Accumulation of starch in Chlamydomonas reinhardtii flagellar mutants

1992 ◽  
Vol 70 (3-4) ◽  
pp. 255-258 ◽  
Author(s):  
Bradford S. Hamilton ◽  
Kazuo Nakamura ◽  
Daniel A. K. Roncari
Keyword(s):  
Energy Storage ◽  
Chlamydomonas Reinhardtii ◽  
Inverse Relationship ◽  
Cell Number ◽  
Energy Utilization ◽  
Wild Type ◽  
Cellular Functions ◽  
Average Cell Size ◽  
Average Cell

Paralyzed flagellar mutants pf-1, pf-2, pf-7, and pf-18 of the green alga Chlamydomonas reinhardtii (Dangeard) were shown to store a significantly greater amount of starch than the motile wild type 137c+. The increase in starch storage was significant relative to protein, chlorophyll, and cell number. Analysis of average cell size revealed that the paralyzed mutants were larger than the wild type. This increase in storage molecule accumulation supports an inverse relationship between chemical energy storage and energy utilization for biomechanical/motile cellular functions. Chlamydomonas reinhardtii provides a useful model for studies of the role of cytoskeletal activity in the energy relationship and balance of organisms.Key words: Chlamydomonas, cytoskeleton, paralyzed flagella, starch, bioenergetics.

Crystal structure of the wild-type and D30A mutant thioredoxin h of Chlamydomonas reinhardtii and implications for the catalytic mechanism

2001 ◽  
Vol 359 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Valeria MENCHISE ◽  
Catherine CORBIER ◽  
Claude DIDIERJEAN ◽  
Michele SAVIANO ◽  
Ettore BENEDETTI ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Proton Transfer ◽  
Chlamydomonas Reinhardtii ◽  
Catalytic Mechanism ◽  
Structural Data ◽  
Careful Analysis ◽  
Wild Type ◽  
Thioredoxin H ◽  
Dynamics Simulations

Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.

scholarly journals Volume, firmness and crumb characteristics of gluten-free bread based on extruded quinoa flour and lactic acid

2020 ◽  
Vol 23 ◽  
Author(s):  
Elvia Murgueytio ◽  
Stalin Santacruz
Keyword(s):  
Lactic Acid ◽  
Specific Volume ◽  
Water Solubility ◽  
Chenopodium Quinoa ◽  
Control Sample ◽  
Cell Number ◽  
Gluten Free ◽  
Average Cell Size ◽  
Average Cell ◽  
Quinoa Flour

Abstract Coeliac disease forces on the developing of gluten-free products. Gluten-free cereals may be modified by techniques like cooking-extrusion or by adding compounds like lactic acid in order to obtain mixtures with adequate viscoelastic properties for the developing of baked products. The present work studies the elaboration of gluten-free bread with extruded quinoa (Chenopodium quinoa Willd) flour and lactic acid. The influence of feeding humidity (18% and 25%) and temperature of extrusion (60 °C and 95 °C) on water absorption index (WAI) and water solubility index (WSI) of extruded flours was investigated. The results showed that feeding humidity led to changes on WAI. Baking process was studied by varying the amount of lactic acid added during bread baking. The specific volume, firmness and crumb characteristics (average cell size and cell number per mm2) of bread were determined. A control sample based on commercial gluten-free flour and no lactic acid was used. The results showed that lactic acid content did not affect bread firmness. Bread prepared with extruded flours at 95 °C, 25% feeding moisture had higher firmness (p < 0.05) than bread prepared with other extruded flours and control sample. Low level of lactic acid (0.2%) led to bread with high specific volume. The use of an extruded quinoa flour with low levels of lactic acid led to a gluten-free bread with a high specific volume and low firmness.

scholarly journals BAX-Dependent and BAX-Independent Regulation of Kiss1 Neuron Development in Mice

Endocrinology ◽  
2010 ◽  
Vol 151 (12) ◽  
pp. 5807-5817 ◽  
Author(s):  
Sheila J. Semaan ◽  
Elaine K. Murray ◽  
Matthew C. Poling ◽  
Sangeeta Dhamija ◽  
Nancy G. Forger ◽  
...  
Keyword(s):  
Sex Difference ◽  
Cell Number ◽  
Sexually Dimorphic ◽  
Neuron Development ◽  
Wild Type ◽  
Th Cell ◽  
Double Label ◽  
D 12 ◽  
Th Mrna

The Kiss1 gene and its product kisspeptin are important regulators of reproduction. In rodents, Kiss1 is expressed in the hypothalamic arcuate (ARC) and anteroventral periventricular (AVPV)/rostral periventricular (PeN) nuclei. In the AVPV/PeN, females have more Kiss1 and tyrosine hydroxylase (TH) neurons than males. We explored the ontogeny of the Kiss1 sex difference, and the role of cell death in establishing Kiss1 and TH cell number. We also determined whether Kiss1 cells in AVPV/PeN coexpress TH. AVPV/PeN Kiss1 neurons were first detected in both sexes on postnatal d 10, but the Kiss1 sex difference did not emerge until postnatal d 12. The role of BAX-mediated apoptosis in generating this sex difference was tested in adult Bax knockout (KO) and wild-type mice. Deletion of Bax did not diminish the sex difference in Kiss1 expression in the AVPV/PeN. TH expression was sexually dimorphic in the AVPV of both wild-type and Bax KO mice but, unlike Kiss1, was not sexually dimorphic in the PeN of either genotype. Double-label analysis determined that most Kiss1 neurons coexpress TH mRNA, but many TH neurons do not coexpress Kiss1, especially in the PeN. These findings suggest that several subpopulations of TH cells reside within the AVPV/PeN, only one of which coexpresses Kiss1. In the ARC, Kiss1 cell number was markedly increased in Bax KO mice of both sexes, indicating that although BAX-dependent apoptosis does not generate the sex difference in either Kiss1 or TH expression in AVPV/PeN, BAX does importantly regulate Kiss1 cell number in the ARC.

scholarly journals A Single Mechanosensitive Channel ProtectsFrancisella tularensissubsp.holarcticafrom Hypoosmotic Shock and Promotes Survival in the Aquatic Environment

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
David R. Williamson ◽  
Kalyan K. Dewan ◽  
Tanmay Patel ◽  
Catherine M. Wastella ◽  
Gang Ning ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Francisella Tularensis ◽  
Mechanosensitive Channel ◽  
Mammalian Host ◽  
Average Cell Size ◽  
Average Cell ◽  
Content Type ◽  
Hypoosmotic Shock ◽  
Osmotic Downshock

ABSTRACTFrancisella tularensissubsp.holarcticais found in North America and much of Europe and causes the disease tularemia in humans and animals. An aquatic cycle has been described for this subspecies, which has caused waterborne outbreaks of tularemia in at least 10 countries. In this study, we sought to identify the mechanosensitive channel(s) required for the bacterium to survive the transition from mammalian hosts to freshwater, which is likely essential for the transmission of the bacterium between susceptible hosts. A single 165-amino-acid MscS-type mechanosensitive channel (FtMscS) was found to protectF. tularensissubsp.holarcticafrom hypoosmotic shock, despite lacking much of the cytoplasmic vestibule domain found in well-characterized MscS proteins from other organisms. The deletion of this channel did not affect virulence within the mammalian host; however,FtMscS was required to survive the transition from the host niche to freshwater. The deletion ofFtMscS did not alter the sensitivity ofF. tularensissubsp.holarcticato detergents, H2O2, or antibiotics, suggesting that the role ofFtMscS is specific to protection from hypoosmotic shock. The deletion ofFtMscS also led to a reduced average cell size without altering gross cell morphology. The mechanosensitive channel identified and characterized in this study likely contributes to the transmission of tularemia between hosts by allowing the bacterium to survive the transition from mammalian hosts to freshwater.IMPORTANCEThe contamination of freshwater byFrancisella tularensissubsp.holarcticahas resulted in a number of outbreaks of tularemia. Invariably, the contamination originates from the carcasses or excreta of infected animals and thus involves an abrupt osmotic downshock as the bacteria enter freshwater. HowF. tularensissurvives this drastic change in osmolarity has not been clear, but here we report that a single mechanosensitive channel protects the bacterium from osmotic downshock. This channel is functional despite lacking much of the cytoplasmic vestibule domain that is present in better-studied organisms such asEscherichia coli; this report builds on previous studies that have suggested that parts of this domain are dispensable for downshock protection. These findings extend our understanding of the aquatic cycle and ecological persistence ofF. tularensis, with further implications for mechanosensitive channel biology.

scholarly journals The Effects of Different Ratios and Concentrations of Benzyladenin and GA4+7 on Fruit Size and Yield of Apple Trees

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 524D-524
Author(s):  
Thomas E. Clark ◽  
Terence L. Robinson ◽  
Alan N. Lakso ◽  
Warren C. Stiles
Keyword(s):  
Fruit Size ◽  
Cell Number ◽  
Fruit Shape ◽  
Total Cell ◽  
Apple Trees ◽  
Total Cell Number ◽  
Average Cell Size ◽  
Crop Load ◽  
Average Cell ◽  
Positive Rate

In 1996, benzyladenine, or GA4+7, or different ratios of BA: GA4+7 (100:1, 10:1 and 1:1) were applied to 10-year-old `Empire' apple trees on M.9 at 10-mm fruit size and 19-year-old `Redchief Delicious' apple trees on M.9 or M.9/MM.111 at 7.6-mm fruit size. Each chemical or combination of BA and GA was applied at three rates (50, 100, or 150 ppm) and at 75 ppm with 1.25 ml of carbaryl/L. At harvest, fruits were sampled from each treatment to determine fruit shape, firmness, color, total cell number, average cell size, and percentage of intercellular space. The positive rate response on fruit size and negative rate response on crop load of `Empire' became less significant for each formulation as the amount of GA4+7 in the formulation increased. The same was true for `Delicious', but less pronounced. At low rates of BA, formulations containing GA resulted in more thinning than BA alone. However, at higher rates of BA, formulations containing GA caused significantly less thinning than BA alone. For treatments combined with carbaryl, crop load increased linearly in `Empire' with increasing amounts of GA4+7 in the formulation. The treatment that provided the largest fruit size for `Empire' was BA@150 ppm, while for `Delicious' it was BA@75 ppm + carbaryl. Both varieties showed the greatest reduction in crop load with the 100:1@75 ppm+ carbaryl treatment when compared to the controls. These data suggest that GA4+7 in formulation with BA may inhibit the thinning action of BA at moderate and high rates.

Measuring dimensions: the regulation of size and shape

Development ◽  
2000 ◽  
Vol 127 (14) ◽  
pp. 2977-2987 ◽  
Author(s):  
S.J. Day ◽  
P.A. Lawrence
Keyword(s):  
Cell Growth ◽  
Cell Survival ◽  
Cell Size ◽  
Characteristic Size ◽  
Cell Number ◽  
Morphogen Gradient ◽  
Average Cell Size ◽  
Average Cell ◽  
Size And Shape ◽  
Drosophila Wing

Over many years evidence has accumulated that plants and animals can regulate growth with reference to overall size rather than cell number. Thus, organs and organisms grow until they reach their characteristic size and shape and then they stop - they can even compensate for experimental manipulations that change, over several fold, cell number or average cell size. If the cell size is altered, the organism responds with a change in cell number and vice versa. We look at the Drosophila wing in more detail: here, both extracellular and intracellular regulators have been identified that link cell growth, division and cell survival to final organ size. We discuss a hypothesis that the local steepness of a morphogen gradient is a measure of length in one axis, a measure that is used to determine whether there will be net growth or not.

scholarly journals Gene deletion reveals roles for annexin A1 in the regulation of lipolysis and IL-6 release in epididymal adipose tissue

2006 ◽  
Vol 291 (6) ◽  
pp. E1264-E1273 ◽  
Author(s):  
James P. Warne ◽  
Christopher D. John ◽  
Helen C. Christian ◽  
John F. Morris ◽  
Roderick J. Flower ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Gene Deletion ◽  
Cell Number ◽  
Receptor Expression ◽  
Epididymal Adipose Tissue ◽  
Wild Type ◽  
Inhibitory Effects ◽  
Tissue Mass

In this study, epididymal adipose tissue from male annexin 1 (ANXA1)-null and wild-type control mice were used to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by Western blot analysis in wild-type tissue and localized predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion, but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release, and increased cAMP accumulation. Qualitatively similar but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1-null mice, an effect that was not associated with changes in β-adrenoceptor mRNA expression. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro, but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1-null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis. It did, however, augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of epididymal adipose tissue to catecholamines, glucocorticoids, and LPS, thereby modulating lipolysis and IL-6 release.

scholarly journals A Pleiotropic Regulator, Frp, Affects Exopolysaccharide Synthesis, Biofilm Formation, and Competence Development in Streptococcus mutans

2006 ◽  
Vol 74 (8) ◽  
pp. 4581-4589 ◽  
Author(s):  
Bing Wang ◽  
Howard K. Kuramitsu
Keyword(s):  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Wild Type Strain ◽  
Transformation Efficiency ◽  
Competence Development ◽  
Wild Type ◽  
Cellular Functions ◽  
In The Wild ◽  
Pleiotropic Regulator

ABSTRACT Exopolysaccharide synthesis, biofilm formation, and competence are important physiologic functions and virulence factors for Streptococcus mutans. In this study, we report the role of Frp, a transcriptional regulator, on the regulation of these traits crucial to pathogenesis. An Frp-deficient mutant showed decreased transcription of several genes important in virulence, including those encoding fructosyltransferase (Ftf), glucosyltransferase B (GtfB), and GtfC, by reverse transcription and quantitative real-time PCR. Expression of Ftf was decreased in the frp mutant, as assessed by Western blotting as well as by the activity assays. Frp deficiency also inhibited the production of GtfB in the presence of glucose and sucrose as well as the production of GtfC in the presence of glucose. As a consequence of the effects on GtfB and -C, sucrose-induced biofilm formation was decreased in the frp mutant. The expression of competence mediated by the competence-signaling peptide (CSP) system, as assessed by comC gene transcription, was attenuated in the frp mutant. As a result, the transformation efficiency was decreased in the frp mutant but was partially restored by adding synthetic CSP. Transcription of the frp gene was significantly increased in the frp mutant under all conditions tested, indicating that frp transcription is autoregulated. Furthermore, complementation of the frp gene in the frp mutant restored transcription of the affected genes to levels similar to those in the wild-type strain. These results suggest that Frp is a novel pleiotropic effector of multiple cellular functions and is involved in the modulation of exopolysaccharide synthesis, sucrose-dependent biofilm formation, and competence development.

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