Structural feature of sorghum chloroplast psbA gene and regulation effectsof its 5 '-noncoding region

Comparative analysis reveals remarkable homology between the sequences of b oth psbA gene nucleotides and the inferred amino acids of sorghum, a C-4 pl ant, and those of rice, a C-3 plant. The 5'-noncoding region of sorghum psb A gene contains the conservative promoter elements, " -35" element and " -1 0" element, like the prokaryote and the promoter element, TATA box, like th e eukaryote. As compared with that of the rice, an extra sequence of 7 bp i s found in the leader sequence of the mRNA in the former. Using an in vitro system, it has been demonstrated that protein factor exists in sorghum chl oroplast protein extract which specifically binds to the 5'-noncoding regio n of psbA gene. Measurement of the expression of luciferase shows a 2-5 tim e greater reaction of the expression plasmids pALqs which contain leader re gion of sorghum psbA gene than that of the expression plasmids pALqr which contain leader region of rice psbA gene in E. coli.