| The encoding genes for SigF are universally present in prokaryotes.But,our understanding on them is mainly limited in Escherichia coli and Bacillus subtilis.Synechocystis sp.PCC 6803,a unicellular cyanobacterium,is widely studied in applied researches.There are nine sigma factors encoded by its genome.SigF belongs to group 3?-factors,which are involved in the transcription of regulons for survival under stress,and play important roles in cellular adaption in various environments.A recent study reported that the pilA1 promoter was recognized exclusively by SigF in Synechocystis PCC 6803,but the detailed mechanism of SigF recognizing the promoter is not clear.In the present study,the role of Synechocystis pilA1 promoter regions in the recognition by SigF was studied and whether the transcription of pilA1 controlled by SigF is conserved in different cyanobacteria was investigated.In this study,we selected WT and ?sigF as the host strains,from which the gfp transcriptional fusion strains with the intact promoter of pilA1 and a series of its mutations were constructed.GFP fluorescence intensity of all strains was measured by the Microplate Reader.Our results revealed that mutations in promoter altered the expression of pilA1.The changes are particularly significant when AT rich and-10 region were mutated,whereas mutation in-35 region exhibited relatively smaller effect,indicating the promoter-10 region and AT rich were critical for the SigF regulation.In addition,we also tested the effect of SigFs from other cyanobacteria on the transcription of Synechocystis pilA1 and the effect of Synechocystis SigF on the transcription of pilA1 genes from other cyanobacteria in Syechocystis PCC 6803 using gfp transcriptional fusion strains.The results showed that SigF from other cyanobacteria are able to transcribe Synechocystis pilA1 gene,and Syenchocystis SigF is also able to transcribe pilA1 genes from other cyanobacteria,suggesting a conserved regulation of pilA1 by SigF in cyanobacteria. |
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