The 2.2 kb EcoRI fragment containing the chloroplast pshA gene from millet (Setaria italica) has been cloned and the nucleotide sequence of the 5’-noncoding region has been determined. The 5’-flanking region is found to contain prokaryote-like promoter structures: compared with prokaryotic promoters, the“-35”box (TTGACA) shows 100% homology while, in the ‘-10’box (TATACT), one different nucleotide is found. In addition, between these two boxes, there is a consensus sequence“TATATA”.just as in prokaryotic promoters. All these results indicate that millet psbA promoter has both prokaryotic and eukaryotic characteristies. The mRNA leader region of millet pshA gene is 87 bp, the same length as sorghum. However, an additional CTATTT sequence is found as compared with rice and an additional TTTT, as with wheat, barley and rye. So the differences between C3 and C4 plants may be universal in the family of Gramineae. Furthermore, computer analysis shows that a small stem-loop structure might be formed in pshA mRNA leader region in these six plants. The above-mentioned additional CTATTT sequence happens to be just located within the stem-loop structure, thus leading to different sizes of the stem-loops among these six species. It is likely that this small secondary structure may have some effect on the expression and regulation of the psbA gene.
