Abstract
How new promoters are originated in the eukaryotic genome is still unknown. We have been addressing this question, with the nuclear genome of Arabidopsis as a model. To explore how newly inserted coding-region sequences acquire transcriptional competency in the nuclear genome, we carried out a promoter-trap experiments with promoter-less LUC ORF randomly integrated into the Arabidopsis genome. As a result, we found that the given LUC construct was occasionally expressed without trapping preexisting genes or promoters in the integrated sites. Scrutiny of those transgenic lines revealed that the insertion of the LUC coding sequence occasionally induced nucleosome remodeling in the vicinity of the 5' end of the ORF, and chromatin landmark of core promoter region was newly formed. This indicates that insertion of the coding region sequences occasionally causes de novo origination of pol II promoters. With the aid of various chimeric constructs, we also found that the ATG initiation codon of the ORF is a one of the key players that induce promoter origination as above. From these findings, we propose a model how pol II promoters are originated in the plant genome.
