| dc.description.abstract | The endoplasmic reticulum (ER) in Arabidopsis thaliana is the source of the calcium signal produced by high-fluence blue light sensed by the junction between the ER and chloroplast, the ER-chloroplast nexus. Photostimulation of this nexus results in an observable and quantifiable cytosolic calcium wave in Arabidopsis seedlings: using FRET analysis, we were able to see both an increase in cytosolic calcium and a decrease in ER luminal calcium. Treatment with cylcopiazonic acid (CPA), an inhibitor of SERCA, an ER Ca2+-ATPase in animals, and ECA1, a homolog in Arabidopsis, caused an initial increase and delayed decrease in cytosolic calcium concentration of the wave. Lower concentrations of CPA resulted in higher magnitudes of this increase and decrease in of [Ca2+]cyt than higher concentrations. Treatment with thapsigargin, an inhibitor of SERCA had less effect, causing a slight increase and decrease in the cytosolic calcium concentration of the observed wave similar to CPA but less extreme. CPA likely inhibits ER calcium regulation and resequestration, allowing more to initially be released and continuously depleting its store of calcium available for release over time. | en |
