Figure 2

asr1469 promoter- gfp was transiently upregulated in heterocysts. A. Map of full length and truncated promoter regions upstream of asr1469 that was used to drive GFP reporter expression. Bent arrow indicates a putative transcription start site from RNA-seq data [25], bent arrow labeled TSS indicates start site identified by differential RNA-seq [26], black bar indicates HetR binding site. B. GFP fusions show transient expression of the full-length asr1469-gfp reporter fusion in heterocysts. Anabaena WT cells were imaged at 0, 21, and 25 hours after nitrogen deprivation in DIC (top), TRITC/autofluorescence (middle), and GFP (bottom) channels. At 21 hours after nitrogen deprivation, 63% of heterocysts showed an increase in fluorescence compared to vegetative cells. By 25 hours after nitrogen deprivation, the majority of heterocysts showed decreased or no GFP fluorescence. Heterocysts are marked with a blue arrowhead.