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Glutathione-mediated regulation of ATP-sulfurylase activity, SO4(2-) uptake, and oxidative stress response in intact canola roots

Lappartient, A.G., Touraine, B.
Plant physiology 1997 v.114 no.1 pp. 177-183
sulfur dioxide, sulfur, metabolism, glutathione, quantitative analysis, glutathione-disulfide reductase, hydrogen peroxide, nutrient deficiencies, stress response, ion transport, adenosine triphosphate, peroxidases, phloem, Brassica napus, oxidation, phosphotransferases (kinases), enzyme activity, roots, ascorbic acid
The dual role of glutathione as a transducer of S status (A.G. Lappartient and B. Touraine [1996] Plant Physiol 111:147-157) and as an antioxidant was examined by comparing the effects of S deprivation, glutathione feeding, and H2O2 (oxidative stress) on SO42- uptake and ATP sulfurylase activity in roots of intact canola (Brassica napus L.). ATP sulfurylase activity increased and SO42- uptake rate severely decreased in roots exposed to 10 mM H2O2, whereas both increased in S-starved plants. In split-root experiments, an oxidative stress response was induced in roots remote from H2O2 exposure, as revealed by changes in the reduced glutathione (GSH) level and the GSH/oxidized glutathione (GSSG) ratio, but there was only a small decrease in SO42- uptake rate and no effect on ATP sulfurylase activity. Feeding plants with GSH increased GSH, but did not affect the GSH/GSSG ratio, and both ATP sulfurylase activity and SO42- uptake were inhibited. The responses of the H2O2-scavenging enzymes ascorbate peroxidase and glutathione reductase to S starvation, GSH treatment, and H2O2 treatment were not to glutathione-mediated S demand regulatory process. We conclude that the regulation of ATP sulfurylase activity and SO42- uptake by S demand is related to GSH rather than to the GSH/GSSG ratio, and is distinct from the oxidative stress response.