The plastid aldolase gene from Chlamydomonas reinhardtii: intron/exon organization, evolution, and promoter structure.

Genomic clones encoding the plastidic fructose-1,6-bisphosphate aldolase of Chlamydomonas reinhardtii were isolated and sequenced. The gene contains three introns which are located within the coding sequence for the mature protein. No introns are located within or near the sequence encoding the transit-peptide, in contrast to the genes for plastidic aldolases of higher plants. Neither the number nor the positions of the three introns of the C. reinhardtii aldolase gene are conserved in the plastidic or cytosolic aldolase genes of higher plants and animals. The 5' border sequences of introns in the aldolase gene of C. reinhardtii exhibit the conserved plant consensus sequence. The 3' acceptor splice sites for introns 1 and 3 show much less similarity to the eukaryotic consensus sequences than do those of intron 2. The plastidic aldolase gene has two tandemly repeated CAAT box motifs in the promoter region. Genomic Southern blots indicate that the gene is encoded by a single locus in the C. reinhardtii genome.