scholarly journals Cytoklepty in the plankton: a host strategy to optimize the bioenergetic machinery of endosymbiotic algae

2020 ◽  
Author(s):  
Uwizeye Clarisse ◽  
Mars Brisbin Margaret ◽  
Gallet Benoit ◽  
Chevalier Fabien ◽  
LeKieffre Charlotte ◽  
...  
Keyword(s):  
Cell Division ◽  
Carbon Fixation ◽  
Carbon Allocation ◽  
Initial Step ◽  
Evolutionary Trajectory ◽  
Photon Propagation ◽  
Propagation Modeling ◽  
Close Proximity ◽  
Endosymbiotic Algae ◽  
Oceanic Carbon

AbstractEndosymbioses have shaped the evolutionary trajectory of life and remain widespread and ecologically important. Investigating modern oceanic photosymbioses can illuminate how algal endosymbionts are energetically exploited by their heterotrophic hosts, and inform on putative initial steps of plastid acquisition in eukaryotes. By combining 3D subcellular imaging with photophysiology, carbon flux imaging and transcriptomics, we show that cell division of algal endosymbionts (Phaeocystis) is blocked within hosts (Acantharia), and that their cellular architecture and bioenergetic machinery are radically altered. Transcriptional evidence indicates that a nutrient-independent mechanism prevents symbiont cell division and decouples nuclear and plastid division. As endosymbiont plastids proliferate, the volume of the photosynthetic machinery volume increases 100-fold in correlation with expansion of a reticular mitochondrial network in close proximity to plastids. Photosynthetic efficiency tends to increase with cell size and photon propagation modeling indicates that the networked mitochondrial architecture enhances light capture. This is accompanied by 150-fold higher carbon uptake and upregulation of genes involved in photosynthesis and carbon fixation, which, in conjunction with a ca.15-fold size increase of pyrenoids demonstrates enhanced primary production in symbiosis. NanoSIMS analysis revealed major carbon allocation to plastids and transfer to the host cell. Invagination of the symbiosome into endosymbionts to optimize metabolic exchanges is strong evidence that the algal metamorphosis is irreversible. Hosts therefore trigger and unambiguously benefit from major bioenergetic remodeling of symbiotic microalgae with important consequences for the oceanic carbon cycle. Unlike other photosymbioses, this interaction represents a so-called cytoklepty, which is a putative initial step towards plastid acquisition.

scholarly journals Cytoklepty in the plankton: A host strategy to optimize the bioenergetic machinery of endosymbiotic algae

2021 ◽  
Vol 118 (27) ◽  
pp. e2025252118
Author(s):  
Clarisse Uwizeye ◽  
Margaret Mars Brisbin ◽  
Benoit Gallet ◽  
Fabien Chevalier ◽  
Charlotte LeKieffre ◽  
...  
Keyword(s):  
Cell Division ◽  
Carbon Fixation ◽  
Carbon Allocation ◽  
Three Dimensional ◽  
Initial Step ◽  
Evolutionary Trajectory ◽  
Photon Propagation ◽  
Propagation Modeling ◽  
Endosymbiotic Algae ◽  
Oceanic Carbon

Endosymbioses have shaped the evolutionary trajectory of life and remain ecologically important. Investigating oceanic photosymbioses can illuminate how algal endosymbionts are energetically exploited by their heterotrophic hosts and inform on putative initial steps of plastid acquisition in eukaryotes. By combining three-dimensional subcellular imaging with photophysiology, carbon flux imaging, and transcriptomics, we show that cell division of endosymbionts (Phaeocystis) is blocked within hosts (Acantharia) and that their cellular architecture and bioenergetic machinery are radically altered. Transcriptional evidence indicates that a nutrient-independent mechanism prevents symbiont cell division and decouples nuclear and plastid division. As endosymbiont plastids proliferate, the volume of the photosynthetic machinery volume increases 100-fold in correlation with the expansion of a reticular mitochondrial network in close proximity to plastids. Photosynthetic efficiency tends to increase with cell size, and photon propagation modeling indicates that the networked mitochondrial architecture enhances light capture. This is accompanied by 150-fold higher carbon uptake and up-regulation of genes involved in photosynthesis and carbon fixation, which, in conjunction with a ca.15-fold size increase of pyrenoids demonstrates enhanced primary production in symbiosis. Mass spectrometry imaging revealed major carbon allocation to plastids and transfer to the host cell. As in most photosymbioses, microalgae are contained within a host phagosome (symbiosome), but here, the phagosome invaginates into enlarged microalgal cells, perhaps to optimize metabolic exchange. This observation adds evidence that the algal metamorphosis is irreversible. Hosts, therefore, trigger and benefit from major bioenergetic remodeling of symbiotic microalgae with potential consequences for the oceanic carbon cycle. Unlike other photosymbioses, this interaction represents a so-called cytoklepty, which is a putative initial step toward plastid acquisition.

scholarly journals Temporal patterns of cell division in natural populations of endosymbiotic algae

1983 ◽  
Vol 28 (5) ◽  
pp. 1009-1014 ◽  
Author(s):  
F. P. Wilkerson ◽  
G. Muller ◽  
Parker L. Muscatine
Keyword(s):  
Cell Division ◽  
Natural Populations ◽  
Temporal Patterns ◽  
Endosymbiotic Algae

Carbon allocation and translocation in chlorsulfuron-treated canola (Brassica napus)

Weed Science ◽  
1997 ◽  
Vol 45 (4) ◽  
pp. 466-469 ◽  
Author(s):  
Songmun Kim ◽  
William H. Vanden Born
Keyword(s):  
Brassica Napus ◽  
Carbon Fixation ◽  
No Reduction ◽  
Carbon Allocation ◽  
Starch Content ◽  
Carbon Exchange ◽  
Net Carbon Exchange

Our objective was to determine if the chlorsulfuron-induced reduction in assimilate export from leaves can be attributed to a shortage of carbohydrates. Treated canola leaves showed no reduction in carbon fixation or carbohydrate production during the first 24 h, but they exuded only 17 to 27% of the amount of sucrose exuded by corresponding control leaves. Exposure of the leaves to higher concentrations of CO2(500 vs. 350 μl L−1) resulted in greater net carbon exchange and higher starch content, but failed to overcome the reduction in sucrose export, presumably because of increased carbon allocation to starch.

scholarly journals Micromanipulation of amyloplasts with optical tweezers in Arabidopsis stems

2020 ◽  
Author(s):  
Yoshinori Abe ◽  
Keisuke Meguriya ◽  
Takahisa Matsuzaki ◽  
Teruki Sugiyama ◽  
Hiroshi Y. Yoshikawa ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Near Infrared ◽  
Initial Step ◽  
Optical Force ◽  
Physical Interaction ◽  
Laser Focus ◽  
Close Proximity ◽  
Endodermal Cells ◽  
Vacuolar Membranes

AbstractIntracellular sedimentation of highly dense, starch-filled amyloplasts toward the gravity vector is likely a key initial step for gravity sensing in plants. However, recent live-cell imaging technology revealed that most amyloplasts continuously exhibit dynamic, saltatory movements in the endodermal cells of Arabidopsis stems. These complicated movements led to questions about what type of amyloplast movement triggers gravity sensing. Here we show that a confocal microscope equipped with optical tweezers can be a powerful tool to trap and manipulate amyloplasts noninvasively, while simultaneously observing cellular responses such as vacuolar dynamics in living cells. A near-infrared (λ = 1064 nm) laser that was focused into the endodermal cells at 1 mW of laser power attracted and captured amyloplasts at the laser focus. The optical force exerted on the amyloplasts was theoretically estimated to be up to 1 pN. Interestingly, endosomes and trans-Golgi networks were trapped at 30 mW but not at 1 mW, which is probably due to lower refractive indices of these organelles than that of the amyloplasts. Because amyloplasts are in close proximity to vacuolar membranes in endodermal cells, their physical interaction could be visualized in real time. The vacuolar membranes drastically stretched and deformed in response to the manipulated movements of amyloplasts by optical tweezers. Our new method provides deep insights into the biophysical properties of plant organelles in vivo and opens a new avenue for studying gravity-sensing mechanisms in plants.

scholarly journals Single-molecule imaging reveals control of parental histone recycling by free histones during DNA replication

2019 ◽  
Author(s):  
Dominika T. Gruszka ◽  
Sherry Xie ◽  
Hiroshi Kimura ◽  
Hasan Yardimci
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Single Molecule ◽  
Replication Fork ◽  
Direct Evidence ◽  
Single Molecule Imaging ◽  
Epigenetic Memory ◽  
Close Proximity ◽  
Egg Extracts ◽  
Fork Stalling

SUMMARYFaithful replication of chromatin domains during cell division is fundamental to eukaryotic development. During replication, nucleosomes are disrupted ahead of the replication fork, followed by their rapid reassembly on daughter strands from the pool of recycled parental and newly synthesized histones. Here, we use single-molecule imaging and replication assays in Xenopus laevis egg extracts to determine the outcome of replication fork encounters with nucleosomes. Contrary to current models, the majority of parental histones are evicted from the DNA, with histone recycling, nucleosome sliding and replication fork stalling also occurring but at lower frequencies. The anticipated local histone transfer only becomes dominant upon depletion of free histones from extracts. Our studies provide the first direct evidence that parental histones remain in close proximity to their original locus during recycling and reveal that provision of excess histones results in impaired histone recycling, which has the potential to affect epigenetic memory.

scholarly journals Axial changes in wood functional traits have limited net effects on stem biomass increment in European beech (Fagus sylvatica)

2020 ◽  
Vol 40 (4) ◽  
pp. 498-510
Author(s):  
Richard L Peters ◽  
Georg von Arx ◽  
Daniel Nievergelt ◽  
Andreas Ibrom ◽  
Jonas Stillhard ◽  
...  
Keyword(s):  
Fagus Sylvatica ◽  
Carbon Fixation ◽  
Carbon Allocation ◽  
Volume Growth ◽  
Ring Width ◽  
European Beech ◽  
Wood Formation ◽  
Tree Level ◽  
Mature Trees ◽  
Anatomical Basis

Abstract During the growing season, trees allocate photoassimilates to increase their aboveground woody biomass in the stem (ABIstem). This ‘carbon allocation’ to structural growth is a dynamic process influenced by internal and external (e.g., climatic) drivers. While radial variability in wood formation and its resulting structure have been intensively studied, their variability along tree stems and subsequent impacts on ABIstem remain poorly understood. We collected wood cores from mature trees within a fixed plot in a well-studied temperate Fagus sylvatica L. forest. For a subset of trees, we performed regular interval sampling along the stem to elucidate axial variability in ring width (RW) and wood density (ρ), and the resulting effects on tree- and plot-level ABIstem. Moreover, we measured wood anatomical traits to understand the anatomical basis of ρ and the coupling between changes in RW and ρ during drought. We found no significant axial variability in ρ because an increase in the vessel-to-fiber ratio with smaller RW compensated for vessel tapering towards the apex. By contrast, temporal variability in RW varied significantly along the stem axis, depending on the growing conditions. Drought caused a more severe growth decrease, and wetter summers caused a disproportionate growth increase at the stem base compared with the top. Discarding this axial variability resulted in a significant overestimation of tree-level ABIstem in wetter and cooler summers, but this bias was reduced to ~2% when scaling ABIstem to the plot level. These results suggest that F. sylvatica prioritizes structural carbon sinks close to the canopy when conditions are unfavorable. The different axial variability in RW and ρ thereby indicates some independence of the processes that drive volume growth and wood structure along the stem. This refines our knowledge of carbon allocation dynamics in temperate diffuse-porous species and contributes to reducing uncertainties in determining forest carbon fixation.

CD38 Expression in B-CLL Is Dynamic and Changes Due to Contact with Activating Stimuli Found within the Leukaemic Microenvironment.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2798-2798 ◽  
Author(s):  
Piers E.M. Patten ◽  
Andrea G.S. Buggins ◽  
Julie Richards ◽  
Andrew Wotherspoon ◽  
Terry John Hamblin ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Division ◽  
Mononuclear Cells ◽  
Proliferative Potential ◽  
Activated T Cells ◽  
Peripheral Blood Mononuclear ◽  
Cd38 Expression ◽  
Close Proximity ◽  
Activated T Lymphocytes

Abstract High levels of CD38 expression in B-cell chronic lymphocytic leukaemia (B-CLL) confer a poor prognosis. Although its role in B-CLL is unknown, signalling through CD38 has been implicated in cell survival, trafficking and proliferation. Since proliferation in B-CLL is thought to take place within both bone marrow (BM) and secondary lymphoid tissue, we investigated whether CD38 expression might vary in response to stimuli that occur in these tissue compartments. Firstly, we compared the percentage CD38 expression of CD5/19 cells on 35 paired PB and BM aspirate B-CLL samples. The mean CD38% was significantly higher in BM than PB in all samples (27% vs 19%, p=0.009) including samples with a PB CD38 of 7% or more (33% vs 42%, p=0.047), indicating that factors present in the BM up regulate CD38 expression. Next, CD38 expression and cell division of B-CLL peripheral blood mononuclear cells (PBMCs) were examined in an in vitro system aimed at mimicking the proliferation centre microenvironment where leukaemic cells are situated in close proximity to activated T lymphocytes. Positively selected T cells from 15 B-CLL patients were activated overnight with CD3/28 beads and subsequently cultured with autologous B-CLL PBMCs. Both the percentage of CD19+ CD38+ cells (29.9% vs 59.9%, p=0.003) and CD38 mean fluorescence intensity (75.1 vs 830.8, p=0.005) increased over the 6 day culture period. B-CLL cell division was assessed using the dye carboxyfluorescein diacetate succinimidyl ester (CFSE) in the same co-culture system. This showed that co-culture with autologous activated T-cells can result in B-CLL cell division, and is preceded by CD38 up regulation. In addition, significantly more B-CLL cells underwent at least one division from patients with an initial CD38 level of 7% or more, as compared to under 7% (24.6% vs 10.9%, p=0.031). To further investigate the relationship between B-CLL cell proliferation, CD38 expression and the role of T-cells we examined tissue sections known to contain paraimmunoblasts and other proliferating B-CLL cells. Four colour confocal microscopy using CD3, Ki67, CD38 and CD23 to label frozen B-CLL lymph nodes was employed. Large Ki67+ CD23+ cells were present in close proximity to CD3+ T-cells and these large B-CLL cells had higher CD38 expression than the surrounding small B-CLL lymphocytes. These results support the proposal that CD38 expression in B-CLL is dynamic and may reflect exposure to T-cell derived stimuli which contribute to proliferation in the BM or LN microenvironment. A possible explanation for the poorer prognosis of patients with higher CD38 expression may be that their disease has more proliferative potential.

scholarly journals Photoreceptor effects on plant biomass, resource allocation, and metabolic state

2016 ◽  
Vol 113 (27) ◽  
pp. 7667-7672 ◽  
Author(s):  
Deyue Yang ◽  
Daniel D. Seaton ◽  
Johanna Krahmer ◽  
Karen J. Halliday
Keyword(s):  
Biomass Production ◽  
Carbon Fixation ◽  
Carbon Allocation ◽  
Plant Biomass ◽  
Tricarboxylic Acid Cycle ◽  
Critical Role ◽  
Marker Genes ◽  
Adult Plant ◽  
Plant Signaling ◽  
Phytochrome Mutants

Plants sense the light environment through an ensemble of photoreceptors. Members of the phytochrome class of light receptors are known to play a critical role in seedling establishment, and are among the best-characterized plant signaling components. Phytochromes also regulate adult plant growth; however, our knowledge of this process is rather fragmented. This study demonstrates that phytochrome controls carbon allocation and biomass production in the developing plant. Phytochrome mutants have a reduced CO2 uptake, yet overaccumulate daytime sucrose and starch. This finding suggests that even though carbon fixation is impeded, the available carbon resources are not fully used for growth during the day. Supporting this notion, phytochrome depletion alters the proportion of day:night growth. In addition, phytochrome loss leads to sizeable reductions in overall growth, dry weight, total protein levels, and the expression of CELLULOSE SYNTHASE-LIKE genes. Because cellulose and protein are major constituents of plant biomass, our data point to an important role for phytochrome in regulating these fundamental components of plant productivity. We show that phytochrome loss impacts core metabolism, leading to elevated levels of tricarboxylic acid cycle intermediates, amino acids, sugar derivatives, and notably the stress metabolites proline and raffinose. Furthermore, the already growth-retarded phytochrome mutants are less responsive to growth-inhibiting abiotic stresses and have elevated expression of stress marker genes. This coordinated response appears to divert resources from energetically costly biomass production to improve resilience. In nature, this strategy may be activated in phytochrome-disabling, vegetation-dense habitats to enhance survival in potentially resource-limiting conditions.

scholarly journals Staphylococcus aureus ClpX localizes at the division septum and impacts transcription of genes involved in cell division, T7-secretion, and SaPI5-excision

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Camilla Jensen ◽  
Marie J. Fosberg ◽  
Ida Thalsø-Madsen ◽  
Kristoffer T. Bæk ◽  
Dorte Frees
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Division ◽  
Molecular Chaperones ◽  
Virulence Genes ◽  
Living Cells ◽  
Cell Physiology ◽  
Peptidoglycan Synthesis ◽  
Close Proximity ◽  
Number Of Genes ◽  
Transcriptional Changes

Abstract In all living cells, molecular chaperones are essential for facilitating folding and unfolding of proteins. ClpX is a highly conserved ATP-dependent chaperone that besides functioning as a classical chaperone can associate with ClpP to form the ClpXP protease. To investigate the relative impact of the ClpXP protease and the ClpX chaperone in cell physiology of the important pathogenic bacterium Staphylococcus aureus, we assessed the transcriptional changes induced by inactivating only ClpXP, or by completely deleting ClpX. This analysis revealed that ClpX has a profound impact on S. aureus cell physiology that is mediated primarily via ClpXP-dependent pathways. As an example, ClpX impacts expression of virulence genes entirely via ClpXP-dependent mechanisms. Furthermore, ClpX controls a high number of genes and sRNAs via pathways involving both ClpXP protease and ClpX chaperone activities; an interesting example being genes promoting excision and replication of the pathogenicity island SaPI5. Independently of ClpP, ClpX, impacts transcription of only a restricted number of genes involved in peptidoglycan synthesis, cell division, and type seven secretion. Finally, we demonstrate that ClpX localizes in single foci in close proximity to the division septum lending support to the idea that ClpX plays a role in S. aureus cell division.

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