RNA synthesis in isolated chloroplasts of Euglena gracilis

Abstract

RNA synthesis in isolated chloroplasts of Euglena gracilis was measured by [14C]ATP incorporation into electrophoretically-separable RNA species. The incorporation kinetics reached a plateau after 30 min incubation. probably due to completing RNA strains which had been initiated previously. We failed to inhibit RNA polymerase activity by addition of 100 μg/ml rifamycin suggesting a lack of transcription initiation in isolated chloroplasts, in contrast to in vivo experiments. A precursor RNA transcript of mol. wt approx. 1.8 × 106 was found both in mostly intact and broken chloroplasts. In the latter this RNA accumulated but was not processed to immediate precursor or mature rRNAs. The 1.8 × 106 size of the presumed initial common precursor for Euglena chloroplast rRNAs is in good agreement with the length of the respective rRNA gene previously determined.