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Open Access Publications from the University of California

Subcellular metal imaging identifies dynamic sites of Cu accumulation in Chlamydomonas.

  • Author(s): Hong-Hermesdorf, Anne
  • Miethke, Marcus
  • Gallaher, Sean D
  • Kropat, Janette
  • Dodani, Sheel C
  • Chan, Jefferson
  • Barupala, Dulmini
  • Domaille, Dylan W
  • Shirasaki, Dyna I
  • Loo, Joseph A
  • Weber, Peter K
  • Pett-Ridge, Jennifer
  • Stemmler, Timothy L
  • Chang, Christopher J
  • Merchant, Sabeeha S
  • et al.

We identified a Cu-accumulating structure with a dynamic role in intracellular Cu homeostasis. During Zn limitation, Chlamydomonas reinhardtii hyperaccumulates Cu, a process dependent on the nutritional Cu sensor CRR1, but it is functionally Cu deficient. Visualization of intracellular Cu revealed major Cu accumulation sites coincident with electron-dense structures that stained positive for low pH and polyphosphate, suggesting that they are lysosome-related organelles. Nano-secondary ion MS showed colocalization of Ca and Cu, and X-ray absorption spectroscopy was consistent with Cu(+) accumulation in an ordered structure. Zn resupply restored Cu homeostasis concomitant with reduced abundance of these structures. Cu isotope labeling demonstrated that sequestered Cu(+) became bioavailable for the synthesis of plastocyanin, and transcriptome profiling indicated that mobilized Cu became visible to CRR1. Cu trafficking to intracellular accumulation sites may be a strategy for preventing protein mismetallation during Zn deficiency and enabling efficient cuproprotein metallation or remetallation upon Zn resupply.

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