Opportunistic heterotrophy in gametophytes of the homosporous fern Ceratopteris richardii

Botany ◽  
2009 ◽  
Vol 87 (8) ◽  
pp. 799-806 ◽  
Author(s):  
Deborah A. Alongi ◽  
Jeffrey P. Hill ◽  
Matthew J. Germino
Keyword(s):  
Sugar Transport ◽  
Light Limitation ◽  
Sugar Uptake ◽  
Growth Media ◽  
Ceratopteris Richardii ◽  
Glucose Depletion ◽  
Homosporous Fern ◽  
Preferential Uptake ◽  
Underlying Mechanisms ◽  
Exogenous Sugar

Fern gametophytes are extremely shade-tolerant, potentially existing for long periods under conditions of extreme light limitation. Many previous studies have demonstrated an increase in gametophyte growth and incidence of spontaneous transition to sporophyte morphology (apogamy) under culture on media containing exogenous sugar. However, these studies did not verify sugar uptake or quantify relative growth on media containing different sugar types. Here, we examine the extent of heterotrophy and underlying mechanisms of sugar transport in photosynthetic gametophytes of the fern Ceratopteris richardii Brongn. Exogenous sugar uptake, growth, and sugar transport were evaluated with assays of exogenous glucose depletion, experimental culture of gametophytes under different sugar and light conditions, and bioinformatic approaches. The glucose from the growth media was significantly depleted by gametophytes growing under all conditions, especially those in the dark compared with those exposed to higher light. Gametophyte area increased similarly when cultured on equimolar concentrations of either glucose or the disaccharide sucrose, likely due to preferential uptake of one of the monomers of sucrose. Although at least one gene with similarity to sucrose transporters is expressed in germinating spores, our results suggest a reliance on monosaccharide transport for exogenous sugar uptake. Glucose assimilation in both light and dark conditions constitutes nutritional opportunism and may enhance gametophyte survival in very low light.

scholarly journals Determinants of target prioritization and regulatory hierarchy for the bacterial small RNA SgrS

2017 ◽  
Author(s):  
Maksym Bobrovskyy ◽  
Jane K. Frandsen ◽  
Jichuan Zhang ◽  
Anustup Poddar ◽  
Muhammad S. Azam ◽  
...  
Keyword(s):  
Small Rna ◽  
Binding Sites ◽  
Sugar Transport ◽  
Enteric Bacteria ◽  
Sugar Uptake ◽  
Rna Chaperone ◽  
Target Mrnas ◽  
Mrna Targets ◽  
Molecular Features ◽  
Response To Stress

ABSTRACTThe mechanisms by which small RNA (sRNA) regulators select and prioritize target mRNAs remain poorly understood, but serve to promote efficient responses to environmental cues and stresses. We sought to uncover mechanisms that establish regulatory hierarchy for a model sRNA, SgrS, found in enteric bacteria and produced under conditions of metabolic stress when sugar transport and metabolism are unbalanced. SgrS post-transcriptionally controls a nine-gene regulon to restore growth and homeostasis under stress conditions. An in vivo reporter system was used to quantify SgrS-dependent regulation of target genes and established that SgrS exhibits a clear preference for certain targets, and regulates those targets efficiently even at low SgrS levels. Higher SgrS concentrations are required to regulate other targets. The position of targets in the regulatory hierarchy is not well-correlated with the predicted thermodynamic stability of SgrS-mRNA interactions or the SgrS-mRNA binding affinity as measured in vitro. Detailed analyses of SgrS interaction with asd mRNA demonstrate that SgrS binds cooperatively to two sites and remodels asd mRNA secondary structure. SgrS binding at both sites increases the efficiency of asd mRNA regulation compared to mutants that have only a single SgrS binding site. Our results suggest that sRNA selection of target mRNAs and regulatory hierarchy are influenced by several molecular features. The sRNA-mRNA interaction, including the number and position of sRNA binding sites on the mRNA and cofactors like the RNA chaperone Hfq, seem to tune the efficiency of regulation of specific mRNA targets.IMPORTANCETo survive, bacteria must respond rapidly to stress and simultaneously maintain metabolic homeostasis. The small RNA (sRNA) SgrS mediates the response to stress arising from imbalanced sugar transport and metabolism. To coordinate the stress response, SgrS regulates genes involved in sugar uptake and metabolism. Intrinsic properties of sRNAs such as SgrS allow them to regulate extensive networks of genes. To date, sRNA regulation of targets has largely been studied in the context of “one sRNA-one target”, and little is known about coordination of multi-gene regulons and sRNA regulatory network structure. Here, we explore the molecular basis for regulatory hierarchy in sRNA regulons. Our results reveal a complex interplay of factors that influence the outcome of sRNA regulation. The number and location of sRNA binding sites on mRNA targets and the participation of an RNA chaperone dictate prioritized regulation of targets to promote an efficient response to stress.

scholarly journals The C-Fern (Ceratopteris richardii) genome: insights into plant genome evolution with the first partial homosporous fern genome assembly

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
D. Blaine Marchant ◽  
Emily B. Sessa ◽  
Paul G. Wolf ◽  
Kweon Heo ◽  
W. Brad Barbazuk ◽  
...  
Keyword(s):  
Genome Evolution ◽  
Green Plant ◽  
Land Plant ◽  
Plant Genome ◽  
Flowering Plant ◽  
Ceratopteris Richardii ◽  
Repeat Elements ◽  
Homosporous Fern ◽  
Homosporous Ferns ◽  
Large Genomes

AbstractFerns are notorious for possessing large genomes and numerous chromosomes. Despite decades of speculation, the processes underlying the expansive genomes of ferns are unclear, largely due to the absence of a sequenced homosporous fern genome. The lack of this crucial resource has not only hindered investigations of evolutionary processes responsible for the unusual genome characteristics of homosporous ferns, but also impeded synthesis of genome evolution across land plants. Here, we used the model fern species Ceratopteris richardii to address the processes (e.g., polyploidy, spread of repeat elements) by which the large genomes and high chromosome numbers typical of homosporous ferns may have evolved and have been maintained. We directly compared repeat compositions in species spanning the green plant tree of life and a diversity of genome sizes, as well as both short- and long-read-based assemblies of Ceratopteris. We found evidence consistent with a single ancient polyploidy event in the evolutionary history of Ceratopteris based on both genomic and cytogenetic data, and on repeat proportions similar to those found in large flowering plant genomes. This study provides a major stepping-stone in the understanding of land plant evolutionary genomics by providing the first homosporous fern reference genome, as well as insights into the processes underlying the formation of these massive genomes.

scholarly journals Model-assisted analysis of the peach pedicel–fruit system suggests regulation of sugar uptake and a water-saving strategy

2020 ◽  
Vol 71 (12) ◽  
pp. 3463-3474
Author(s):  
Dario Constantinescu ◽  
Gilles Vercambre ◽  
Michel Génard
Keyword(s):  
Sugar Transport ◽  
Water Saving ◽  
Lower Pressure ◽  
Sugar Concentration ◽  
Sugar Uptake ◽  
Pressure Potential ◽  
High Sugar Concentration ◽  
High Sugar ◽  
Diurnal Patterns ◽  
Assisted Analysis

Abstract We develop a model based on the biophysical representation of water and sugar flows between the pedicel, fruit xylem and phloem, and the fruit apoplast and symplast in order to identify diurnal patterns of transport in the pedicel–fruit system of peach. The model predicts that during the night water is mainly imported to the fruit through the xylem, and that fruit phloem–xylem transfer of water allows sugar concentrations in the phloem to be higher in the fruit than in the pedicel. This results in relatively high sugar transport to the fruit apoplast, leading to relatively high sugar uptake by the fruit symplast despite low sugar concentrations in the pedicel. At midday, the model predicts a xylem backflow of water driven by a lower pressure potential in the xylem than in the fruit apoplast. In addition, fruit xylem-to-phloem transfer of water decreases the fruit phloem sugar concentration, resulting in moderate sugar uptake by the fruit symplast, despite the high sugar concentration in the pedicel. Globally, the predicted fruit xylem–phloem water transfers buffer the sugar concentrations in the fruit phloem and apoplast, leading to a diurnally regulated uptake of sugar. A possible fruit xylem-to-apoplast recirculation of water through the fruit phloem reduces water lost by xylem backflow at midday.

CsSWEET1a and CsSWEET17 Mediate Growth and Freezing Tolerance by Promoting Sugar Transport across the Plasma Membrane

2020 ◽  
Vol 61 (9) ◽  
pp. 1669-1682
Author(s):  
Lina Yao ◽  
Changqing Ding ◽  
Xinyuan Hao ◽  
Jianming Zeng ◽  
Yajun Yang ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Freezing Tolerance ◽  
Sugar Transport ◽  
Bimolecular Fluorescence Complementation ◽  
Freezing Stress ◽  
Sugar Uptake ◽  
Wild Type ◽  
Alternatively Spliced ◽  
Germination And Growth ◽  
Two Hybrid

Abstract Sugars Will Eventually be Exported Transporters (SWEETs) are important in plant biological processes. Expression levels of CsSWEET1a and CsSWEET17 are induced by cold acclimation (CA) and cold stress in Camellia sinensis. Here, we found that CsSWEET17 was alternatively spliced, and its exclusion (Ex) transcript was associated with the CA process. Both plasma membrane-localized CsSWEET1a and CsSWEET17 transport hexoses, but cytoplasm-localized CsSWEET17-Ex does not. These results indicate that alternative splicing may be involved in regulating the function of SWEET transporters in response to low temperature in plants. The extra C-terminal of CsSWEET17, which is not found in the tonoplast fructose transporter AtSWEET17, did not affect its plasma membrane localization but promoted its sugar transport activities. The overexpression (OE) of CsSWEET1a and CsSWEET17 genes resulted in an increased sugar uptake in Arabidopsis, affecting plant germination and growth. The leaf and seed sizes of the CsSWEET17-OE lines were significantly larger than those of the wild type. Moreover, the OE of CsSWEET1a and CsSWEET17 significantly reduced the relative electrolyte leakage levels under freezing stress. Compared with the wild type, the expression of AtCWINV genes was suppressed in both CsSWEET1a-OE and CsSWEET17-OE lines, indicating the alteration in sugar contents in the cell walls of the OE lines. Furthermore, the interaction between CsSWEET1a and CsSWEET17 was confirmed using yeast two-hybrid and bimolecular fluorescence complementation assays. We showed that CsSWEET1a and CsSWEET17 form homo-/heterodimers in the plasma membrane and mediate the partitioning of sugars between the cytoplasm and the apoplast, thereby regulating plant growth and freezing tolerance.

scholarly journals Caffeine inhibits glucose transport by binding at the GLUT1 nucleotide-binding site

2015 ◽  
Vol 308 (10) ◽  
pp. C827-C834 ◽  
Author(s):  
Jay M. Sage ◽  
Anthony J. Cura ◽  
Kenneth P. Lloyd ◽  
Anthony Carruthers
Keyword(s):  
Binding Site ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
Cytochalasin B ◽  
Sugar Transport ◽  
Nucleotide Binding ◽  
Nucleotide Binding Site ◽  
Sugar Uptake ◽  
Glucose Transporter 1 ◽  
Intracellular Atp

Glucose transporter 1 (GLUT1) is the primary glucose transport protein of the cardiovascular system and astroglia. A recent study proposes that caffeine uncompetitive inhibition of GLUT1 results from interactions at an exofacial GLUT1 site. Intracellular ATP is also an uncompetitive GLUT1 inhibitor and shares structural similarities with caffeine, suggesting that caffeine acts at the previously characterized endofacial GLUT1 nucleotide-binding site. We tested this by confirming that caffeine uncompetitively inhibits GLUT1-mediated 3- O-methylglucose uptake in human erythrocytes [ Vmax and Km for transport are reduced fourfold; Ki(app) = 3.5 mM caffeine]. ATP and AMP antagonize caffeine inhibition of 3- O-methylglucose uptake in erythrocyte ghosts by increasing Ki(app) for caffeine inhibition of transport from 0.9 ± 0.3 mM in the absence of intracellular nucleotides to 2.6 ± 0.6 and 2.4 ± 0.5 mM in the presence of 5 mM intracellular ATP or AMP, respectively. Extracellular ATP has no effect on sugar uptake or its inhibition by caffeine. Caffeine and ATP displace the fluorescent ATP derivative, trinitrophenyl-ATP, from the GLUT1 nucleotide-binding site, but d-glucose and the transport inhibitor cytochalasin B do not. Caffeine, but not ATP, inhibits cytochalasin B binding to GLUT1. Like ATP, caffeine renders the GLUT1 carboxy-terminus less accessible to peptide-directed antibodies, but cytochalasin B and d-glucose do not. These results suggest that the caffeine-binding site bridges two nonoverlapping GLUT1 endofacial sites—the regulatory, nucleotide-binding site and the cytochalasin B-binding site. Caffeine binding to GLUT1 mimics the action of ATP but not cytochalasin B on sugar transport. Molecular docking studies support this hypothesis.

The effects of hydrocortisone and thyroxine treatments on development of duodenal morphology, alkaline phosphatase, and sugar transport in chicken (Gallus gallus) embryos

1982 ◽  
Vol 60 (12) ◽  
pp. 3447-3455 ◽  
Author(s):  
D. L. Mallon ◽  
T. W. Betz
Keyword(s):  
Alkaline Phosphatase ◽  
Thyroid Hormones ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Sugar Transport ◽  
Gallus Gallus ◽  
Sugar Uptake ◽  
Chicken Embryos ◽  
Sugar Absorption

The ability of thyroxine (T4) and hydrocortisone (H), alone or together, to cause precocious duodenal development was tested in chicken embryos. Correlations in the levels of duodenal enzymic, structural, and absorptive properties were compared in intact and treated embryos. Duodenal alkaline phosphatase activity, morphogenesis, and sugar absorption develop together in untreated embryos. Precocious alkaline phosphatase activity, morphogenesis, and α-methylglucoside uptake were correlated after H and T4 treatments. These parameters also responded significantly to T4 treatments alone. The levels of the alkaline phosphatase activity in 16.5-day embryos were three times normal after H plus T4 treatment. No parameters changed significantly after H treatment alone. Parallel increases in alkaline phosphatase activity and morphogenesis probably reflect duodenal participation in sugar uptake functions, at least for duodenal maintenance. Adrenocorticoids and thyroid hormones could be involved in these aspects of normal duodenal development.

scholarly journals Dihydrocytochalasin B. Biological effects and binding to 3T3 cells.

1978 ◽  
Vol 76 (2) ◽  
pp. 360-370 ◽  
Author(s):  
S J Atlas ◽  
S Lin
Keyword(s):  
Cell Motility ◽  
Morphological Changes ◽  
Biological Effects ◽  
Sugar Transport ◽  
Sugar Uptake ◽  
3T3 Cells ◽  
Binding Studies ◽  
High Affinity ◽  
Undetermined Function ◽  
Induced Changes

Dihydrocytochalasin B (H2CB) does not inhibit sugar uptake in BALB/c 3T3 cells. Excess H2CB does not affect inhibition of sugar uptake by cytochalasin B (CB), indicating that it does not compete with CB for binding to high-affinity sites. As in the case of CB, H2CB inhibits cytokinesis and changes the morphology of the cells. These results demonstrate that the effects of CB on sugar transport and on cell motility and morphology involve separate and independent sites. Comparison of the effects of H2CB, CB, and cytochalasin D (CD) indicates that treatment of cells with any one of the compounds results in the same series of morphological changes; the cells undergo zeiosis and elongation at 2-4 microM CB and become arborized and rounded up at 10-50 microM CB. H2CB is slightly less potent than CB, whereas CD is five to eight times more potent than CB in causing a given state of morphological change. These results indicate that the cytochalasin-induced changes in cell morphology are mediated by a specific site(s) which can distinguish the subtle differences in the structures of the three compounds. Competitive binding studies indicate that excess H2CB displaces essentially all of the high-affinity bound [3H]CB, but, at less than 5 x 10(-5) M H2CB is not so efficient as unlabeled CB in the displacement reaction. In contrast, excess CD displaces up to 40% of the bound [3H]CB. These results suggest that three different classes of high-affinity CB binding sites exist in 3T3 cells: sites related to sugar transport, sites related to cell motility and morphology, and sites with undetermined function.

Antheridiogen concentration and spore size predict gametophyte size in Ceratopteris richardii

Botany ◽  
2012 ◽  
Vol 90 (3) ◽  
pp. 175-179 ◽  
Author(s):  
Mike Ganger ◽  
Tiffany Sturey
Keyword(s):  
Sex Determination ◽  
Environmental Sex Determination ◽  
Wild Type ◽  
Ceratopteris Richardii ◽  
Spore Size ◽  
Male Development ◽  
Homosporous Fern ◽  
Type C ◽  
Slow Growing ◽  
Genetic Mutants

In many plants females invest more in reproduction than males. In organisms that exhibit environmental sex determination, individuals in low-quality environments or who are slow growing are expected to develop into males. The gametophytes of Ceratopteris richardii Brongn., a homosporous fern, may develop as males or hermaphrodites. Hermaphrodites secrete a pheromone called antheridiogen that induces undifferentiated spores to develop as males. Given that induction is not 100% in the presence of antheridiogen, it is hypothesized that resources may alter C. richardii gender decisions. An experiment was undertaken to determine (i) whether spore size predicts gender, (ii) whether spore size predicts gametophyte size, (iii) whether antheridiogen negatively affects the growth of C. richardii, and (iv) whether wild-type C. richardii and him1 mutants (genetic mutants disposed to male development regardless of antheridiogen presence) behave similarly in their response to antheridiogen. Spore size was not predictive of gender but was positively related to both male and hermaphrodite gametophyte size. Antheridiogen was found to slow the growth of male and hermaphrodite gametophytes of the wild type and male gametophytes of the him1 mutant. These results are supportive of the idea that gender may be determined indirectly through antheridiogen’s effect on gametophyte growth.

scholarly journals The Hexose-Proton Cotransport System of Chlorella

1974 ◽  
Vol 64 (5) ◽  
pp. 568-581 ◽  
Author(s):  
Ewald Komor ◽  
Widmar Tanner
Keyword(s):  
Sugar Transport ◽  
Protonated Form ◽  
Weak Acid ◽  
Sugar Uptake ◽  
Sugar Accumulation ◽  
Maximal Velocity ◽  
Uptake System ◽  
High Affinity ◽  
Ph Values ◽  
Proton Concentration

The proton concentration in the medium affects the maximal velocity of sugar uptake with a Km of 0.3 mM (high affinity uptake). By decreasing the proton concentration a decrease in high affinity sugar uptake is observed, in parallel the activity of a low affinity uptake system (Km of 50 mM) rises. Both systems add up to 100%. The existence of the carrier in two conformational states (protonated and unprotonated) has been proposed therefore, the protonated form with high affinity to 6-deoxyglucose, the unprotonated form with low affinity. A plot of extrapolated Vmax values at low substrate concentration versus proton concentration results in a Km for protons of 0.14 µM, i.e. half-maximal protonation of the carrier is achieved at pH 6.85. The stoichiometry of protons cotransported per 6-deoxyglucose is close to 1 at pH 6.0–6.5. At higher pH values the stoichiometry continuously decreases; at pH 8.0 only one proton is cotransported per four molecules of sugar. Whereas the translocation of the protonated carrier is strictly dependent on sugar this coupling is less strict for the unprotonated form. Therefore at alkaline pH a considerable net efflux of accumulated sugar can occur. The dependence of sugar accumulation on pH has been measured. The decrease in accumulation with higher pH values can quantitatively be explained by the decrease in the amount of protonated carrier. The properties of the unprotonated carrier resemble strikingly the properties of carrier at the inner side of the membrane. The inside pH of Chlorella was measured with the weak acid 5,5-dimethyl-2, 4-oxazolidinedion (DMO). At an outside pH of 6.5 the internal pH was found to be 7.2. To explain the extent of sugar accumulation it has to be assumed that the membrane potential also contributes to active sugar transport in this alga.

scholarly journals Molecular Physiology of Sugar Catabolism in Lactococcus lactis IL1403

2001 ◽  
Vol 183 (13) ◽  
pp. 3817-3824 ◽  
Author(s):  
Sergine Even ◽  
Nic D. Lindley ◽  
Muriel Cocaign-Bousquet
Keyword(s):  
Lactococcus Lactis ◽  
Translational Regulation ◽  
Sugar Transport ◽  
Enzyme Synthesis ◽  
Glycolytic Enzyme ◽  
Growth Media ◽  
Translational Efficiency ◽  
Molecular Physiology

ABSTRACT The metabolic characteristics of Lactococcus lactisIL1403 were examined on two different growth media with respect to the physiological response to two sugars, glucose and galactose. Analysis of specific metabolic rates indicated that despite significant variations in the rates of both growth and sugar consumption, homolactic fermentation was maintained for all cultures due to the low concentration of either pyruvate-formate lyase or alcohol dehydrogenase. When the ionophore monensin was added to the medium, flux through glycolysis was not increased, suggesting a catabolic flux limitation, which, with the low intracellular concentrations of glycolytic intermediates and high in vivo glycolytic enzyme capacities, may be at the level of sugar transport. To assess transcription, a novel DNA macroarray technology employed RNA labeled in vitro with digoxigenin and detection of hybrids with an alkaline phosphatase-antidigoxigenin conjugate. This method showed that several genes of glycolysis were expressed to higher levels on glucose and that the genes of the mixed-acid pathway were expressed to higher levels on galactose. When rates of enzyme synthesis are compared to transcript concentrations, it can be deduced that some translational regulation occurs with threefold-higher translational efficiency in cells grown on glucose.

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