scholarly journals Inorganic carbon concentrating mechanisms in free‐living and symbiotic dinoflagellates and chromerids

2020 ◽  
Vol 56 (6) ◽  
pp. 1377-1397 ◽  
Author(s):  
John A. Raven ◽  
David J. Suggett ◽  
Mario Giordano
Keyword(s):  
Inorganic Carbon ◽  
Free Living ◽  
Carbon Concentrating Mechanisms ◽  
Symbiotic Dinoflagellates

scholarly journals Structural rearrangements drive extensive genome divergence between symbiotic and free-living Symbiodinium

2019 ◽  
Author(s):  
Raúl A. González-Pech ◽  
Timothy G. Stephens ◽  
Yibi Chen ◽  
Amin R. Mohamed ◽  
Yuanyuan Cheng ◽  
...  
Keyword(s):  
Genome Size ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Sequence Divergence ◽  
Gene Families ◽  
Homologous Gene ◽  
Structural Rearrangements ◽  
Free Living ◽  
Symbiotic Dinoflagellates ◽  
Genome Assemblies

AbstractSymbiodiniaceae are predominantly symbiotic dinoflagellates critical to corals and other reef organisms. Symbiodinium is a basal symbiodiniacean lineage and includes symbiotic and free-living taxa. However, the molecular mechanisms underpinning these distinct lifestyles remain little known. Here, we present high-quality de novo genome assemblies for the symbiotic Symbiodinium tridacnidorum CCMP2592 (genome size 1.3 Gbp) and the free-living Symbiodinium natans CCMP2548 (genome size 0.74 Gbp). These genomes display extensive sequence divergence, sharing only ~1.5% conserved regions (≥90% identity). We predicted 45,474 and 35,270 genes for S. tridacnidorum and S. natans, respectively; of the 58,541 homologous gene families, 28.5% are common to both genomes. We recovered a greater extent of gene duplication and higher abundance of repeats, transposable elements and pseudogenes in the genome of S. tridacnidorum than in that of S. natans. These findings demonstrate that genome structural rearrangements are pertinent to distinct lifestyles in Symbiodinium, and may contribute to the vast genetic diversity within the genus, and more broadly in Symbiodiniaceae. Moreover, the results from our whole-genome comparisons against a free-living outgroup support the notion that the symbiotic lifestyle is a derived trait in, and that the free-living lifestyle is ancestral to, Symbiodinium.

scholarly journals Latitudinal trends in stable isotope signatures and carbon concentrating mechanisms of northeast Atlantic rhodoliths

2017 ◽  
Author(s):  
Laurie C. Hofmann ◽  
Svenja Heesch
Keyword(s):  
Stable Isotope ◽  
Red Algae ◽  
Free Living ◽  
Shallow Marine ◽  
Northeast Atlantic ◽  
Stable Isotope Signatures ◽  
Carbon Concentrating Mechanisms

Abstract. Rhodoliths are free-living calcifying red algae that form extensive beds in shallow marine benthic environments (

scholarly journals Carbon concentrating mechanisms maintain bloom biomass and CO<sub>2</sub> depletion in eutrophic lake ecosystems

2016 ◽  
Author(s):  
Ana M. Morales-Williams ◽  
Alan D. Wanamaker Jr. ◽  
John A. Downing
Keyword(s):  
Inorganic Carbon ◽  
Phytoplankton Bloom ◽  
Dissolved Inorganic Carbon ◽  
Negative Relationship ◽  
Eutrophic Lake ◽  
Anthropogenic Pressure ◽  
Phytoplankton Blooms ◽  
Eutrophic Lakes ◽  
Lake Ecosystems ◽  
Carbon Concentrating Mechanisms

Abstract. Harmful phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO2 depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO3−) across their cell membrane when CO2 concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO2 depletion, we measured δ13C signatures of dissolved inorganic carbon (δ13CDIC) and phytoplankton particulate organic carbon (δ13Cphyto) in sixteen mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO2 stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton δ13C signatures, as well as a significant non-linear negative relationship between water column ρCO2 and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO2 or HCO3− during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO2 drops below atmospheric equilibrium. Our results indicate active HCO3− uptake via CCMs may be an important mechanism maintaining phytoplankton blooms when CO2 is depleted. Further increases in anthropogenic pressure, eutrophication, and harmful cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.

Studies on a nudibranch that contains zooxanthellae. II. Contribution of zooxanthellae to animal respiration (CZAR) in Pteraeolidia ianthina with high and low densities of zooxanthellae

1986 ◽  
Vol 228 (1253) ◽  
pp. 511-521 ◽  
Keyword(s):  
Mitotic Index ◽  
Specific Growth ◽  
Symbiotic Association ◽  
Diel Pattern ◽  
Fixed Carbon ◽  
Free Living ◽  
Carbon Demand ◽  
Symbiotic Dinoflagellates ◽  
Specific Growth Rates ◽  
Relationship Of

Daily budgets of photosynthetically fixed carbon were constructed for Pteraeolidia ianthina with high and low densities of zooxanthellae, for irradiances typical of latitude 34° S in winter, spring and summer. Whereas nudibranchs with high densities of zooxanthellae were potentially phototrophic with respect to carbon, animals with densities of zooxanthellae less than 0.5 x 10 6 cells mg -1 protein were not. The proportion of dividing zooxanthellae (mitotic index) in P. ianthina was followed over 48 hours. The diel pattern of mitotic index was asynchronous; the indices were higher in animals with low densities of zooxanthellae (20.1±6.2%) than in animals with high densities of zooxanthellae (4.7±1.8%). Specific growth rates of zooxanthellae, calculated from mitotic indices, ranged between 0.100 and 0.399 d -1 , indicating that zooxanthellae in P . ianthina have the potential to grow at rates comparable to those found in free-living and other symbiotic dinoflagellates. Zooxanthellae in the host photosynthesized at similar rates, irrespective of their density in P . ianthina . Because of the greater amount of newly synthesized carbon dedicated to the population growth of zooxanthellae, low-density populations did not have excess organic carbon available for host respiration. High density populations, however, were able to supply 79% of the animal’s respiratory carbon demand in winter, 121% in spring and 173% in summer. These results demonstrate that the metabolic relationship of zooxanthellae and their invertebrate hosts may change during the establishment of a symbiotic association.

scholarly journals The carbonic anhydrase CAH1 is an essential component of the carbon-concentrating mechanism in Nannochloropsis oceanica

2017 ◽  
Vol 114 (17) ◽  
pp. 4537-4542 ◽  
Author(s):  
Christopher W. Gee ◽  
Krishna K. Niyogi
Keyword(s):  
Carbonic Anhydrase ◽  
Molecular Mechanisms ◽  
Inorganic Carbon ◽  
Carbonic Anhydrases ◽  
Nannochloropsis Oceanica ◽  
Essential Component ◽  
Protein Levels ◽  
Photosynthetic Organisms ◽  
Carbon Concentrating Mechanisms ◽  
Carbonic Anhydrase 1

Aquatic photosynthetic organisms cope with low environmental CO2 concentrations through the action of carbon-concentrating mechanisms (CCMs). Known eukaryotic CCMs consist of inorganic carbon transporters and carbonic anhydrases (and other supporting components) that culminate in elevated [CO2] inside a chloroplastic Rubisco-containing structure called a pyrenoid. We set out to determine the molecular mechanisms underlying the CCM in the emerging model photosynthetic stramenopile, Nannochloropsis oceanica, a unicellular picoplanktonic alga that lacks a pyrenoid. We characterized CARBONIC ANHYDRASE 1 (CAH1) as an essential component of the CCM in N. oceanica CCMP1779. We generated insertions in this gene by directed homologous recombination and found that the cah1 mutant has severe defects in growth and photosynthesis at ambient CO2. We identified CAH1 as an α-type carbonic anhydrase, providing a biochemical role in CCM function. CAH1 was found to localize to the lumen of the epiplastid endoplasmic reticulum, with its expression regulated by the external inorganic carbon concentration at both the transcript and protein levels. Taken together, these findings show that CAH1 is an indispensable component of what may be a simple but effective and dynamic CCM in N. oceanica.

scholarly journals Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes

2017 ◽  
Vol 14 (11) ◽  
pp. 2865-2875 ◽  
Author(s):  
Ana M. Morales-Williams ◽  
Alan D. Wanamaker Jr. ◽  
John A. Downing
Keyword(s):  
Inorganic Carbon ◽  
Phytoplankton Bloom ◽  
Dissolved Inorganic Carbon ◽  
Negative Relationship ◽  
Anthropogenic Pressure ◽  
Phytoplankton Blooms ◽  
Eutrophic Lakes ◽  
Bicarbonate Uptake ◽  
Carbon Concentrating Mechanisms ◽  
Photosynthetic Fractionation

Abstract. Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO2 depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO3−) across their cell membrane when CO2 concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO2 depletion, we measured the δ13C signatures of dissolved inorganic carbon (δ13CDIC) and phytoplankton particulate organic carbon (δ13Cphyto) in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass–balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO2 stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton δ13C signatures as well as a significant nonlinear negative relationship between water column ρCO2 and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO2 or HCO3− during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO2 drops below atmospheric equilibrium. Our results indicate that active HCO3− uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO2 is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.

scholarly journals The evolution of inorganic carbon concentrating mechanisms in photosynthesis

2008 ◽  
Vol 363 (1504) ◽  
pp. 2641-2650 ◽  
Author(s):  
John A Raven ◽  
Charles S Cockell ◽  
Christina L De La Rocha
Keyword(s):  
Vascular Plants ◽  
Crassulacean Acid Metabolism ◽  
Inorganic Carbon ◽  
Acid Metabolism ◽  
Oxygen Species ◽  
Biochemical Mechanism ◽  
Cam Plants ◽  
Carbon Concentrating Mechanisms ◽  
Almost All ◽  
Nitrogen Phosphorus

Inorganic carbon concentrating mechanisms (CCMs) catalyse the accumulation of CO 2 around rubisco in all cyanobacteria, most algae and aquatic plants and in C 4 and crassulacean acid metabolism (CAM) vascular plants. CCMs are polyphyletic (more than one evolutionary origin) and involve active transport of , CO 2 and/or H + , or an energized biochemical mechanism as in C 4 and CAM plants. While the CCM in almost all C 4 plants and many CAM plants is constitutive, many CCMs show acclimatory responses to variations in the supply of not only CO 2 but also photosynthetically active radiation, nitrogen, phosphorus and iron. The evolution of CCMs is generally considered in the context of decreased CO 2 availability, with only a secondary role for increasing O 2 . However, the earliest CCMs may have evolved in oxygenic cyanobacteria before the atmosphere became oxygenated in stromatolites with diffusion barriers around the cells related to UV screening. This would decrease CO 2 availability to cells and increase the O 2 concentration within them, inhibiting rubisco and generating reactive oxygen species, including O 3 .

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