title: Metabolomic analysis of the salt-sensitive mutants reveals changes in amino acid and fatty acid composition important to long-term salt stress in Synechocystis sp. PCC 6803.
abstract: Early studies in cyanobacteria have found that few genes induced by short-term salt shock (15-60 min) display a stable induction in the long-term (>1 day) salt-acclimated cells; meanwhile, most of the genes responsive to long-term salt stress were different from those by short-term salt shock, suggesting that different regulatory mechanisms may be involved for short-term and long-term salt stress responses. In our previous work using the model cyanobacterium Synechocystis sp. PCC 6803, sll1734 encoding CO2 uptake-related protein (CupA) and three genes encoding hypothetical proteins (i.e., ssr3402, slr1339, and ssr1853) were found induced significantly after a 3-day salt stress, and the corresponding gene knockout mutants were found salt sensitive. To further decipher the mechanisms that these genes may be involved, in this study, we performed a comparative metabolomic analysis of the wild-type Synechocystis and the four salt-sensitive mutants using a gas chromatography-mass spectrometry (GC-MS) approach. A metabolomic data set that consisted of 60 chemically classified metabolites was then subjected to a weighted correlation network analysis (WGCNA) to identify the metabolic modules and hub metabolites specifically related to each of the salt-stressed mutants. The results showed that two, one, zero, and two metabolic modules were identified specifically associated with the knockout events of sll1734, ssr3402, slr1339, and ssr1853, respectively. The mutant-associated modules included metabolites such as lysine and palmitic acid, suggesting that amino acid and fatty acid metabolisms are among the key protection mechanisms against long-term salt stresses in Synechocystis. The metabolomic results were further confirmed by quantitative reverse-transcription PCR analysis, which showed the upregulation of lysine and fatty acid synthesis-related genes. The study provided new insights on metabolic networks involved in long-term salt stress response in Synechocystis.
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering Technology, Tianjin University, Tianjin, 300072, People's Republic of China.
authors.forename: Jiangxin
authors.initials: J
authors.lastname: Wang
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Zhang
authors.forename: Mengliang
authors.initials: M
authors.lastname: Shi
authors.forename: Lianju
authors.initials: L
authors.lastname: Gao
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Niu
authors.forename: Rigen
authors.initials: R
authors.lastname: Te
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Weiwen
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D053263:Gene Regulatory Networks; D053858:Metabolic Networks and Pathways; D055442:Metabolome / Q000235:genetics*; D025341:Principal Component Analysis; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological; D046939:Synechocystis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D005227:Fatty Acids; D012965:Sodium Chloride