Ribulose 1,5-Diphosphate Carboxylase Synthesis in Euglena

Abstract

Regreening cultures were transferred back into darkness after harvesting the cells by centrifugation and resuspending them in an equivalent volume of Hutner's medium (15).Inhibitors were dissolved in the appropriate culture medium and sterilized by Seitz filtration before being added to cultures at times indicated under "Results."Inhibitors. The D-threo-isomer of chloramphenicol was used exclusively throughout this work (8). The final concentration of inhibitors used was D-threo-chloramphenicol, 1 mg/ml; cyclohemixide, 15 ,g/ml; 5-fluorouracil, 5 mm; rifampicin, 250 ,ug/ml. NaH'4C03 into acid-stable product was determined exactly as described previously (21). RESULTS AND DISCUSSIONEuglena RuDPCase has been recently purified and characterized (22). This enzyme has the high mol wt and distinctive quaternary structure which is typical for this enzyme isolated from higher plants and green algae (11,16,18,20,27). In the presence of sodium dodecyl sulfate, the enzyme dissociates into two nonidentical subunits of mol wt 55,000 and 15,000; eight 600 www.plantphysiol.org on May 9, 2018 -Published by Downloaded from

Development of Ribulose-1,5-Diphosphate Carboxylase in Castor Bean Cotyledons

“…In contrast, light was required to initiate RuDP Case synthesis in dark-grown etiolated leaves (9, 13) and dark-grown Euglena (17). When dark-grown cultures of E. gracifis regreening in the light were transferred back into darkness, there was a dramatic increase in RuDP Case activity (10,11) and the same phenomenon was found when castor bean cotyledons developing in the light were put into the dark. As far as we are aware, castor bean cotyledons are the first recorded photosynthetic higher plant tissue in which maximum development of RuDP Case activity occurs in the dark and in which there is a partial repression of RuDP Case activity by light.…”

“…The activity of this enzyme increases along with other enzymic and structural components of the developing chloroplast, for 3 to 4 days, by which time the cells are photosynthetically competent (4,7). If at any time during the regreening process Euglena cells are transferred back into darkness there is a striking continued synthesis of RuDP Case in the dark (10,11). As with Euglena, light initiates the synthesis of RuDP Case in dark-grown etiolated higher plant tissues (9,13), but the effect of subsequent darkening in RuDP Case activity has not been investigated.…”

Ribulose Diphosphate Carboxylase Synthesis in Euglena

“…The regulation of biosynthesis and assembly of such multimeric proteins over the Euglena cell cycle has been little investigated. Preliminary experiments with regreening Euglena cultures suggest that under these conditions, the synthesis of RuDP Case subunits may not be in synchrony (11,12). Further progress is dependent on methods for detecting nascent RuDP Case subunits, and with this objective in view, we have produced antibodies to Euglena RuDP Case subunits and determined their specificity.…”