Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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The gene sml0013 of Synechocystis sp. strain PCC 6803 encodes for a novel subunit of the NDH1 complex that is ubiquitous distributed among cyanobacteria.

ABSTRACT: The NDH1 complex fulfils numerous tasks in the cyanobacterial cell such as respiration, cyclic electron flow, and inorganic carbon concentration. Despite the immense progress in our understanding of structure/function relation of the cyanobacterial NDH1 complex, the subunits catalysing the NAD(P)H docking and oxidation are still missing. The gene sml0013 of Synechocystis 6803 encodes for a small protein of unknown function for that homologs exist in all completely known cyanobacterial genomes. The protein exhibits weak similarities to the NDF6 protein, which was reported from Arabidopsis chloroplasts as a NDH subunit (Ishikawa et al. 2008). A sml0013 inactivation mutant of Synechocystis 6803 was generated and characterized. It showed only weak differences regarding growth and pigmentation at various culture conditions; most remarkably it exhibited a glucose-sensitive phenotype in the light. The genome-wide expression pattern of the M-NM-^Tsml0013::Km mutant was almost identical to wild type when grown under high CO2 conditions as well as after shifts to low CO2 conditions. However, measurements of the photosystem I redox kinetic in cells of the M-NM-^Tsml0013::Km mutant revealed differences to wild type such as a decreased capability of cyclic electron flow as well as of utilization of electrons from catabolic processes. These results suggest that the Sml0013 protein (named NdhP) represent a novel subunit of the cyanobacterial NDH1 complex mediating its coupling to the respiratory or photosynthetic electron flow. Gene expression of Synechocystis sp. PCC 6803 WT and a M-NM-^Tsml0013::Km mutant was monitored at HC conditions (5% CO2) and at 24h after a shift to LC conditions (ambient air containing 0.035% CO2). Each condition was sampled in biological duplicates.

ORGANISM(S): Synechocystis sp. PCC 6803

SUBMITTER: Jens Georg

PROVIDER: E-GEOD-48415 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The catalytic core of the RNA polymerase of most eubacteria is composed of two M-NM-1 subunits and M-NM-2, M-NM-2M-bM-^@M-^Y and M-OM-^I subunits. In Escherichia coli, the M-OM-^I subunit (encoded by the rpoZ gene) has been suggested to assist M-NM-2M-bM-^@M-^Y during RNA polymerase core assembly. The function of the M-OM-^I subunit is particularly interesting in cyanobacteria because the cyanobacterial M-NM-2M-bM-^@M-^Y is split to N-terminal M-NM-3 and C-terminal M-NM-2M-bM-^@M-^Y subunits. The M-bM-^HM-^FrpoZ strain of the cyanobacterium Synechocystis sp. PCC 6803 grew well in standard conditions although the mutant cells showed low light-saturated photosynthetic activity, low Rubisco content and accumulated high quantities of protective carotenoids and M-NM-1-tocopherol. The M-bM-^HM-^FrpoZ strain contained 15% less of the primary M-OM-^C factor, SigA, than the control strain, and recruitment of SigA to the RNA polymerase core was inefficient in M-bM-^HM-^FrpoZ. Thus, a cyanobacterial RNA polymerase holoenzyme lacking the M-OM-^I subunit contains less frequently the primary M-OM-^C factor. A DNA microarray analysis revealed that this leads to specific down-regulation of highly expressed genes, like genes encoding subunits for Rubisco, ATP synthase, NADH-dehydrogenase and carbon concentrating mechanisms. On the contrary, many genes showing only low or moderate expression in the control strain were up-regulated in M-bM-^HM-^FrpoZ. A conserved -10 region was detected in promoters showing up or down-regulation in M-bM-^HM-^FrpoZ, but -35 regions of down-regulated genes completely differed from -35 regions of up-regulated genes. Cells from cyanobacteria Synechocystis sp. PCC 6803 named as control strain (CS) and RNA polymerase omega subunit inactivation strain, M-NM-^TrpoZ, were harvested (A730=1, 40 mL) directly from standard growth conditions (continuous illumination at the PPFD of 40 M-BM-5mol m-2s-1, 32M-BM-0C, ambient CO2). From three to four independent experiments were performed at each conditions.

Project description:Cyanobacteria are phototrophic prokaryotes that can convert inorganic carbon as CO2 into organic carbon compounds at the expense of light energy. In addition, they need only a few inorganic nutrients and can be cultivated in high densities using non-arable land and seawater. This features qualified cyanobacteria as attractive organisms for the production of third generation biofuels as part of the development of future CO2-neutral energy production. Synechocystis sp. PCC 6803 represents one of the most widely used cyanobacterial model strains. On the basis of its available genome sequence and genetic tools, many strains of Synechocystis have been generated that produce different biotechnological products. Efficient isoprene production is an attractive goal, since this compound represents not only an energy-rich biofuel but is also used as chemical feedstock. Here, we report on our attempts to generate isoprene-producing strains of Synechocystis. The cDNA of a codon-optimized plant isoprene synthase (IspS) was cloned under the control of different Synechocystis promoters, which ensure strong constitutive or light-regulated ispS expression. The expression of the ispS gene was quantified by qPCR, whereas the amount of isoprene was quantified using GC-MS. Incubation of our strains at different salt conditions had marked impact on the isoprene production rates. Under low salt conditions, a good correlation was found between ispS expression and isoprene production rate. However, the cultivation of isoprene production strains under salt-supplemented conditions decreased isoprene production despite the fact that ispS expression was salt-stimulated. The characterization of the metabolome of isoprene producing strains indicated that isoprene production might be limited by insufficient precursor levels. Our isoprene production rates under low salt conditions were 2 - 6.5times higher compared to the previous report of Lindberg et al. (2010). These results can be used to guide future attempts establishing the isoprene production with cyanobacterial host systems.

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Dataset Information

The gene sml0013 of Synechocystis sp. strain PCC 6803 encodes for a novel subunit of the NDH1 complex that is ubiquitous distributed among cyanobacteria.

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