Einfluß von Ammonium und Sulfat auf die Glutathion-Produktion in Suspensionskulturen von Nicotiana tabacum

Abstract

Summary Release and accumulation of glutathione in the medium of suspension cultures of Nicotiana tabacum var. SAMSUN grown photoheterotrophically in a modified MURASHIGE-SKOOG medium are controlled by the mineral nutrition of the cells. In batch cultures the glutathione accumulation is limited by the sulfur supply of the medium, the sulfate concentration in a range from 0.3 mM to 1.73 mM influencing the duration of accumulation but not the rate of GSH release into the medium. After the sulfate supply of the medium has been exhausted, the GSH level in the medium declines. The increase in cell protein during this period indicates that GSH is taken up by the cells and used as sulfur source. Besides high concentrations of sulfate the surplus production of glutathione is depending on the supply of the tabacco cells with ammonium. In cultures grown with 60 mM nitrate as sole nitrogen source up to 7 micromoles glutathione per liter are found in the medium in contrast to 700 micromoles accumulated in the medium of cultures supplied with 20 mM ammonium and 40 mM nitrate. There is no difference in the glutathione content of cells grown with ammonium-nitrate and with nitrate alone, and the addition of ammonia to nitrate grown cells results in a fast increase of glutathione in the medium. The present data support the idea that glutathione can function as storage and transport form of cysteine. They also pose the question how the glutathione synthesis is regulated in cells assimilating ammonium-nitrate.