Mutational analysis of the maize chloroplast ATPase-beta subunit gene promoter: the isolation of promoter mutants in E. coli and their characterization in a chloroplast in vitro transcription system.

This paper describes the use of Escherichia coli to isolate Bal31 deletion mutants and single-base substitution mutants that functionally define the promoter of the maize chloroplast beta-ATPase gene (atpB). Promoter function in E. coli and in a chloroplast in vitro transcription system was determined by S1 nuclease protection experiments using RNA products from each mutant. The results show that in vitro the chloroplast RNA polymerase responds to the promoter point mutations in a quantitatively similar fashion to the E. coli RNA polymerase. Deletion analysis demonstrates that sequences 5' of the -35 region are not necessary for chloroplast promoter function in vitro and that the presence of an adjacent promoter drastically decreases the transcriptional activity of the atpB promoter in E. coli.