Fig. 6.

The Norf4 peptide. a Datasets from the previously performed primary transcriptome analysis showed that Norf4 expression responded positively to nitrogen depletion in both Synechocystis 6803 [21] and Synechocystis 6714 [20], when 11 different growth conditions were tested. The mRNAs of norf4 and gap1 are co-regulated and overlap by several hundred nt. The previously mapped transcriptional start sites are labelled by black arrows. b Northern blot analysis of norf4 mRNA accumulation in a time course experiment up to 72 h after the removal of nitrogen. The same RNA samples were used as in Fig. 4. c The signals obtained from the Northern blots (panel b) were evaluated densitometrically after normalization by the level of 5S rRNA. The relative norf4 expression is shown with respect to the maximum expression after transfer to nitrogen-free conditions (24 h = 100%). The bands at 200 nt (filled circles) and at 800 nt (empty circles) were analyzed separately from each other. d Multiple sequence alignment of 35 homologs from 51 different cyanobacterial genome sequences (homologs are identical among 12 Microcystis, five Crocosphaera watsonii and two Fischerella genome sequences)