Co-regulation of nuclear genes encoding plastid ribosomal proteins by light and plastid signals during seedling development in tobacco and Arabidopsis.

Genes encoding plastid ribosomal proteins are distributed between the nuclear and plastid genomes in higher plants, and coordination of their expression is likely to be required for functional plastid protein synthesis. A custom microarray has been used to examine the patterns of accumulation of transcripts from plastid and nuclear genes encoding plastid ribosomal proteins during seedling development in tobacco and Arabidopsis. The transcripts accumulate coordinately during early seedling development and show similar responses to light and to inhibitors, such as norflurazon and lincomycin, affecting plastid signaling. Computational analysis of the promoters of these genes revealed a shared initiator motif and common cis-elements characteristic of photosynthesis genes, specifically the GT-1 element, and the I-box. Analysis of the RPL27 gene of Arabidopsis thaliana indicated that transcription initiates from an initiator-like region. Deletion analysis of the RPL27 promoter in transgenic plants revealed that the identified shared cis-elements were not all required for wild-type expression patterns, and full developmental, light- and plastid-regulation can be conveyed by a region of the promoter from -235 to +1 relative to the transcription start site.