Figure 6.

Analysis of the promoter activity of NfdnaK2. A, Schematic of a nested series of NfdnaK2 promoter regions. Promoter1 (−300 to −1 bp region), Promoter2 (−690 to −1 bp region), Promoter3 (−940 to −1 bp region), and Promoter2-1 (−690 to −300 bp region) for promoter activity analysis. B, Measurements of luminescence driven by the NfdnaK2 promoter regions in the transgenic Nostoc sp. PCC 7120 carrying the LuxAB reporter fused with different promoter segments of the NfdnaK2 gene. Three individual cultures of wild-type (WT) and different transgenic Nostoc sp. PCC 7120 strains were incubated under grown condition (25°C and 30 µmol photons m⁻² s⁻¹), and the values of relative bioluminescence intensities (in relative luminescence units [RLUs]) are shown as the mean ± sd of three independent replicates. C, Time course of luminescence intensity in the transgenic Nostoc sp. PCC 7120 carrying the luxAB reporter gene fused with the Promoter1 and Promoter2 segments of the NfdnaK2 promoter in the process of dehydration. Cells of three strains were harvested on nylon membranes by filtration and put on the solid BG11 medium containing 2% (w/v) agar in the incubator for dehydration treatment for different periods of time. Each treatment was repeated independently three times, and data are shown as the mean ± sd of three independent replicates. The wild-type Nostoc sp. PCC 7120 strain was used as a negative control for luminescence measurements.