excess. Importantly, details of metal sensing mechanisms and cross talk to ROS-sensing mechanisms are so far poorly documented in plants.
authors.affiliation: Biology Department, Colorado State University, Fort Collins, CO 80523, USA. kravet@lamar.colostate.edu
authors.forename: Karl
authors.initials: K
authors.lastname: Ravet
authors.forename: Marinus
authors.initials: M
authors.lastname: Pilon
mesh_terms: D002736:Chloroplasts / Q000378:metabolism; D003300:Copper / Q000378:metabolism* / Q000633:toxicity; D006706:Homeostasis; D007501:Iron / Q000378:metabolism* / Q000633:toxicity; D008670:Metals / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010944:Plants / Q000187:drug effects / Q000378:metabolism*; D010970:Plastocyanin / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D008670:Metals; D017382:Reactive Oxygen Species; D003300:Copper; D010970:Plastocyanin; D007501:Iron; D013482:Superoxide Dismutase