Nucleus-encoded 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. My previous research on mitochondrial transcription in the model plant Arabidopsis has led 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 employi) a differential transcriptome sequencing (dRNA-seq) 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 RPOTmpiii) in vitro transcription and interaction assays to validate the function of these elements and parameters in controlling transcription.The proposed research will generate fundamental knowledge on transcriptional processes in plants. It will clarify how plastid gene expression, and thus chloroplast biogenesis and photosynthesis, can be controlled via RPOTp and RPOTmp. My expertise in organellar transcription, the interdisciplinary strategy applied and new collaborations established during this project will contribute to excellent research outcomes and broaden research interests and competences of the host institute, which will strongly support me in obtaining a permanent senior position in research following my current junior professor appointment.