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Recovery of sulfate transport into heterotrophic tobacco cells from inhibition by reduced glutathione.

Wiederherstellung des Sulfattransports in heterotrophe Tabakzellen nach Hemmung durch reduziertes Glutathion
: Kemper, O.; Rennenberg, H.; Thoene, B.

Physiologia plantarum (1989), Nr.76, S.271-276
ISSN: 0031-9317
Fraunhofer IFU; 2002 in Helmholtz-Gesellschaft integriert
Cycloheximid; Einfließen; Proteinsynthese; Puromycin; regulation; Schwefelernährung; Tabak

In heterotrophic tobacco cells (Nicotiana tabacum L. cv. Samsun) inhibition of sulfate transport by reduced glutathione (GSH) is a reversible process. When GSH was removed from the culture medium subsequent to a 10-h treatment with 1 mM GSH, sulfate transport began to recover after a lag period of ca 4 h and reached the transport rates of controls without GSH within another 3-4 h. Recovery was prevented when inhibitors of protein synthesis, i.e. cycloheximide or puromycin, were added to the medium upon removal of GSH, even if low concentrations (cycloheximide 1 myM; puromycin 250 myM) were applied. At these low concentrations the rate of synthesis of sulfate transport entities was maintained at the rate of degradation in the absence of GSH. The post-transcriptional polyadenylation inhibitor cordycepin and the transcription inhibitor alpha-amanitin only slightly reduced recovery of sulfate transport from inhibition by GSH. Apparently, protein synthesis is required for this recovery, sug gesting that inhibition of synthesis of sulfate carrier entities is the mechanism of action of GSH on sulfate transport in heterotrophic tobacco cells. An initial rate of net increase in sulfate transport during recovery from inhibition of GSH of 3.6 plus minus 0.2 U h minus 1 was calculated (1 U = 1 nmol sulfate (g DW) minus high 1 min high minus 1). This rate of increase is small compared with the rate of decrease in sulfate transport at maximum inhibition by cycloheximide (110 plus minus 3 U h high minus minus 1). However, with increasing time of exposure without GSH.