Chloroplast Ca Fluxes into and across Thylakoids Revealed by Thylakoid-Targeted Aequorin Probes.

Chloroplasts require a fine-tuned control of their internal Ca concentration, which is crucial for many aspects of photosynthesis and for other chloroplast-localized processes. Increasing evidence suggests that calcium regulation within chloroplasts also may influence Ca signaling pathways in the cytosol. To investigate the involvement of thylakoids in Ca homeostasis and in the modulation of chloroplast Ca signals in vivo, we targeted the bioluminescent Ca reporter aequorin as a YFP fusion to the lumen and the stromal surface of thylakoids in Arabidopsis ().