Promoter activities of genes cpcT2 and cpcS2 in Nostoc PCC 7120

To study the promoter activities of genes cpcT 2 and cpcS 2, several upstream DNA fragments of these two genes with different lengths were selected. These fragments were fused with promoterless gfp (reporter gene) for constructing five recombinant plasmids. Then, these recombinant plasmids were transferred into Nostoc PCC 7120 by conjugation. The promoter activities of genes cpcT 2 and cpcS 2 were determined by observing the fluorescence of green fluorescent protein (GFP) with a fluorescence microscope. The result showed that the 1 300 bp (−1 300 to 0 bp) and 2 600 bp (−2 600 to 0 bp) upstream fragments of cpcT 2 had strong promoter activity and the promoter activity of the 680 bp (−680 to 0 bp) fragment was weaker than that of two above fragments of cpcT 2. The 2 000 bp (−2 000 to 0 bp) upstream fragment of cpcS 2 revealed weak promoter activity. This showed that a strong promoter of cpcT 2 was located in the upstream fragment between −680 and −1 300 bp.