Transcription of repetitive DNA in condensed plant chromatin

Polyadenylated transcripts homologous to highly repetitive DNA were found in root tips of Vicia faba by Northern blot hybridization. Electron microscope autoradiography using [3H]uridine as a probe revealed transcription of condensed chromatin in various higher plants. This is consistent with the general rule that highly repetitive DNA is located within condensed chromatin, but it is new that this chromatin fraction is active in RNA synthesis to a considerable amount. Semi-quantitative comparison of the intensity of transcription in species with widely differing 2C DNA contents by means of light microscope autoradiography revealed an inverse relationship between the amount of 2C DNA (and condensed chromatin), and the rate of RNA synthesis.