Faculty Opinions recommendation of Diurnal regulation of photosynthetic light absorption, electron transport and carbon fixation in two contrasting oceanic environments.

2019 ◽  
Author(s):  
John Marra
Keyword(s):  
Electron Transport ◽  
Light Absorption ◽  
Carbon Fixation ◽  
Diurnal Regulation ◽  
Oceanic Environments

scholarly journals Diurnal regulation of photosynthetic light absorption, electron transport and carbon fixation in two contrasting oceanic environments

2019 ◽  
Vol 16 (7) ◽  
pp. 1381-1399 ◽  
Author(s):  
Nina Schuback ◽  
Philippe D. Tortell
Keyword(s):  
Electron Transport ◽  
Light Absorption ◽  
Carbon Fixation ◽  
Spatial Scales ◽  
Marine Phytoplankton ◽  
Optical Data ◽  
Reaction Centre ◽  
Phytoplankton Productivity ◽  
Ne Pacific ◽  
Insight Into

Abstract. Understanding the dynamics of marine phytoplankton productivity requires mechanistic insight into the non-linear coupling of light absorption, photosynthetic electron transport and carbon fixation in response to environmental variability. In the present study, we examined the variability of phytoplankton light absorption characteristics, light-dependent electron transport and 14C-uptake rates over a 48 h period in the coastal subarctic north-east (NE) Pacific. We observed an intricately coordinated response of the different components of the photosynthetic process to diurnal irradiance cycles, which acted to maximize carbon fixation, while simultaneously preventing damage by excess absorbed light energy. In particular, we found diurnal adjustments in pigment ratios, excitation energy transfer to reaction centre II (RCII), the capacity for non-photochemical quenching (NPQ), and the light efficiency (α) and maximum rates (Pmax) of RCII electron transport (ETRRCII) and 14C uptake. Comparison of these results from coastal waters to previous observations in offshore waters of the subarctic NE Pacific provides insight into the effects of iron limitation on the optimization of photosynthesis. Under iron-limited, low-biomass conditions, there was a significant reduction of iron-rich photosynthetic units per chlorophyll a, which was partly offset by higher light absorption and electron transport per photosystem II (PSII). Iron deficiency limited the capacity of phytoplankton to utilize peak midday irradiance for carbon fixation and caused an upregulation of photoprotective mechanisms, including NPQ, and the decoupling of light absorption, electron transport and carbon fixation. Such decoupling resulted in an increased electron requirement (Φe,C) and decreased quantum efficiency (ΦC) of carbon fixation at the iron-limited station. In both coastal and offshore waters, Φe,C and ΦC correlated strongly to NPQ, albeit with a significantly different slope. We discuss the implications of our results for the interpretation of bio-optical data and the parameterization of numerical productivity models, both of which are vital tools in monitoring marine photosynthesis over large temporal and spatial scales.

scholarly journals Diurnal regulation of photosynthetic light absorption, electron transport and carbon fixation in two contrasting oceanic environments

2019 ◽  
Author(s):  
Nina Schuback ◽  
Phillipe D. Tortell
Keyword(s):  
Electron Transport ◽  
Light Absorption ◽  
Carbon Fixation ◽  
Spatial Scales ◽  
Marine Phytoplankton ◽  
Optical Data ◽  
Photochemical Quenching ◽  
Phytoplankton Productivity ◽  
Ne Pacific ◽  
Insight Into

Abstract. Understanding the dynamics of marine phytoplankton productivity requires mechanistic insight into the non-linear coupling of light absorption, photosynthetic electron transport and carbon fixation in response to environmental variability. In the present study, we examined the variability of phytoplankton light absorption characteristics, light-dependent electron transport and 14C-uptake rates over a 48 hour period in the coastal Subarctic NE Pacific. We observed an intricately coordinated response of the different components of the photosynthetic process to diurnal irradiance cycles, which acted to maximise carbon fixation while simultaneously preventing damage by excess absorbed light energy. In particular, we found diurnal adjustments in pigment ratios, excitation energy transfer to reaction center II (RCII), the capacity for non-photochemical quenching (NPQ), and the light efficiency (α) and maximum rates (Pmax) of RCII electron transport (ETRRCII) and 14C-uptake. Comparison of these results from coastal waters to previous observations in offshore waters of the Subarctic NE Pacific provided insight into the effects of iron limitation on the optimization of photosynthesis. Under iron-limiting conditions, there was a significant reduction of iron-rich photosynthetic units per chlorophyll a, which was partly offset by higher light absorption and electron transport per photosystem II. Iron deficiency limited the capacity of phytoplankton to utilize peak mid-day irradiance for carbon fixation, and caused an upregulation of photo-protective mechanisms, including NPQ, and the decoupling of light absorption, electron transport and carbon fixation. Such decoupling resulted in an increased electron requirement (Φe,C) and decreased quantum efficiency (ΦC) of carbon fixation at the iron-limited station. In both coastal and off-shore waters, Φe,C and ΦC correlated strongly to NPQ. We discuss the implications of our results for the interpretation of bio-optical data, and the parameterization of numerical productivity models, both of which are vital tools in monitoring marine photosynthesis over large temporal and spatial scales.

scholarly journals Phycobilisomes Harbor FNRL in Cyanobacteria

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Haijun Liu ◽  
Daniel A. Weisz ◽  
Mengru M. Zhang ◽  
Ming Cheng ◽  
Bojie Zhang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Energy Transfer ◽  
Electron Transport ◽  
Carbon Fixation ◽  
Close Association ◽  
Reaction Centers ◽  
Light Energy ◽  
Fine Tuning ◽  
Cyclic Electron Transport ◽  
Cross Link

ABSTRACT Cyanobacterial phycobilisomes (PBSs) are photosynthetic antenna complexes that harvest light energy and supply it to two reaction centers (RCs) where photochemistry starts. PBSs can be classified into two types, depending on the presence of allophycocyanin (APC): CpcG-PBS and CpcL-PBS. Because the accurate protein composition of CpcL-PBS remains unclear, we describe here its isolation and characterization from the cyanobacterium Synechocystis sp. strain 6803. We found that ferredoxin-NADP+ oxidoreductase (or FNRL), an enzyme involved in both cyclic electron transport and the terminal step of the electron transport chain in oxygenic photosynthesis, is tightly associated with CpcL-PBS as well as with CpcG-PBS. Room temperature and low-temperature fluorescence analyses show a red-shifted emission at 669 nm in CpcL-PBS as a terminal energy emitter without APC. SDS-PAGE and quantitative mass spectrometry reveal an increased content of FNRL and CpcC2, a rod linker protein, in CpcL-PBS compared to that of CpcG-PBS rods, indicative of an elongated CpcL-PBS rod length and its potential functional differences from CpcG-PBS. Furthermore, we combined isotope-encoded cross-linking mass spectrometry with computational protein structure predictions and structural modeling to produce an FNRL-PBS binding model that is supported by two cross-links between K69 of FNRL and the N terminus of CpcB, one component in PBS, in both CpcG-PBS and CpcL-PBS (cross-link 1), and between the N termini of FNRL and CpcB (cross-link 2). Our data provide a novel functional assembly form of phycobiliproteins and a molecular-level description of the close association of FNRL with phycocyanin in both CpcG-PBS and CpcL-PBS. IMPORTANCE Cyanobacterial light-harvesting complex PBSs are essential for photochemistry in light reactions and for balancing energy flow to carbon fixation in the form of ATP and NADPH. We isolated a new type of PBS without an allophycocyanin core (i.e., CpcL-PBS). CpcL-PBS contains both a spectral red-shifted chromophore, enabling efficient energy transfer to chlorophyll molecules in the reaction centers, and an increased FNRL content with various rod lengths. Identification of a close association of FNRL with both CpcG-PBS and CpcL-PBS brings new insight to its regulatory role for fine-tuning light energy transfer and carbon fixation through both noncyclic and cyclic electron transport.

scholarly journals Genome wide transcriptomic analysis of the soil ammonia oxidizing archaeon Nitrososphaera viennensis upon exposure to copper limitation

2020 ◽  
Vol 14 (11) ◽  
pp. 2659-2674 ◽  
Author(s):  
Carolina Reyes ◽  
Logan H. Hodgskiss ◽  
Melina Kerou ◽  
Thomas Pribasnig ◽  
Sophie S. Abby ◽  
...  
Keyword(s):  
Electron Transport ◽  
Carbon Fixation ◽  
Ammonia Oxidation ◽  
Transcriptomic Analysis ◽  
Sequence Motifs ◽  
Conserved Sequence ◽  
Model Soil ◽  
Ammonia Oxidizing Archaea ◽  
Nitrite Production ◽  
Cu Uptake

Abstract Ammonia-oxidizing archaea (AOA) are widespread in nature and are involved in nitrification, an essential process in the global nitrogen cycle. The enzymes for ammonia oxidation and electron transport rely heavily on copper (Cu), which can be limited in nature. In this study the model soil archaeon Nitrososphaera viennensis was investigated via transcriptomic analysis to gain insight regarding possible Cu uptake mechanisms and compensation strategies when Cu becomes limiting. Upon Cu limitation, N. viennensis exhibited impaired nitrite production and thus growth, which was paralleled by downregulation of ammonia oxidation, electron transport, carbon fixation, nucleotide, and lipid biosynthesis pathway genes. Under Cu-limitation, 1547 out of 3180 detected genes were differentially expressed, with 784 genes upregulated and 763 downregulated. The most highly upregulated genes encoded proteins with a possible role in Cu binding and uptake, such as the Cu chelator and transporter CopC/D, disulfide bond oxidoreductase D (dsbD), and multicopper oxidases. While this response differs from the marine strain Nitrosopumilus maritimus, conserved sequence motifs in some of the Cu-responsive genes suggest conserved transcriptional regulation in terrestrial AOA. This study provides possible gene regulation and energy conservation mechanisms linked to Cu bioavailability and presents the first model for Cu uptake by a soil AOA.

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