Chloroplasts sigma factors act in concert with PEP, the bacterial-type plastid RNA polymerase. Using a sigma knockout line from Arabidopsis thaliana, we investigated mutant-specific changes in plastid gene expression at RNA level. One characteristic feature was the appearance of a long transcript that spans the atpB-E operon and extends considerably into the far-upstream region of atpB. This region reveals a cluster of typical promoter elements for NEP, the second (phage-type) plastid RNA polymerase. The NEP promoter cluster can help maintain RNA synthesis in situations where no functional sigma factor is available for PEP. © 2006 Federation of European Biochemical Societies.
Schweer, J., Loschelder, H., & Link, G. (2006). A promoter switch that can rescue a plant sigma factor mutant. FEBS Letters, 580(28–29), 6617–6622. https://doi.org/10.1016/j.febslet.2006.11.010