A SYNECHOCOCCUS PCC7942 ΔCCMM (CYANOPHYCEAE) MUTANT PSEUDOREVERTS TO AIR GROWTH WITHOUT REGAINING CARBOXYSOMES1

Emlyn-Jones, Daniel; Woodger, Fiona J.; Andrews, T. John; Price, G. Dean; Whitney, Spencer M.

doi:10.1111/j.1529-8817.2006.00236.x

Cited by 14 publications

(6 citation statements)

References 40 publications

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“…This may be particularly essential for those cells that do not produce small carboxysome-like structures. Of note, a previous study reported that a carboxysome-less pseudorevertant Δ ccmM Syn7942 mutant could survive in air ( 40 ). Further investigations are needed to tackle this question.…”

Section: Discussionmentioning

confidence: 99%

Rubisco accumulation factor 1 (Raf1) plays essential roles in mediating Rubisco assembly and carboxysome biogenesis

Huang

Kong

Sun

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Carboxysomes are membrane-free organelles for carbon assimilation in cyanobacteria. The carboxysome consists of a proteinaceous shell that structurally resembles virus capsids and internal enzymes including ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), the primary carbon-fixing enzyme in photosynthesis. The formation of carboxysomes requires hierarchical self-assembly of thousands of protein subunits, initiated from Rubisco assembly and packaging to shell encapsulation. Here we study the role of Rubisco assembly factor 1 (Raf1) in Rubisco assembly and carboxysome formation in a model cyanobacterium, Synechococcus elongatus PCC7942 (Syn7942). Cryo-electron microscopy reveals that Raf1 facilitates Rubisco assembly by mediating RbcL dimer formation and dimer–dimer interactions. Syn7942 cells lacking Raf1 are unable to form canonical intact carboxysomes but generate a large number of intermediate assemblies comprising Rubisco, CcaA, CcmM, and CcmN without shell encapsulation and a low abundance of carboxysome-like structures with reduced dimensions and irregular shell shapes and internal organization. As a consequence, the Raf1-depleted cells exhibit reduced Rubisco content, CO2-fixing activity, and cell growth. Our results provide mechanistic insight into the chaperone-assisted Rubisco assembly and biogenesis of carboxysomes. Advanced understanding of the biogenesis and stepwise formation process of the biogeochemically important organelle may inform strategies for heterologous engineering of functional CO2-fixing modules to improve photosynthesis.

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Section: Discussionmentioning

confidence: 99%

Rubisco accumulation factor 1 (Raf1) plays essential roles in mediating Rubisco assembly and carboxysome biogenesis

Huang

Kong

Sun

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Under high CO 2 concentration (1% v/v), the Δ ccmKLMN mutant maintains flux ratios in central pathways similar to the control strain. In previous reports, quantitative RT-PCR and microarrays were used to monitor the abundance of gene transcripts in both ΔccmM and wild type cyanobacterial cells grown in high CO 2 conditions (Emlyn-Jones et al, 2006; Hackenberg et al, 2012). Despite large transcriptional changes seen in genes involved in photosynthesis, high-light stress, and N assimilation in the Δ ccmKLMN mutant, little-to-no transcriptional change was detected in its carbon uptake (i.e., genes encoding carbon transporter systems and transcriptional regulators), the Calvin Cycle, and other central metabolic pathways.…”

Section: Discussionmentioning

confidence: 99%

Cyanobacterial carboxysome mutant analysis reveals the influence of enzyme compartmentalization on cellular metabolism and metabolic network rigidity

Abernathy

Czajka

Allen

et al. 2019

Metabolic Engineering

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Cyanobacterial carboxysomes encapsulate carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Genetic deletion of the major structural proteins encoded within the ccm operon in Synechococcus sp. PCC 7002 (ΔccmKLMN) disrupts carboxysome formation and significantly affects cellular physiology. Here we employed both metabolite pool size analysis and isotopically nonstationary metabolic flux analysis (INST-MFA) to examine metabolic regulation in cells lacking carboxysomes. Under high CO2 environments (1%), the ΔccmKLMN mutant could recover growth and had a similar central flux distribution as the control strain, with the exceptions of moderately decreased photosynthesis and elevated biomass protein content and photorespiration activity. Metabolite analyses indicated that the ΔccmKLMN strain had significantly larger pool sizes of pyruvate (> 18 folds), UDPG (uridine diphosphate glucose), and aspartate as well as higher levels of secreted organic acids (e.g., malate and succinate). These results suggest that the ΔccmKLMN mutant is able to largely maintain a fluxome similar to the control strain by changing in intracellular metabolite concentrations and metabolite overflows under optimal growth conditions. When CO2 was insufficient (0.2%), provision of acetate moderately promoted mutant growth. Interestingly, the removal of microcompartments may loosen the flux network and promote RuBisCO side-reactions, facilitating redirection of central metabolites to competing pathways (i.e., pyruvate to heterologous lactate production). This study provides important insights into metabolic regulation via enzyme compartmentation and cyanobacterial compensatory responses.

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“…Other widely studied cyanobacterial strains grow significantly slower; for example, Synechocystis sp. PCC 6803 which was reported to have a doubling time of 12 h at (Vermass et al, 1988 ), and Synechococcus elongatus PCC 7942 with a doubling time of 6–7 h (Mori et al, 1996 ; Emlyn-Jones et al, 2006 ).…”

Section: Discussionmentioning

confidence: 99%

Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002

et al. 2014

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Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm) or phycocyanin (630 nm) as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates were generally proportional to the total incident irradiance at values <275 μmol photons m−2 · s−1 and were not affected by the ratio of 630:680 nm wavelengths. Notably, under monochromatic light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60–70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased ~40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.

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A SYNECHOCOCCUS PCC7942 ΔCCMM (CYANOPHYCEAE) MUTANT PSEUDOREVERTS TO AIR GROWTH WITHOUT REGAINING CARBOXYSOMES¹

Cited by 14 publications

References 40 publications

Rubisco accumulation factor 1 (Raf1) plays essential roles in mediating Rubisco assembly and carboxysome biogenesis

Rubisco accumulation factor 1 (Raf1) plays essential roles in mediating Rubisco assembly and carboxysome biogenesis

Cyanobacterial carboxysome mutant analysis reveals the influence of enzyme compartmentalization on cellular metabolism and metabolic network rigidity

Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002

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