Kinetics of Accumulation of Ribulose-1,5-bisphosphate Carboxylase during Greening in Euglena gracilis

Abstract

The accumulation of ribulose-1,5-bisphosphate carboxylase (RuBPCase) MATERIALS AND METHODS Euglena gracilis strain Z Pringsheim was grown in the dark to a density of 106 cells ml1' on Hutner's pH 3.5 medium and then greened on pH 6.8 'resting' medium as before (9).In experiments with DCMU, dark-grown resting or greening cell cultures were divided into four equal portions. The first received DCMU (from a stock solution of 10 mm DCMU in absolute ethanol) and ethanol at final concentrations of 10 jAM and 17 mm respectively. The second received an equivalent amount of ethanol. The third received DCMU at a final concentration of 10 Mm. In this case, DCMU was suspended by magnetic stirring at a concentration of 1 mm in sterile distilled H20 and an appropriate aliquot was added immediately to the third flask. The fourth received an equivalent amount of sterile distilled H20. Then all four cultures were placed in the light and incubated for the desired time. When necessary, DCMU was removed by centrifuging an aliquot of culture for 2 min at 300g at room temperature under sterile conditions. Pelleted cells were resuspended in fresh sterile resting medium and put back in the light. Control cultures lacking DCMU were treated the same way.Cell density, Chl, RuBPCase activity, and photosynthetic CO2 fixation were measured as described (9). RuBPCase content per cell was determined with an antibody to the holoenzyme also as described (9). Paramylum concentration was measured according to Freyssinet et al. (10).

Post-transcriptional regulation by light of the biosynthesis ofEuglena ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit

“…1A show that the bleached Euglena cells contain low levels of mature S SU, as previously reported by Pineau [19] and Freyssinet et al [6,7], and that these levels remain almost constant during the first 12 h of illumination of the cells. After 12 h, a net increase of mature S S U can be observed until the greening of the cells is completed.…”

“…Freyssinet et al [6,7] reported that Euglena synthesizes low levels of Rubisco in the dark and that a net synthesis of this enzyme requires light, indicating that the synthesis of Rubisco is photoregulated.…”

Photo and Nutritional Regulation of Euglena Organelle Development

“…Chloroplast development is blocked by respiratory inhibitors and uncouplers (Evans 1971;Fong and Schiff 1977;Klein et al 1972) while inhibitors of photosynthesis have little effect on chlorophyll synthesis in resting cells during the first 24 h of light exposure but are inhibitory after this time Smillie 1970, 1971;Freyssinet et al 1984a, b;Horrum and Schwartzbach 1981;Schiff et al 1967) when the majority of paramylum has been consumed. The inhibition of chlorophyll synthesis by inhibitors of photosynthesis can be overcome by provision of a utilizable carbon source (Freyssinet et al 1984b;Horrum and Schwartzbach 1981). The amount of chlorophyll synthesized , the length of the lag period of chlorophyll synthesis (Freyssinet and Schwob 1976), the length of the dark period of potentiation (Freyssinet 1976) and the amount of RUBISCO produced (Freyssinet et al 1984b) are proportional to the level of paramylum present prior to light exposure.…”

“…The inhibition of chlorophyll synthesis by inhibitors of photosynthesis can be overcome by provision of a utilizable carbon source (Freyssinet et al 1984b;Horrum and Schwartzbach 1981). The amount of chlorophyll synthesized , the length of the lag period of chlorophyll synthesis (Freyssinet and Schwob 1976), the length of the dark period of potentiation (Freyssinet 1976) and the amount of RUBISCO produced (Freyssinet et al 1984b) are proportional to the level of paramylum present prior to light exposure. Taken together these results suggest that the aerobic breakdown of cellular reserves provides the carbon and energy required for the early stages of chloroplast development while photosynthesis becomes the major carbon and energy source during the latter stages of plastid development.…”

Amino acid sequence of the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit from Euglena

“…In previous work on this enzyme we have studied the effect of various treatments on its synthesis during greening of Euglena (7,8), and determined the occurrence of the enzyme (9) and of the gene for the LSU (10) …”