Sizes, locations, and directions of transcription of two genes on a cloned maize chloroplast DNA sequence.

mRNA for the large subunit (LS) of ribulose-1,5-bisphosphate carboxylase [3-phospho-D-glycerate carboxylase (dimerizing), EC 4.1.1.39] of Zea mays is complementary to an uninterrupted 1600-base-pair-long chloroplast DNA sequence that has been mapped precisely within the 4350-base-pair-long chloroplast DNA fragment Bam 9 to which it had been traced earlier [Bedbrook, J. R., Coen, D. M., Beaton, A. R., Bogorad, L. & Rich, A. (1979) J. Biol. Chem. 254, 905-910]. An additional 1400-base-pair-long uninterrupted region that is colinear with a chloroplast RNA has been detected on Bam 9. The transcript from this region is part of a 2200-nucleotide-long RNA. The remainder of the DNA sequence for the 2200-base-pair RNA maps outside Bam 9. The 1600-base-pair LS gene and the gene for the 2200-nucleotide transcript are close to one another. They are separated by an untranscribed intercistronic "gap" about 330 base pairs long. These two closely packed genes are inverted on the chromosome-i.e., their 3' termini are at opposite ends of the untranscribed gap and they map on opposite strands.