Furthermore, in some of the experiments the promoter activity was almost abolished for construct B, while other experiments showed only a low activity. The part of the promoter click here retained in construct A but lost in construct
B contains no known putative binding sites for transcriptional regulators. It should be noted that the differences of expression between the longer promoter fragments (constructs A-D) were significant within experiments (three independent measurements) but not always between the experiments. However, all experiments showed the same general expression pattern for fragments A-D even though the actual levels differed. The difference between the longer promoter fragments (construct learn more A-D) and the shortest fragment (construct E) were significant between all experiments. As expected, the positive control pPrbcL-gfp showed very high expression levels in all experiments (data not shown). Figure 4 Expression from the hupSL promoter deletions. Measurements of GFP fluorescence intensity
in living cells grown under nitrogen fixing conditions. Nostoc punctiforme ATCC 29133 cells were transformed with vector constructs containing truncated versions of the hupSL-promoter (A-E) fused to the reporter gene gfp (see Figs. 1 and 2). All values are normalised to the expression from the promoter less reporter vector, pSUN202 (negative control) and the GFP intensity is shown as relative intensity compared to the negative control. All measurements however were performed in triplicates. In situ localization of hupSL transcript To investigate selleck compound if the truncated parts of the hupSL promoter, except from being important for the expression levels, also affected the cellular localization of hupSL transcription fluorescence
microscopy was used to view the living cells. Furthermore, this study was carried out to analyze if the high transcription level of the shortest promoter fragment (construct E, promoter fragment stretching from -57 to tsp) was the result of a general low expression in all cells rather than high specific expression in the heterocyst. Images of the filaments were taken using bright field and fluorescence microscopy and then merging the images. The micrographs showed that promoter fragments A-D had heterocyst specific expression (Fig. 5). Surprisingly, even the shortest promoter construct E showed a heterocyst specific expression (Fig. 5). The promoter region of PrbcL fused to gfp, used as a positive control, gave, as expected, high expression primarily in vegetative cells [49, 50] (Fig. 5). Figure 5 In situ localization of hupSL transcript. Micrographs showing localization of the GFP expression from the hupSL promoter in nitrogen fixing filaments of Nostoc punctiforme ATCC 29133. N. punctiforme cells were transformed with a self replicative vector, pSUN202, containing deletions of the hupSL promoter fused to gfp (see Fig. 1).