title: Enhanced limonene production in cyanobacteria reveals photosynthesis limitations.
abstract: Terpenes are the major secondary metabolites produced by plants, and have diverse industrial applications as pharmaceuticals, fragrance, solvents, and biofuels. Cyanobacteria are equipped with efficient carbon fixation mechanism, and are ideal cell factories to produce various fuel and chemical products. Past efforts to produce terpenes in photosynthetic organisms have gained only limited success. Here we engineered the cyanobacterium Synechococcus elongatus PCC 7942 to efficiently produce limonene through modeling guided study. Computational modeling of limonene flux in response to photosynthetic output has revealed the downstream terpene synthase as a key metabolic flux-controlling node in the MEP (2-C-methyl-d-erythritol 4-phosphate) pathway-derived terpene biosynthesis. By enhancing the downstream limonene carbon sink, we achieved over 100-fold increase in limonene productivity, in contrast to the marginal increase achieved through stepwise metabolic engineering. The establishment of a strong limonene flux revealed potential synergy between photosynthate output and terpene biosynthesis, leading to enhanced carbon flux into the MEP pathway. Moreover, we show that enhanced limonene flux would lead to NADPH accumulation, and slow down photosynthesis electron flow. Fine-tuning ATP/NADPH toward terpene biosynthesis could be a key parameter to adapt photosynthesis to support biofuel/bioproduct production in cyanobacteria.
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843.|Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.|Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, TX 77843.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843.|Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.|College of Life Science, Tonghua Normal University, Jilin 134002, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Key Laboratory of Computational Biology, Chinese Academy of Sciences (CAS)-German Max Planck Society (MPG) Partner Institute for Computational Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: Changpeng
authors.initials: C
authors.lastname: Xin
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843.|Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.|College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fujian 350002, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.
authors.forename: Yanbing
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.
authors.forename: Su
authors.initials: S
authors.lastname: Sun
authors.affiliation: Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843.
authors.forename: Runze
authors.initials: R
authors.lastname: Li
authors.affiliation: Key Laboratory of Computational Biology, Chinese Academy of Sciences (CAS)-German Max Planck Society (MPG) Partner Institute for Computational Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China.
authors.forename: Xin-Guang
authors.initials: XG
authors.lastname: Zhu
authors.affiliation: Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.|Department of Veterinary Pathobiology, Texas A&M University, College Station, TX 77843.
authors.forename: Susie Y
authors.initials: SY
authors.lastname: Dai
authors.affiliation: Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843; prentzepis@tamu.edu syuan@tamu.edu.|Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Rentzepis
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843; prentzepis@tamu.edu syuan@tamu.edu.|Synthetic and Systems Biology Innovation Hub, Texas A&M University, College Station, TX 77843.|Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, TX 77843.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Yuan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D056804:Biofuels; D053138:Cyclohexenes / Q000378:metabolism*; D004896:Erythritol / Q000031:analogs & derivatives / Q000378:metabolism; D007218:Industrial Microbiology; D007700:Kinetics; D000077222:Limonene; D060847:Metabolic Engineering; D053858:Metabolic Networks and Pathways; D008954:Models, Biological; D009249:NADP / Q000378:metabolism; D010788:Photosynthesis; D040901:Proteomics; D013403:Sugar Phosphates / Q000378:metabolism; D046940:Synechococcus / Q000378:metabolism*; D013729:Terpenes / Q000378:metabolism*
chemical_list: C114232:2-C-methylerythritol 4-phosphate; D056804:Biofuels; D053138:Cyclohexenes; D013403:Sugar Phosphates; D013729:Terpenes; D009249:NADP; D000255:Adenosine Triphosphate; D000077222:Limonene; D004896:Erythritol
keywords: MEP; advanced biofuel; limonene; photosynthesis; terpene