Diurnal changes of subcellular glutathione content in Arabidopsis thaliana
B. Zechmann
The aim of this study was to investigate diurnal changes of subcellular glutathione content in leaves of Arabidopsis thaliana by immunohistochemistry and quantitative transmission electron microscopy. The results revealed major diurnal changes in glutathione content. The highest content was found within 2 - 3 h of exposure to light (increase of 489 % in mitochondria, 318 % in plastids, 857 % in nuclei, 511 % in peroxisomes, and 900 % in the cytosol when compared to that during darkness), followed by a strong drop (49 % in mitochondria and the cytosol, 53 % in plastids, 68 % in nuclei, 38 % in peroxisomes) within the next 1 - 2 h. Glutathione content was 67 % lower in mitochondria, 76 % in plastids, 73 % in nuclei, 50 % in peroxisomes, and 68 % in the cytosol at the end of the light period which lasted for 8 h when compared to highest content. Lowest glutathione content was found in most cell compartments at the very end of the dark period. In context with previous studies it could be concluded that low glutathione content at the end of the dark period was caused by lack of glycine and cysteine due to lack of photorespiration and decreased sulfur uptake and assimilation during darkness. The rapid increase of glutathione content observed within 3 h of light was most probably caused by a strong increase in glutathione synthesis triggered by increased glycine and cysteine content. The strong drop of glutathione after that period was most probably due to elevated glutathione degradation rate or increased use of glutathione for phytochelatin synthesis.
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