A gene encoding the tryptophan synthase beta subunit of Arabidopsis thaliana

The DNA sequence of a tryptophan synthase gene and the flanking 5' and 3' regions has been determined for Arabidopsis thaliana. The sequence encodes only the beta subunit domain, indicating that alpha and beta subunits are specified by separate genes. The gene contains four introns and encodes 470 amino acid residues. The plant amino acid sequence is highly conserved with respect to corresponding microbial sequences. The NH2-terminal amino acid sequence is characteristic of chloroplast transit peptides. Identity of the sequences of the genomic exons and a cDNA clone and the presence of cellular RNA corresponding in size and 5' sequence to the gene indicate that the gene is expressed. Analysis of Arabidopsis genomic DNA suggests the presence of a second gene for the beta subunit.