Fig. 1

Schematic representation of the metabolic pathway of a cyanobacterial cell, engineered to produce either isoprene or bisabolene, and the steps chosen as targets for gene knockdown (in red). Blue arrows represent enzymatic steps which are present in the native metabolism but were overexpressed for enhanced terpenoid production. Green arrows represent heterologous expression of isoprene synthase from Eucalyptus globulus and bisabolene synthase from Abies grandis for isoprene and bisabolene production, respectively. PP: pentose phosphate; CBB: Calvin Benson Bassham; TCA: tricarboxylic acid; G6P: glucose 6-phosphate; F6P: fructose 6-phosphate; G3P: glyceraldehyde 3-phosphate; E4P: erythrose 4-phosphate; 3PG: 3-phosphoglycerate; PEP: phosphoenolpyruvate; AA: amino acids; Pyr: pyruvate; Acetyl-CoA: acetyl coenzyme A; OAA: oxaloacetate; Mal: malate; DXP: deoxy-d-xylulose 5-phosphate; TPP: thiamine pyrophosphate; IPP: isopentenyl pyrophosphate; DMAPP: dimethylallyl pyrophosphate; FPP: farnesyl pyrophosphate; GGPP: geranylgeranyl pyrophosphate; Sqln: squalene; Chla: chlorophyll a; Iso: isoprene; Bis: bisabolene; Phytyl-PP: phytyl pyrophosphate; ADP: adenosine diphosphate; ATP: adenosine triphosphate; DXS: Deoxy-d-xylulose-5-phosphate synthase; IDI: IPP:DMAPP isomerase; Gpi: glucose 6-phosphate isomerase; CcmA: 3-Deoxy-d-arabinoheptulosonate 7-phosphate (DAHP) synthase; PEPc: PEP carboxylase; IlvB /IlvG: catalytic subunit isoforms of acetolactate synthase; DDH: d-lactate dehydrogenase; ThiG: thiazole synthase; CrtE: polyprenyl transferase; Sqs: squalene synthase; EgIspS: isoprene synthase from Eucalyptus globulus; AgB: bisabolene synthase from Abies grandis; ChlP: geranylgeranyl pyrophosphate reductase; CrtB: phytoene synthase; AtpB: β-subunit of ATP synthase