title: Overexpression of flv3 improves photosynthesis in the cyanobacterium Synechocystis sp. PCC6803 by enhancement of alternative electron flow.
abstract: BACKGROUND
  To ensure reliable sources of energy and raw materials, the utilization of sustainable biomass has considerable advantages over petroleum-based energy sources. Photosynthetic algae have attracted attention as a third-generation feedstock for biofuel production, because algae cultivation does not directly compete with agricultural resources, including the requirement for productive land and fresh water. In particular, cyanobacteria are a promising biomass feedstock because of their high photosynthetic capability.
  
  
  RESULTS
  In the present study, the expression of the flv3 gene, which encodes a flavodiiron protein involved in alternative electron flow (AEF) associated with NADPH-coupled O2 photoreduction in photosystem I, was enhanced in Synechocystis sp. PCC6803. Overexpression of flv3 improved cell growth with corresponding increases in O2 evolution, intracellular ATP level, and turnover of the Calvin cycle. The combination of in vivo (13)C-labeling of metabolites and metabolomic analysis confirmed that the photosynthetic carbon flow was enhanced in the flv3-overexpressing strain.
  
  
  CONCLUSIONS
  Overexpression of flv3 improved cell growth and glycogen production in the recombinant Synechocystis sp. PCC6803. Direct measurement of metabolic turnover provided conclusive evidence that CO2 incorporation is enhanced by the flv3 overexpression. Increase in O2 evolution and ATP accumulation indicates enhancement of the AEF. Overexpression of flv3 improves photosynthesis in the Synechocystis sp. PCC6803 by enhancement of the AEF.
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan ; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075 Japan.
authors: Tomohisa
authors: T
authors: Hasunuma
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan ; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075 Japan.
authors: Mami
authors: M
authors: Matsuda
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan ; Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075 Japan.
authors: Youhei
authors: Y
authors: Senga
authors: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan.
authors: Shimpei
authors: S
authors: Aikawa
authors: Kobe University Center for Inland Sea, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan.
authors: Masakazu
authors: M
authors: Toyoshima
authors: Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan.
authors: Ginga
authors: G
authors: Shimakawa
authors: Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan ; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda, Tokyo, 102-0075 Japan.
authors: Chikahiro
authors: C
authors: Miyake
authors: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan ; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda, Tokyo, 102-0075 Japan ; Biomass Engineering Program, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama, 230-0045 Japan.
authors: Akihiko
authors: A
authors: Kondo
keywords: Alternative electron flow; Carbon metabolism; Metabolite profiling; Photosynthesis; Synechocystis sp. PCC6803; flv3
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