Invertase Enzyme Activity Research Articles

Effects of different coated slow-release calcium peroxide on microbial characteristics of gleyed paddy soil

To explore the effects of different coated slow-release calcium peroxide on soil microbial characteristics in gleyed paddy field, we set seven treatments by simulation test in a greenhouse, including CK (none calcium peroxide), calcium peroxide powder, calcium peroxide particle and other four coated slow-release calcium peroxide treatments. Samples were collected in same tillering stage of early season rice. The results showed that all the applications of calcium peroxide could improve the concentrations of active soil organic carbon, soil available nutrients, soil microbial biomass, culturable microorganism population, as well as soil enzyme activity. The coated slow-release calcium peroxide had stronger effects than calcium peroxide particles and calcium peroxide powder. The calcium peroxide coated by ethyl cellulose was the most effective, which enhanced soil active organic carbon, soil microbial biomass carbon, nitrogen, phosphorus by 19.4%, 11.4%, 121.5% and 127.2%, soil alkaline hydrolysis nitrogen and available phosphorus by 4.0% and 45.5%, soil culturable bacteria and culturable microorganism population by 137.3% and 113.7%, fungi and actinomyces number were increased by 33.6% and 44.7%. The enzyme activities of invertase, phosphatase, urease as well as catalase were increased by 92.4%, 91.8%, 112.5% and 17.1%, respectively. The results could provide reference for improving gleyed paddy field with coated calcium peroxide.

Effects of Ultraviolet-C Pretreatment on Sugar Metabolism in Yellow Peaches during Shelf Life

To investigate the influence of ultraviolet-C (UVC) radiation pretreatment on the sugar metabolism of yellow peaches (cv. Beinong2 × 60–24–7) during storage, the concentrations of soluble sugar (sucrose, fructose, glucose, and sorbitol), and related gene expression were determined. During UVC pretreatment, peaches were subjected to a dose of 4 kJ·m−2 when they were placed at 15 cm under a UVC lamp tube for 10 minutes at 25 °C. Then, they remained at 15 ± 2 °C for 10 days. Peaches stored at 15 ± 2 °C immediately after picking were used as the control group (CG). UVC pretreatment reduced the ethylene production rate and resulted in a significant increase in the accumulation of sucrose during days 2 to 8 of the storage period, followed by a lower concentration of fructose and glucose and the upregulation of PpaSS1. The expression levels of PpaSPS2, PpaSS1, and PpaST3 were significantly correlated with fructose concentration, and those of PpaSPS2 and PpaST2 were significantly correlated with glucose concentration. The enzyme activity of sucrose phosphate synthase (SPS) was positively correlated with PpaSPS2, PpaSS2, and PpaST2. The enzyme activities of sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) were positively correlated with PpaSS1, PpaST1, and Ppani, respectively. Expressions of PpSPS1 and PpSPS2 in UVC-pretreated peaches were upregulated on storage days 8 and 2, and there was a UVC-induced peak in SPS activity on storage days 4 and 8, which resulted in the rapid accumulation of sucrose. UVC pretreatment could upregulate the gene expression of PpaSS1 on day 2, which could improve and maintain the quality of peaches for consumption.

Heavy metal concentration, potential ecological risk assessment and enzyme activity in soils affected by a lead-zinc tailing spill in Guangxi, China

In 1976, a tailing dam collapse accident at the Xingping Lead–Zinc Mine in Guangxi Province, China, led to the spillage of mining wastewater and sludge into downstream agricultural lands in Side Village. Heavy metal concentrations, soil pollution and soil enzyme activity were analysed to understand the pollution characteristics of the agricultural lands along the Side stream by this accident. The tailing soil (TS), natural forest soil without spill contamination (NFS) and four representative agricultural soils were selected. The four agricultural soil sites located at the entrance of the stream to the agricultural soil (EnS), the upstream region (US), the middle stream (MS) and at the exit of the stream (ExS) from the village, respectively. The results showed that the soil pH values and heavy metal concentrations were in the order of tailing soil TS > ExS > MS > US > EnS > NFS. The concentration of Pb ranked highest among the analysed elements followed by Zn, Cd, Mn and Cu. The concentrations of Pb, Zn, Cd Mn and Cu 10530.41, 1708.58, 8.32, 885.61 and 104.51 mg kg−1, respectively. Soil pollution assessments by single pollution index, synthesis pollution index and individual/comprehensive potential ecological risk analysis explicated all the soils reached the heavily polluted level and presented extremely high ecological risk grades. Pb, Zn and Cd were the dominant pollutants. The soil enzyme activities of invertase, protease and urease exhibited the opposite distribution pattern as those of the heavy metal concentrations, while the inversely results were observed for the activity of catalase.

Effects of foliar application of magnesium sulfate on photosynthetic characteristics, dry matter accumulation and its translocation, and carbohydrate metabolism in grain during wheat grain filling

Our previous studies showed that foliar applied magnesium sulfate during the booting stage can effectively increase wheat grain weight. To explore the effects of foliar application of magnesium sulfate during wheat grain filling on photosynthetic characteristics of flag leaf and grain filling, an experiment was conducted using winter wheat cultivars to assess the effects of foliar application of magnesium sulphate on photosynthetic characteristics of flag leaves, carbohydrate metabolism in grains, and dry matter translocation in different organs in the Zhoumai 27 and Aikang 58 cultivars at different growth stages. The results indicated throughout the different stages of growth, the flag leaves exhibited a high net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration (Tr), and a decrease in the concentration of intercellular CO2 (Ci). Therefore, foliar application of magnesium sulfate during the booting stage maintained high canopy photosynthesis after anthesis. Simultaneously, exogenous supply of magnesium sulphate enhanced the sucrose synthase (SUS) and invertase (INV) enzyme activities in detached wheat grains, meanwhile reinforced the activities of most starch synthesis enzyme such as ADP-glucose pyrophosphorylase and soluble starch synthase, and consequently lead to a higher content of grain starch. Furthermore, field experiment also confirmed foliar application of magnesium sulphate can improve superior dry matter accumulation and translocation in grain.

Identification and impact of stable prognostic biochemical markers for cold-induced sweetening resistance on selection efficiency in potato (Solanum tuberosum L.) breeding programs

Biochemical markers for cold-induced sweetening (CIS) resistance were tested for their stability over years and their use in selection of parents for crossing to achieve high selection efficiency in potato breeding programs.Two regulatory enzymes directly associated with reducing sugar (RS) accumulation during potato tubers cold storage were tested as a predictor for CIS resistance. These enzymes were studied in 33 potato clones from various breeding programs over four years. Clones with the presence of A-II isozymes of UDP-glucose pyrophosphorylase (UGPase) and low activity of vacuolar acid invertase (VAcInv) enzyme had increased resistance to cold-induced sweetening (CIS). Depending on the levels of these enzymes, clones were divided into class A, class B and class C. Clones categorized as class A had average RS of 0.73 mg per g FW after six months at 5.5°C storage. Class B and C had average RS of 1.15 and 3.80 mg per g FW respectively. The enzyme activity was closely associated with RS accumulation over long-term cold storage.The biochemical markers were found to be stable over the years. Repeated-measure analysis showed 75% chance of maintaining class from one year to the next and a 25% chance of switching, No clone switched between class A and class C, even across all four years. Application of these biochemical markers can identify clones with CIS resistance early in the selection process. Biochemical markers were used to select parents for crossing and six families were established. Results showed that with both parents from class A, 95% of their offspring had desirable glucose levels and chip color, which dropped to 52% when one parent was from class A and other from class B. These results suggest that two regulatory enzymes, i.e., UGPase and VAcInv, can be used as stable prognostic biochemical markers for CIS resistance for precise parent selection resulting in progenies with significantly higher percentage of clones with acceptable processing quality.

The sensitivity of soil microbial respiration declined due to crop straw addition but did not depend on the type of crop straw.

An incubation experiment was conducted to investigate whether the type of crop straw added to soil influenced the temperature sensitivity of soil microbial respiration. The soil for incubation was collected from a winter wheat-soybean rotation cropland. Five temperature levels (5, 10, 15, 20, and 25 °C), five crop straw types (soybean, peanut, rice, winter wheat, and maize), and a control (CK, no crop straw addition) were established. Soil microbial respiration rates were measured on days 1, 2, 3, 5, 7, 10, 14, 20, and 27 after crop straw addition using an infrared CO2 analyser. Soil enzyme activities of invertase, urea, and catalase and the dissolved organic carbon (DOC) content were measured after incubation. Estimated Q10 (temperature sensitivity of soil microbial respiration) ranged from 1.472 ± 0.045 to 1.970 ± 0.020 and showed no significant (P > 0.05) difference between straw addition treatments, but there was significantly (P < 0.001) higher temperature sensitivity (1.970 ± 0.020) for CK. A significant (P = 0.002) relationship was found between the Q10 of cumulative soil microbial respiration and basal soil microbial respiration (soil microbial respiration at 0 °C). Moreover, a marginally significant (P < 0.1) relationship was found between the Q10 at different incubation stages and basal soil microbial respiration. A quadratic function was used to explain the relationship between estimated basal microbial respiration and the lignin content. Soil microbial respiration was positively correlated with the activities of invertase, urease, and catalase and the dissolved organic carbon (DOC) content in all treatments. This study indicated that crop straw addition significantly (P < 0.001) reduced the Q10 of soil microbial respiration and that the types of crop straw added to soil did not significantly (P > 0.05) change the Q10 value.

Устойчивость микробиологической активности дерново-подзолистой почвы в условиях применения диатомита и цеолита

Устойчивость микробиологической активности дерново-подзолистой почвы в условиях применения диатомита и цеолита

Amelioration of cadmium stress in Withania somnifera by ROS management: active participation of primary and secondary metabolism

Cadmium (Cd) is considered as a non-essential heavy metal with substantial toxicity on environment. Withania somnifera, a reputed therapeutic herb exhibits vast pharmacological activities due to the presence of steroidal lactones-withanolides. The present study deals with reactive oxygen species (ROS) management through primary and secondary metabolism as adaptive response, on exogenous Cd exposure of W. somnifera. Increased invertase enzyme activity resulted in higher reducing sugars in plant under Cd stress to provide additional carbon source and NADH or NADPH. Higher activities of proline metabolic pathway enzymes such as ornithine aminotransferase (OAT) and pyrroline-5-corboxylate synthase (P5CS) resulted in elevated proline accumulation. The considerable participation of phenylpropanoid metabolism also found dominantly upregulated. Increased enzyme activities of phenylalanine ammonia lyase (PAL), shikimate dehydrogenase (SKDH), glucose-6-phosphate dehydrogenase (G6PDH), and cinnamyl alcohol dehydrogenase (CADH) resulted in phenolics and flavonoids accumulation under higher Cd stress. Upregulation of glutathione-S-transferase (GST) activity conferred its role in Cd chelation. In addition, glutamate oxaloacetate transaminase (GOT), amyl esterase (EST) and diaphorase (DIA) established their participation in Cd tolerance mechanism. Thus, present study elucidated major role of proline and phenylpropanoid metabolism in providing the osmoticum and antioxidants to the plants under Cd stress. The information may be helpful in developing stress resistant plants by targeting these pathways using conventional and molecular approaches.

SOIL MICROBIAL POPULATION AND SOIL ENZYME ACTIVITY ON PT BUKIT ASAM VARIOUS RECLAIMED LAND SITES IN SOUTH SUMATRA

Open mining activities result in decreased microbial biomass and negatively impacts soil fertility. Soil microbes play a role in the decomposition of soil organic matter and in nutrient cycles through the process of mineralization by the enzymes they produce. The purpose of this study was to analyse soil fertility levels in PT Bukit Asam’s various reclaimed land sites at Muara Enim Regency, South Sumatra, Indonesia, as determined by these areas’ microbial populations and soil enzyme activity. The research was conducted by using the explorative method in PT Bukit Asam’s various reclaimed land. Soil sample from 7 different reclamation age area were analysed. Our results showed that soil conditions and soil enzyme activity vary by reclamation age. At KTU, a 12-year-old reclaimed land site, urease enzyme activity had a value of 68.83 mg NH4+.g-1dm.h-1 with a microbial population of 82.64 x 104 CFU.g-1soil. The highest phosphatase enzyme activity value of 95.66 mg pNP.g-1 dm.h-1 was found on the 9-year-old SP702 reclaimed land site, with a soil pH of 5.23. Cellulase enzyme activity on the 21-year-old Udongan reclaimed site had a value of 21.51 mg GE.g-1dm.h-1 with a cellulolytic microbial population of 1.9 x 104 CFU.g-1soil, higher than on other reclamation sites. Invertase enzyme activity on the 15-year-old Tupak reclaimed land site had a value of 24.37 mg GE.g-1dm.h-1. Soil enzyme activity can be an indicator of soil quality and soil microbial activity as it relates to all forms of biochemical transformations occurring in the soil and is highly sensitive to environmental changes.

Characterization of Fructan Metabolism During Jerusalem Artichoke (Helianthus tuberosus L.) Germination.

The inulin-type fructans in Jerusalem artichoke (Helianthus tuberosus L.) tubers exhibit different degrees of polymerization and are critical for germination. We aimed to characterize the sugar metabolism dynamics in the tubers without bud eyes or shoots (T) and BE/S of indoor- and field-grown Jerusalem artichokes during germination. Ht1-FEH II and Ht1-FEH III (1-fructan exohydrolases II and III, inulin-degrading enzymes) expression increased 5 days after planting indoors, whereas Ht1-FEH II expression increased 72 days after planting in the field in T and BE/S. Ht1-SST (sucrose:sucrose 1-fructosyl transferase, inulin synthesis initiator), and Ht1-FFT (fructan:fructan 1-fructosyl transferase, inulin elongator) expression generally decreased in indoor-grown T. The enzyme activities of 1-FEH and 1-FFT were unchanged during germination in both indoor- and field-grown T and BE/S, whereas 1-SST activity decreased in indoor-grown T, while 1-FEH and 1-FFT activities increased as a function of germination time in BE/S of both indoor- and field-grown tubers. The total soluble sugar content gradually decreased in T after germination indoors or in the field, while at the end of germination, the sucrose and fructan contents decreased, and fructose content increased in the field. The enzyme activities of soluble vacuolar (VI) or neutral invertase (NI) did not change significantly, except at the late germination stage. Sucrose synthase (SS) and sucrose-phosphate synthase (SPS) activities were not significantly changed in T and BE/S in indoor-grown artichokes, while SS activity gradually increased, and SPS activity gradually decreased in field-grown artichokes, alongside sucrose degradation. Compared to T, BE/S generally had higher enzyme activities of 1-FEH and 1-FFT, promoting inulin hydrolysis. This work shows that the process of tuber germination is similar indoors and in the field, and germination studies can therefore be conducted in either environment.

Determining Invertase Enzyme Activity Using Isothermal Titration Calorimetry

Invertase catalyzes the hydrolysis of sucrose producing fructose and glucose. Invertase is widely used in the food industry because it possesses a lower crystallinity than sucrose at higher concentrations and is sweeter than sucrose. Invertase enzyme activity is typically measured using an endpoint coupled‐secondary reaction. The glucose produced by the invertase‐catalyzed reaction reacts with 4‐hydroxybenzoic acid hydrazide to produce yellow anions that can then be measured spectrophotometrically. Contrary to the standard method for measuring invertase activity, single injection isothermal titration calorimetry (ITC) directly measures heat generated by invertase continuously. ITC provides rapid and efficient measurement for enzyme activity. However, recent studies have shown that the single injection ITC measurements cannot separate km and kcat because the enzyme does not reach saturation. We recently demonstrated that single injection ITC can be used to measure the stability of invertase activity. Here we further characterize the relationship between the peak invertase activity and the peak heat‐rate. Additionally, previous ITC measurements of invertase activity have demonstrated that there is a delay in peak invertase activity. We elucidate the dependence of this delay in activity on the sucrose concentration. Single injection ITC is uniquely positioned to provide insight into the mechanistic action of invertase that cannot be determined using coupled reactions.Support or Funding InformationBuild DairyBYU MEG GrantThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Increasing tree diversity enhances microbial and enzyme activities in temperate Iranian forests

Our findings show the differential impacts of tree types (hornbeam–ironwood natural forest and plantations of ash, maple, cypress and pine) on soil physical–chemical characteristics and how dominant tree species regulate the size and activity of soil microbial and enzymes. Soil microbial and enzyme activities have an important influence on nutrient cycling. The variation in soil carbon (C) and nitrogen (N) microbial indices as well as enzyme activities were determined under hornbeam–ironwood natural forest and 25-years old plantations of ash, maple, cypress and pine in northern Iran. Four soil profiles were dug along the four parallel transects in the central part of each forest stand, resulting in 16 soil samples for each stand at a depth of 0–15 cm. The results showed significant differences in most of studied soil physico-chemical properties among different land covers. Soil microbial basal respiration (MR) and substrate induced respiration (SIR) were found to be significantly higher under natural forest than in the plantation stands. Microbial biomass C (MBC) did not differ for the forest stands, whereas natural forest had significantly higher qCO2 (MR: MBC), microbial entropy (MBC: Corg) and C availability index (MR: SIR) values. The establishment of plantations reduced the values of soil microbial biomass N, mineral nitrogen (NH4–N and NO3–N) and N mineralization with the least under coniferous stands of cypress and pine, while greater amounts were observed under natural forest. With replacement in the type of tree species from natural forest to plantations, acid phosphatase, arylsulphatase and invertase enzyme activities decreased significantly in the topsoil, whereas like natural forest, ash plantation improved urease enzyme. This research recommends conservation of natural forests for increase of soil quality and plantation of suitable native broad-leaved species for rehabilitation of degraded natural forests.

Physiological and Biochemical Indicators of Growth Promoting Effect of Caliterpenone on Mentha arvensis

Mentha arvensis is an herbaceous, edible plant with strong aromatic and medicinal property. An experiment was conducted to investigate the physiological and biochemical changes associated with possible growth promoting effect of caliterpenone on Mentha arvensis. After 45 days of 0.01 mM caliterpenone spray treatment fresh aerial leaves were used for assessment of various parameters. Significant increase was seen in chlorophyll content (P ≤ 0.05), total sugar content (P ≤ 0.05), soluble and bound protein content, moisture content (P ≤ 0.05), specific activity of invertase enzyme along with phenotypic growth features (P ≤ 0.01) after caliterpenone treatment. In light of the present findings study concludes that caliterpenone, a natural phyllocladane diterpenoid isolated from the leaves of Callicarpa macrophylla is a natural, efficient and economic plant growth promoter, which significantly promotes the plant growth without any additional chemical load on soil.

&lt;b&gt;Antifungal compounds extracted from rice bran fermentation applied to bakery product conservation

The objective of this study was to apply a natural extract derived from the biomass of fermented rice bran as conservative, aiming to increase the shelf life of pizza doughs. The substrate, rice bran, was placed in tray bioreactors and inoculated with Rhizopus oryzae , whose initial concentration was 4 x 10 6 spores g -1 of bran fungus. The phenolic extracts, in average concentration of 2.47 mg g -1 , were applied on the pizzas doughts stored at room temperature. These pizza doughs treated increased by more than ten days life compared with those that were applied conventional conservatives. Thus, this extract phenolic derivative of rice bran showed to be promise as conservative, with results that indicate less fungal contamination as glucosamine, score of molds and yeasts, and invertase enzyme activity in 17.66 µg g -1 , 1.3 x 10 1 CFU g -1 and 0.04 mg min. proteins -1 , respectively.

Predictive Markers for Cold-Induced Sweetening Resistance in Cold Stored Potatoes (Solanum tuberosum L.)

An approach has been developed to screen a large number of potato clones for cold induced sweetening (CIS) resistance in breeding programs. Two key enzymes responsible for reducing sugar accumulation during cold storage were identified. Clones with the A-II isozymes of UDP-glucose pyrophosphorylase coupled with low activity of vacuolar acid invertase enzyme had increased resistance to CIS by forming less suc, which is subsequently hydrolyzed to the undesirable reducing sugars, glc and fru. Six named cultivars and 192 genetically diverse clones from various breeding programs in USA were analyzed over two years for the two key enzymes and sugar concentration in cold stored tubers. The predictability for CIS resistance during cold storage was 94% both years. Clones classified as class A accumulated low concentration of reducing sugar glc during cold storage. It is suggested that these two predictor enzymes can be used for screening parents and selections in potato breeding program.

High Pressure Pasteurization of Sugarcane Juice: Evaluation of Microbiological Shelf Life and Quality Evolution During Refrigerated Storage

In this study, sugarcane juice subjected to both high-pressure processing (HPP) and thermal pasteurization (TP) was used to compare the changes in microbial levels, physicochemical properties, antioxidant capacity, sugar content, activity of sucrose neutral invertase, and sensory analysis during 28 days of refrigerated storage. Results showed that HPP treatment of 600 MPa and TP significantly reduced aerobic bacteria, coliform, and yeast counts. At day 28 of storage, HPP-treated juice (600 MPa/6 min) displayed no significant differences when compared to the fresh juice in terms of physicochemical properties such as total titratable acidity, pH, and total soluble solids. Although significant differences were observed in HPP-treated juice in color, antioxidants, and antioxidant capacity, the extent of the differences was substantially lower than that in thermal-treated juice, indicating that HPP treatment can retain better quality of sugarcane juice. After HPP treatment of 600 MPa and TP, invertase enzyme activity on day 7 declined to 87.69 and 82.86 %, respectively, which could possibly prevent sucrose conversion to fructose and glucose during refrigerated storage. Sensory testing showed no significant difference between HPP-treated juice and fresh juice, while TP reduced the acceptance of sugarcane juice. Collectively, this study indicated that HPP pasteurization can successfully reduce the microbial load in sugarcane juice. Meanwhile, HPP treatment maintains stable quality and inhibits enzyme activity, and thus, it can effectively extend shelf-life during refrigerated storage. Thus, HPP has a great potential in the development of drinks with fresh sugarcane juice.

Impact of an organic formulation (panchakavya) on the bioleaching of copper and lead in contaminated mine soil

The study was aimed to evaluate the potential of organic formulation, panchakavya, for enhancing the biological leaching of Pb and Cu in contaminated mine soil. Response surface methodology based Box–Behnken design was used to optimize the variables such as incubation time, panchakavya concentration, and agitation rate. The maximum bioleaching (Pb=64% and Cu=49%) was observed after 54h of incubation with 10mL panchakavya at 120rpm. Statistics-based contour and three-dimensional plots were generated to understand the relationship between Pb and Cu bioleaching and variables. High-performance liquid chromatography analysis showed the presence of lactic (25.88mgg−1), citric (0.14mgg−1), succinic (0.14mgg−1), malic (0.66mgg−1), and acetic (0.44mgg−1) acids in panchakavya, which may have a vital role in the removal of metals from the contaminated soil. Soil fraction studies indicate a significant increase of Pb (45%) in the exchangeable fraction of panchakavya-treated soil. XRD studies confirmed the role of panchakavya induced calcite and other minerals in the precipitation of metal ions. A significant increase in the enzyme activities of phosphatase, dehydrogenase, urease, amylase, invertase, and cellulase were observed in the panchakavya-treated soil.

Effects of the Biocontrol Agent Aspergillus flavipes on the Soil Microflora and Soil Enzymes in the Rooting Zone of Pepper Plants Infected with Phytophthora capsici

AbstractThis study examined the effect of ASD strain (Aspergillus flavipes), isolated from continuous cropping soil for pepper and named by the sampling position, on soil microflora and soil enzymes in rooting zone soil of healthy and diseased (Phytophthora capsici) pepper plants. Results showed that the ASD strain could significantly reduce the number of bacteria and actinomycetes, with a significant increase in fungi in the rhizosphere soil of both healthy and diseased plants. With increasing colonization time of the ASD strain, the number of bacteria and actinomycetes decreased initially and then increased gradually, while the number of fungi was first increased significantly and later decreased slowly. The soil enzyme activities of urease, acid phosphatase, invertase and dehydrogenase were significantly increased by the ASD strain, while the activity of catalase was not significantly increased. As time from inoculation with the ASD strain increased, the activities of various enzymes were higher than controls. Maximum enzyme activities were found on the tenth day after ADS inoculation. The response of soil enzyme activities affected by the ASD strain was as follows: urease &gt; dehydrogenase &gt; invertase &gt; acid phosphatase &gt; catalase. These results suggest that the biocontrol of ASD strain could improve the micro ecology of rhizosphere soil.

24-Epibrassinolide regulates carbohydrate metabolism and increases polyamine content in cucumber exposed to Ca(NO3)2 stress

This study focuses on the impact of carbohydrate metabolism and endogenous polyamines levels in leaves of cucumber seedlings under salt stress by exogenous BRs. The effects of 24-epibrassinolide (EBL) on carbohydrate metabolism and endogenous content of polyamines were investigated in cucumber seedlings (Cucumis sativus L. cv. Jinyou No. 4) exposed to salinity stress [80 mM Ca(NO3)2]. Spraying of exogenous EBL partially enhanced the enzyme activities of sucrose phosphate synthase, sucrose synthase and acid invertase; thus, raising the level of sucrose, fructose and total soluble sugars. The amylase activity was also increased by EBL, companied by the rising of sucrose level. These results indicated that EBL improved the carbohydrate metabolism of cucumber under Ca(NO3)2 stress. Moreover, EBL raised the levels of soluble conjugated and insoluble bound polyamines while lowered the free polyamines content, particularly putrescine. Our experiment demonstrated that exogenous EBL elevated stability of cellular membrane and positively improve the carbohydrate metabolism in cucumber growing under Ca(NO3)2 stress.

Cloning and characterization of acid invertase genes in the roots of the metallophyte Kummerowia stipulacea (Maxim.) Makino from two populations: Differential expression under copper stress

The roots of metallophytes serve as the key interface between plants and heavy metal-contaminated underground environments. It is known that the roots of metallicolous plants show a higher activity of acid invertase enzymes than those of non-metallicolous plants when under copper stress. To test whether the higher activity of acid invertases is the result of increased expression of acid invertase genes or variations in the amino acid sequences between the two population types, we isolated full cDNAs for acid invertases from two populations of Kummerowia stipulacea (from metalliferous and non-metalliferous soils), determined their nucleotide sequences, expressed them in Pichia pastoris, and conducted real-time PCR to determine differences in transcript levels during Cu stress. Heterologous expression of acid invertase cDNAs in P. pastoris indicated that variations in the amino acid sequences of acid invertases between the two populations played no significant role in determining enzyme characteristics. Seedlings of K. stipulacea were exposed to 0.3µM Cu2+ (control) and 10µM Cu2+ for 7 days under hydroponics׳ conditions. The transcript levels of acid invertases in metallicolous plants were significantly higher than in non-metallicolous plants when under copper stress. The results suggest that the expression of acid invertase genes in metallicolous plants of K. stipulacea differed from those in non-metallicolous plants under such conditions. In addition, the sugars may play an important role in regulating the transcript level of acid invertase genes and acid invertase genes may also be involved in root/shoot biomass allocation.