MAPPING OF PROMOTERS FOR THE NUCLEUS-ENCODED PLASTID RNA-POLYMERASE (NEP) IN THE IOJAP MAIZE MUTANT

Plastid genes of higher plants may be transcribed by the plastid-encod ed or the nucleus-encoded plastid RNA polymerases (PEP or NEP). The ob jective of this study was to identify NEP promoters in maize. To separ ate the NEP and PEP transcription activity, NEP pro meter mapping was carried out in the iojap maize mutant which lacks the PEP. We report h ere that atpB, an ATPase subunit gene has promoters for both NEP and P EP, while clpP, a protease subunit gene, and the rpoB operon, encoding three PEP subunit genes, are exclusively transcribed from NEP promote rs. The maize NEP promoters share sequence homology around the transcr iption initiation site, including the ATAGAATA/GAA loose consensus ide ntified for tobacco, suggesting conservation of the NEP transcription machinery between monocots and dicots.