THE ATPB AND RBCL PROMOTERS IN PLASTID DNAS OF A WIDE DICOT RANGE

The plastid atpB-rbcL intergene has been analyzed within a wide range of plants covering the major dicot lineages. New sequences from 13 pla nt species were determined and aligned with three already-known sequen ces. The promoters of the rbcL and the atpB genes were localized and a nalyzed according to published observations in spinach and tobacco. Th e evolutionary conservation of two atpB promoters, separated hv 111-26 2 nucleotides, is strong support that both are functionally active, an d it also allows a discrimination between the previously reported atpB transcripts. Moreover, the radically distinct sequences of the two at pB promoters suggest that they interact with two distinct initiation c omplexes. The alignment also confirms the much higher conservation of the leader sequence in the rbcL mRNA than in the atpB mRNA among dicot s, presuming a function at the posttranscriptional level.