The sequence of the chloroplast atpB gene and its flanking regions in Chlamydomonas reinhardtii

The chloroplast (cp)-encoded CF, ATPase p-subunit gene (a@)of Chlumydomonas reinhardtii and its flanking regions have been sequenced. The derived amino acid (aa)sequence is highly homologous to that of the b-subunit gene in Escherichia coli, bovine heart mitochondria, and higher plant cp. In contrast to all other cp genomes, the CF, E subunit gene (atpE)does not lie at the 3' end of the atpB gene but maps to a position 92 kb away in the other single-copy region. Northern blots confirm that the /I subunit is not encoded as part of a dicistronic message as it is in higher plants. The region just upstream from the atpB gene in C. reinhardtii contains two small open reading frames (ORFs)and not the gene for the large subunit of ribulose-1,5- bisphosphate carboxylase/oxygenase as is found in cp genomes of higher plants. No transcripts for either ORF were detected, but the codon usage in these ORFs as well as in the atpB gene follows the unique pattern of codon usage previously seen in other cp genes in C. reinhardtii.