CHARACTERIZATION OF PLASTID DNA-TRANSCRIPTION IN RIBOSOME DEFICIENT PLASTIDS OF HEAT-BLEACHED BARLEY LEAVES

Plastid DNA transcription was studied in heat-bleached ribosome deficient plastids of barley seedlings grown for 7 days at an elevated temperature of 34-degrees-C, which does not permit the formation of plastid ribosomes. Based on equal numbers of plastids, the overall incorporation of P-32-UTP into elongating transcripts during transcription in lysed plastids derived from heat-bleached sections of barley primary foliage leaves and from control leaves was in the same order of magnitude. Hybridization of radiolabelled run-on transcripts to filter bound DNA-fragments of barley plastid DNA revealed that all of the genes transcribed in ribosome containing plastids are also active in heat-bleached ribosome deficient plastids. Our data indicate that the principal RNA-polymerase activity of plastids is nuclear encoded.