The divergently transcribed rbcL and atpB genes of tobacco plastid DNA are separated by nineteen base pairs.

The in vivo transcripts of the tobacco chloroplast gene for the beta subunit of the ATPase (atpB) were examined. In tobacco, like spinach, the atpB gene encodes multiple transcripts. Six tobacco atpB transcripts are present in vivo, with 5' ends at positions "-90", "-255", "-290", "-490", "-500" and "-610" relative to the translation initiation site. The 5' end of the atpB gene ("-610" position) is 20 base pairs from the 5' end of the rbcL gene, coded for on the complementary strand. The "-255", "-490" and "-610" regions are recognized as promoters in vitro by spinach chloroplast and E. coli RNA polymerases.