Nucleotide sequence of the 5.6 kbp psbB operon of pea chloroplast DNA

Abstract

The nucleotide sequence of a 5.7 kbp region of pea (Pisum sativum L.) chloroplast DNA containing the psbB operon and a putative promotor and termination site has been determined and compared to the corresponding sequences from spinach, maize, tobacco and the liverwort Marchantia polymorpha. The organization of the operon is the same as for the other species, i.e. psbB/psbH/petB/petD. These genes code for a 56 kDa chlorophyll‐binding photosystem 2 (PS2) polypeptide, an 8 kDa PS2 polypeptide, cytochrome b6 (24 kDa) and subunit 4 (18 kDa) of the cytochrome b6/f complex. Two short and oppositely directed putative polypeptide genes are located between psbB and psbH. The petB and petD genes contain introns of 818 and 715 bp, respectively. The psbB, petB and petD proteins encoded in the pea operon are 89–98% homologous to those from the other species, while the pea psbH protein has a homology of 65–96% to that of the other species. The nucleotide sequences of introns and intergenic regions from the higher plants are 60–70% homologous. From comparisons with spinach sequences we conclude that the primary pea transcript probably has a length of 5603 bases.