Fig. 6: A model schematically represents the dual function of cHO-dependent phycobiliprotein during the acclimation of aquatic cyanobacteria to nitrogen fluctuations.

In the tetrapyrrole biosynthetic pathway, cHO catalyzes the reaction of c-type heme to biliverdin IXα (left side, see blue arrow), which is of great importance for the synthesis, assembly and function of phycobiliprotein during recovery from nitrogen chlorosis. The cHO-dependent phycobiliprotein is important for the cell growth via assembling into phycobilisome as light-harvesting function after the nitrate is added to chlorotic cells (left side) and decomposing into nitrogen source as nitrogen-storage function after the nitrate is removed from the culture medium (right side).