Regulation of rDNA transcription in plastids of higher plants

Plastid rDNA expression changes with plastid differentiation, plant develop ment and plant growth conditions. Plastid rDNA operons are preceded by diff erent promoter structures that are recognised by different types of RNA pol ymerase in a species-specific and development-dependent manner. Present kno wledge on regulation of rDNA transcription obtained with plant material cor responding to different developmental stages and/or different plant species is summarised. Results indicate the creation of new and unique transcripti onal regulatory mechanisms during the evolutionary integration process of t he cyanobacterial ancestor into the present-day multi-cellular organism. (C ) 2000 Societe francaise de biochimie et biologie moleculaire / Editions sc ientifiques et medicales Elsevier SAS.