Variability of the pyrenoid-based CO2 concentrating mechanism in hornworts (Anthocerotophyta)

2002 ◽  
Vol 29 (3) ◽  
pp. 407 ◽  
Author(s):  
David Hanson ◽  
T. John Andrews ◽  
Murray R. Badger
Keyword(s):  
Active Site ◽  
Inorganic Carbon ◽  
Growth Form ◽  
Carbon Isotope Discrimination ◽  
Dissolved Inorganic Carbon ◽  
Co2 Exchange ◽  
Co2 Concentrating Mechanism ◽  
Concentrating Mechanism ◽  
C3 Photosynthesis ◽  
Catalytic Rate

Hornworts (Anthocerotophyta) are the only group of land plants with pyrenoid-containing chloroplasts. CO2 exchange and carbon isotope discrimination values (Δ13C) values have previously demonstrated the presence of a CO2 concentrating mechanism (CCM) in some pyrenoid-containing species. We have examined hornwort CCM function by using a combined fluorometer/mass spectrometer based technique to compare pyrenoid-containing (PhaeocerosProsk. and Notothylas Sull.) and pyrenoid-lacking (Megaceros Campbell) hornworts, with the liverwort Marchantia polymorphaL. that has standard C3 photosynthesis and a thalloid growth form similar to hornworts. We found that Notothylas has more CCM activity than Phaeoceros, and that Megaceros has the least CCM activity. Notothylas and Phaeoceros had compensation points from 11–13 parts per million (ppm) CO2, lower K0.5(CO2) than Marchantia, negligible photorespiration, and they accumulate a pool of dissolved inorganic carbon (DIC) between 19–108 nmol mg–1 chlorophyll. Megaceroshad an intermediate compensation point of 31 ppm CO2 (compared with 64 ppm CO2 in Marchantia), a lower K0.5(CO2) than Marchantia, and some photorespiration, but no DIC pool. We also determined the catalytic rate of carboxylation per active site of Rubisco for all four species (Marchantia, 2.6 s–1; Megaceros, 3.3 s–1; Phaeoceros, 4.2 s–1; Notothylas 4.3 s-1), and found that Rubisco content was 3% of soluble protein for pyrenoid-containing species, 4% for Megaceros and 8% for Marchantia.

scholarly journals Identification of Two Genes, sll0804 and slr1306, as Putative Components of the CO2-Concentrating Mechanism in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2008 ◽  
Vol 190 (24) ◽  
pp. 8234-8237 ◽  
Author(s):  
Shulu Zhang ◽  
Kevin W. Spann ◽  
Laurie K. Frankel ◽  
James V. Moroney ◽  
Terry M. Bricker
Keyword(s):  
Inorganic Carbon ◽  
Carbon Concentrating Mechanism ◽  
Co2 Concentrating Mechanism ◽  
Concentrating Mechanism ◽  
Synechocystis Sp ◽  
Pcc 6803

ABSTRACT Insertional transposon mutations in the sll0804 and slr1306 genes were found to lead to a loss of optimal photoautotrophy in the cyanobacterium Synechocystis sp. strain PCC 6803 grown under ambient CO2 concentrations (350 ppm). Mutants containing these insertions (4BA2 and 3ZA12, respectively) could grow photoheterotrophically on glucose or photoautotrophically at elevated CO2 concentrations (50,000 ppm). Both of these mutants exhibited an impaired affinity for inorganic carbon. Consequently, the Sll0804 and Slr1306 proteins appear to be putative components of the carbon-concentrating mechanism in Synechocystis sp. strain PCC 6803.

scholarly journals Radiocarbon isotopic evidence for assimilation of atmospheric CO<sub>2</sub> by the seagrass <i>Zostera marina</i>

2015 ◽  
Vol 12 (20) ◽  
pp. 6251-6258 ◽  
Author(s):  
K. Watanabe ◽  
T. Kuwae
Keyword(s):  
Carbon Source ◽  
Zostera Marina ◽  
Inorganic Carbon ◽  
Aquatic Vegetation ◽  
Dissolved Inorganic Carbon ◽  
Isotope Analysis ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Isotopic Signatures ◽  
Seagrass Meadows

Abstract. Submerged aquatic vegetation takes up water-column dissolved inorganic carbon (DIC) as a carbon source across its thin cuticle layer. It is expected that marine macrophytes also use atmospheric CO2 when exposed to air during low tide, although assimilation of atmospheric CO2 has never been quantitatively evaluated. Using the radiocarbon isotopic signatures (Δ14C) of the seagrass Zostera marina, DIC and particulate organic carbon (POC), we show quantitatively that Z. marina takes up and assimilates atmospheric modern CO2 in a shallow coastal ecosystem. The Δ14C values of the seagrass (−40 to −10 ‰) were significantly higher than those of aquatic DIC (−46 to −18 ‰), indicating that the seagrass uses a 14C-rich carbon source (atmospheric CO2, +17 ‰). A carbon-source mixing model indicated that the seagrass assimilated 0–40 % (mean, 17 %) of its inorganic carbon as atmospheric CO2. CO2 exchange between the air and the seagrass might be enhanced by the presence of a very thin film of water over the air-exposed leaves during low tide. Our radiocarbon isotope analysis, showing assimilation of atmospheric modern CO2 as an inorganic carbon source, improves our understanding of the role of seagrass meadows in coastal carbon dynamics.

Seasonal dissolved inorganic carbon variations in the Greenland Sea and implications for atmospheric CO2 exchange

1999 ◽  
Vol 46 (6-7) ◽  
pp. 1473-1496 ◽  
Author(s):  
Lisa A. Miller ◽  
Melissa Chierici ◽  
Truls Johannessen ◽  
Thomas T. Noji ◽  
Francisco Rey ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
Greenland Sea

Influence of the carbon concentrating mechanism on carbon stable isotope discrimination by the marine diatom Thalassiosira pseudonana

1998 ◽  
Vol 76 (6) ◽  
pp. 1098-1103 ◽  
Author(s):  
Anthony S Fielding ◽  
David H Turpin ◽  
Robert D Guy ◽  
Stephen E Calvert ◽  
David W Crawford ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Inorganic Carbon ◽  
Carbon Isotope Discrimination ◽  
Thalassiosira Pseudonana ◽  
Marine Phytoplankton ◽  
Marine Diatom ◽  
Carbon Concentrating Mechanism ◽  
Fractionation Factor ◽  
Isotope Discrimination ◽  
Concentrating Mechanism

There is no clear explanation why phytoplankton δ13C values are more negative in colder waters, but one current theory suggests that because colder waters hold more CO2, there is less diffusional limitation of CO2. This results in more discrimination against 13C and more negative phytoplankton δ13Cvalues. However, many species are able to actively take up CO2 or HCO3-, the latter being the major inorganic carbon species present in the dissolved inorganic carbon (DIC) pool of modern oceans. A previous study suggests that carbon concentrating mechanism (CCM) induction would affect carbon isotope discrimination, and this study confirms the presence of a relationship between discrimination and induction of a CCM in the marine diatom Thalassiosira pseudonana. CCM induction was measured by determining the half-saturation constant of photosynthesis (K0.5DIC). Values of K0.5DIC increased from 85 to 470 m M DIC over a range of ambient DIC levels from 0.2 to 2.7 mM. The fractionation factor increased from 10 to 21.3omicron over this same range. There was a significant relationship between K0.5DIC and the fractionation factor suggesting that CCM induction state influences carbon isotope discrimination. Other factors that influence discrimination may act through CCM induction.Key words: carbon isotope discrimination, carbon concentrating mechanism, Thalassiosira pseudonana, active carbon uptake, marine phytoplankton.

scholarly journals Distribution of dissolved inorganic carbon and related parameters in the Thermaikos Gulf (Eastern Mediterranean)

2006 ◽  
Vol 7 (1) ◽  
pp. 63 ◽  
Author(s):  
E. KRASAKOPOULOU ◽  
CH. ANAGNOSTOU ◽  
E. SOUVERMEZOGLOU ◽  
E. PAPATHANASSIOU ◽  
S. RAPSOMANIKIS
Keyword(s):  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Eastern Mediterranean ◽  
Co2 Exchange ◽  
Extensive Study ◽  
Atmospheric Co2 ◽  
Small Scale ◽  
Gas Transfer ◽  
Transfer Velocity

Data on the distribution of dissolved inorganic carbon (measured as TCO2) and related parameters in the Thermaikos Gulf were obtained during May 1997. High TCO2 concentrations were recorded close to the bottom, especially in the northern part of the gulf, as a result of organic matter remineralisation. The positive relatively good correlation between TCO2 and both apparent oxygen utilisation (AOU) and phosphate at the last sampling depth confi rmed the regenerative origin of a large proportion of TCO2. The comparatively conservative behaviour of alkalinity, together with the relatively low value of the homogenous buffer factor β (β = ∂lnfCO2/∂lnTCO2) revealed that calcifi cation or carbonate dissolution takes place on a very small scale, simultaneously with the organic carbon production. The correlations between fCO2 and chlorophyll α, as well as AOU and the surface temperature, revealed that the carbon dioxide fi xation through the biological activity is the principal factor that modulates the variability of fCO2. A rough first estimate of the magnitude of the air-sea CO2 exchange and the potential role of the Thermaikos Gulf in the transfer of atmospheric CO2 was also obtained. The results showed that during May 1997, the Thermaikos Gulf acted as a weak sink for atmospheric CO2 at a rate of -0.60 - -1.43 mmol m-2 d-1, depending on which formula for the gas transfer velocity was used, and in accordance to recent reports regarding other temperate continental shelves. Extensive study of the dissolved inorganic carbon and related parameters, and continuous shipboard measurements of fCO2 a and fCO2 w during all seasons are necessary to safely quantify the role of the Thermaikos Gulf in the context of the coastal margins CO2 dynamics.

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