Response to Phosphate Deprivation in Brassica nigra Suspension Cells

Abstract

Suspension cells of Brassica nigra responded to Pi deprivation by increasing their potential for Pi influx and by raising the active levels of intracellular, cell surface, and secreted acid phosphatases. These responses, however, were temporally distinct. Phosphate influx capacity increased 15-fold in parallel to a 10-fold decrease in endogenous Pi during 7 days of culture in basal growth medium. In contrast, intracellular and cell surface phosphatase activities changed only after alterations in cellular phosphorus status had been in place for a number of days. Even in nutrient sufficient cells the secretion of phosphatase remained relatively high as did the acfivities of the other phosphatases. The cell surface acid phosphatase had a Km of approximately 10 times that of the influx process and molybdate was a much stronger inhibitor of this phosphatase activity. From these results it appears that Pi absorption and the production or activation of phosphatases are regulated in a distinct manner. In addition, Pi uptake into Brassica nigra cells does not appear to directly involve the cell surface phosphatase under Pi-deficient conditions.

Influência dos diferentes períodos de colheita na expressão de isoenzimas em sementes de cevada

“…Essa enzima tem sido amplamente caracterizada, em plantas, e sua atividade aumenta naquelas que apresentam deficiência de fósforo. De acordo com Duff et al (1989) e Lefebvre et al (1990), o incremento na atividade de ACP sob baixas concentrações de fósforo tem sido reportado para um grande número de espécies e órgãos vegetais. Essa enzima também participa de reações de hidrólise de ésteres, podendo atuar sobre fosfolipídios de membrana e provocar a peroxidação desses lipídios.…”

Metabolic Adaptations of Plant Respiration to Nutritional Phosphate Deprivation

“…At the metabolic level, much attention has been devoted to the effect of Pi status on the secretion of acid phosphatases, Pi uptake rates, and other mechanisms that may serve to increase the availability of Pi to Pi-deprived cells (Goldstein et al, 1989;Lefebvre et al, 1990;Duff et al, 1991aDuff et al, , 1991b. The effects of Pi nutrition on the rates of photosynthesis and photosynthate partitioning in leaves have also been well documented (Thorsteinsson and Tillberg, 1987;Lauer et al, 1989;Fredeen et al, 1990).…”

Effects of Phosphorus Limitation on Respiratory Metabolism in the Green Alga Selenastrum minutum

“…At the metabolic level, much attention has been devoted to the effect of Pi status on the activity and secretion of extracellular phosphatases, Pi uptake rate, and other mechanisms which may serve to increase Pi availability to Pi deprived cells (12,17). Also, the role of Pi in regulating the rate of photosynthesis and the partitioning of photosynthate has been studied extensively (1,5,11,23,24,26,28,29,32).…”