Starch Phosphorylase Activity Research Articles

Exogenous Hemin alleviates NaCl stress by promoting photosynthesis and carbon metabolism in rice seedlings

It is widely known that salt stress restricts rice growth and productivity severely. However, little information is available regarding the stage of rice seedlings subjected to the Heme oxygenase 1 (HO-1) inducer, Hemin. This study aimed to investigate the effects of salt stress on two rice varieties (Huanghuazhan and Xiangliangyou 900) and the effect of Hemin in promoting photosynthesis, carbohydrate metabolism, and key enzymes under salt-stress conditions. At the stage of three leaves and one heart, Huanghuazhan (HHZ) and Xiangliangyou 900 (XLY900) were sprayed with 5 μmol·L−1 Hemin and then subjected to 50 mM NaCl stress. The results showed that NaCl stress decreased the contents of chlorophyll a, chlorophyll b, and carotenoids. Furthermore, the net photosynthetic rate (Pn) decreased remarkably and the starch content was also lowered. However, NaCl treatment enhanced the concentration of sucrose and soluble sugar, simultaneously enhancing the sucrose metabolism. Nevertheless, the foliar spraying of exogenous Hemin mediated the increase in fructose and starch content, along with the activities of key enzymes’ soluble acid invertase (SAInv), basic/neutral invertase (A/N-Inv), and sucrose synthase (SS) in rice leaves under NaCl stress. The sucrose phosphate synthase (SPS) in leaves decreased significantly, and the fructose accumulation in leaves increased. Hemin also mediated the increase of starch content and the α-amylase, total amylase, and starch phosphorylase (SP) activities under NaCl stress. Under stress conditions, the application of the Heme oxygenase 1 (HO-1) inhibitor, ZnPP failed to alleviate the damage to rice seedlings by NaCl stress. The ZnPP treatment showed similar tendency to the NaCl treatment on pigment content, gas exchange parameters and carbon metabolism related products and enzymes. However, ZnPP decreased carotenoids, fructose, starch content and enzyme activities related to starch metabolism. The regulation effect of Hemin on HuangHuaZhan was better than XiangLiangYou 900. These results indicate that Hemin improved the effects of salt stress on the photosynthesis and physiological characteristics of rice leaves as a result of enhanced carbohydrate metabolism. Thus, Hemin could alleviate the damage caused by salt stress to a certain extent.

Emulsification-based interfacial synthesis of citral-loaded hollow MIL-88A for the inhibition of potato tuber sprouting

Economic value of the global potato harvest is impacted by sprouting during storage. We examined how sprouting might be reduced or eliminated using citral, a naturally occurring component in citrus fruit peel. The current study integrated both loading and sustained release of citral using emulsification-based interfacial synthesis of hollow MIL-88A. The structural properties and compositions of MIL-88A and hollow MIL-88A were confirmed using SEM, EDS, and XRD. BET analysis showed a surface area of 30.36 m2 g−1, pore volume of 0.21 cm3 g−1, and an average pore radius of 13.56 nm for hollow MIL-88A. Citral was successfully loaded into 10 g of MIL-88A and hollow MIL-88A, with a total citral load of 0.21 cm3 and 1.82 cm3, respectively. The citral-loaded hollow MIL-88A induced a sustained release of citral, which effectively inhibited the sprouting, leading to higher starch content by 41%, lower weight losses, reducing sugar content, α-Amylase, β-amylase, and starch phosphorylase activities by 75%, 55%, 34%, 31%, and 43%, respectively. The citral-loaded hollow MIL-88A might inhibit sprouting by suppressing gibberellin and indole-3-acetic acid while maintaining abscisic acid.

The Associated With Carbon Conversion Rate and Source-Sink Enzyme Activity in Tomato Fruit Subjected to Water Stress and Potassium Application.

Carbon metabolism in higher plants is a basic physiological metabolism, and carbon allocation and conversion require the activity of various enzymes in metabolic processes that alter the content and overall composition of sugars in the sink organ. However, it is not known how various enzymes affect carbon metabolism when tomato plants are subjected to water stress or treated with potassium. Although the process of carbon metabolism is very complex, we used the carbon conversion rate to compare and analyze the enzyme activities related to sugar metabolism and find out which carbon conversion rate are the most important. Results showed that water stress and potassium increased carbon import flux in the fruit, which was beneficial to carbon accumulation. Water deficit increased the activity of sucrose synthase (SuSy) and starch phosphorylase (SP) and decreased the activity of sucrose phosphate synthase (SPS) and adenosine diphosphate glucose pyrophosphorylase (AGPase) in the source. Water stress increased the activity of acid invertase (AI), SuSy and SP but decreased the activity of AGPase in the sink. Potassium modified the balance of enzymes active in sugar and starch metabolism by increasing the activity of AI, SuSy, SPS and SP and significantly decreasing the activity of AGPase, resulting in increase of hexose. Canonical correlational analysis revealed that the carbon conversion rate was mainly affected by the relative rate of conversion of sucrose to fructose and glucose [p1(t)] and glucose to starch [p5m(t)]. SuSy and AGPase had the greatest effect on enzyme activity in the fruit; respectively regulated p1(t) and p5m(t).

Arbuscular Mycorrhiza Improves Photosynthesis and Restores Alteration in Sugar Metabolism in Triticum aestivum L. Grown in Arsenic Contaminated Soil.

Contamination of agricultural soil by arsenic (As) is a serious menace to environmental safety and global food security. Symbiotic plant–microbe interaction, such as arbuscular mycorrhiza (AM), is a promising approach to minimize hazards of As contamination in agricultural soil. Even though the potential of AM fungi (AMF) in redeeming As tolerance and improving growth is well recognized, the detailed metabolic and physiological mechanisms behind such beneficial effects are far from being completely unraveled. The present study investigated the ability of an AM fungus, Rhizophagus intraradices, in mitigating As-mediated negative effects on photosynthesis and sugar metabolism in wheat (Triticum aestivum) subjected to three levels of As, viz., 0, 25, and 50 mg As kg–1 of soil, supplied as sodium arsenate. As exposure caused significant decrease in photosynthetic pigments, Hill reaction activity, and gas exchange parameters such as net photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration. In addition, As exposure also altered the activities of starch-hydrolyzing, sucrose-synthesizing, and sucrose-degrading enzymes in leaves. Colonization by R. intraradices not only promoted plant growth but also restored As-mediated impairments in plant physiology. The symbiosis augmented the concentration of photosynthetic pigments, enhanced Hill reaction activity, and improved leaf gas exchange parameters and water use efficiency of T. aestivum even at high dose of 50 mg As kg–1 of soil. Furthermore, inoculation with R. intraradices also restored As-mediated alteration in sugar metabolism by modulating the activities of starch phosphorylase, α-amylase, β-amylase, acid invertase, sucrose synthase, and sucrose-phosphate synthase in leaves. This ensured improved sugar and starch levels in mycorrhizal plants. Overall, the study advocates the potential of R. intraradices in bio-amelioration of As-induced physiological disturbances in wheat plant.

Exogenous supplementation of melatonin alters representative organic acids and enzymes of respiratory cycle as well as sugar metabolism during arsenic stress in two contrasting indica rice cultivars

The objective of the present investigation was to understand the impact of exogenously applied melatonin on mitochondrial respiration and sugar metabolism in two contrasting rice cultivars, viz., Khitish (arsenic-susceptible) and Muktashri (arsenic-tolerant) under arsenic-stress. Melatonin effectively restored the level of organic acids like pyruvic acid, malic acid and more particularly citric acid by 33 % in Khitish which were lowered during arsenic-stress, whereas their levels were further elevated in Muktashri to provide energy for defence against arsenic-induced injury. Arsenic-exposure led to a significant inhibition in enzyme activities as well as corresponding transcript level of key respiratory enzymes, viz., pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, intriguingly more prominently in case of Khitish. Conversely, melatonin supplementation, irrespective of cultivars, considerably improved the activity of the above enzymes and corresponding gene expressions during stress, indicating acceleration in the rate of Krebs cycle. Melatonin supplementation also stimulated the accumulation of total soluble sugars by 62 % and 25 %, reducing sugars by 50 % and 44 % and non-reducing sugars by 75 % and 14 % in Khitish and Muktashri respectively, concomitant with higher activities of acid invertase, sucrose synthase and sucrose phosphate synthase enzymes, along with the expression of corresponding genes. Enhanced starch accumulation via regulation of alpha amylase and starch phosphorylase activities and gene expression, by melatonin also contributed towards better stress tolerance. Overall, this work illustrated the efficacy of melatonin in the regulation of representative organic acids and enzymes of respiratory cycle along with starch and sugar metabolism in rice cultivars under arsenic toxicity.

Silver-nanoparticle and abscisic acid modulate sub1A quantitative trait loci functioning towards submergence tolerance in rice (Oryza sativa L.)

An experiment was conducted to explore the silver-nanoparticles (Ag-NPs) and abscisic acid (ABA) to elicit sub1A quantitative trait loci (QTL) responses under submergence stress. Rice genotypes cv. Swarna and Swarna Sub1 were pre-treated with 100 mg ml−1Ag-NP [Ag-NP(+)] and 10 μM ABA [ABA(+)] at 7-day-old seedlings for 1 day in two separate sets and subsequent transfer to complete submergence for 5 days. sub1A QTL regulatory APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) expression was mitigated for both genotypes under submergence; however, retrieved with Ag-NP(+) and ABA(+) variably. ABA(+) had recorded affirmative responses than Ag-NP(+) in net assimilation rate, relative growth rate, chlorophyll content, and metal accumulation under stress. cv. Swarna Sub1 under submergence had better recovery of proline and relative water content than others. Phenolics, flavonoids, carotenoids, and lycopene content were more influenced by ABA(+) than Ag-NP(+) to recover under submergence. The development of superoxide and hydrogen peroxide had a positive and fair correlation with nicotinamide adenine dinucleotide phosphate oxidase (EC 1.6.3.1) activity under submergence. cv. Swarna Sub1 responded better under submergence through invertase (EC 3.2.1.26), starch phosphorylase (EC 2.4.1.1) and sucrose synthase (EC 2.4.1.13) activity more with ABA(+) than Ag-NP(+). The functioning of sub1A QTL for anaerobic metabolism was improved in cv. Swarna Sub1 than cv. Swarna with the support of polymorphic expression of alcohol dehydrogenase (EC 1.1.1.1). Finally, given results may arise the prospect for mitigation submergence stress by Ag-NP(+) and ABA(+) through modulation of cellular responses affiliated to sub1A QTL.

Fluoride Stress-Mediated Regulation of Tricarboxylic Acid Cycle and Sugar Metabolism in Rice Seedlings in Absence and Presence of Exogenous Calcium

The aim of the current study was to investigate the regulation of tricarboxylic acid (TCA) cycle and sugar metabolism in the seedlings of the rice variety, Khitish, during fluoride stress, either in absence or presence of exogenous calcium compounds, viz., calcium hydroxide and calcium nitrate. The inhibitory effect of fluoride stress on energy production was reflected by lowered levels of pyruvic acid, citric acid and malic acid, substantial interference with the respiratory enzymes such as PDH, CS, IDH and SDH, and inhibiting the expression of the concerned genes. Seed priming with both calcium compounds elevated the organic acid levels, restored the activity of the above enzymes and expression of the corresponding genes. On the contrary, the enhanced fumarase and MDH activity and MDH gene expression, during fluoride stress, was lowered by calcium pre-treatment. The sucrose level, together with SPS and SS activity and expression of the corresponding genes were restored to higher levels, concomitant with lowered INV activity and gene expression, in presence of calcium compounds, suggesting lesser utilization of sucrose to combat fluoride stress. The efficacy of calcium compounds in conserving starch as the major food reserve, without provoking its catabolic breakdown, was established on the basis of enhanced starch content with lowered α-amylase and starch phosphorylase activity and corresponding gene expression. The present communication for the first time documented the detrimental impact of fluoride stress on TCA cycle metabolites and majority of the enzymes, and endogenous sucrose and starch accumulation, as well as highlighted the reversal of the negative effects with the exogenous application of calcium compounds.

Do carbohydrate metabolism and partitioning contribute to the higher salt tolerance of Hordeum marinum compared to Hordeum vulgare?

The aim of the present work was to check whether carbohydrate metabolism and partitioning contribute to the higher salt tolerance of the facultative halophyte Hordeum marinum compared to the glycophyte Hordeum vulgare. Seedlings with the same size from the two species were hydroponically grown at 0 (control), 150, and 300 mM NaCl for 3 weeks. H. marinum maintained higher relative growth rate, which was concomitant with a higher aptitude to maintain better shoot tissue hydration and membrane integrity under saline conditions compared to H. vulgare. Gas exchanges were reduced in the two species under saline conditions, but an increase in their water use efficiency was recorded. H. marinum exhibited an increase in leaf soluble sugar concentrations under saline conditions together with an enhancement in the transglucosidase DPE2 (EC 2.4.1.25) activity at 300 mM NaCl. However, H. vulgare showed a high increase in starch phosphorylase (EC 2.4.1.1) activity under saline conditions together with a decrease in leaf glucose and starch concentrations at 300 mM NaCl. In roots, both species accumulated glucose and fructose at 150 mM NaCl, but H. marinum exhibited a marked decrease in soluble sugar concentrations and an increase in starch concentration at 300 mM NaCl. Our data constitute an initiation to the involvement of carbohydrate metabolism and partitioning in salt responses of barley species and further work is necessary to elucidate how their flexibility confers higher tolerance to H. marinum compared to H. vulgare.

Maltose Processing and Not β-Amylase Activity Curtails Hydrolytic Starch Degradation in the CAM Orchid Phalaenopsis.

Crassulacean acid metabolism (CAM) is one of the three photosynthetic pathways in higher plants and is characterized by high water use efficiency. This mainly relies on major nocturnal CO2 fixation sustained by degradation of storage carbohydrate such as starch to provide phosphoenolpyruvate (PEP) and energy. In contrast to C3 plants where starch is mainly degraded by the hydrolytic route, different observations suggested the phosphorolytic route to be a major pathway for starch degradation in CAM plants. To elucidate the interplay and relevant contributions of the phosphorolytic and hydrolytic pathways for starch degradation in CAM, we assessed diel patterns for metabolites and enzymes implicated in both the hydrolytic route (β-amylase, DPE1, DPE2, maltase) and the phosphorolytic route (starch phosphorylase) of starch degradation in the CAM orchid Phalaenopsis “Edessa.” By comparing the catalytic enzyme activities and starch degradation rates, we showed that the phosphorolytic pathway is the major route to accommodate nocturnal starch degradation and that measured activities of starch phosphorylase perfectly matched calculated starch degradation rates in order to avoid premature exhaustion of starch reserves before dawn. The hydrolytic pathway seemed hampered in starch processing not by β-amylase but through insufficient catalytic capacity of both DPE2 and maltase. These considerations were further corroborated by measurements of enzyme activities in the CAM model plant Kalanchoë fedtschenkoi and strongly contradict with the situation in the C3 plant Arabidopsis. The data support the view that the phosphorolytic pathway might be the main route of starch degradation in CAM to provide substrate for PEP with additional hydrolytic starch breakdown to accommodate mainly sucrose synthesis.

Growth and metabolic activities of cowpea seedlings exposed to artificial pond wastewater-treated soil

PurposeThe increase in demand for fish has necessitated the establishment of fish pond. The discharge of spent pond water pollutes the adjoining surroundings. The aim of this investigation was to determine the suitability of artificial pond wastewater (APWW) as source of manure for crop cultivation.MethodCowpea seeds were planted in polybags containing soil treated with varied amount of artificial pond wastewater. Thereafter, growth and various metabolic properties of cowpea seedlings were determined using standard procedures.ResultsArtificial pond wastewater treatment of soil increased significantly (P < 0.05) the growth parameters, content of biomolecules and activities of alpha amylase, starch phosphorylase and peroxidase when compared to the control. Exposure of the seedlings to APWW did not alter most oxidative stress markers compared to the control. In addition, APWW in soil significantly (P < 0.05) increases the levels of vitamin C but had no alterations in the activities of succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and sulphite oxidase (SO) of the cowpea seedlings compared to those of the controls. The activities of aldehyde oxidase (AO) and xanthine oxidase (XO) significantly (P < 0.05) increased compared with the control.ConclusionThe major effects of APWW on plants were stimulation of growth parameters, increase in concentration of macromolecules as well as increase in activities of starch-metabolizing enzymes, and peroxidase activity with no adverse effect on antioxidant, respiratory and drug-metabolizing enzymes, thus, suggesting that artificial pond wastewater has positive effect on cowpea seedlings and can act as organic fertilizer for cowpea cultivation.

Modulation of photosynthetic parameters, sugar metabolism, polyamine and ion contents by silicon amendments in wheat (Triticum aestivum L.) seedlings exposed to arsenic.

The objective of the present investigation was to consider the effectiveness of exogenous silicate supplementation in reviving the arsenate imposed alterations on pigment content, Hill activity, photosynthetic parameters, sugar metabolism, polyamine, and ion contents in wheat (Triticum aestivum L. cv. PBW-343) seedlings. Experiments were conducted under different levels of arsenate (0, 25μM, 50μM, and 100μM) in combination with silicate (0, 5mM) in a hydroponic environment with modified Hoagland's solution for 21days to determine the ameliorative role of silicon (Si). Arsenate exposure led to a decline in chlorophyll content by 28% and Hill activity by 30% on an average along with photosynthetic parameters. Activity of starch phosphorylase increased causing a subsequent decrease in starch contents by 26%. Degradation of starch enhanced sugar contents by 61% in the test cultivar. Dose-dependant increments in the activities of carbohydrate metabolizing enzymes viz., sucrose synthase, sucrose phosphate synthase, and acid invertase were also noted. Putrescine content was significantly enhanced along with a consequent decline in spermidine and spermine contents. The macro- and micronutrient contents declined proportionally with arsenate imposition. Conversely, silicate amendments irrespective of all arsenate concentrations brought about considerable alterations in all parameters tested with respect to arsenate treatment alone. Marked improvement in pigment content and Hill activity also improved the gas exchange parameters. Soluble sugar contents decreased and starch contents were enhanced. Increase in polyamine contents improved the ionic balance in the test cultivar as well. This study highlights the potentiality of silicon in ameliorating the ecotoxicological risks associated with arsenic pollution and the probable ability of silicon to offer an approach in mitigating arsenate-induced stress leading to restoration of growth and metabolism in wheat seedlings.

Plastidial starch phosphorylase is highly associated withstarch accumulation process in developing squash (Cucurbita sp.) fruit.

We investigated changes in starch content and starch metabolic enzyme activities in developing and postharvest squash of distinct species, Cucurbita maxima and Cucurbita moschata, which accumulate high and low levels of starch, respectively. The total activity of starch phosphorylase in developing fruits significantly correlated (r = 0.99) to the amount of starch among Cucurbita species (C. maxima, C. moschata and C. pepo). Separable activity of a plastidial L-form phosphorylase in C. maxima fruit markedly increased corresponding with starch accumulation. We isolated two genes (CmPhoL1 and CmPhoH1) encoding an L-form and a cytosolic H-form phosphorylase from C. maxima fruit. The expression of CmPhoL1 in the fruit dramatically increased at the beginning of starch accumulation. Recombinant CmPhoL1 enzyme showed similar kinetic parameters in both glucan synthesis and phosphorolysis: this enzyme can catalyze the invertible reaction in vitro depending on the concentration of substrates. These results suggest that CmPhoL1 plays a role in the starch accumulation process during squash development, but the aid of other starch synthetic enzymes may be required for in vivo glucan synthesis reaction by CmPhoL1. An importance of plastidial starch phosphorylase in the starch accumulation in the fruit organ was indicated.

Effects of soil treatment with abattoir effluent on morphological and biochemical profiles of cowpea seedlings (&lt;i&gt;V.unguiculata&lt;/i&gt;) grown in gasoline polluted soil

The effects of abattoir wastewater treated soil on morphological and biochemical profiles of cowpea seedlings ( Vigna unguiculata ) grown in gasoline polluted soil was studied. Percentage germination, shoot length, root length and leaf area of cowpea seedlings grown in gasoline treated soil decreased significantly (P < 0.05) when compared to the control. Moreover, gasoline contaminated soil significantly (p<0.05) decreased levels of total sugar, total protein, total amino acids, total chlorophyll, chlorophyll a and b, and β-carotene contents of the leaves as well as significant (p<0.05) decrease in the activities of α-amylase and starch phosphorylase in the cotyledon compared to seedlings in the control. Cowpea seedlings grown in gasoline contaminated soil also showed alterations in antioxidant enzymes when compared to the control. However, treatment of gasoline contaminated soils with abattoir wastewater (AWW) substantially improved the growth parameters, chlorophyll and β-carotene contents of the cowpea seedlings. The activities of α-amylase and starch phosphorylase, in addition to the antioxidant enzymes were considerably enhanced by AWW treatment. These findings showed in clear terms that abattoir wastewater may be a suitable manorial material for remediating gasoline contaminated soils as well as mitigate toxic effects of gasoline on exposed plants. Keywords : Abattoir, Cowpea, Amylase, Phosphorylase, Antioxidants

Regulation of Growth and Carbohydrate Metabolism in Rice (Oryza Sativa L.) seedlings by Selenium and Sulphate

Selenium is an essential and also toxic trace element for organisms including plants. We studied the role of selenium (Na2SeO4) on growth and carbohydrate metabolism and its interaction with sulphate (Na2SO4) in rice (Oryza sativa L. cv. Satabdi) seedlings. Low concentration of selenium (2µM) showed stimulatory effect on growth as opposed to its higher concentration (50µM). Selenium was found to accumulate in a dose dependent linear pattern in the plant tissues. Exposure to selenate increased both reducing and non reducing sugar contents in the rice seedlings accompanied with an increase in the activities of sugar metabolizing enzymes like Sucrose Synthase (EC 2.4.1.13) and Sucrose Phosphate Synthase (EC 2.4.1.14). An increase in Starch Phosphorylase (EC 2.4.1.1) activity corresponded with the reduction in starch contents in the rice seedlings. Since Selenium is chemically analogous to sulphate, simultaneous application of sodium sulphate (10mM) and selenate (Na2SeO4) was found to ameliorate partially or totally all the tested parameters under selenate treatment alone resulting in alteration of growth and development of the test seedlings.

THE EFFECT OF ABATTOIR WASTE WATER ON THE METABOLISM OF COWPEA SEEDLINGS GROWN IN DIESEL CONTAMINATED SOIL

The effects of abattoir waste water on the macromolecules (total sugar, protein, amino acid, beta carotene and chlorophyll) of cowpea grown on diesel contaminated soil at various concentrations (0.1%, 0.25%, 0.5%, 1.0% and 2.0%) as well as the activities of alpha amylase, starch phosphorylase and oxidative stress markers (lipid peroxidation, superoxide dismutase activity, catalase activity and xanthine oxidase) in cowpea seedlings were investigated. The results showed that diesel imposed environmental stress in cowpea seedlings. This is indicated by the decrease in total sugar, total protein and amino acids and a decrease in the chlorophyll contents of the leaves of 12-day-old seedlings. The activities of alpha amylase and starch phosphorylase in the cotyledon of 4-day-old seedlings were inhibited by the various diesel concentrations in the control treatment, but abattoir waste water ameliorated the effect of diesel toxicity. Also, the results indicated that the petroleum product caused a significant increase in lipid peroxidation and a significant decrease in the activities of the antioxidant enzymes: Superoxide dismutase, catalase and xanthine oxidase activities in the control; but abattoir waste water ameliorated the effect of these stresses posed by the diesel contaminated soil. The following observations, therefore, suggest that abattoir wastewater is capable of remediating the undesirable effects of diesel contamination on cowpea seedlings.

Leaf carbohydrates influence transcriptional and post-transcriptional regulation of nocturnal carboxylation and starch degradation in the facultative CAM plant, Mesembryanthemum crystallinum

Nocturnal degradation of transitory starch is a limiting factor for the optimal function of crassulacean acid metabolism and must be coordinated with phosphoenolypyruvate carboxylase (PEPC)-mediated CO2 uptake to optimise carbon gain over the diel cycle. The aim of this study was to test the hypothesis that nocturnal carboxylation is coordinated with starch degradation in CAM via a mechanism whereby the products of these pathways regulate diel transcript abundance and enzyme activities for both processes. To test this hypothesis, a starch and CAM-deficient mutant of Mesembryanthemum crystallinum was compared with wild type plants under well-watered and saline (CAM-inducing) conditions. Exposure to salinity increased the transcript abundance of genes required for nocturnal carboxylation, starch and sucrose degradation in both wild type and mutant, but the transcript abundance of several of these genes was not sustained over the dark period in the low-carbohydrate, CAM-deficient mutant. The diel pattern of transcript abundance for PEPC mirrored that of PEPC protein, as did the transcripts, protein, and activity of chloroplastic starch phosphorylase in both wild type and mutant, suggesting robust diel coordination of these metabolic processes. Activities of several amylase isoforms were low or lacking in the mutant, whilst the activity of a cytosolic isoform of starch phosphorylase was significantly elevated, indicating contrasting modes of metabolic regulation for the hydrolytic and phosphorylytic routes of starch degradation. Externally supplied sucrose resulted in an increase in nocturnal transcript abundance of genes required for nocturnal carboxylation and starch degradation. These results demonstrate that carbohydrates impact on transcriptional and post-transcriptional regulation of nocturnal carboxylation and starch degradation in CAM.

Role of starch hydrolytic enzymes and phosphatases in relation to under water seedling establishment in rice

The activities of starch hydrolyzing enzymes and phosphatases were studied in seedlings of three Indica rice (Oryza sativa L.) cultivars, namely Panikekoa & T 1471 that showed good capacity for seedling establishment under submergence (tolerant) and IR 42 which had poor under water seedling establishment capacity (susceptible). Under submergence the total amylolytic activities were significantly higher in susceptible cultivars compared to the tolerant cultivars. Likely, the activities of α-amylase, debranching enzymes and α-glucosidase were also higher in susceptible cultivar IR 42. The activities of starch phosphorylase were comparatively higher in tolerant cultivars than susceptible cultivars. Susceptible cultivars maintained higher activities of both acid and alkaline phosphatase as well as phytase activities. Tolerant cultivars with higher seed biomass and low activity of hydrolytic enzymes might sustain the supply of food materials for longer period and hence, survived and established themselves under water.

UV-C treatment affects browning and starch metabolism of minimally processed lily bulb

The effects of 4.5kJm−2 UV-C radiation on the quality of minimally processed lily bulb, such as browning, growth of microorganism, total phenolic content, starch, total soluble sugar, reducing sugar content, the activities of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), α-amylase, β-amylase, starch phosphorylase and the antioxidant activity were studied. Results showed that UV-C treatment inhibited browning index and microbial growth by approximately 37% and 32% respectively. Compared with the control, PPO and POD activities of UV-C treated minimally processed lily bulb were reduced by about 26% and 18% respectively, while total phenolic content was increased by 13%. UV-C treatment down-regulated the activities of α-amylase, β-amylase and starch phosphorylase, which resulted in higher content of starch, total soluble sugar content and lower content of reducing sugar. The antioxidant activity and PAL activity were higher than the control during storage. These results indicated UV-C treatment could effectively maintain quality of minimally processed lily bulb stored at 4±1°C. Therefore, UV-C radiation might be an effective and safe alternative technology for minimally processed lily bulb.

Amelioration of salinity stress by NaCl pretreatment with reference to sugar metabolism in legumes Cajanas cajan L. and Vigna mungo L.

The effect of salinity stress and its amelioration by pretreatment with low concentration of NaCl (50mM) on growth and sugar metabolism in arhar (cv. T120) and maskalai (cv. WBU109) seedlings were studied. Salinity was found to be more toxic for root growth than shoot growth. Fresh weight and dry weight of the seedlings gradually decreased with increasing concentrations of NaCl treatment. It was demonstrated that direct germination on NaCl solution increased both reducing sugar and non-reducing sugar contents while decreased the starch contents which were to some extent decreased by pretreatment of seeds with 50mM NaCl prior to germination in salt solutions. Salinity stress also affected the activites of different sugar metabolizing enzymes. The increase in the activities of starch phosphorylase, sucrose phosphate synthase, sucrose synthase and decrease in the activities of acid invertase were observed in directly salt treated test seedlings that were altered by pretreatment with sublethal concentration of NaCl in both the cultivars arhar (cv. T120) and maskalai (cv. WBU109) seeds. Thus the application of pretreatment by sublethal concentration of NaCl in both arhar (cv. T120) and maskalai (cv. WBU109) seeds exhibited significant alteration of all the partinent parameters tested under salinity stress and the effect of pretreatment in most of the parameters were more prominent in arhar (cv. T120) with compared to maskalai (cv. WBU109) seedlings.

Low oxygen storage modulates invertase activity to attenuate cold-induced sweetening and loss of process quality in potato (Solanum tuberosum L.)

Russet Burbank and Innovator are mid- to late-season frozen-processing cultivars with inherently different dormancy periods and susceptibilities to low temperature-induced sweetening (LTS). In contrast to Russet Burbank, which is highly prone to accumulation of reducing sugars (Glc+Fru) when stored below 8–9°C, Innovator tubers exhibit moderate resistance to LTS and retain process quality longer at lower temperatures (4–6°C). However, Innovator’s LTS resistance is not robust and often varies across production regions. Here we show that low O2 storage modulates LTS to reveal metabolic differences intrinsic to these cultivars. Changes in tuber respiration, process quality, reducing sugars, sucrose, starch phosphorylase and invertase activities were compared at 4 and 8°C in 2.5 and 21kPa O2 over a 212-d storage period. Tuber respiration declined rapidly as O2 level decreased from 21 to 2.5kPa during acclimation at 8°C. Respiration rates then fell further as the temperature was lowered from 8 to 4°C, but this response was greatly muted for tubers at 2.5 versus 21kPa O2. Tubers at 21kPa O2 completed their cold-induced respiratory acclimation response (RAR) within 7 d compared with 13 d at 2.5kPa O2, and the RAR was much greater for tubers at 2.5kPa O2. While reducing sugars increased most rapidly in tubers over the first 30 d at 4°C, Innovator tubers had lower invertase activity and sweetened less than Russet Burbank tubers, characterizing its LTS-resistant phenotype. Low O2 greatly attenuated these initial LTS responses for both cultivars; however, the effect was only temporary in Innovator. LTS resumed in Innovator tubers from 93 to 212 d with reducing sugar levels increasing to equal that of Russet Burbank tubers stored at 4°C and 21kPa O2. Activities of α-1,4 glucan phosphorylase (SP) were higher in Russet Burbank than Innovator and increased progressively over the storage period regardless of temperature and oxygen concentration. Innovator tubers stored at 2.5kPa O2 had higher SP activities from 30 to 153 d at 4 and 8°C compared with tubers stored at 21kPa O2, which correlated well with increased sucrose buildup and earlier sprouting. The low O2-mediated inhibition of LTS was largely a consequence of reduced invertase activities.