Compartmental Analysis Suggests Macropinocytosis at the Onset of Diatom Valve Formation

Brasser, H. J.; Strate, van der Han; Gieskes, W.W.C.; Krijger, Gerard C.; Vrieling, Engel G.; Wolterbeek, H. Th.

doi:10.1007/s12633-010-9059-2

Cited by 12 publications

(8 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…"Si" storage pools in diatom cells, if present, provide "Si" for the production of new valves. 22,23 The reported concentrations up to ca. 300 mM intracellular "Si" within the storage pool 24−28 strongly exceed the solubility of monosilicic acid (∼ 2 mM/150 ppm, pH < 9).…”

Section: ■ Introductionmentioning

confidence: 99%

“…One of the most spectacular examples of such silica biomineralizing organisms are diatoms that are unicellular algae living in fresh and marine water habitats. − Diatoms preferentially take up “Si” as monosilicic acid (Si(OH) 4 ) , via special “Si” transport (SIT) proteins. − Active transport is necessary because the concentration of silicic acid in natural waters is low. − The SIT proteins determine “Si” uptake at low Si(OH) 4 concentrations, whereas the uptake is diffusion-controlled at high Si(OH) 4 levels. , However, the intracellular “Si” processing, transport, and transfer into the silica deposition vesicle (SDV) are rather poorly understood. − Numerous publications report the existence of intracellular “Si” storage pools in diatoms. “Si” storage pools in diatom cells, if present, provide “Si” for the production of new valves. , The reported concentrations up to ca. 300 mM intracellular “Si” within the storage pool − strongly exceed the solubility of monosilicic acid (∼ 2 mM/150 ppm, pH < 9). − “Si” species are assumed to be stabilized via association with “organic material” such as special proteins, thus forming intracellular soluble Si(OH) 4 pools .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Bioinspired Insights into Silicic Acid Stabilization Mechanisms: The Dominant Role of Polyethylene Glycol-Induced Hydrogen Bonding

et al. 2014

View full text Add to dashboard Cite

Mono- and disilicic acids were stabilized by uncharged polyethylene glycols (PEGs) in silica-supersaturated solutions (the starting solution contained 500 ppm/8.3 mM sodium orthosilicate, Na2SiO3·5H2O, expressed as SiO2) at pH = 7, most likely by hydrogen bonding between the silanol groups and -CH2-CH2-O-ether moieties. The stabilization was monitored by measuring molybdate-reactive silica and also by a combination of liquid- and solid-state (29)Si NMR spectroscopy. It depends on PEG concentration (20-100 ppm) and molecular weight (1550-20,000 Da). Two narrow (29)Si NMR signals characteristic for monosilicic acid (Q(0)) and disilicic acid (Q(1)) can be observed in (29)Si NMR spectra of solutions containing PEG 10000 with intensities distinctly higher than the control, that is, in the absence of PEG. Silica-containing precipitates are observed in the presence of PEG, in contrast to the gel formed in the absence of PEG. These precipitates exhibit similar degrees of silica polycondensation as found in the gel as can be seen from the (29)Si MAS NMR spectra. However, the (2)D HETCOR spectra show different (1)H NMR signal shifts: The signal due to H-bonded SiOH/H2O, which is found at 6 ppm in the control, is shifted to ~7 ppm in the PEG-containing precipitate. This indicates the formation of slightly stronger H-bonds than in the control sample, most likely between PEG and the silica species. The presence of PEG in these precipitates is unequivocally proven by (13)C CP MAS NMR spectroscopy. The (13)C signal of PEG significantly shifts and is much narrower in the precipitates as compared to the pristine PEG, indicating that PEG is embedded into the silica or at least bound to its surface (or both), and not phase separated. FT-IR spectra corroborate the above arguments. The H-bonding between silanol and ethereal O perturbs the band positions attributed to vibrations involving the O atom. This work may invoke an alternative way to envision silica species stabilization (prior to biosilica formation) in diatoms by investigating possible scenarios of uncharged biomacromolecules playing a role in biosilica synthesis.

show abstract

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bioinspired Insights into Silicic Acid Stabilization Mechanisms: The Dominant Role of Polyethylene Glycol-Induced Hydrogen Bonding

et al. 2014

View full text Add to dashboard Cite

show abstract

“…However, classical pinocytosis is not cost-effective in terms of bioenergetics, membrane recycling, and kinetics, and thus, it cannot be the primary mechanism of silicon uptake in diatoms (23). Lately, a mathematical model based on compartmental analysis supporting the macropinocytosis-mediated silicon uptake hypothesis during initial and early valve formation when a high quantity of silicon is required, albeit without morphological and molecular evidence, was presented (24).…”

mentioning

confidence: 99%

Evidence for a Regulatory Role of Diatom Silicon Transporters in Cellular Silicon Responses

Shrestha

Hildebrand

2015

Eukaryot Cell

View full text Add to dashboard Cite

The utilization of silicon by diatoms has both global and small-scale implications, from oceanic primary productivity to nanotechnological applications of their silica cell walls. The sensing and transport of silicic acid are key aspects of understanding diatom silicon utilization. At low silicic acid concentrations (<30 M), transport mainly occurs through silicic acid transport proteins (SITs), and at higher concentrations it occurs through diffusion. Previous analyses of the SITs were done either in heterologous systems or without a distinction between individual SITs. In the present study, we examined individual SITs in Thalassiosira pseudonana in terms of transcript and protein abundance in response to different silicic acid regimes and examined knockdown lines to evaluate the role of the SITs in transport, silica incorporation, and lipid accumulation resulting from silicon starvation. SIT1 and SIT2 were localized in the plasma membrane, and protein levels were generally inversely correlated with cellular silicon needs, with a distinct response being found when the two SITs were compared. We developed highly effective approaches for RNA interference and antisense knockdowns, the first such approaches developed for a centric diatom. SIT knockdown differentially affected the uptake of silicon and the incorporation of silicic acid and resulted in the induction of lipid accumulation under silicon starvation conditions far earlier than in the wild-type cells, suggesting that the cells were artificially sensing silicon limitation. The data suggest that the transport role of the SITs is relatively minor under conditions with sufficient silicic acid. Their primary role is to sense silicic acid levels to evaluate whether the cell can proceed with its cell wall formation and division processes. Silicon, a member of group 14 of the periodic table containing carbon, germanium, and lead, is one of the most abundant elements (27.7%) of the Earth's crust second only to oxygen (46.6%) (1). Dissolved silica in the form of orthosilicic acid, Si(OH) 4 , derived from the weathering of the Earth's crust (2), is an essential nutrient for a few groups of organisms of marine and freshwater environments, such as diatoms, radiolaria, silicoflagellates, and sponges (3). Diatoms require a large quantity of silicon, which is biomineralized to form their unique siliceous cell wall (frustule) in various shapes and morphologies with highly intricate and ornate architectures. Diatoms contribute about 40% of the total ocean organic carbon production, and they dominate ocean Si production (4, 5). Though silicon does not appear to be directly involved in cellular metabolic processes, diatoms require silicon for progression of cell cycle events, such as cell division and DNA replication (5-8). Silicon requirements are tightly coupled to cell cycle progression, a unique feature of diatoms (7). Deprivation of Si arrests the cell cycle at G 1 , G 2 , or M phase, depending upon the diatom species. In Thalassiosira pseudonana, upon Si depletion the ...

show abstract

“…There have been few computational models though for describing transport and pre-synthesis of intracellular silicon, mainly in cell cytoplasm. They usually calculate the temporal changes of silicon amount or the timing of silicon synthesis and its relation to other nutrients regarding to the cell cycle (Brasser et al 2012;Flynn and Martin-Jézéquel 2000).…”

Section: Synthesis Of Silica In Diatoms: Reaction-diffusion Modelmentioning

confidence: 99%

Modeling Biosilicification at Subcellular Scales

Javaheri

Cronemberger

Kaandorp

2013

Biomedical Inorganic Polymers

View full text Add to dashboard Cite

Biosilicification occurs in many organisms. Sponges and diatoms are major examples of them. In this chapter, we introduce a modeling approach that describes several biological mechanisms controlling silicification. Modeling biosilicification is a typical multiscale problem where processes at very different temporal and spatial scales need to be coupled: processes at the molecular level, physiological processes at the subcellular and cellular level, etc. In biosilicification morphology plays a fundamental role, and a spatiotemporal model is required. In the case of sponges, a particle simulation based on diffusion-limited aggregation is presented here. This model can describe fractal properties of silica aggregates in first steps of deposition on an organic template. In the case of diatoms, a reaction-diffusion model is introduced which can describe the concentrations of chemical components and has the possibility to include polymerization chain of reactions.

show abstract

Compartmental Analysis Suggests Macropinocytosis at the Onset of Diatom Valve Formation

Cited by 12 publications

References 39 publications

Bioinspired Insights into Silicic Acid Stabilization Mechanisms: The Dominant Role of Polyethylene Glycol-Induced Hydrogen Bonding

Bioinspired Insights into Silicic Acid Stabilization Mechanisms: The Dominant Role of Polyethylene Glycol-Induced Hydrogen Bonding

Evidence for a Regulatory Role of Diatom Silicon Transporters in Cellular Silicon Responses

Modeling Biosilicification at Subcellular Scales

Contact Info

Product

Resources

About