title: Proteomic and metabolomic analyses reveal metabolic responses to 3-hydroxypropionic acid synthesized internally in cyanobacteriumSynechocystissp. PCC 6803.
abstract: BACKGROUND
  3-hydroxypropionic acid (3-HP) is an important platform chemical with a wide range of applications. In our previous study, the biosynthetic pathway of 3-HP was constructed and optimized in cyanobacteriumSynechocystissp. PCC 6803, which led to 3-HP production directly from CO2at a level of 837.18 mg L-1(348.8 mg/g dry cell weight). As the production and accumulation of 3-HP in cells affect cellular metabolism, a better understanding of cellular responses to 3-HP synthesized internally inSynechocystiswill be important for further increasing 3-HP productivity in cyanobacterial chassis.
  
  
  RESULTS
  Using a engineered 3-HP-producing SM strain, in this study, the cellular responses to 3-HP internally produced were first determined using a quantitative iTRAQ-LC-MS/MS proteomics approach and a LC-MS-based targeted metabolomics. A total of 2264 unique proteins were identified, which represented about 63 % of all predicted protein inSynechocystisin the proteomic analysis; meanwhile intracellular abundance of 24 key metabolites was determined by a comparative metabolomic analysis of the 3-HP-producing strain SM and wild type. Among all identified proteins, 204 proteins were found up-regulated and 123 proteins were found down-regulated, respectively. The proteins related to oxidative phosphorylation, photosynthesis, ribosome, central carbon metabolism, two-component systems and ABC-type transporters were up-regulated, along with the abundance of 14 metabolites related to central metabolism. The results suggested that the supply of ATP and NADPH was increased significantly, and the precursor malonyl-CoA and acetyl-CoA may also be supplemented when 3-HP was produced at a high level inSynechocystis. Confirmation of proteomic and metabolomic results with RT-qPCR and gene-overexpression strains of selected genes was also conducted, and the overexpression of three transporter genes putatively involved in cobalt/nickel, manganese and phosphate transporting (i.e.,sll0385,sll1598andsll0679) could lead to an increased 3-HP production inSynechocystis.
  
  
  CONCLUSIONS
  The integrative analysis of up-regulated proteome and metabolome data showed that to ensure the high-efficient production of 3-HP and the normal growth ofSynechocystis, multiple aspects of cells metabolism including energy, reducing power supply, central carbon metabolism, the stress responses and protein synthesis were enhanced inSynechocystis. The study provides an important basis for further engineering cyanobacteria for high 3-HP production.
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China ; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, People's Republic of China.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China ; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072 People's Republic of China ; Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, People's Republic of China ; SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, People's Republic of China.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Zhang
keywords: 3-HP; Biosynthesis; Metabolomics; Proteomics; Response; Synechocystis