pTAC3 and pTAC14 are required for binding of Plastid Encoded RNA Polymerase to DNA

Plastid Encoded RNA Polymerase (PEP) is a bacterial type multisubunit RNA polymerase responsible for the bulk of transcription in chloroplasts. It contains four core subunits, which are orthologs of their cyanobacterial counterparts. In Arabidopsis thaliana PEP associates with 12 PEP-associated proteins (PAPs), which serve as peripheral subunits of the RNA polymerase. The exact contributions of PAPs to PEP function remain poorly understood. We show that a peripheral subunit of PEP, PAP1 (pTAC3), binds the same genomic loci as RpoB, a core subunit of PEP. PAP1 (pTAC3) and another peripheral PEP subunit, PAP7 (pTAC14), are required for RpoB binding to DNA. RpoB and another core PEP subunit, RpoC1, are expressed in pap1 (ptac3) and pap7 (ptac14) mutants. We propose that the peripheral subunits of PEP are required for the recruitment of core PEP subunits to DNA. pTAC3, binds the same genomic loci as RpoB, a core subunit of PEP. PAP1 pTAC3 and another peripheral PEP subunit, PAP7 The data consists of 3 replicates of RpoB ChIP-seq in Col0 wt, ptac3 and ptac14 mutants, and pTAC3 ChIP on Col0 wt and ptac3 mutant