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1.
Plant Physiol ; 188(2): 1229-1247, 2022 02 04.
Article in English | MEDLINE | ID: mdl-34865141

ABSTRACT

In Angiosperms, the development of the vascular system is controlled by a complex network of transcription factors. However, how nutrient availability in the vascular cells affects their development remains to be addressed. At the cellular level, cytosolic sugar availability is regulated mainly by sugar exchanges at the tonoplast through active and/or facilitated transport. In Arabidopsis (Arabidopsis thaliana), among the genes encoding tonoplastic transporters, SUGAR WILL EVENTUALLY BE EXPORTED TRANSPORTER 16 (SWEET16) and SWEET17 expression has been previously detected in the vascular system. Here, using a reverse genetics approach, we propose that sugar exchanges at the tonoplast, regulated by SWEET16, are important for xylem cell division as revealed in particular by the decreased number of xylem cells in the swt16 mutant and the accumulation of SWEET16 at the procambium-xylem boundary. In addition, we demonstrate that transport of hexoses mediated by SWEET16 and/or SWEET17 is required to sustain the formation of the xylem secondary cell wall. This result is in line with a defect in the xylem cell wall composition as measured by Fourier-transformed infrared spectroscopy in the swt16swt17 double mutant and by upregulation of several genes involved in secondary cell wall synthesis. Our work therefore supports a model in which xylem development partially depends on the exchange of hexoses at the tonoplast of xylem-forming cells.


Subject(s)
Arabidopsis/growth & development , Arabidopsis/genetics , Hexoses/metabolism , Inflorescence/growth & development , Inflorescence/genetics , Xylem/growth & development , Xylem/genetics , Arabidopsis/metabolism , Biological Transport/genetics , Genetic Variation , Genotype , Inflorescence/metabolism , Mutation , Vacuoles/physiology , Xylem/metabolism
2.
J Exp Bot ; 72(10): 3688-3703, 2021 05 04.
Article in English | MEDLINE | ID: mdl-33712830

ABSTRACT

Cassava storage roots are among the most important root crops worldwide, and represent one of the most consumed staple foods in sub-Saharan Africa. The vegetatively propagated tropical shrub can form many starchy tuberous roots from its stem. These storage roots are formed through the activation of secondary root growth processes. However, the underlying genetic regulation of storage root development is largely unknown. Here we report distinct structural and transcriptional changes occurring during the early phases of storage root development. A pronounced increase in auxin-related transcripts and the transcriptional activation of secondary growth factors, as well as a decrease in gibberellin-related transcripts were observed during the early stages of secondary root growth. This was accompanied by increased cell wall biosynthesis, most notably increased during the initial xylem expansion within the root vasculature. Starch storage metabolism was activated only after the formation of the vascular cambium. The formation of non-lignified xylem parenchyma cells and the activation of starch storage metabolism coincided with increased expression of the KNOX/BEL genes KNAT1, PENNYWISE, and POUND-FOOLISH, indicating their importance for proper xylem parenchyma function.


Subject(s)
Cambium , Manihot , Cambium/genetics , Cambium/metabolism , Gene Expression Regulation, Plant , Indoleacetic Acids , Manihot/genetics , Manihot/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Plant Roots/metabolism
3.
J Exp Bot ; 71(16): 4930-4943, 2020 08 06.
Article in English | MEDLINE | ID: mdl-32361766

ABSTRACT

Most cellular sucrose is present in the cytosol and vacuoles of plant cells; however, little is known about the effect of this sucrose compartmentation on plant properties. Here, we examined the effects of altered intracellular sucrose compartmentation in Arabidopsis thaliana leaves by heterologously expressing the sugar beet (Beta vulgaris) vacuolar sucrose loader BvTST2.1 and by generating lines with reduced vacuolar invertase activity (amiR vi1-2). Heterologous expression of BvTST2.1 led to increased monosaccharide levels in leaves, whereas sucrose levels remained constant, indicating that vacuolar invertase activity in mesophyll vacuoles exceeds sucrose uptake. This notion was supported by analysis of tobacco (Nicotiana benthamiana) leaves transiently expressing BvTST2.1 and the invertase inhibitor NbVIF. However, sucrose levels were strongly elevated in leaf extracts from amiR vi1-2 lines, and experiments confirmed that sucrose accumulated in the corresponding vacuoles. The amiR vi1-2 lines exhibited impaired early development and reduced seed weight. When germinated in the dark, amiR vi1-2 seedlings were less able to convert sucrose into monosaccharides than the wild type. Cold temperatures strongly down-regulated both VI genes, but the amiR vi1-2 lines showed normal frost tolerance. These observations indicate that increased vacuolar sucrose levels fully compensate for the effects of low monosaccharide concentrations on frost tolerance.


Subject(s)
Arabidopsis , Arabidopsis/genetics , Arabidopsis/metabolism , Gene Expression Regulation, Plant , Homeostasis , Plant Development , Seeds/metabolism , Sucrose , Vacuoles/metabolism , beta-Fructofuranosidase/genetics , beta-Fructofuranosidase/metabolism
4.
Plant J ; 102(6): 1202-1219, 2020 06.
Article in English | MEDLINE | ID: mdl-31950549

ABSTRACT

Cassava is an important staple crop in sub-Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin-Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse-grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement.


Subject(s)
Manihot/metabolism , Plant Roots/metabolism , Carbohydrate Metabolism , Crop Production , Manihot/growth & development , Metabolic Networks and Pathways , Photosynthesis , Plant Leaves/metabolism , Plant Roots/growth & development , Plant Stems/metabolism , Ribulose-Bisphosphate Carboxylase/metabolism
5.
Curr Protoc Plant Biol ; 4(4): e20102, 2019 12.
Article in English | MEDLINE | ID: mdl-31834991

ABSTRACT

Cassava plays an important role as a staple food for more than 800 million people in the world due to its ability to maintain relatively high productivity even in nutrient-depleted soils. Even though cassava has been the focus of several breeding programs and has become a strong focus of research in the last few years, relatively little is currently known about its metabolism and metabolic composition in different tissues. In this article, the absolute content of sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, carotenoids, chlorophylls, tocopherols, and total protein as well as starch quality is described based on multiple analytical techniques, with protocols specifically adjusted for material from different cassava tissues. Moreover, quantification of secondary metabolites relative to internal standards is presented using both non-targeted and targeted metabolomics approaches. The protocols have also been adjusted to apply to freeze-dried material in order to allow processing of field harvest samples that typically will require long-distance transport. © 2019 The Authors. Basic Protocol 1: Metabolic profiling by gas chromatography-mass spectrometry (GC-MS) Support Protocol 1: Preparation of freeze-dried cassava material Support Protocol 2: Preparation of standard compound mixtures for absolute quantification of metabolites by GC-MS Support Protocol 3: Preparation of retention-time standard mixture Basic Protocol 2: Determination of organic acids and phosphorylated intermediates by ion chromatography-mass spectrometry (IC-MS) Support Protocol 4: Preparation of standards and recovery experimental procedure Basic Protocol 3: Determination of soluble sugars, starch, and free amino acids Alternate Protocol: Determination of soluble sugars and starch Basic Protocol 4: Determination of anions Basic Protocol 5: Determination of elements Basic Protocol 6: Determination of total protein Basic Protocol 7: Determination of non-targeted and targeted secondary metabolites Basic Protocol 8: Determination of carotenoids, chlorophylls, and tocopherol Basic Protocol 9: Determination of starch quality.


Subject(s)
Manihot , Amino Acids , Gas Chromatography-Mass Spectrometry , Metabolomics , Starch
6.
J Exp Bot ; 70(12): 3241-3254, 2019 06 28.
Article in English | MEDLINE | ID: mdl-30958535

ABSTRACT

Sugar allocation from source to sink (young) leaves, critical for plant development, relies on activities of plasma membrane sugar transporters. However, the key sugar unloading mechanism to sink leaves remains elusive. SWEET transporters mediate sugar efflux into reproductive sinks; therefore, they are promising candidates for sugar unloading during leaf growth. Transcripts of SlSWEET1a, belonging to clade I of the SWEET family, were markedly more abundant than those of all other 30 SlSWEET genes in young leaves of tomatoes. High expression of SlSWEET1a was also detected in reproductive sinks, such as flowers. SlSWEET1a was dominantly expressed in leaf unloading veins, and the green fluorescent protein (GFP) fusion protein was localized to the plasma membrane using Arabidopsis protoplasts, further implicating this carrier in sugar unloading. In addition, yeast growth assays and radiotracer uptake analyses further demonstrated that SlSWEET1a acted as a low-affinity (Km ~100 mM) glucose-specific carrier with a passive diffusion manner. Finally, virus-induced gene silencing of SlSWEET1a expression reduced hexose accumulation to ~50% in young leaves, with a parallel 2-fold increase in mature leaves. Thus, we propose a novel function for SlSWEET1a in the uptake of glucose into unloading cells as part of the sugar unloading mechanism in sink leaves of tomato.


Subject(s)
Glucose/metabolism , Plant Proteins/genetics , Solanum lycopersicum/genetics , Biological Transport , Solanum lycopersicum/metabolism , Plant Leaves/metabolism , Plant Proteins/metabolism
7.
J Geriatr Phys Ther ; 42(2): 86-97, 2019.
Article in English | MEDLINE | ID: mdl-28452837

ABSTRACT

BACKGROUND AND PURPOSE: A growing population of older adults will require health care professionals to become increasingly knowledgeable in geriatric care. Patient ratings, functional measures, and emphasis on health and wellness should be part of geriatric physical therapy practice. The purpose of the current study was to examine relationships between self-rated health (SRH) and movement-related variables in older adults using the International Classification of Functioning, Disability, and Health (ICF) as a research framework. Associations between body mass index (BMI), gait, and balance confidence were also explored. METHODS: Thirty older adults (mean age = 74.1 years; 18 women and 12 men) participated in the study and completed the following questionnaires: SRH, Short Activities-specific Balance Confidence scale, Keele Assessment of Participation, and the Neighborhood Environment Walkability Scale-Abbreviated. Spatiotemporal gait parameters, BMI, and isokinetic knee extensor strength were also assessed. RESULTS: Bivariate results indicated significant associations between SRH and double-support time during gait (rs = -0.6, P < .001), gait speed (rs = 0.4, P = .05), step length (rs = 0.4, P = .05), BMI (rs = -0.4, P = .015), and hilliness of neighborhood (rs = -0.4, P = .015). Individual regression models, controlling for education and age, demonstrated that double-support time was the strongest predictor of SRH (R = 0.50, P = .001). Comparisons of the low versus high BMI groups indicated more favorable balance confidence and gait characteristics for the low BMI group, particularly in double support (t = -3.8, P = .001). CONCLUSIONS: SRH should be considered as a quick, patient-focused assessment of health in older adults. Measures of double-support time and BMI may provide clinicians with useful information about their geriatric patients' overall health and function.


Subject(s)
Gait , Health Status , Surveys and Questionnaires , Aged , Aged, 80 and over , Body Mass Index , Exercise Test , Female , Humans , International Classification of Functioning, Disability and Health , Male , Muscle Strength , Postural Balance , Quadriceps Muscle/physiology , Walking Speed
8.
Plant Physiol ; 179(2): 569-587, 2019 02.
Article in English | MEDLINE | ID: mdl-30482788

ABSTRACT

Sucrose (Suc) is one of the most important types of sugars in plants, serving inter alia as a long-distance transport molecule, a carbon and energy storage compound, an osmotically active solute, and fuel for many anabolic reactions. Suc biosynthesis and degradation pathways are well known; however, the regulation of Suc intracellular distribution is poorly understood. In particular, the cellular function of chloroplast Suc reserves and the transporters involved in accumulating these substantial Suc levels remain uncharacterized. Here, we characterize the plastidic sugar transporter (pSuT) in Arabidopsis (Arabidopsis thaliana), which belongs to a subfamily of the monosaccharide transporter-like family. Transport analyses with yeast cells expressing a truncated, vacuole-targeted version of pSuT indicate that both glucose and Suc act as substrates, and nonaqueous fractionation supports a role for pSuT in Suc export from the chloroplast. The latter process is required for a correct transition from vegetative to reproductive growth and influences inflorescence architecture. Moreover, pSuT activity affects freezing-induced electrolyte release. These data further underline the central function of the chloroplast for plant development and the modulation of stress tolerance.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/physiology , Cold-Shock Response/physiology , Flowers/physiology , Symporters/metabolism , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/genetics , Chloroplasts/metabolism , Gene Expression Regulation, Plant , Gene Knockout Techniques , Membrane Transport Proteins/genetics , Membrane Transport Proteins/metabolism , Monosaccharide Transport Proteins/genetics , Monosaccharide Transport Proteins/metabolism , Mutation , Plants, Genetically Modified , Plastids/metabolism , Protein Domains , Saccharomyces cerevisiae/genetics , Sucrose/metabolism , Symporters/chemistry , Symporters/genetics
9.
Nat Commun ; 9(1): 3489, 2018 08 28.
Article in English | MEDLINE | ID: mdl-30154480

ABSTRACT

To fulfill its role in protein biogenesis, the endoplasmic reticulum (ER) depends on the Hsp70-type molecular chaperone BiP, which requires a constant ATP supply. However, the carrier that catalyzes ATP uptake into the ER was unknown. Here, we report that our screen of gene expression datasets for member(s) of the family of solute carriers that are co-expressed with BiP and are ER membrane proteins identifies SLC35B1 as a potential candidate. Heterologous expression of SLC35B1 in E. coli reveals that SLC35B1 is highly specific for ATP and ADP and acts in antiport mode. Moreover, depletion of SLC35B1 from HeLa cells reduces ER ATP levels and, as a consequence, BiP activity. Thus, human SLC35B1 may provide ATP to the ER and was named AXER (ATP/ADP exchanger in the ER membrane). Furthermore, we propose an ER to cytosol low energy response regulatory axis (termed lowER) that appears as central for maintaining ER ATP supply.


Subject(s)
Endoplasmic Reticulum/metabolism , Membrane Proteins/metabolism , Mitochondrial Membranes/metabolism , Adenosine Diphosphate/metabolism , Adenosine Triphosphate/metabolism , Amino Acid Sequence , Biological Transport/physiology , Cytosol/metabolism , Electrophoresis, Polyacrylamide Gel , HeLa Cells , Humans , Membrane Proteins/chemistry , Molecular Sequence Data , Monosaccharide Transport Proteins/chemistry , Monosaccharide Transport Proteins/genetics , Monosaccharide Transport Proteins/metabolism , Real-Time Polymerase Chain Reaction , Sequence Homology, Amino Acid
10.
Plant Cell Physiol ; 59(7): 1290-1299, 2018 Jul 01.
Article in English | MEDLINE | ID: mdl-29444312

ABSTRACT

The sessile lifestyle of higher plants is accompanied by their remarkable ability to tolerate unfavorable environmental conditions. This is because, during evolution, plants developed a sophisticated repertoire of molecular and metabolic reactions to cope with changing biotic and abiotic challenges. In particular, the abiotic factors light intensity and ambient temperature are characterized by altering their amplitude within comparably short periods of time and are causative for onset of dynamic plant responses. These rapid responses in plants are also classified as 'acclimation reactions' which differ, due to their reversibility and duration, from non-reversible 'adaptation reactions'. In this review, we demonstrate the remarkable importance of stress-induced changes in carbohydrate homeostasis of plants exposed to high light or low temperatures. These changes represent a co-ordinated process comprising modifications of (i) the concentrations of selected sugars; (ii) starch turnover; (iii) intracellular sugar compartmentation; and (iv) corresponding gene expression patterns. The critical importance of these individual processes has been underlined in the recent past by the analyses of a large number of mutant plants. The outcome of these analyses raised our understanding of acclimation processes in plants per se but might even become instrumental to develop new concepts for directed breeding approaches with the aim to increase abiotic stress tolerance of crop species, which in most cases have high stress sensitivity. The latter direction of plant research is of special importance since abiotic stress stimuli strongly impact on crop productivity and are expected to become even more pronounced because of human activities which alter environmental conditions rapidly.


Subject(s)
Carbohydrate Metabolism/physiology , Plants/metabolism , Stress, Physiological/physiology , Biological Transport , Cold-Shock Response/physiology , Fructans/metabolism , Sugars/metabolism , Temperature
11.
Diabet Med ; 34(7): 1000-1004, 2017 07.
Article in English | MEDLINE | ID: mdl-28173619

ABSTRACT

BACKGROUND: Children with neonatal diabetes often present with diabetic ketoacidosis and hence are at risk of cerebral oedema and subsequent long-term neurological deficits. These complications are difficult to identify because neurological features can also occur as a result of the specific genetic aetiology causing neonatal diabetes. CASE REPORTS: We report two cases of neonatal diabetes where ketoacidosis-related cerebral oedema was the major cause of their permanent neurological disability. Case 1 (male, 18 years, compound heterozygous ABCC8 mutation) and case 2 (female, 29 years, heterozygous KCNJ11 mutation) presented with severe diabetic ketoacidosis at 6 and 16 weeks of age. Both had reduced consciousness, seizures and required intensive care for cerebral oedema. They subsequently developed spastic tetraplegia. Neurological examination in adulthood confirmed spastic tetraplegia and severe disability. Case 1 is wheelchair-bound and needs assistance for transfers, washing and dressing, whereas case 2 requires institutional care for all activities of daily living. Both cases have first-degree relatives with the same mutation with diabetes, who did not have ketoacidosis at diagnosis and do not have neurological disability. DISCUSSION: Ketoacidosis-related cerebral oedema at diagnosis in neonatal diabetes can cause long-term severe neurological disability. This will give additional neurological features to those directly caused by the genetic aetiology of the neonatal diabetes. Our cases highlight the need for increased awareness of neonatal diabetes and earlier and better initial treatment of the severe hyperglycaemia and ketoacidosis often seen at diagnosis of these children.


Subject(s)
Brain Edema/etiology , Developmental Disabilities/etiology , Diabetes Mellitus/physiopathology , Diabetic Ketoacidosis/etiology , Diabetic Neuropathies/etiology , Hyperglycemia/etiology , Quadriplegia/etiology , Adolescent , Adult , Brain Edema/physiopathology , Developmental Disabilities/physiopathology , Diabetes Mellitus/blood , Diabetes Mellitus/genetics , Diabetic Ketoacidosis/physiopathology , Diabetic Neuropathies/physiopathology , Disabled Persons , Family Health , Female , Humans , Hyperglycemia/physiopathology , Male , Mutation , Potassium Channels, Inwardly Rectifying/genetics , Quadriplegia/physiopathology , Quality of Life , Severity of Illness Index , Sulfonylurea Receptors/genetics
13.
New Phytol ; 202(1): 188-197, 2014 Apr.
Article in English | MEDLINE | ID: mdl-24329902

ABSTRACT

Arabidopsis vacuoles harbor, besides sugar transporter of the TMT-type, an early response to dehydration like 6 (ERDL6) protein involved in glucose export into the cytosol. However, the mode of transport of ERDL6 and the plant's feedback to overexpression of its activity on essential properties such as, for example, seed germination or freezing tolerance, remain unexplored. Using patch-clamp studies on vacuoles expressing AtERDL6 we demonstrated directly that this carrier operates as a proton-driven glucose exporter. Overexpression of BvIMP, the closest sugar beet (Beta vulgaris) homolog to AtERDL6, in Arabidopsis leads surprisingly to impaired seed germination under both conditions, sugar application and low environmental temperatures, but not under standard conditions. Upon cold treatment, BvIMP overexpressor plants accumulated lower quantities of monosaccharides than the wild-type, a response in line with the reduced frost tolerance of the transgenic Arabidopsis plants, and the fact that cold temperatures inhibits BvIMP transcription in sugar beet leaves. With these findings we show that the tight control of vacuolar sugar import and export is a key requisite for cold tolerance and seed germination of plants.


Subject(s)
Adaptation, Physiological , Arabidopsis/physiology , Germination , Glucose/metabolism , Plant Proteins/metabolism , Protons , Seeds/growth & development , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Beta vulgaris , Biocatalysis , Biological Transport , Carbohydrate Metabolism , Electric Conductivity , Freezing , Gene Expression Regulation, Plant , Light-Harvesting Protein Complexes/genetics , Light-Harvesting Protein Complexes/metabolism , Monosaccharide Transport Proteins/genetics , Monosaccharide Transport Proteins/metabolism , Photosystem II Protein Complex/genetics , Photosystem II Protein Complex/metabolism , Plant Proteins/genetics , Plants, Genetically Modified , RNA, Messenger/genetics , RNA, Messenger/metabolism , Seeds/genetics , Signal Transduction , Starch/metabolism , Vacuoles/metabolism
14.
Plant Physiol ; 163(3): 1338-52, 2013 Nov.
Article in English | MEDLINE | ID: mdl-24028846

ABSTRACT

Here, we report that SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTER (SWEET16) from Arabidopsis (Arabidopsis thaliana) is a vacuole-located carrier, transporting glucose (Glc), fructose (Fru), and sucrose (Suc) after heterologous expression in Xenopus laevis oocytes. The SWEET16 gene, similar to the homologs gene SWEET17, is mainly expressed in vascular parenchyma cells. Application of Glc, Fru, or Suc, as well as cold, osmotic stress, or low nitrogen, provoke the down-regulation of SWEET16 messenger RNA accumulation. SWEET16 overexpressors (35SPro:SWEET16) showed a number of peculiarities related to differences in sugar accumulation, such as less Glc, Fru, and Suc at the end of the night. Under cold stress, 35SPro:SWEET16 plants are unable to accumulate Fru, while under nitrogen starvation, both Glc and Fru, but not Suc, were less abundant. These changes of individual sugars indicate that the consequences of an increased SWEET16 activity are dependent upon the type of external stimulus. Remarkably, 35SPro:SWEET16 lines showed improved germination and increased freezing tolerance. The latter observation, in combination with the modified sugar levels, points to a superior function of Glc and Suc for frost tolerance. 35SPro:SWEET16 plants exhibited increased growth efficiency when cultivated on soil and showed improved nitrogen use efficiency when nitrate was sufficiently available, while under conditions of limiting nitrogen, wild-type biomasses were higher than those of 35SPro:SWEET16 plants. Our results identify SWEET16 as a vacuolar sugar facilitator, demonstrate the substantial impact of SWEET16 overexpression on various critical plant traits, and imply that SWEET16 activity must be tightly regulated to allow optimal Arabidopsis development under nonfavorable conditions.


Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , Carrier Proteins/genetics , Gene Expression Regulation, Plant , Monosaccharide Transport Proteins/genetics , Vacuoles/metabolism , Adaptation, Physiological/genetics , Arabidopsis/growth & development , Arabidopsis/metabolism , Arabidopsis Proteins/metabolism , Biomass , Blotting, Northern , Carrier Proteins/metabolism , Cold Temperature , Down-Regulation/drug effects , Fructose/metabolism , Fructose/pharmacology , Germination/genetics , Glucose/metabolism , Glucose/pharmacology , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Microscopy, Confocal , Monosaccharide Transport Proteins/metabolism , Mutation , Nitrogen/metabolism , Nitrogen/pharmacology , Osmotic Pressure , Plants, Genetically Modified , Reverse Transcriptase Polymerase Chain Reaction , Sucrose/metabolism , Sucrose/pharmacology
15.
Curr Biol ; 23(8): 697-702, 2013 Apr 22.
Article in English | MEDLINE | ID: mdl-23583552

ABSTRACT

In higher plants, soluble sugars are mainly present as sucrose, glucose, and fructose. Sugar allocation is based on both source-to-sink transport and intracellular transport between the different organelles and depends on actual plant requirements. Under abiotic stress conditions, such as nitrogen limitation, carbohydrates accumulate in plant cells. Despite an increasing number of genetic studies, the genetic architecture determining carbohydrate composition is poorly known. Using a quantitative genetics approach, we determined that the carrier protein SWEET17 is a major factor controlling fructose content in Arabidopsis leaves. We observed that when SWEET17 expression is reduced, either by induced or natural variation, fructose accumulates in leaves, suggesting an enhanced storage capacity. Subcellular localization of SWEET17-GFP to the tonoplast and functional expression in Xenopus oocytes showed that SWEET17 is the first vacuolar fructose transporter to be characterized in plants. Physiological studies in planta provide evidence that SWEET17 acts to export fructose out of the vacuole. Overall, our results suggest that natural variation in leaf fructose levels is controlled by the vacuolar fructose transporter SWEET17. SWEET17 is highly conserved across the plant kingdom; thus, these findings offer future possibilities to modify carbohydrate partitioning in crops.


Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Arabidopsis/genetics , Arabidopsis/metabolism , Fructose/metabolism , Membrane Transport Proteins/genetics , Membrane Transport Proteins/metabolism , Animals , Carbohydrate Metabolism , Cloning, Molecular , Plant Leaves/metabolism , Polymerase Chain Reaction , Quantitative Trait Loci , Sequence Analysis, DNA , Stress, Physiological , Xenopus
16.
Diabet Med ; 29(10): e398-401, 2012 Oct.
Article in English | MEDLINE | ID: mdl-22803842

ABSTRACT

BACKGROUND: We describe an unplanned pregnancy in a 19-year-old with lipodystrophic diabetes caused by a mutation in the peroxisome proliferator-activated receptor gamma (PPARG) gene. The pregnancy was complicated by poor compliance with treatment, severe hypertriglyceridaemia and pancreatitis. CASE REPORT: The patient presented at 6 weeks' gestation with an HbA(1c) of 140 mmol/mol (15%), cholesterol 8.1 mmol/l and triglycerides 20.1 mmol/l. She wished to continue the pregnancy so lipid-lowering therapy was discontinued. She was severely insulin resistant and poorly compliant with diet and medication. A continuous subcutaneous insulin infusion was required for efficient delivery of large doses of basal insulin, alongside injected mealtime boluses, (up to 300 units insulin per day). At 17 weeks' gestation she developed acute pancreatitis secondary to hypertriglyceridaemia (triglycerides > 100 mmol/l) and required plasmapheresis. Lipid-lowering therapy was reinstated in the third trimester and plasmapheresis was required repeatedly to maintain triglycerides < 10 mmol/l. Delivery was arranged at 32 weeks, because of deteriorating glycaemic and lipid control (blood pressure was normal). Following betamethasone for fetal lung maturation, 20 units/h of intravenous insulin were required to maintain glycaemic control. A baby boy with significant subsequent developmental delay was delivered. DISCUSSION: The features of PPARG mutations are discussed, with literature on lipodystrophy and pancreatitis in pregnancy reviewed. There are few documented cases of pregnancy in women with PPARG mutations. The notable features of this case include the consequences of non-concordance with treatment, the use of continuous subcutaneous insulin infusion to treat insulin-resistant diabetes and the need for repeated plasmapheresis during pregnancy to avert pancreatitis.


Subject(s)
Diabetes Mellitus, Type 1/genetics , Hypertriglyceridemia/genetics , Lipodystrophy/genetics , Mutation , PPAR gamma/genetics , Pancreatitis/genetics , Pregnancy in Diabetics , Blood Glucose/metabolism , Developmental Disabilities , Diabetes Mellitus, Type 1/blood , Diabetes Mellitus, Type 1/complications , Diabetes Mellitus, Type 1/physiopathology , Diet , Female , Humans , Hypertriglyceridemia/blood , Infant, Newborn , Lipodystrophy/blood , Male , Pancreatitis/blood , Patient Compliance , Pregnancy , Pregnancy Complications/genetics , Pregnancy Outcome , Pregnancy in Diabetics/blood , Pregnancy in Diabetics/genetics , Pregnancy in Diabetics/physiopathology , Pregnancy, Unplanned , Young Adult
17.
Plant Physiol ; 157(4): 1664-76, 2011 Dec.
Article in English | MEDLINE | ID: mdl-21984725

ABSTRACT

Subcellular sugar partitioning in plants is strongly regulated in response to developmental cues and changes in external conditions. Besides transitory starch, the vacuolar sugars represent a highly dynamic pool of instantly accessible metabolites that serve as energy source and osmoprotectant. Here, we present the molecular identification and functional characterization of the vacuolar glucose (Glc) exporter Arabidopsis (Arabidopsis thaliana) Early Responsive to Dehydration-Like6 (AtERDL6). We demonstrate tonoplast localization of AtERDL6 in plants. In Arabidopsis, AtERDL6 expression is induced in response to factors that activate vacuolar Glc pools, like darkness, heat stress, and wounding. On the other hand, AtERDL6 transcript levels drop during conditions that trigger Glc accumulation in the vacuole, like cold stress and external sugar supply. Accordingly, sugar analyses revealed that Aterdl6 mutants have elevated vacuolar Glc levels and that Glc flux across the tonoplast is impaired under stress conditions. Interestingly, overexpressor lines indicated a very similar function for the ERDL6 ortholog Integral Membrane Protein from sugar beet (Beta vulgaris). Aterdl6 mutant plants display increased sensitivity against external Glc, and mutant seeds exhibit a 10% increase in seed weight due to enhanced levels of seed sugars, proteins, and lipids. Our findings underline the importance of vacuolar Glc export during the regulation of cellular Glc homeostasis and the composition of seed reserves.


Subject(s)
Arabidopsis/metabolism , Glucose/metabolism , Homeostasis/physiology , Monosaccharide Transport Proteins/metabolism , Seeds/metabolism , Arabidopsis/genetics , Beta vulgaris/genetics , Biological Transport , Carbohydrates/physiology , Gene Expression Regulation, Plant , Germination , Glucose Transport Proteins, Facilitative/genetics , Glucose Transport Proteins, Facilitative/metabolism , Monosaccharide Transport Proteins/genetics , Mutation , Plant Proteins/genetics , Plant Proteins/metabolism , Plants, Genetically Modified , Seeds/genetics , Vacuoles/metabolism
18.
Waste Manag ; 31(2): 215-24, 2011 Feb.
Article in English | MEDLINE | ID: mdl-20117924

ABSTRACT

In Sweden, leaching tests with deionized water (D.W.) are utilized in risk assessment of materials entering landfills, but implementation of these results to evaluate the risk of spreading of pollutants in the environment is difficult. One problem is that most leaching procedures only consider heavy metals release, whereas organic pollutants are left out. The aim of the present study was to assess the possible pollutant mitigation in four remediated soils, three with heavy metals and one with polycyclic aromatic hydrocarbons (PAH) contamination. The mitigation was evaluated by standardized batch and column leaching tests utilizing three different leaching solutions: D.W., a weak ionic solution (0.001 M CaCl(2)) and an artificially made soil water (ASW). In general, batch leaching tests implied larger contaminant removal than column leaching test, possibly due to the more rough treatment of the soil particles, and guidelines would at times be exceeded by the batch leaching test but not by column leaching tests. Utilization of CaCl(2) was found to release less heavy metal than D.W., whereas the metals mobilized by ASW were removed from solution by the filtration of soil leachates. Low molecular weight PAH was most efficiently mobilized by CaCl(2), while D.W. worked better for high molecular weight PAH. Despite very low initial PAH-concentrations, tap- and groundwater criteria were exceeded by all leaching solutions.


Subject(s)
Environmental Restoration and Remediation/methods , Metals, Heavy/analysis , Polycyclic Aromatic Hydrocarbons/analysis , Soil , Waste Products/analysis , Water Pollutants, Chemical/analysis , Calcium Chloride/chemistry , Metals, Heavy/toxicity , Polycyclic Aromatic Hydrocarbons/toxicity , Sweden , Water/chemistry
19.
J Hazard Mater ; 172(2-3): 1033-40, 2009 Dec 30.
Article in English | MEDLINE | ID: mdl-19699582

ABSTRACT

Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2 x CMC* of a non-ionic, alkyl glucoside surfactant at pH 12 (Ca(OH)(2)). This combination managed to reach Swedish threshold values within 1 0 min of treatment when performed at elevated temperature (50 degrees C), with initial contaminant concentrations of As=105+/-4 mg/kg and US-EPA PAH(16)=46.0+/-2.3mg/kg. The main mechanisms behind the removal were the pH effect for As and a combination of SOM ionization as a result of high pH and micellar solubilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characteristics of the leaching solution due to the elevated pressure utilized. The ecotoxicological evaluation, Microtox, demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to increased availability of contaminants and toxicity of soil washing solutions to the test organism.


Subject(s)
Polycyclic Aromatic Hydrocarbons/isolation & purification , Soil Pollutants/isolation & purification , Wood/chemistry , Chelating Agents , Decontamination , Micelles , Pilot Projects , Polycyclic Aromatic Hydrocarbons/toxicity , Soil , Solubility , Surface-Active Agents , Toxicity Tests
20.
Ann Clin Biochem ; 45(Pt 1): 99-101, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18275684

ABSTRACT

We describe the case of a gentleman who initially presented with isolated cranial diabetes insipidus and has subsequently developed progressive anterior pituitary failure. In addition, he has been found to have evidence of mesenteric fibrosis and primary sclerosing cholangitis. We suggest that his pituitary disease may also be caused by progressive fibrosis and that these separate pathological entities may be linked by the unifying diagnosis of progressive multifocal fibrosclerosis, a rare fibro-inflammatory process involving multiple organ systems.


Subject(s)
Fibrosis/pathology , Sclerosis/pathology , Biopsy , Fibrosis/surgery , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Sclerosis/surgery
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