Mechanisms Controlling Transcription of the Plastid Genome

Nucleus-encoded organellar phage-type RNA polymerases are indispensable for the transcription of the mitochondrial and chloroplast genomes. They have fundamental roles in the biogenesis of the respiratory and photosynthetic compartments of plant cells. Previous research on mitochondrial transcription in the model plant Arabidopsis has lead to the discovery of gene-specific transcriptional functions of the phage-type RNA polymerases RPOTm and RPOTmp in mitochondria and assigned individual roles to these enzymes in the biogenesis of the respiratory chain. RPOTmp is additionally found in plastids where its role and the role of a second phage-type enzyme, RPOTp, are largely unresolved. The proposed project aims to comprehensively define the functions of RPOTp and RPOTmp in plastids. It will employ i) a differential transcriptome sequencing strategy and complementary molecular biology approaches to determine the gene specificities of these enzymes and generate a plastid genome-wide map of transcription start sites used by RPOTp or RPOTmp in plastids. ii) computational methods to identify potential cis-regulatory elements or parameters of plastid genes that direct the transcriptional activities of RPOTp and RPOTmp iii) in vitro transcription and interaction assays to validate the function of these elements and parameters in controlling transcription.