Figure 8. Proposed model of metabolic co-regulation between DAPG and pyoluteorin biosynthetic pathways in P. protegens.
Phloroglucinol (PG) is synthesized by the type III polyketide synthase PhlD in the DAPG biosynthetic pathway, and processed into PG-Cl and PG-Cl2 by the halogenase PltM encoded in the pyoluteorin gene cluster. The PG-Cl and PG-Cl2 putatively bind to regulator PltR and induce transcription of pyoluteorin biosynthetic genes and prompt production of pyoluteorin. In these two pathways, the final products (DAPG and pyoluteorin), the biosynthesis intermediate (PG) and its derivatives (PG-CL, PG-Cl2) can be released and used by bacteria and function as cell-cell communication signals.