The cAMP receptor protein, SyCRP1 acts as a transcriptional repressor of CO2-concentrating mechanism genes at high inorganic carbon levels in cyanobacteria
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ABSTRACT:
ORGANISM(S): Geminocystis herdmanii PCC 6308
PROVIDER: GSE295773 | GEO | 2025/10/05
REPOSITORIES: GEO
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Project description:Diatoms are responsible for ~40% of marine primary productivity1, fueling the oceanic carbon cycle and contributing to natural carbon sequestration in the deep ocean2. Diatoms rely on energetically expensive carbon concentrating mechanisms (CCMs) to fix carbon efficiently at modern levels of CO23–5. How diatoms may respond over the short and long-term to rising atmospheric CO2 remains an open question. Here we use nitrate-limited chemostats to show that the model diatom Thalassiosira pseudonana rapidly responds to increasing CO2 by differentially expressing gene clusters that regulate transcription and chromosome folding and subsequently reduces transcription of photosynthesis and respiration gene clusters under steady-state elevated CO2. These results suggest that exposure to elevated CO2 first causes a shift in regulation and then a metabolic rearrangement. Genes in one CO2-responsive cluster included CCM and photorespiration genes that share a putative cyclic-AMP responsive cis-regulatory sequence, implying these genes are co-regulated in response to CO2 with cAMP as an intermediate messenger. We verified cAMP-induced down-regulation of CCM gene δ-CA3 in nutrient-replete diatom cultures by inhibiting the hydrolysis of cAMP. These results indicate an important role for cAMP in down-regulating CCM and photorespiration genes under elevated CO2 and provide insights into mechanisms of diatom acclimation in response to climate change.
2015-04-17 | GSE67971 | GEO
Project description:The general acclimation of cyanobacteria to low carbon (LC) conditions includes coordinated alterations of gene expression and metabolism. To analyze possible signals for LC sensing and compensating reactions, we compared wild-type (WT) cells with two mutants of Synechocystis, the carboxysome-less mutant ccmM and the photorespiratory mutant ΔglcD1/D2. Metabolic phenotyping revealed that the mutant ΔccmM accumulated high 2-phosphoglycolate (2PG) levels while the ΔglcD1/D2 mutant accumulated glycolate, indicating oxygenase activity of RubisCO at high carbon (HC). The changes in the metabolite spectrum were compared to alterations in the global gene expression pattern. Cells of HC-grown mutants ΔccmM and ΔglcD1/D2 showed altered mRNA levels for many genes involved in photosynthesis, high light stress, and N-assimilation, while LC-specific genes such as those for inorganic carbon (Ci) transporters were not increased. After a shift to LC, mutant ΔglcD1/D2 revealed gene expression changes similar to WT cells, while mutant ΔccmM showed no differential expression of most LC-induced genes under identical conditions. In fact, none of the genes for Ci transporters or other components of the carbon concentrating mechanism (CCM) displayed higher transcript levels in the ΔccmM mutant. This finding renders a direct role for 2PG as a metabolic signal component for the induction of CCM during LC acclimation less likely. Because, the transcription pattern of ΔglcD1/D2 under LC showed specific differences compared to WT, a potential role for glycolate as a signal molecule that may trigger expression of parts of the CCM is proposed. Transcriptional profiling of carboxysomal and photorespiratory mutants of Synechocystis sp. PCC 6803 under high carbon (HC) and low carbon (LC) conditions relative to the wildtype response.
2011-12-30 | E-GEOD-31672 | biostudies-arrayexpress
Project description:Diatoms are responsible for ~40% of marine primary productivity1, fueling the oceanic carbon cycle and contributing to natural carbon sequestration in the deep ocean2. Diatoms rely on energetically expensive carbon concentrating mechanisms (CCMs) to fix carbon efficiently at modern levels of CO23–5. How diatoms may respond over the short and long-term to rising atmospheric CO2 remains an open question. Here we use nitrate-limited chemostats to show that the model diatom Thalassiosira pseudonana rapidly responds to increasing CO2 by differentially expressing gene clusters that regulate transcription and chromosome folding and subsequently reduces transcription of photosynthesis and respiration gene clusters under steady-state elevated CO2. These results suggest that exposure to elevated CO2 first causes a shift in regulation and then a metabolic rearrangement. Genes in one CO2-responsive cluster included CCM and photorespiration genes that share a putative cyclic-AMP responsive cis-regulatory sequence, implying these genes are co-regulated in response to CO2 with cAMP as an intermediate messenger. We verified cAMP-induced down-regulation of CCM gene ?-CA3 in nutrient-replete diatom cultures by inhibiting the hydrolysis of cAMP. These results indicate an important role for cAMP in down-regulating CCM and photorespiration genes under elevated CO2 and provide insights into mechanisms of diatom acclimation in response to climate change. In steady-state experiments: axenic T. pseudonana cells in four biological replicates (duplicate chemostats x 2 experimental runs) were acclimated to nitrate-limitation at 70% (1.5 day-1) of max growth rate for >10 days (>15 generations) under continuous light of 80 µmol photons·m?2·s?1. Cell biomass was maintained at ~2 x 105 cells·mL?1 by 10 ?M nitrate and carbonate chemistry stabilized to 300, 475 or 800 ?atm CO2, verified by pH and DIC measurements. Transition samples and carbonate chemistry were collected daily from chemostat cultures as CO2 levels were increased from ~300-800 ?atm at a rate ? 0.2 ?atm·min?1 over four consecutive days (6 generations) after pre-acclimation to 300 ?atm CO2 and nitrate-limitation.
2015-04-17 | E-GEOD-67971 | biostudies-arrayexpress
Project description:The general acclimation of cyanobacteria to low carbon (LC) conditions includes coordinated alterations of gene expression and metabolism. To analyze possible signals for LC sensing and compensating reactions, we compared wild-type (WT) cells with two mutants of Synechocystis, the carboxysome-less mutant ccmM and the photorespiratory mutant ΔglcD1/D2. Metabolic phenotyping revealed that the mutant ΔccmM accumulated high 2-phosphoglycolate (2PG) levels while the ΔglcD1/D2 mutant accumulated glycolate, indicating oxygenase activity of RubisCO at high carbon (HC). The changes in the metabolite spectrum were compared to alterations in the global gene expression pattern. Cells of HC-grown mutants ΔccmM and ΔglcD1/D2 showed altered mRNA levels for many genes involved in photosynthesis, high light stress, and N-assimilation, while LC-specific genes such as those for inorganic carbon (Ci) transporters were not increased. After a shift to LC, mutant ΔglcD1/D2 revealed gene expression changes similar to WT cells, while mutant ΔccmM showed no differential expression of most LC-induced genes under identical conditions. In fact, none of the genes for Ci transporters or other components of the carbon concentrating mechanism (CCM) displayed higher transcript levels in the ΔccmM mutant. This finding renders a direct role for 2PG as a metabolic signal component for the induction of CCM during LC acclimation less likely. Because, the transcription pattern of ΔglcD1/D2 under LC showed specific differences compared to WT, a potential role for glycolate as a signal molecule that may trigger expression of parts of the CCM is proposed.
2011-12-30 | GSE31672 | GEO
Project description:We used RNA-Seq to query the Chlamydomonas reinhardtii transcriptome for regulation by CO2 concentration and by the transcription regulator CIA5(CCM1). Both CO2 concentration and CIA5 are known to play roles in induction of an essential CO2-concentrating mechanism (CCM), but the degree of interaction and the extent of global regulation beyond the CCM were not previously understood. We compared the transcriptome of a wild type strain vs. a cia5 strain under 3 CO2 supply conditions: high CO2 (H-CO2; 5%); low CO2 (L-CO2; 0.03 to 0.05%); and very-low CO2 (VL-CO2; <0.02%). Our goals were to: 1) reveal candidate genes that, through changes in their expression, distinguish multiple acclimation states induced by H-CO2, L-CO2, and VL-CO2; 2) reveal genes regulated directly or indirectly by CIA5; and 3) reveal genes responding to the interaction between CIA5 and changes in CO2 concentration. Our results revealed a small group of genes as encoding putative Ci transporters based on their expression patterns. The results also showed a massive and much broader impact on global gene regulation by CIA5/CCM1, which directly or indirectly affected 15% of the Chlamydomonas genome. The transcriptomes under L-CO2 and VL-CO2 conditions were not significantly different, suggesting that these two acclimation states must be controlled by mechanisms operating beyond transcript abundance.
2012-08-10 | GSE33927 | GEO
Project description:We used RNA-Seq to query the Chlamydomonas reinhardtii transcriptome for regulation by CO2 concentration and by the transcription regulator CIA5(CCM1). Both CO2 concentration and CIA5 are known to play roles in induction of an essential CO2-concentrating mechanism (CCM), but the degree of interaction and the extent of global regulation beyond the CCM were not previously understood. We compared the transcriptome of a wild type strain vs. a cia5 strain under 3 CO2 supply conditions: high CO2 (H-CO2; 5%); low CO2 (L-CO2; 0.03 to 0.05%); and very-low CO2 (VL-CO2; <0.02%). Our goals were to: 1) reveal candidate genes that, through changes in their expression, distinguish multiple acclimation states induced by H-CO2, L-CO2, and VL-CO2; 2) reveal genes regulated directly or indirectly by CIA5; and 3) reveal genes responding to the interaction between CIA5 and changes in CO2 concentration. Our results revealed a small group of genes as encoding putative Ci transporters based on their expression patterns. The results also showed a massive and much broader impact on global gene regulation by CIA5/CCM1, which directly or indirectly affected 15% of the Chlamydomonas genome. The transcriptomes under L-CO2 and VL-CO2 conditions were not significantly different, suggesting that these two acclimation states must be controlled by mechanisms operating beyond transcript abundance. Both 137c wild type (cc125) and cia5 mutant were induced for 4 hours induction under H-CO2 (5%), L-CO2 (300~500 ppm), and VL-CO2 (100~200 ppm) conditions. 2 biological replicates were done for each strain -CO2 combination.
2012-08-10 | E-GEOD-33927 | biostudies-arrayexpress
Project description:One-third of global CO2 fixation is mediated by eukaryotic algae. Nearly all algae enhance their carbon assimilation by operating a CO2 concentrating mechanism (CCM), built around a mysterious organelle called the pyrenoid. Here, we leveraged new tools to determine the localizations of 146 candidate CCM proteins in the model alga Chlamydomonas reinhardtii. Twelve of the tagged proteins localized to the pyrenoid in six distinct sub-pyrenoid localizations: matrix, membrane tubules, plates, a mesh layer, and two punctate layers. Many stromal proteins can access the pyrenoid matrix. The proteins with access to the matrix tend to be small, suggesting that the pyrenoid may show protein size selectivity. Contrary to current models, the carbonic anhydrase CAH6 is in the flagella. Affinity purification mass spectrometry of 38 CCM-related proteins reveals dozens of additional components, including novel Rubisco interacting proteins, photosystem I assembly factor candidates and inorganic carbon flux components. Together, our spatial interactome reveals new protein components, sub-compartments and biophysical characteristics that open doors to a detailed molecular characterization of the algal CCM.
2018-01-24 | PXD007664 | Pride
Project description:Diatoms are a major primary producer accounting for 20% of the global primary production. Their massive carbon fixation is driven by the CO2-concentrating mechanisms (CCM), in which CO2 is actively supplied to the Rubisco localized in the pyrenoid, a membrane-less organelle of the plastid. To promote CO2 fixation, CO2 concentration in the pyrenoid matrix is assumed to be elevated while leakage of CO2 is minimized. However, due to the lack of information on the structural basis of diatom pyrenoid, the mechanism allowing efficient CO2 supply in conjunction with pyrenoid structure remains to be elucidated. While isolation of diatom pyrenoid is technically difficult due to structural instability, here we applied in vivo crosslinking using photo amino acids (pAA) which enabled us to obtain Rubisco enriched fractions. Based on LC-MS/MS analysis of the RbcL-enriched fraction, we identified a novel protein that surrounds the pyrenoid like a shell and hence named a Pyshell (Pyrenoid shell). Using genome-edited mutants, Pyshell was demonstrated to be a critical component required for growth under CO2-limiting conditions. The comprehensive analysis and identification of the pyrenoid component gave an important insight into the molecular basis driving the oceanic primary production.
2024-05-04 | PXD041920 | JPOST Repository
Project description:Limited systems-level understanding of CO2 concentrating mechanism (CCM) and metabolic adaption in response to different CO2-level in wild oleaginous algae has hindered the development of microalgal feedstock and the knowledge of its role in global warming and oceanic acidification. Nannochloropsis are a group of small unicellular microalgae widely distributed in oceans and fresh water, which implies that it plays a crucial role in biogeochemical cycles impinged on global climate change. In addition, Nannochloropsis has been used for flue gas fixation in many large-scale and pilot-scale outdoor cultivation facilities for photosynthetic production of fuels and chemicals. To untangle the intricate genome-wide networks underlying CCM and metabolic adjustment under different CO2 concentrations in Nannochloropsis, we applied high-throughput mRNA-sequencing and reconstructed the structure and dynamics of the genome-wide functional network underlying robust microalgal CCM and in Nannochloropsis oceanica, by tracking the genome-wide, single-base-resolution transcript change for the complete time-courses of different CO2 concentrations.
2019-07-16 | GSE55861 | GEO
Project description:Acclimation to low CO2 conditions in cyanobacteria involves the coordinated regulation of genes mainly encoding components of the carbon concentration mechanism (CCM). Making use of several independent microarray datasets a core set of CO2-regulated genes was defined for the model strain Synechocystis sp. PCC 6803. On the transcriptional level, the CCM is mainly regulated by the well-characterized transcriptional regulators NdhR and CmpR, whereas the role of an additional regulatory protein, namely cyAbrB2 belonging to the widely distributed AbrB regulator family that was originally characterized in the genus Bacillus, is less defined. Here we present results of transcript profiling of the wild type and a ΔcyabrB2 mutant of Synechocystis sp. PCC 6803 after shifts from high CO2 (5% in air, HC) to low CO2 (0.04%, LC). Evaluation of the transcriptomic data revealed that cyAbrB2 is involved in the regulation of several CCM-related genes such as sbtA/B, ndhF3/ndhD3/cupA and cmpABCD under LC conditions, but apparently acts supplementary to the main regulators. Under HC conditions, cyAbrB2 deletion changes the expression of photosystem II subunits, light-harvesting components, and Calvin-Benson-Bassham cycle enzymes.
2016-09-19 | GSE82120 | GEO