FIG 4.

Heatmap showing expression levels of secondary metabolite genes in WT PCC 7806 and the ΔmcyB mutant (MT) with (mc) and without (co) MC-LR treatment. Expression levels are given as median log₂ values as indicated in the color code bar at the top. The assignment of four of the six gene clusters to the biosynthesis of aeruginosin (1), microcystin (2), cyanopeptolin (3), and microcyclamide (4) is indicated on the right along with IPF numbers of genes and gene abbreviations. Two cryptic clusters encode polyketide synthase complexes presumably involved in the synthesis of an aromatic polyketide (PKSI/PKSIII) and an enediyne type polyketide (PKSit).