Characterization of the structure and expression of a highly conserved ribosomal protein gene, L9, from pea.

The eukaryotic ribosomal protein (RP) L9 is highly conserved in nature, and its gene is expressed to high levels in the actively growing tissues of pea. The transcriptional activity of the gene is highest in root, cambial and shoot meristems and immature tissues of the plant. Promoter deletion analysis using constructs employing the reporter gene gus were stably transferred into tobacco and revealed that the fully functional promoter is found in the first 316bp upstream from the start codon. Transgenic pea plants carrying one of these constructs show that translational efficiency mirrors gene transcription; gene expression appears to be developmentally regulated at the level of transcription. The coding region of the gene shares 80% amino acid homology with Arabidopsis and 76% homology with rice. Comparisons of the gene structure to that of the human, fruit fly, yeast, and Arabidopsis homologues reveal a close relationship in both promoter structure and intron insertion sites with the Arabidopsis gene. A nucleotide sequence alignment of the pea gene with other plant RP genes revealed that a sequence, -TTAGGGTTTT-, was commonly found in the forward and/or the inverted orientation at or near the TATA boxes of the promoters of these genes and may have a role in regulating the coordinate production of the RP genes in plants.