The chloroplast gene for ribosomal protein CL23 is functional in tobacco.

Chloroplast rpl23 loci potentially coding for a polypeptide homologous to the E. coli L23 ribosomal protein are frame-shifted in spinach and several other plants, indicating that these loci are pseudogenes. In tobacco, rpl23 constitutes a continuous open reading frame of 93 codons and its transcript initiates at least 66 bp upstream from the initiation codon. The N-terminal amino acid sequence of a 13 kDa protein from the 50 S subunit of tobacco chloroplast ribosomes matches that derived from the tobacco rpl23 locus. This shows that rpl23 is a functional gene in tobacco.