title: Regulation of pepc gene expression in Anabaena sp. PCC 7120 and its effects on cyclic electron flow around photosystem I and tolerances to environmental stresses.
abstract: Since pepc gene encoding phosphoenolpyruvate carboxylase (PEPCase) has been cloned from Anabaena sp. PCC 7120 and other cyanobacteria, the effects of pepc gene expression on photosynthesis have not been reported yet. In this study, we constructed mutants containing either upregulated (forward) or downregulated (reverse) pepc gene in Anabaena sp. PCC 7120. Results from real-time quantitative polymerase chain reaction (RT-qPCR), Western blot and enzymatic analysis showed that PEPCase activity was significantly reduced in the reverse mutant compared with the wild type, and that of the forward mutant was obviously increased. Interestingly, the net photosynthesis in both the reverse mutant and the forward mutant were higher than that of the wild type, but dark respiration was decreased only in the reverse mutant. The absorbance changes of P700 upon saturation pulse showed the photosystem I (PSI) activity was inhibited, as reflected by Y(I), and Y(NA) was elevated, and dark reduction of P700(+) was stimulated, indicating enhanced cyclic electron flow (CEF) around PSI in the reverse mutant. Additionally, the reverse mutant photosynthesis was higher than that of the wild type in low temperature, low and high pH, and high salinity, and this implies increased tolerance in the reverse mutant through downregulated pepc gene.
authors.affiliation: Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Shanghai Ocean University, Ministry of Education Shanghai, Shanghai, 201306, China.
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Jia
authors.forename: Peng-Peng
authors.initials: PP
authors.lastname: Zhang
authors.forename: Ding-Ji
authors.initials: DJ
authors.lastname: Shi
authors.forename: Hua-Ling
authors.initials: HL
authors.lastname: Mi
authors.forename: Jia-Cheng
authors.initials: JC
authors.lastname: Zhu
authors.forename: Xi-Wen
authors.initials: XW
authors.lastname: Huang
authors.forename: Pei-Min
authors.initials: PM
authors.lastname: He
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D017033:Anabaena / Q000235:genetics*; D019069:Cell Respiration; D003624:Darkness; D015536:Down-Regulation / Q000235:genetics; D004579:Electron Transport; D004777:Environment; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005822:Genetic Vectors; D006863:Hydrogen-Ion Concentration; D009154:Mutation / Q000235:genetics; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D011789:Quantum Theory; D054712:Salinity; D013312:Stress, Physiological / Q000235:genetics*; D013696:Temperature; D015854:Up-Regulation / Q000235:genetics
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex
keywords: Anabaena sp. PCC 7120; cyclic electron flow; pepc gene; photosynthesis; tolerance