Complexity and abundance of ribonucleic acid transcribed from restriction endonuclease fragments of Euglena chloroplast deoxyribonucleic acid during chloroplast development

Abstract

Chloroplast DNA from Euglena gracilis was used to construct a partial library of recombinant plasmids representing 45% of the DNA. Each plasmid was radioactively labeled in vitro by nick translation and hybridized in liquid to a vast excess of total cellular RNA isolated either from cells grown continually in the dark or from cells containing developing chloroplasts. The complexity and abundance of the RNA that hybridized to the different chloroplast restriction endonuclease DNA fragments were calculated from the RNA-DNA hybridization saturation values and the pseudo-first-order hybridization rate constants, respectively. The complexity of these transcripts showed little change during chloroplast development. In several cases, the complexity of the RNA was greater than expected for asymmetrical transcription, suggesting the possibility that transcription may be symmetrical in some regions of chloroplast DNA. The abundance of the transcripts ranged from 0.0001% to nearly 10% of the total cellular RNA, and in some cases changed by as much as 5-10-fold during chloroplast development.