Mobilization Of Carbohydrate Reserves Research Articles

Mobilization of fat body glycogen and haemolymph trehalose under nutritional stress in Bombyx mori larvae in relation to their physiological age and the duration of food deprivation

In insects, fat body glycogen and haemolymph trehalose are principal carbohydrate reserves. Here, in Bombyx mori (Linnaeus, 1758), we report an accelerated fat body glycogen accumulation in feeding 5th instar larvae, when they reach the terminal growth period (TGP). Haemolymph trehalose and glucose levels, however, fluctuated between 7–21 mM and 0.8–10 mM, respectively, depending on the larval physiological age. Food deprivation triggered a dramatic increase in mobilization of glycogen in larvae at TGP than at active growth period (AGP), mobilized almost 78% of stored glycogen at an initial 12 h of food deprivation, possibly by increasing the percentage of active glycogen phosphorylase, as observed. This rapid glycogen mobilization, along with meeting the energy demand of starving tissues, might also have provided glucose for trehalose synthesis, as evident by observed hypertrehalosemia. A prolonged food deprivation (24–48 h) triggered hypotrehalosemia along with an increase in the enzyme activity of trehalase, and the transcript level of trehalase-2, indicating the utilization of trehalose as an energy source for the demanding tissues. Further, in TGP larvae, a prolonged food deprivation increased the level of haemolymph glucose (1.8–3.5 mM) as well as glucose/trehalose ratio, and this suggests that the fat body might have released the glucose molecules directly into the haemolymph, instead of utilizing it for trehalose synthesis, possibly to minimize the expenditure of energy. Thus, short-term food deprivation triggered an initial glycogen mobilization whereas, prolonged food deprivation led to the utilization of trehalose as an energy source. Hence, mobilization of carbohydrate reserves varied depending on the larval physiological age and the extent of food deprivation period. The future investigation can expand our understanding on the role of glucose as an important haemolymph sugar along with trehalose.

Enzymatic Studies with Reference to Antifertility Potential of Piper betle Linn. Leaf Stalk Extract in Male Albino Rats

The betel leaf (Tambula patra brint) is extensively cultivated in warm moist parts of India for its leaves; the antifertility properties of the betel plant were studied in both male and female rats. It was suggested that the contraceptive effect of the extract of leaf stalk of piper betel Linn is mainly on the maturation process of spermatozoa in epididymis without influencing hysteric hormonal profiles. The main aim of this study was to evaluate the antifertility efficacy of piper betel Linn leaf stalk extract with reference to some marker enzymes. In this study healthy male albino rats were administered with betel leaf stalk extract, at the dose rate of 150 mg/Kg/ day through oral gavage, for 15 days. The enzymatic changes were observed over control male rats. The observed reduction in Glucose-6-Phosphate dehydrogenase activity in testis, suggests that decreased level of operation of hexose mono phosphate pathway and also mobilization of carbohydrate reserves in to Hexose mono phosphate (HMP) pathway. Increased Succinate dehydrogenase is an indicative of better energy utilization due to the production of intermediates in the tricarboxylic acid cycle. The significant decrease in testicular Glutamate dehydrogenase activities (a biochemical indicator used to assess injury to the mitochondria) may imply reduction in the amount of energy being made available to the sperm cells. The total phosphorylase activity was highly depleted suggesting the Original Research Article Naik and Changamma; ARRB, 5(3): 246-253, 2015; Article no. ARRB.2015.026 247 overall degradation of the enzyme, possibly for inhibiting glycogenolysis in response to betel leaf stalk extract. The depleted aldolase levels indicate decreased mobilization of glucose in to Embden-Mayeroff pathway in testis. Thus the extract administration does not affect the normal energy metabolism; it affects the sperm energy metabolism. Hence, sperm metabolic processes are disrupted. It also brings the alterations in chemical composition of seminal plasma and prostatic fluid leads to sperm anomalies.

UCP4 expression changes in larval and pupal fat bodies of the beetle Zophobas atratus under adipokinetic hormone treatment

We investigated the influence of adipokinetic hormone (AKH), an insect neurohormone, on uncoupling protein 4 (ZaUCP4) expression and activity in larval and pupal fat body mitochondria of the beetle Zophobas atratus in relation to intermediary metabolism. Homologous Tenmo-AKH was administered to the beetle larvae and pupae as either a single dose or as two doses of 20pmol during a 24h interval. In the larval and pupal fat bodies, downregulation of ZaUCP4 expression at the mRNA and protein levels was observed 24h and 48h after AKH treatment, respectively. In both developmental stages, ZaUCP4 activity was lowered in fat body mitochondria 48h after AKH treatment. In the AKH-injected larvae, changes in ZaUCP4 expression were accompanied by the mobilization of carbohydrate reserves, no change in the concentration of total lipids and an increase in the free fatty acid level. In contrast, AKH had no effect on carbohydrate metabolism in the pupal fat body but induced lipid mobilization. It seems that AKH influences ZaUCP4 expression by triggering multiple events and that it has different physiological roles in controlling intermediary metabolism in the fat body of the beetle larvae and pupae.

Shifts in biomass and resource allocation patterns following defoliation in Eucalyptus globulus growing with varying water and nutrient supplies

In woody species, potential mechanisms to compensate for tissue loss to herbivory and diseases have been related to post-event shifts in growth, biomass and internal resource allocation patterns, as modulated by external resource limitations. We examined the interactive effects of belowground resource limitations by varying nutrient and water availability, and aboveground carbon limitation imposed by a single defoliation event (40% leaf removal) on stem growth, whole-tree and within-tree resource allocation patterns (total non-structural carbohydrate and nitrogen) and below- and aboveground biomass allocation patterns in 8-month-old, field-grown Eucalyptus globulus Labill. saplings. Two months after treatments were imposed, the direction of the stem growth response to defoliation depended on the abiotic treatment. Five months after defoliation, however, we found little evidence that resource availability constrained the expression of tolerance to defoliation. With the exception of the combined low-nutrient and low-water supply treatment, saplings grown with (1) adequate water and nutrient supplies and even with (2) low-water supply or (3) low-nutrient supply were able to compensate for the 40% foliage loss. The observed compensatory responses were attributed to the activation of several short- and longer-term physiological mechanisms including reduced biomass allocation to coarse roots, mobilization of carbohydrate reserves, robust internal N dynamics and increased ratio of foliage to wood dry mass.

Patch Distribution and Within-Patch Dynamics of the Seagrass Zostera noltii Hornem. in Los Toruños Salt-Marsh, Cádiz Bay, Natural Park, Spain

Patch distribution and small-scale ( i.e. , within-patch) temporal variability in plant morphology, biomass, shoot density, tissue nutrient content and growth were studied in the intertidal seagrass Zostera noltii at Los Toruāos salt-marsh (Cádiz, Spain). The area covered by Z. noltii was 7.3%, and decreased exponentially with depth. The lack of recruitment from seedlings largely explained the normal patch size distribution observed. Overall, lower biomass, shoot density, above-ground to below-ground biomass ratios and higher leaf elongation rates were recorded at the patch edge, where biomass dynamics were primarily controlled by recruitment and mortality processes. In contrast, temporal variation in above-ground biomass in the patch centre depended largely on changes in shoot leaf number and size. There was no correlation between total biomass and shoot density in the patch centre suggesting that below-ground biomass may be space-limited. Low aboveground biomass and shoot elongation rates were recorded in May, regardless of position within the patch, and were coincident with the abundance of Ulva sp. mats. Light reduction by Ulva canopies also resulted in a mobilization of carbohydrate reserves. Such resource reallocation may represent an important short-term survival strategy, maintaining leaf and rhizome elongation capacity.

Effect of low temperature on dormancy breaking and growth after planting in lily bulblets regenerated in vitro

Lilies regenerating on scale segments may develop dormancy in vitro depending on the culture conditions. The dormancy is broken by storage for several weeks at a low temperature (5 °C). The effect of the low temperature on sprouting, time of leaf emergence and further bulb growth was studied. Dormant and non-dormant bulblets were regenerated in vitro on bulb scale segments cultured at 20 °C or 15 °C, respectively. The low temperature not only affected the number of sprouted bulblets but also the time of emergence. The longer the cold storage, the faster and more uniform leaf emergence occurred. Both dormant and non-dormant bulblets grew faster after a low temperature treatment of six weeks. Thus, during dormancy breaking the tissue is prepared not only for sprouting but also for subsequent bulb growth. These processes are rather independent as low temperature stimulates growth in non-dormant bulblets whereas these bulblets sprout also without treatment at low temperature. Moreover, the hormone gibberellin induces rapid sprouting but has no influence on further bulb growth. Good growth in bulblets exposed to the low temperature coincided with production of an increased leaf weight. However, the relationship is not absolute as bulblets that were cold-treated for six weeks grew larger than bulblets cold-treated for four weeks but the formation of leaf biomass was similar. During storage at low temperature starch was hydrolyzed in the bulb scales and sugars accumulated. This indicates that during this period, preparation for later bulb growth involves mobilization of carbohydrate reserves which play a role in leaf growth and development of the photosynthetic apparatus. Starch hydrolysis proceeded in the outer scales after planting. Approximately six weeks later, the switch from source to sink took place in the bulblet, which became visible as a deposition of starch in the middle scales.

Effects of light availability on growth, architecture and nutrient content of the seagrass Zostera noltii Hornem

The growth vs. irradiance response of the seagrass Zostera noltii from Cadiz Bay Natural Park (southwestern Spain) was characterised. Plants were exposed along 14 days to different light treatments (1%, 7%, 42% and 100% surface irradiance, SI), using shade screens in an outdoor mesocosm. Growth at 100% SI (1.6 mg DW plant −1 day −1) was lower than that at 42% SI (2.4 mg DW plant −1 day −1), suggesting photoinhibition. The minimum light requirement estimated was 0.8 mol photons m −2 day −1 (2% SI). Light availability affected the pattern of plant development and the overall plant growth. The contribution of the apical shoots to the aboveground production was nearly constant (c.a. 1.13 cm plant −1 day −1) regardless of the light level (except at 1% SI). In contrast, recruitment and growth of lateral shoots arising from the main rhizome axes accounted for the observed differences in aboveground growth. Rhizome branching was only observed at 42% SI. The possibility of a light threshold for rhizome branching could explain the seasonality of shoot recruitment, as well as the observed decrease in shoot density along depth (or light) gradients in seagrass meadows. Carbon demands at low irradiances (1% and 7% SI) were partially met by mobilization of carbohydrate reserves (sucrose in belowground and starch in aboveground parts). Plant nitrogen content decreased with increasing light, especially in belowground parts, reaching critical levels for growth.

α-Galactosidase is synthesized in tomato seeds during development and is localized in the protein storage vacuoles

The localization of the enzyme α-galactosidase (EC 3.2.1.22) was investigated during its synthesis in developing tomato (Lycopersicon esculentum Mill.) cv. Trust seeds. This enzyme is also present in germinating seeds, where it is involved in the mobilization of carbohydrate reserves during and following seed germination. Subcellular fractionation of developing tomato seeds revealed that there is a cosedimentation between α-galactosidase activity and protein storage vacuoles in a density gradient, which is dependent upon the presence of membranes. A second approach to localizing this enzyme involved the transient transformation of protoplasts from developing tomato seeds. A reporter construct, coding for tomato α-galactosidase, fused N-terminally to the bacterial enzyme chloramphenicol acetyltransferase was used for transient expression. Immunofluorescence microscopy revealed a colocalization between the α-galactosidase - chloramphenicol acetyltransferase fusion protein and the α-tonoplast intrinsic protein, and a partial colocalization with the dark intrinsic protein (both vacuolar proteins). These data indicate that the protein storage vacuole is the intracellular location for α-galactosidase in developing tomato seeds.Key words: α-galactosidase, protein storage vacuole, seed development, seed protoplasts, tomato, tonoplast intrinsic protein.

Changes of enzyme activities associated with the mobilization of carbohydrate reserves (fructans) from the stem of wheat during kernel filling

Wheat plants were grown at a day/night temperature of 18/13°C under glasshouse conditions. Twenty‐two d after anthesis, one set of plants was shaded to 50% of the normal photon fluence rate, another was ‘degrained’ by selective spikelet removal which left only the grains in the five central spikelets; a further set was left as control. Individual plants were harvested at days 22, 30 or 42 after anthesis. Extracts from the peduncle and the penultimate internode were prepared to determine the activities of sucrose phosphate synthase, sucrose synthase, fructan exohydrolase and acid invertase, and to assess the concentration of hexose sugars, sucrose and fructans. Measurements were also made of ear and individual grain weights, and stem f. wt and d. wt. There was a decline in the amount of fructans with time, more pronounced in ‘shaded’ (source‐limited) than in control plants. By contrast, in ‘degrained’ (sink‐limited) plants, the amount of fructans in the stem initially rose, then decreased, with a concomitant increase in the amount of fructose. The shifts in sugar content of the wheat culm reflected both the sink demand of the ear and source activity. The activity of fructan exohydrolase correlated with the carbohydrate changes. Under limited photosynthate assimilation, the mobilization of fructans from the internodes towards the ear was related to an increase in this enzyme, whereas the other enzymes played a less direct role in the mobilization of fructan reserves from the wheat stem.

Purification and characterization of α-glucan phosphorylase from Bacillus stearothermophilus

α-Glucan phosphorylase (GP, EC 2.4.1.1) catalyzes the reversible phosphorolysis of glucan and is considered to play a central role in the mobilization of carbohydrate reserves. The structural gene for GP has already been cloned and sequenced from Bacillus stearothermophilus TRBE14 [Takata et al., J. Bacteriol., 179, 4689–4698 1997; DDBJ/EMBL/GenBank accession No. D87026]. This enzyme was expressed in Escherichia coli and purified to homogeneity, and its enzymatic properties were analyzed. At pH 7, GP was stable up to 40°C, and the optimum temperature for activity was 50°C. The enzyme was stable in the pH range 6.5 to 11, and the optimum pH was 7. A test of substrate preference demonstrated that starch and glycogen were more reactive substrates than linear maltodextrin. The smallest acceptor for a synthetic reaction was maltotetraose (G4), and G4 was left as a final product after the phosphorolysis of a linear saccharide. ADP-glucose and UDP-glucose strongly inhibted this enzyme activity. Although the substrate specificity and type of inhibitors are similar to those of its counterpart from E. coli, B. stearothermophilus GP had about a 100-fold higher affinity, and much higher specific activity for glycogen than the E. coli enzyme. These results suggest that the rates of glycogen degradation in the two species may be different from each other.

Changes in carbohydrate composition and α-amylase expression during germination and seedling growth of starch-deficient endosperm mutants of maize

Kernels of 28 different maize ( Zea mays L.) genotypes consisting of several inbreds isogenic for the starch-deficient endosperm mutations sugary 1 ( su1), sugary1 sugary enhancer 1 ( su1se1), and shrunken2 ( sh2) were used to study the effect of these mutations on carbohydrate composition and α-amylase expression during germination and seedling growth in comparison to normal starchy kernels ( Su). Sugar (fructose, glucose, sucrose, and maltose), WSP (water-soluble polysaccharide), and insoluble starch contents were determined for endosperm and scutellar tissues for each of the genotypes at four stages of seedling development. While initial levels of endosperm sucrose were higher in the endosperm mutants, they rapidly declined by radicle emergence and remained low thereafter. Mobilization of carbohydrate reserves was most reduced in the sh2 genotypes. Collectively, these factors represent a limited carbon supply for the developing sh2 seedling which may impact seedling vigor. A more significant negative correlation was observed between percentage germination and endosperm sugar content than between percentage germination and scutellar sugar content. High initial levels of endosperm sucrose in the mutants correlate with a severe reduction of α-amylase (EC 3.2.1.1) transcript abundance. The same correlation does not hold for glucose and maltose, as at later stages of germination, levels were significantly higher in the Su genotype while the α-amylase mRNA levels remained high. Furthermore, the ratio of α-amylase enzyme activity to transcript abundance was considerably lower in the sh2 aleurone compared to the Su aleurone at radicle emergence. Genotype specific differences in α-amylase gene expression strongly correlate with endosperm sugar content and composition during germination.

Aspects of Carbohydrate Partitioning in Ornamental Geophytes

Ornamental geophytes comprise a large and diverse group of plants characterized by underground storage organs that serve the obvious function of reserve storage and subsequent supply during early stages of shoot growth. Relative to many agronomic and horticultural crops, the fundamental physiological bases of carbon metabolism, partitioning, and utilization in geophytes are unclear. One reason is diversity in organ morphology (bulb, corm, tuber, root, rhizome, etc.), storage carbohydrate (starch, fructan, glucomannan, etc.), and growth habit (e.g., synanthous vs. hysteranthous flowering). Knowledge of factors that control accumulation and mobilization of carbohydrate reserves may lead to manipulations that considerably improve the quality and culture of these crops. We are utilizing a variety of techniques and experimental systems to study selected internal and external controls or influences on geophyte carbohydrate metabolism and partitioning. Specific examples to be discussed include bulb storage temperature effects on starch and fructan metabolism in Tulipa, effects of carbon source and dormancy breaking treatments on starch and glucomannan metabolism in in vitro-grown Lilium bulblets, photoperiod control of fructan accumulation in Dahlia seedlings, and biochemical and molecular features of soluble and wall-bound invertases in developing Lilium longiflorum flower buds.

Heavy metal-hormone interactions in rice plants: Effects on growth, net photosynthesis, and carbohydrate distribution

The effect of external applications of gibberellins (GA3) and abscisic acid (ABA) on the growth, carbohydrate content, and net photosynthesis of heavy metal-stressed rice plants (Oryza sativa cv. Bahia) was investigated. Treatment with cadmium (0.1 mm) and nickel (0.5 mm) inhibited rice growth and stimulated carbohydrate accumulation, especially in seeds from which seedlings were developing, stems, and first leaves. The addition of GA3 (14 μm) to the rice culture solution together with Cd or Ni partially reversed the effects of heavy metals, stimulating growth as well as mobilization of carbohydrate reserves in seeds from which seedlings had developed. GA3 increased the sugar content in roots and second and third leaves and also modified the carbohydrate distribution pattern compared with heavy metal-treated plants. In contrast to GA3, ABA (19 μm) supplied to rice cultures potentiated the effect of heavy metals, inhibiting the growth of young leaves and the translocation of storage products from source to sink organs. In addition, sugars were accumulated in roots and second leaf but not in the third leaf, the extension in length of which was also inhibited by the treatment. Net photosynthesis rates recovered transitorily in Cd-treated plants after the addition of hormones. The possible relationship between growth and carbohydrate distribution, as well as the involvement of hormones, in the response of plant to heavy metal stress is discussed.

Effect of aluminium and calcium on growth of wheat seedlings and germination of seeds

Abstract Two separate experiments were conducted to investigate the aluminium (Al) and calcium (Ca) effects on wheat seedling growth and on seed germination. Wheat (Tritcum aestivum L, cs Yangmai No. 5) seedlings were grown for a 15‐day period and treated with 0.5 mM Al with low Ca (1 mM Ca) or high Ca (5 mM Ca). The growth of seedlings was signficantly inhibited by Al. Supplement of Ca improved the growth of Al‐treated plants, increased dry matter weight of plant and leaf area, and decreased shoot/root ratio. This showed that Ca ameliorated Al toxicity in wheat. In experiments on seed germination, Al concentrations less than 2 mM in the germinating medium had little or no visible effect on length of shoot and root of germinating seed. The germinating rate of seed was not affected significantly by Al, when Al concentrations lower than 5 mM Al. The addition of 3 mM Ca did not increase the length of shoot and root and germination rate of seeds. Both pretreatments with 6 mM Ca and 1 μM GA had no significant effect on the length of shoot and root and amylolytic activity of Al‐treated germinating seeds. No significant differences were found in the total amylolytic activity in Al‐treated and control seeds two days and five days after germination. The results of Al and Ca effects on seedlings and seed germination showed that Al‐toxicity on germinating seeds was different from on seedling growth. The high concentrations of Al inhibit growth of roots and shoots of germinating seeds by other toxicity mechanism rather than interaction of Al with Ca and mobilization of carbohydrate reserves.

The family of glycogen phosphorylases: structure and function.

Glycogen phosphorylase plays a central role in the mobilization of carbohydrate reserves in a wide variety of organisms and tissues. While rabbit muscle phosphorylase remains the most studied and best characterized of phosphorylases, recombinant DNA techniques have led to the recent appearance of primary sequence data for a wide variety of phosphorylase enzymes. The functional properties of rabbit muscle phosphorylases are reviewed and then compared to properties of phosphorylases from other tissues and organisms. Tissue expression patterns and the chromosomal localization of mammalian phosphorylases are described. Differences in functional properties among phosphorylases are related to new structural information. Evolutionary relationships among phosphorylases as afforded by comparative analysis of proteins and gene sequences are discussed.

Lysophosphatidylserine as histamine releaser in mice and rats.

Lysophosphatidylserine is a specific inducer of histamine release in isolated mast cells. To determine whether a similar effect is manifest in vivo, the phospholipid was injected (1-5 mg/kg i.v.) into mice and rats. A dose-dependent rise in blood histamine was observed in both animals. The several-fold increase in blood histamine occurred in the first minutes and was followed by a slower decline toward normal values. A second dose of lysophosphatidylserine was without effect. Systemic manifestations (depression, hypothermia, hypotension) were associated with the increased blood histamine level. When the tissue histamine stores accessible to lysophosphatidylserine were previously decreased by repeated phospholipid injections, no systemic symptoms occurred. Mobilization of carbohydrate reserves was also manifest during the action of lysophosphatidylserine. Prior treatment with compound 48/80 induced sustained refractoriness to lysophosphatidylserine. Structure-activity relationship demonstrated that the property to induce histamine release was linked to the structure of serine head group. Thus, other natural phospholipids or lysophospholipids were inactive. It is concluded that in analogy with the effect seen in vitro lysophosphatidylserine produces in vivo release of mast cell histamine.