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Sample records for leaf phosphoenolpyruvate carboxylase-kinase

  1. Nitric oxide regulation of leaf phosphoenolpyruvate carboxylase-kinase activity: implication in sorghum responses to salinity.

    PubMed

    Monreal, José A; Arias-Baldrich, Cirenia; Tossi, Vanesa; Feria, Ana B; Rubio-Casal, Alfredo; García-Mata, Carlos; Lamattina, Lorenzo; García-Mauriño, Sofía

    2013-11-01

    Nitric oxide (NO) is a signaling molecule that mediates many plant responses to biotic and abiotic stresses, including salt stress. Interestingly, salinity increases NO production selectively in mesophyll cells of sorghum leaves, where photosynthetic C₄ phosphoenolpyruvate carboxylase (C₄ PEPCase) is located. PEPCase is regulated by a phosphoenolpyruvate carboxylase-kinase (PEPCase-k), which levels are greatly enhanced by salinity in sorghum. This work investigated whether NO is involved in this effect. NO donors (SNP, SNAP), the inhibitor of NO synthesis NNA, and the NO scavenger cPTIO were used for long- and short-term treatments. Long-term treatments had multifaceted consequences on both PPCK gene expression and PEPCase-k activity, and they also decreased photosynthetic gas-exchange parameters and plant growth. Nonetheless, it could be observed that SNP increased PEPCase-k activity, resembling salinity effect. Short-term treatments with NO donors, which did not change photosynthetic gas-exchange parameters and PPCK gene expression, increased PEPCase-k activity both in illuminated leaves and in leaves kept at dark. At least in part, these effects were independent on protein synthesis. PEPCase-k activity was not decreased by short-term treatment with cycloheximide in NaCl-treated plants; on the contrary, it was decreased by cPTIO. In summary, NO donors mimicked salt effect on PEPCase-k activity, and scavenging of NO abolished it. Collectively, these results indicate that NO is involved in the complex control of PEPCase-k activity, and it may mediate some of the plant responses to salinity.

  2. A functional calvin cycle is not indispensable for the light activation of C4 phosphoenolpyruvate carboxylase kinase and its target enzyme in the maize mutant bundle sheath defective2-mutable1

    PubMed

    Smith; Langdale; Chollet

    1998-09-01

    We used a pale-green maize (Zea mays L.) mutant that fails to accumulate ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) to test the working hypothesis that the regulatory phosphorylation of C4 phosphoenolpyruvate carboxylase (PEPC) by its Ca2+-insensitive protein-serine/threonine kinase (PEPC kinase) in the C4 mesophyll cytosol depends on cross-talk with a functional Calvin cycle in the bundle sheath. Wild-type (W22) and bundle sheath defective2-mutable1 (bsd2-m1) seeds were grown in a controlled environment chamber at 100 to 130 &mgr;mol m-2 s-1 photosynthetic photon flux density, and leaf tissue was harvested 11 d after sowing, following exposure to various light intensities. Immunoblot analysis showed no major difference in the amount of polypeptide present for several mesophyll- and bundle-sheath-specific photosynthetic enzymes apart from Rubisco, which was either completely absent or very much reduced in the mutant. Similarly, leaf net CO2-exchange analysis and in vitro radiometric Rubisco assays showed that no appreciable carbon fixation was occurring in the mutant. In contrast, the sensitivity of PEPC to malate inhibition in bsd2-m1 leaves decreased significantly with an increase in light intensity, and there was a concomitant increase in PEPC kinase activity, similar to that seen in wild-type leaf tissue. Thus, although bsd2-m1 mutant plants lack an operative Calvin cycle, light activation of PEPC kinase and its target enzyme are not grossly perturbed.

  3. Light Modulation of Maize Leaf Phosphoenolpyruvate Carboxylase 1

    PubMed Central

    Huber, Steven C.; Sugiyama, Tatsuo; Akazawa, Takashi

    1986-01-01

    Phosphoenolpyruvate carboxylase (PEPC) was extracted from maize (Zea mays L. cv Golden Cross Bantam T51) leaves harvested in the dark or light and was partially purified by (NH4)2SO4 fractionation and gel filtration to yield preparations that were 80% homogeneous. Malate sensitivity, PEPC activity, and PEPC protein (measured immunochemically) were monitored during purification. As reported previously, PEPC from dark leaves was more sensitive to malate inhibition compared to enzyme extracted from light leaves. Extraction and purification in the presence of malate stabilized the characteristics of the two forms. During gel filtration on Sephacryl S-300, all of the PEPC activity and PEPC protein emerged in a single high molecular weight peak, indicating that no inactive dissociated forms (dimers, monomers) were present. However, there was a slight difference between the light and dark enzymes in elution volume during gel filtration. In addition, specific activity (units at pH 7/milligram PEPC protein) decreased through the peak for both enzyme samples; because the dark enzyme emerged at a slightly higher elution volume, it contained enzyme with a relatively lower specific activity. The variation in specific activity of the dark enzyme corresponded with changes in malate sensitivity. Immunoblotting of samples with different specific activity and malate sensitivity, obtained from gel filtration, revealed only a single polypeptide with a relative molecular mass of 100,000. When the enzyme was extracted and purified in the absence of malate, characteristic differences of the light and dark enzymes were lost, the enzymes eluted at the same volume during gel filtration, and specific activity was constant through the peak. We conclude that maize leaf PEPC exists in situ as a tetramer of a single polypeptide and that subtle conformation changes can affect both enzymic activity and sensitivity to malate inhibition. Images Fig. 6 PMID:16665065

  4. Effect of Light and NO3− on Wheat Leaf Phosphoenolpyruvate Carboxylase Activity

    PubMed Central

    Le Van Quy; Foyer, Christine; Champigny, Marie-Louise

    1991-01-01

    Phosphoenolpyruvate carboxylase (PEPcase) activity was studied in excised leaves of wheat (Triticum aestivum L.) in the dark and in the light, in presence of either N-free (low-NO3− leaves) or 40 millimolar KNO3 (high-NO3− leaves) nutrient solutions. PEPcase activity increased to 2.7-fold higher than that measured in dark-adapted tissue (control) during the first 60 minutes and continued to increase more slowly to 3.8-fold that of the control. This level was reached after 200 minutes exposure of the leaves to light and high NO3−. In contrast, the lower rate of increase recorded for low-NO3− leaves ceased after 60 minutes of exposure to light at 2.3-fold the control level. The short-term NO3− effect increased linearly with the level of NO3− uptake. In immunoprecipitation experiments, the antibody concentration for PEPcase precipitation increased with the protein extracts from the different treatments in the order: control, illuminated low-NO3− leaves, illuminated high-NO3− leaves. This order also applied with regard to a decreasing sensitivity to malate and an increasing stimulation by okadaic acid (an inhibitor of P-protein phosphatases). Following these studies, 32P labeling experiments were carried out in vivo. These showed that the light-induced change in the properties of the PEPcase was due to an alteration in the phosphorylation state of the protein and that this effect was enhanced in high-NO3− conditions. Based on the responses of PEPcase and sucrose phosphate synthase in wheat leaves to light and NO3−, an interpretation of the role of NO3− as either an inhibitor of P-protein phosphatase(s) or activator of protein kinase(s) is inferred. In the presence of NO3−, the phosphorylation state of both PEPcase and sucrose phosphate synthase is increased. This causes activation of the former enzyme and inhibition of the latter. We suggest that NO3− modulates the relative protein kinase/protein phosphatase ratio to favor increased

  5. Activity and quantity of ribulose bisphosphate carboxylase-and phosphoenolpyruvate carboxylase-protein in two Crassulacean acid metabolism plants in relation to leaf age, nitrogen nutrition, and point in time during a day/night cycle.

    PubMed

    Winter, K; Foster, J G; Schmitt, M R; Edwards, G E

    1982-05-01

    Activity of ribulose 1,5-bisphosphate (RuBP) carboxylase in leaf extracts of the constitutive Crassulacean acid metabolism (CAM) plant Kalanchoe pinnata (Lam.) Pers. decreased with increasing leaf age, whereas the activity of phosphoenolpyruvate (PEP) carboxylase increased. Changes in enzyme activities were associated with changes in the amount of enzyme proteins as determined by immunochemical analysis, sucrose density gradient centrifugation, and SDS gel electrophoresis of leaf extracts. Young developing leaves of plants which received high amounts of NO 3 (-) during growth contained about 30% of the total soluble protein in the form of RuBP carboxylase; this value declined to about 17% in mature leaves. The level of PEP carboxylase in young leaves of plants at high NO 3 (-) was an estimated 1% of the total soluble protein and increased to approximately 10% in mature leaves, which showed maximum capacity for dark CO2 fixation. The growth of plants at low levels of NO 3 (-) decreased the content of soluble protein per unit leaf area as well as the extractable activity and the percentage contribution of both RUBP carboxylase and PEP carboxylase to total soluble leaf protein. There was no definite change in the ratio of RuBP carboxylase to PEP carboxylase activity with a varying supply of NO 3 (-) during growth. It has been suggested (e.g., Planta 144, 143-151, 1978) that a rhythmic pattern of synthesis and degradation of PEP carboxylase protein is involved in the regulation of β-carboxylation during a day/night cycle in CAM. No such changes in the quantity of PEP carboxylase protein were observed in the leaves of Kalanchoe pinnata (Lam.) Pers. or in the leaves of the inducible CAM plant Mesembryanthemum crystallinum L.

  6. Salinity promotes opposite patterns of carbonylation and nitrosylation of C4 phosphoenolpyruvate carboxylase in sorghum leaves.

    PubMed

    Baena, Guillermo; Feria, Ana B; Echevarría, Cristina; Monreal, José A; García-Mauriño, Sofía

    2017-08-21

    Carbonylation inactivates sorghum C 4 PEPCase while nitrosylation has little impact on its activity but holds back carbonylation. This interplay could be important to preserve photosynthetic C4 PEPCase activity in salinity. Previous work had shown that nitric acid (NO) increased phosphoenolpyruvate carboxylase kinase (PEPCase-k) activity, promoting the phosphorylation of phosphoenolpyruvate carboxylase (PEPCase) in sorghum leaves (Monreal et al. in Planta 238:859-869, 2013b). The present work investigates the effect of NO on C4 PEPCase in sorghum leaves and its interplay with carbonylation, an oxidative modification frequently observed under salt stress. The PEPCase of sorghum leaves could be carbonylated in vitro and in vivo, and this post-translational modification (PTM) was accompanied by a loss of its activity. Similarly, PEPCase could be S-nitrosylated in vitro and in vivo, and this PTM had little impact on its activity. The S-nitrosylated PEPCase showed increased resistance towards subsequent carbonylation, both in vitro and in vivo. Under salt shock, carbonylation of PEPCase increased in parallel with decreased S-nitrosylation of the enzyme. Subsequent increase of S-nitrosylation was accompanied by decreased carbonylation. Taken together, the results suggest that S-nitrosylation could contribute to maintain C4 PEPCase activity in stressed sorghum plants. Thus, salt-induced NO synthesis would be protecting photosynthetic PEPCase activity from oxidative inactivation while promoting its phosphorylation, which will guarantee its optimal functioning in suboptimal conditions.

  7. The Importance of the Strictly Conserved, C-terminal Glycine Residue in Phosphoenolpyruvate Carboxylase for Overall Catalysis: Mutagenesis and Truncation of GLY-961 in the Sorghum C4 Leaf Isoform

    SciTech Connect

    Xu,W.; Ahmed, S.; Moriyama, H.; Chollet, R.

    2006-01-01

    Phosphoenolpyruvate carboxylase (PEPC) is a 'multifaceted', allosteric enzyme involved in C4 acid metabolism in green plants/microalgae and prokaryotes. Before the elucidation of the three-dimensional structures of maize C4 leaf and Escherichia coli PEPC, our truncation analysis of the sorghum C4 homologue revealed important roles for the enzyme's C-terminal {alpha}-helix and its appended QNTG{sup 961} tetrapeptide in polypeptide stability and overall catalysis, respectively. Collectively, these functional and structural observations implicate the importance of the PEPC C-terminal tetrapeptide for both catalysis and negative allosteric regulation. We have now more finely dissected this element of PEPC structure-function by modification of the absolutely conserved C-terminal glycine of the sorghum C4 isoform by site-specific mutagenesis (G961(A/V/D)) and truncation ({Delta}C1/C4). Although the C4 polypeptide failed to accumulate in a PEPC{sup -} strain (XH11) of E. coli transformed with the Asp mutant, the other variants were produced at wild-type levels. Although neither of these four mutants displayed an apparent destabilization of the purified PEPC homotetramer, all were compromised catalytically in vivo and in vitro. Functional complementation of XH11 cells under selective growth conditions was restricted progressively by the Ala, {Delta}C1 and Val, and {Delta}C4 modifications. Likewise, steady-state kinetic analysis of the purified mutant enzymes revealed corresponding negative trends in k{sub cat} and k{sub cat}/K0.5 (phosphoenolpyruvate) but not in K{sub 0.5} or the Hill coefficient. Homology modeling of these sorghum C-terminal variants against the structure of the closely related maize C4 isoform predicted perturbations in active-site molecular cavities and/or ion-pairing with essential, invariant Arg-638. These collective observations reveal that even a modest, neutral alteration of the PEPC C-terminal hydrogen atom side chain is detrimental to enzyme

  8. Phosphoenolpyruvate carboxylase regulation in C4-PEPC-expressing transgenic rice during early responses to drought stress.

    PubMed

    Liu, Xiaolong; Li, Xia; Zhang, Chen; Dai, Chuanchao; Zhou, Jiayu; Ren, Chenggang; Zhang, Jinfei

    2017-02-01

    Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) has important functions in C4 photosynthesis and biosynthesis of intermediate metabolites. In this study, the drought resistance of C4-PEPC-expressing transgenic rice (Oryza sativa, line PC) plants was assessed using simulated drought conditions [i.e. polyethylene glycol (PEG)-6000 treatment]. The dry weight of PC plants was higher than that of wild-type (WT) plants following treatment with 15% PEG-6000 for 16 days. Furthermore, the water use efficiency, relative water content and proline content in PC plants were higher than those of WT plants, as were C4-PEPC activity and transcript levels following treatment with 5% PEG-6000 for 2 h. The protein kinase activities and transcript levels of sucrose non-fermenting-1-related protein kinases (SnRKs) genes, such as SnRK1a, OsK24 and OsK35 were also higher in PC plants than in WT plants following treatment with 5% PEG-6000 for 2 h. Additionally, phosphoenolpyruvate carboxylase kinase (PPCK, EC 4.1.1.32) activities and transcript levels (e.g. PPCK1 and PPCK2) increased following drought treatment. These changes were regulated by signaling molecules, such as calcium, nitric oxide and hydrogen peroxide. Furthermore, the -1095 to -416 region of the C4-PEPC promoter in PC plants was demethylated following exposure to drought conditions for 1 h. The demethylation coincided with an increase in C4-PEPC expression. Our data suggest that the demethylation of the C4-PEPC promoter and the phosphorylation catalyzed by PPCK have key roles in conferring drought tolerance to the transgenic rice plants.

  9. Identification and expression of a soybean nodule-enhanced PEP-carboxylase kinase gene (NE-PpcK) that shows striking up-/down-regulation in vivo.

    PubMed

    Xu, Wenxin; Zhou, You; Chollet, Raymond

    2003-05-01

    Various isoforms of plant phosphoenolpyruvate carboxylase (PEPC (Ppc)) are controlled post-translationally by an intricate interaction between allosteric regulation and reversible protein phosphorylation. In leaves and root nodules of legumes, these changes in PEPC phosphorylation state are governed primarily by PEPC-kinase (PpcK), a novel, 'minimal but functional' Ser/Thr kinase. To date, this plant-specific kinase has been investigated in molecular terms exclusively in non-leguminous plants, such as Crassulacean-acid-metabolism (CAM) species and Arabidopsis. As an important extension of our earlier biochemical studies on this dedicated kinase and PEPC phosphorylation in soybean (Glycine max) nodules, we now report the molecular cloning of the first legume PpcK from a soybean nodule cDNA library, which encodes a functional, 31.0 kDa PpcK polypeptide. Besides displaying organ, developmental, and spatial expression properties that are strikingly up-regulated in mature nodules, the expression pattern of this transcript is distinct from that of a second soybean PpcK isogene (GmPpcK). The steady-state abundance of this former, nodule-enhanced transcript (NE-PpcK) is markedly influenced by photosynthate supply from the shoots. This latter up-/down-regulation of NE-PpcK transcript level occurs in vivo in concert with the corresponding changes in the nodule PpcK activity, the phosphorylation-state of PEPC, and the abundance of a previously identified, nodule-enhanced transcript (GmPEPC7) that encodes the target enzyme (NE-Ppc). Furthermore, genomic Southern analysis and inspection of the public database indicate that there are at least three distinct PpcK and Ppc isogenes in soybean. Collectively, these and recent findings with Arabidopsis implicate the existence of multiple PpcK-Ppc'expression-partners' in plants, exemplified by NE-PpcK and NE-Ppc in the soybean nodule.

  10. Phosphorylation of Phosphoenolpyruvate Carboxylase is Essential for Maximal and Sustained Dark CO2 Fixation and Core Circadian Clock Operation in the Obligate Crassulacean Acid Metabolism Species Kalanchoë fedtschenkoi.

    PubMed

    Boxall, Susanna F; Dever, Louisa V; Knerova, Jana; Gould, Peter D; Hartwell, James

    2017-09-08

    Phosphoenolpyruvate carboxylase (PPC; EC 4.1.1.31) catalyzes primary nocturnal CO2 fixation in Crassulacean acid metabolism (CAM) species. CAM PPC is regulated post-translationally by a circadian clock controlled protein kinase called phosphoenolpyruvate carboxylase kinase (PPCK). PPCK phosphorylates PPC during the dark period, reducing its sensitivity to feedback inhibition by malate, and thus enhancing nocturnal CO2 fixation to stored malate. Here, we report the generation and characterization of transgenic RNAi lines of the obligate CAM species Kalanchoë fedtschenkoi with reduced levels of KfPPCK1 transcripts. Plants with reduced or no detectable dark phosphorylation of PPC displayed up to a 66% reduction in total dark period CO2 fixation. These perturbations paralleled reduced malate accumulation at dawn and decreased nocturnal starch turnover. Loss of oscillations in the transcript abundance of KfPPCK1 was accompanied by a loss of oscillations in the transcript abundance of many core circadian clock genes, suggesting that perturbing the only known link between CAM and the circadian clock feeds back to perturb the central circadian clock itself. This work shows that clock control of KfPPCK1 prolongs the activity of PPC throughout the dark period in K. fedtschenkoi, optimizing CAM-associated dark CO2 fixation, malate accumulation, CAM productivity and core circadian clock robustness. © 2017 American Society of Plant Biologists. All rights reserved.

  11. Diurnal Regulation of Phosphoenolpyruvate Carboxylase from Crassula1

    PubMed Central

    Wu, Min-Xian; Wedding, Randolph T.

    1985-01-01

    Phosphoenolpyruvate carboxylase appears to be located in or associated with the chloroplasts of Crassula. As has been found with this enzyme in other CAM plants, a crude extract of leaves gathered during darkness and rapidly assayed for phosphoenolpyruvate carboxylase (PEPc) activity is relatively insensitive to inhibition by malate. After illumination begins, the PEPc activity becomes progressively more sensitive to malate. This enzyme also shows a diurnal change in activation by glucose-6-phosphate, with the enzyme from dark leaves more strongly activated than that from leaves in the light. When the enzyme is partially purified in the presence of malate, the characteristic sensitivity of the day leaf enzyme is largely retained. Partial purification of the enzyme from dark leaves results in a small increase in sensitivity to malate inhibition. Partially purified enzyme is found by polyacrylamide gel electrophoresis analysis to have two bands of PEPc activity. In enzymes from dark leaves, the slower moving band predominates, but in the light, the faster moving band is preponderant. Both of these bands are shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be composed of the same subunit of 103,000 daltons. The enzyme partially purified from night leaves has a pH optimum of 5.6, and is relatively insensitive to malate inhibition over the range from pH 4.5 to 8. The enzyme from day leaves has a pH optimum of 6.6 and is strongly inhibited by malate at pH values below 7, but becomes insensitive at higher pH values. Gel filtration of partially purified PEPc showed two activity peaks, one corresponding approximately to a dimer of the single subunit, and the other twice as large. The larger protein was relatively insensitive to malate inhibition, the smaller was strongly inhibited by malate. Kinetic studies showed that malate is a mixed type inhibitor of the sensitive, day, enzyme, increasing Km for phosphoenolpyruvate and reducing Vmax. With the

  12. Phosphoenolpyruvate Carboxykinase in Plants Exhibiting Crassulacean Acid Metabolism 1

    PubMed Central

    Dittrich, P.; Campbell, Wilbur H.; Black, C. C.

    1973-01-01

    Phosphoenolpyruvate carboxykinase has been found in significant activities in a number of plants exhibiting Crassulacean acid metabolism. Thirty-five species were surveyed for phosphoenolpyruvate carboxykinase, phosphoenolpyruvate carboxylase, ribulose diphosphate carboxylase, malic enzyme, and malate dehydrogenase (NAD). Plants which showed high activities of malic enzyme contained no detectable phosphoenolpyruvate carboxykinase, while plants with high activities of the latter enzyme contained little malic enzyme. It is proposed that phosphoenolpyruvate carboxykinase acts as a decarboxylase during the light period, furnishing CO2 for the pentose cycle and phosphoenolpyruvate for gluconeogenesis. Some properties of phosphoenolpyruvate carboxykinase in crude extracts of pineapple leaves were investigated. The enzyme required Mn2+, Mg2+, and ATP for maximum activity. About 60% of the activity could be pelleted, along with chloroplasts and mitochondria, in extracts from leaves kept in the dark overnight. PMID:16658562

  13. Multiple cDNAs of phosphoenolpyruvate carboxylase in the C4 dicot Flaveria trinervia.

    PubMed

    Poetsch, W; Hermans, J; Westhoff, P

    1991-11-04

    We have isolated and characterized cDNA clones for the leaf-specific C4-phosphoenolpyruvate carboxylase (PEPCase) from the dicotyledonous C4 plant Flaveria trinervia. The isolation of multiple cDNAs indicates that in this plant the C4 isoform is encoded by a small subgroup of the PEPCase gene family. The deduced amino acid sequence reveals a higher degree of similarity to the CAM and C3 isozymes of the dicotyledonous, facultative CAM plant Mesembryanthemum crystallinum than to the C4 PEPCases of monocotyledonous origin.

  14. Effects of heterologous expression of phosphoenolpyruvate carboxykinase and phosphoenolpyruvate carboxylase on organic acid production in Aspergillus carbonarius.

    PubMed

    Yang, Lei; Lübeck, Mette; Lübeck, Peter S

    2015-11-01

    Aspergillus carbonarius has a potential as a cell factory for production of various organic acids. In this study, the organic acid profile of A. carbonarius was investigated under different cultivation conditions. Moreover, two heterologous genes, pepck and ppc, which encode phosphoenolpyruvate carboxykinase in Actinobacillus succinogenes and phosphoenolpyruvate carboxylase in Escherichia coli, were inserted individually and in combination in A. carbonarius to enhance the carbon flux toward the reductive TCA branch. Results of transcription analysis and measurement of enzyme activities of phosphoenolpyruvate carboxykinase and phosphoenolpyruvate carboxylase in the corresponding single and double transformants demonstrated that the two heterologous genes were successfully expressed in A. carbonarius. The production of citric acid increased in all the transformants in both glucose- and xylose-based media at pH higher than 3 but did not increase in the pH non-buffered cultivation compared with the wild type.

  15. Limited proteolysis of Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase.

    PubMed

    Herrera, L; Encinas, M V; Jabalquinto, A M; Cardemil, E

    1993-08-01

    Incubation of Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase with trypsin under native conditions cases a time-dependent loss of activity and the production of protein fragments. Cleavage sites determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and sequence analyses identified protease-sensitive peptide bonds between amino acid residues at positions 9-10 and 76-77. Additional fragmentation sites were also detected in a region approximately 70-80 amino acids before the carboxyl end of the protein. These results suggest that the enzyme is formed by a central compact domain comprising more than two thirds of the whole protein structure. From proteolysis experiments carried out in the presence of substrates, it could be inferred that CO2 binding specifically protects position 76-77 from trypsin action. Intrinsic fluorescence measurements demonstrated that CO2 binding induces a protein conformational change, and a dissociation constant for the enzyme CO2 complex of 8.2 +/- 0.6 mM was determined.

  16. Anapleurotic CO/sub 2/ fixation by phosphoenolpyruvate carboxylase in C/sub 3/ plants. [Nicotiana tabacum

    SciTech Connect

    Melzer, E.; O'Leary, M.H.

    1987-05-01

    The role of phosphoenolpyruvate carboxylase in photosynthesis in the C/sub 3/ plant Nicotiana tabacum has been probed by measurement of the /sup 13/C content of various materials. Whole leaf and purified ribulose bisphosphate carboxylase are within the range expected for C/sub 3/ plants. Aspartic acid purified following acid hydrolysis of this ribulose bisphosphate carboxylase is enriched in /sup 13/C compared to whole protein. Carbons 1-3 of this aspratic acid are in the normal C/sub 3/ range, but carbon-4 (obtained by treatment of the aspartic acid with aspartate ..beta..-decarboxylase) has an isotopic composition in the range expected for products of C/sub 4/ photosynthesis (-5%), and it appears that more than half of the aspartic acid is synthesized by phosphoenolpyruvate carboxylase using atmospheric CO/sub 2//HCO/sub 3//sup -/. Thus, a primary role of phosphoenolpyruvate carboxylase in C/sub 3/ plants appears to be the anapleurotic synthesis of four-carbon acids.

  17. Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria.

    PubMed Central

    Postma, P W; Lengeler, J W; Jacobson, G R

    1993-01-01

    Numerous gram-negative and gram-positive bacteria take up carbohydrates through the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS). This system transports and phosphorylates carbohydrates at the expense of PEP and is the subject of this review. The PTS consists of two general proteins, enzyme I and HPr, and a number of carbohydrate-specific enzymes, the enzymes II. PTS proteins are phosphoproteins in which the phospho group is attached to either a histidine residue or, in a number of cases, a cysteine residue. After phosphorylation of enzyme I by PEP, the phospho group is transferred to HPr. The enzymes II are required for the transport of the carbohydrates across the membrane and the transfer of the phospho group from phospho-HPr to the carbohydrates. Biochemical, structural, and molecular genetic studies have shown that the various enzymes II have the same basic structure. Each enzyme II consists of domains for specific functions, e.g., binding of the carbohydrate or phosphorylation. Each enzyme II complex can consist of one to four different polypeptides. The enzymes II can be placed into at least four classes on the basis of sequence similarity. The genetics of the PTS is complex, and the expression of PTS proteins is intricately regulated because of the central roles of these proteins in nutrient acquisition. In addition to classical induction-repression mechanisms involving repressor and activator proteins, other types of regulation, such as antitermination, have been observed in some PTSs. Apart from their role in carbohydrate transport, PTS proteins are involved in chemotaxis toward PTS carbohydrates. Furthermore, the IIAGlc protein, part of the glucose-specific PTS, is a central regulatory protein which in its nonphosphorylated form can bind to and inhibit several non-PTS uptake systems and thus prevent entry of inducers. In its phosphorylated form, P-IIAGlc is involved in the activation of adenylate cyclase and thus in the

  18. The active site structure and mechanism of phosphoenolpyruvate utilizing enzymes

    SciTech Connect

    Cheng, K.C.

    1989-01-01

    Arginine specific reagents showed irreversible inhibition of avian liver mitochondrial phosphoenolpyruvate carboxykinase. Potent protection against modification was elicited by CO{sub 2} or CO{sub 2} in the presence of other substrates. Labeling of enzyme with (7-{sup 14}C) phenylglyoxal showed that 1 or 2 arginines are involved in CO{sub 2} binding and activation. Peptide map studies showed this active site arginine residues is located at position 289. Histidine specific reagents showed pseudo first order inhibition of avian mitochondrial phosphoenolpyruvate carboxykinase activity. The best protection against modification was elicited by IDP or IDP and Mn{sup +2}. One histidine residue is at or near the phosphoenolpyruvate binding site as demonstrated in the increased absorbance at 240 nm and proton relaxation rate studies. Circular dichroism studies reveal that enzyme structure was perturbed by diethylpyrocarbonate modification. Metal binding studies suggest that this enzyme has only one metal binding site. The putative binding sites from several GTP and phosphoenolpyruvate utilizing enzymes are observed in P-enolpyruvate carboxykinase from different species.

  19. Activating Phosphoenolpyruvate Carboxylase and Phosphoenolpyruvate Carboxykinase in Combination for Improvement of Succinate Production

    PubMed Central

    Tan, Zaigao; Zhu, Xinna; Chen, Jing; Li, Qingyan

    2013-01-01

    Phosphoenolpyruvate (PEP) carboxylation is an important step in the production of succinate by Escherichia coli. Two enzymes, PEP carboxylase (PPC) and PEP carboxykinase (PCK), are responsible for PEP carboxylation. PPC has high substrate affinity and catalytic velocity but wastes the high energy of PEP. PCK has low substrate affinity and catalytic velocity but can conserve the high energy of PEP for ATP formation. In this work, the expression of both the ppc and pck genes was modulated, with multiple regulatory parts of different strengths, in order to investigate the relationship between PPC or PCK activity and succinate production. There was a positive correlation between PCK activity and succinate production. In contrast, there was a positive correlation between PPC activity and succinate production only when PPC activity was within a certain range; excessive PPC activity decreased the rates of both cell growth and succinate formation. These two enzymes were also activated in combination in order to recruit the advantages of each for the improvement of succinate production. It was demonstrated that PPC and PCK had a synergistic effect in improving succinate production. PMID:23747698

  20. Phosphoenolpyruvate carboxykinase in cherry (Prunus avium L.) fruit during development.

    PubMed

    Walker, Robert P; Battistelli, Alberto; Moscatello, Stefano; Chen, Zhi-Hui; Leegood, Richard C; Famiani, Franco

    2011-11-01

    In this study the abundance and location of phosphoenolpyruvate carboxykinase (PEPCK) was determined in the flesh and skin of the sweet cherry (Prunus avium L.) cultivar Durone Nero II during development. PEPCK was not present in young fruit but appeared in both tissues as the fruit increased in size. In these there was no net dissimilation of malic acid, which accounts for the bulk of their organic acid contents when PEPCK was present. To assist in understanding the function of PEPCK, the abundance of a number of other enzymes was determined. These enzymes were aspartate aminotransferase (AspAT), glutamine synthetase (GS), phosphoenolpyruvate carboxylase (PEPC), pyruvate, orthophosphate dikinase (PPDK), and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco). A potential role for PEPCK in the regulation of pH and the utilization of malate in gluconeogenesis in the flesh and skin of cherries is presented.

  1. Phosphoenolpyruvate Provision to Plastids Is Essential for Gametophyte and Sporophyte Development in Arabidopsis thaliana[C][W

    PubMed Central

    Prabhakar, Veena; Löttgert, Tanja; Geimer, Stefan; Dörmann, Peter; Krüger, Stephan; Vijayakumar, Vinod; Schreiber, Lukas; Göbel, Cornelia; Feussner, Kirstin; Feussner, Ivo; Marin, Kay; Staehr, Pia; Bell, Kirsten; Flügge, Ulf-Ingo; Häusler, Rainer E.

    2010-01-01

    Restriction of phosphoenolpyruvate (PEP) supply to plastids causes lethality of female and male gametophytes in Arabidopsis thaliana defective in both a phosphoenolpyruvate/phosphate translocator (PPT) of the inner envelope membrane and the plastid-localized enolase (ENO1) involved in glycolytic PEP provision. Homozygous double mutants of cue1 (defective in PPT1) and eno1 could not be obtained, and homozygous cue1 heterozygous eno1 mutants [cue1/eno1(+/−)] exhibited retarded vegetative growth, disturbed flower development, and up to 80% seed abortion. The phenotypes of diminished oil in seeds, reduced flavonoids and aromatic amino acids in flowers, compromised lignin biosynthesis in stems, and aberrant exine formation in pollen indicate that cue1/eno1(+/−) disrupts multiple pathways. While diminished fatty acid biosynthesis from PEP via plastidial pyruvate kinase appears to affect seed abortion, a restriction in the shikimate pathway affects formation of sporopollonin in the tapetum and lignin in the stem. Vegetative parts of cue1/eno1(+/−) contained increased free amino acids and jasmonic acid but had normal wax biosynthesis. ENO1 overexpression in cue1 rescued the leaf and root phenotypes, restored photosynthetic capacity, and improved seed yield and oil contents. In chloroplasts, ENO1 might be the only enzyme missing for a complete plastidic glycolysis. PMID:20798327

  2. The phosphoenolpyruvate/phosphate translocator is required for phenolic metabolism, palisade cell development, and plastid-dependent nuclear gene expression.

    PubMed

    Streatfield, S J; Weber, A; Kinsman, E A; Häusler, R E; Li, J; Post-Beittenmiller, D; Kaiser, W M; Pyke, K A; Flügge, U I; Chory, J

    1999-09-01

    The Arabidopsis chlorophyll a/b binding protein (CAB) gene underexpressed 1 (cue1) mutant underexpresses light-regulated nuclear genes encoding chloroplast-localized proteins. cue1 also exhibits mesophyll-specific chloroplast and cellular defects, resulting in reticulate leaves. Both the gene underexpression and the leaf cell morphology phenotypes are dependent on light intensity. In this study, we determine that CUE1 encodes the plastid inner envelope phosphoenolpyruvate/phosphate translocator (PPT) and define amino acid residues that are critical for translocator function. The biosynthesis of aromatics is compromised in cue1, and the reticulate phenotype can be rescued by feeding aromatic amino acids. Determining that CUE1 encodes PPT indicates the in vivo role of the translocator in metabolic partitioning and reveals a mesophyll cell-specific requirement for the translocator in Arabidopsis leaves. The nuclear gene expression defects in cue1 suggest that a light intensity-dependent interorganellar signal is modulated through metabolites dependent on a plastid supply of phosphoenolpyruvate.

  3. Structural and functional studies of phosphoenolpyruvate carboxykinase from Mycobacterium tuberculosis.

    PubMed

    Machová, Iva; Snášel, Jan; Dostál, Jiří; Brynda, Jiří; Fanfrlík, Jindřich; Singh, Mahavir; Tarábek, Ján; Vaněk, Ondřej; Bednárová, Lucie; Pichová, Iva

    2015-01-01

    Tuberculosis, the second leading infectious disease killer after HIV, remains a top public health priority. The causative agent of tuberculosis, Mycobacterium tuberculosis (Mtb), which can cause both acute and clinically latent infections, reprograms metabolism in response to the host niche. Phosphoenolpyruvate carboxykinase (Pck) is the enzyme at the center of the phosphoenolpyruvate-pyruvate-oxaloacetate node, which is involved in regulating the carbon flow distribution to catabolism, anabolism, or respiration in different states of Mtb infection. Under standard growth conditions, Mtb Pck is associated with gluconeogenesis and catalyzes the metal-dependent formation of phosphoenolpyruvate. In non-replicating Mtb, Pck can catalyze anaplerotic biosynthesis of oxaloacetate. Here, we present insights into the regulation of Mtb Pck activity by divalent cations. Through analysis of the X-ray structure of Pck-GDP and Pck-GDP-Mn2+ complexes, mutational analysis of the GDP binding site, and quantum mechanical (QM)-based analysis, we explored the structural determinants of efficient Mtb Pck catalysis. We demonstrate that Mtb Pck requires presence of Mn2+ and Mg2+ cations for efficient catalysis of gluconeogenic and anaplerotic reactions. The anaplerotic reaction, which preferably functions in reducing conditions that are characteristic for slowed or stopped Mtb replication, is also effectively activated by Fe2+ in the presence of Mn2+ or Mg2+ cations. In contrast, simultaneous presence of Fe2+ and Mn2+ or Mg2+ inhibits the gluconeogenic reaction. These results suggest that inorganic ions can contribute to regulation of central carbon metabolism by influencing the activity of Pck. Furthermore, the X-ray structure determination, biochemical characterization, and QM analysis of Pck mutants confirmed the important role of the Phe triad for proper binding of the GDP-Mn2+ complex in the nucleotide binding site and efficient catalysis of the anaplerotic reaction.

  4. Regulation of Phosphoenolpyruvate Carboxylase and Crassulacean Acid Metabolism Induction in Mesembryanthemum crystallinum L. by Cytokinin 1

    PubMed Central

    Schmitt, Jürgen M.; Piepenbrock, Mechtild

    1992-01-01

    Phosphoenolpyruvate carboxylase (PEPCase), the key enzyme of Crassulacean acid metabolism, is induced by water stress in leaves of Mesembryanthemum crystallinum. In water-stressed plants or excised leaves, exogenous cytokinin suppresses PEPCase transcript accumulation in the leaves. Cytokinin (6-benzylaminopurine) used in concentrations from 5 to 500 micromolar (a) inhibits the upregulation of PEPCase transcripts, enzyme activity, and Crassulacean acid metabolism induction in salt-stressed intact plants when sprayed once daily during the stress period, (b) inhibits the accumulation of PEPCase mRNA in leaves from well-watered plants, (c) down-regulates PEPCase transcripts within 8 hours in prestressed, intact plants after a single spraying of an individual leaf, (d) inhibits accumulation of PEPCase transcripts in excised, wilting leaves, and (e) accelerates the net decrease of PEPCase transcripts in excised leaves from prestressed plants under rehydration conditions. When roots, the main site of cytokinin biosynthesis, are excised, PEPCase induction under drought stress is intensified. We propose that roots, acting as sensors of soil water status, may regulate PEPCase gene expression in the leaves with cytokinin as a signal transducer. ImagesFigure 2Figure 7 PMID:16669088

  5. Phosphoenolpyruvate carboxylase in mistletoe leaves: Regulation of gene expression, protein content, and covalent modification.

    PubMed

    Li, Xuemei; Wanek, Wolfgang; Nehls, U.; Popp, Marianne; Hampp, Rüdiger; Rennenberg, Heinz; Einig, Werner

    2001-07-01

    Seasonal changes in the activity of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31), a key enzyme in the interaction of carbohydrate and nitrogen metabolism, were studied in leaves of the C3 semiparasitic mistletoe, Viscum album, growing on different host trees. Maximum extractable PEPCase activities were higher in leaves of mistletoes growing on Betula pendula and Alnus glutinosa hosts compared with those on the conifers, Abies alba and Larix decidua. Independent of host, maximum extractable PEPCase activities were high in spring and autumn while low in summer. Samples with higher PEPCase activities showed higher amounts of PEPCase protein and higher PEPCase mRNA levels. A curvilinear correlation between leaf total nitrogen content and the maximum extractable PEPCase activity as well as PEPCase mRNA level suggested that nitrogen might affect the activity of PEPCase of mistletoe by up-regulating gene expression. In addition to extractable activity, seasonal changes of the PEPCase activation state, the ratio of activities resulting from limited:non-limited assays, were found, which was correlated to the variation of malate content in leaves of mistletoe. ATP-dependent activation of PEPCase was characterized by an increase in I0.5(L-malate), indicating that PEPCase of leaves of mistletoes is probably regulated via phosphorylation.

  6. An engineered phosphoenolpyruvate carboxylase redirects carbon and nitrogen flow in transgenic potato plants.

    PubMed

    Rademacher, Thomas; Häusler, Rainer E; Hirsch, Heinz-Josef; Zhang, Li; Lipka, Volker; Weier, Dagmar; Kreuzaler, Fritz; Peterhänsel, Christoph

    2002-10-01

    Phosphoenolpyruvate carboxylase (PEPC) plays a central role in the anaplerotic provision of carbon skeletons for amino acid biosynthesis in leaves of C3 plants. Furthermore, in both C4 and CAM plants photosynthetic isoforms are pivotal for the fixation of atmospheric CO2. Potato PEPC was mutated either by modifications of the N-terminal phosphorylation site or by an exchange of an internal cDNA segment for the homologous sequence of PEPC from the C4 plant Flaveria trinervia. Both modifications resulted in enzymes with lowered sensitivity to malate inhibition and an increased affinity for PEP. These effects were enhanced by a combination of both mutated sequences and pulse labelling with 14CO2 in vivo revealed clearly increased fixation into malate for this genotype. Activity levels correlated well with protein levels of the mutated PEPC. Constitutive overexpression of PEPC carrying both N-terminal and internal modifications strongly diminished plant growth and tuber yield. Metabolite analysis showed that carbon flow was re-directed from soluble sugars and starch to organic acids (malate) and amino acids, which increased four-fold compared with the wild type. The effects on leaf metabolism indicate that the engineered enzyme provides an optimised starting point for the installation of a C4-like photosynthetic pathway in C3 plants.

  7. Activity of phosphoenolpyruvate carboxylase of an anthracycline-producing streptomycete.

    PubMed

    Dekleva, M L; Strohl, W R

    1988-11-01

    During fermantation studies on the production of anthracycline antibiotics by Streptomyces C5, it was observed that among the intermediate metabolism enzymes tested, only phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) increased significantly in specific activity during stationary phase. The specific activity of the Streptomyces C5 PEPCase increased ca. 3-fold during antibiotic production phase from the logarithmic phase levels. To characterize the regulation of the enzyme further, the Streptomyces C5 PEPCase was purified 150-fold from crude extracts. Acetyl-CoA and Mg2+ were shown to be required for PEPCase activity. The activity of the partially purified PEPCase was stimulated slightly by fructose 1,6-bisphosphate and AMP, and was inhibited severely by oxaloacetate, aspartate, malate, succinate, ATP, citrate, and CoASH.

  8. Octameric structure of Staphylococcus aureus enolase in complex with phosphoenolpyruvate

    PubMed Central

    Wu, Yunfei; Wang, Chengliang; Lin, Shenglong; Wu, Minhao; Han, Lu; Tian, Changlin; Zhang, Xuan; Zang, Jianye

    2015-01-01

    Staphylococcus aureus is a Gram-positive bacterium with strong pathogenicity that causes a wide range of infections and diseases. Enolase is an evolutionarily conserved enzyme that plays a key role in energy production through glycolysis. Additionally, enolase is located on the surface of S. aureus and is involved in processes leading to infection. Here, crystal structures of Sa_enolase with and without bound phosphoenolpyruvate (PEP) are presented at 1.6 and 2.45 Å resolution, respectively. The structure reveals an octameric arrangement; however, both dimeric and octameric conformations were observed in solution. Furthermore, enzyme-activity assays show that only the octameric variant is catalytically active. Biochemical and structural studies indicate that the octameric form of Sa_enolase is enzymatically active in vitro and likely also in vivo, while the dimeric form is catalytically inactive and may be involved in other biological processes. PMID:26627653

  9. Phosphoenolpyruvate Carboxykinase as the Sole Anaplerotic Enzyme in Saccharomyces cerevisiae▿

    PubMed Central

    Zelle, Rintze M.; Trueheart, Josh; Harrison, Jacob C.; Pronk, Jack T.; van Maris, Antonius J. A.

    2010-01-01

    Pyruvate carboxylase is the sole anaplerotic enzyme in glucose-grown cultures of wild-type Saccharomyces cerevisiae. Pyruvate carboxylase-negative (Pyc−) S. cerevisiae strains cannot grow on glucose unless media are supplemented with C4 compounds, such as aspartic acid. In several succinate-producing prokaryotes, phosphoenolpyruvate carboxykinase (PEPCK) fulfills this anaplerotic role. However, the S. cerevisiae PEPCK encoded by PCK1 is repressed by glucose and is considered to have a purely decarboxylating and gluconeogenic function. This study investigates whether and under which conditions PEPCK can replace the anaplerotic function of pyruvate carboxylase in S. cerevisiae. Pyc− S. cerevisiae strains constitutively overexpressing the PEPCK either from S. cerevisiae or from Actinobacillus succinogenes did not grow on glucose as the sole carbon source. However, evolutionary engineering yielded mutants able to grow on glucose as the sole carbon source at a maximum specific growth rate of ca. 0.14 h−1, one-half that of the (pyruvate carboxylase-positive) reference strain grown under the same conditions. Growth was dependent on high carbon dioxide concentrations, indicating that the reaction catalyzed by PEPCK operates near thermodynamic equilibrium. Analysis and reverse engineering of two independently evolved strains showed that single point mutations in pyruvate kinase, which competes with PEPCK for phosphoenolpyruvate, were sufficient to enable the use of PEPCK as the sole anaplerotic enzyme. The PEPCK reaction produces one ATP per carboxylation event, whereas the original route through pyruvate kinase and pyruvate carboxylase is ATP neutral. This increased ATP yield may prove crucial for engineering of efficient and low-cost anaerobic production of C4 dicarboxylic acids in S. cerevisiae. PMID:20581175

  10. Temperature Responses of C4 Photosynthesis: Biochemical Analysis of Rubisco, Phosphoenolpyruvate Carboxylase, and Carbonic Anhydrase in Setaria viridis1[OPEN

    PubMed Central

    Boyd, Ryan A.; Gandin, Anthony; Cousins, Asaph B.

    2015-01-01

    The photosynthetic assimilation of CO2 in C4 plants is potentially limited by the enzymatic rates of Rubisco, phosphoenolpyruvate carboxylase (PEPc), and carbonic anhydrase (CA). Therefore, the activity and kinetic properties of these enzymes are needed to accurately parameterize C4 biochemical models of leaf CO2 exchange in response to changes in CO2 availability and temperature. There are currently no published temperature responses of both Rubisco carboxylation and oxygenation kinetics from a C4 plant, nor are there known measurements of the temperature dependency of the PEPc Michaelis-Menten constant for its substrate HCO3−, and there is little information on the temperature response of plant CA activity. Here, we used membrane inlet mass spectrometry to measure the temperature responses of Rubisco carboxylation and oxygenation kinetics, PEPc carboxylation kinetics, and the activity and first-order rate constant for the CA hydration reaction from 10°C to 40°C using crude leaf extracts from the C4 plant Setaria viridis. The temperature dependencies of Rubisco, PEPc, and CA kinetic parameters are provided. These findings describe a new method for the investigation of PEPc kinetics, suggest an HCO3− limitation imposed by CA, and show similarities between the Rubisco temperature responses of previously measured C3 species and the C4 plant S. viridis. PMID:26373659

  11. Temperature Responses of C4 Photosynthesis: Biochemical Analysis of Rubisco, Phosphoenolpyruvate Carboxylase, and Carbonic Anhydrase in Setaria viridis.

    PubMed

    Boyd, Ryan A; Gandin, Anthony; Cousins, Asaph B

    2015-11-01

    The photosynthetic assimilation of CO2 in C4 plants is potentially limited by the enzymatic rates of Rubisco, phosphoenolpyruvate carboxylase (PEPc), and carbonic anhydrase (CA). Therefore, the activity and kinetic properties of these enzymes are needed to accurately parameterize C4 biochemical models of leaf CO2 exchange in response to changes in CO2 availability and temperature. There are currently no published temperature responses of both Rubisco carboxylation and oxygenation kinetics from a C4 plant, nor are there known measurements of the temperature dependency of the PEPc Michaelis-Menten constant for its substrate HCO3 (-), and there is little information on the temperature response of plant CA activity. Here, we used membrane inlet mass spectrometry to measure the temperature responses of Rubisco carboxylation and oxygenation kinetics, PEPc carboxylation kinetics, and the activity and first-order rate constant for the CA hydration reaction from 10°C to 40°C using crude leaf extracts from the C4 plant Setaria viridis. The temperature dependencies of Rubisco, PEPc, and CA kinetic parameters are provided. These findings describe a new method for the investigation of PEPc kinetics, suggest an HCO3 (-) limitation imposed by CA, and show similarities between the Rubisco temperature responses of previously measured C3 species and the C4 plant S. viridis. © 2015 American Society of Plant Biologists. All Rights Reserved.

  12. Salt Stress Increases the Level of Translatable mRNA for Phosphoenolpyruvate Carboxylase in Mesembryanthemum crystallinum1

    PubMed Central

    Ostrem, James A.; Olson, Steve W.; Schmitt, Jürgen M.; Bohnert, Hans J.

    1987-01-01

    Mesembryanthemum crystallinum responds to salt stress by switching from C3 photosynthesis to Crassulacean acid metabolism (CAM). During this transition the activity of phosphoenolpyruvate carboxylase (PEPCase) increases in soluble protein extracts from leaf tissue. We monitored CAM induction in plants irrigated with 0.5 molar NaCl for 5 days during the fourth, fifth, and sixth week after germination. Our results indicate that the age of the plant influenced the response to salt stress. There was no increase in PEPCase protein or PEPCase enzyme activity when plants were irrigated with 0.5 molar NaCl during the fourth and fifth week after germination. However, PEPCase activity increased within 2 to 3 days when plants were salt stressed during the sixth week after germination. Immunoblot analysis with anti-PEPCase antibodies showed that PEPCase synthesis was induced in both expanded leaves and in newly developing axillary shoot tissue. The increase in PEPCase protein was paralleled by an increase in PEPCase mRNA as assayed by immunoprecipitation of PEPCase from the in vitro translation products of RNA from salt-stressed plants. These results demonstrate that salinity increased the level of PEPCase in leaf and shoot tissue via a stress-induced increase in the steady-state level of translatable mRNA for this enzyme. Images Fig. 2 Fig. 3 Fig. 4 PMID:16665596

  13. Phosphoenolpyruvate carboxylase activity and concentration in the endosperm of developing and germinating castor oil seeds.

    PubMed

    Sangwan, R S; Singh, N; Plaxton, W C

    1992-06-01

    Monospecific polyclonal antibodies against maize leaf phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) were utilized to examine the subunit composition and developmental profile of endosperm PEPC in developing and germinating castor oil seeds (Ricinus communis L. cv Baker 296). PEPC from developing endosperm consists of a single type of 100-kilodalton subunit, whereas the enzyme from 2- to 5-day germinated endosperm appears to contain equal proportions of immunologically related 103- and 108-kilodalton subunits. The maximal activity of PEPC in developing endosperms (2.67 micromoles oxaloacetate produced per minute per gram fresh weight) is approximately 20-fold and threefold greater than that of fully mature (dry seed) and germinating endosperms, respectively. The most significant increase in the activity and concentration of endosperm PEPC occurs during the middle cotyledon to full cotyledon stage of seed development; this period coincides with the most active phase of storage oil accumulation by ripening castor oil seeds. The data are compatible with the recent proposal (RG Smith, DA Gauthier, DT Dennis, DH Turpin [1992] Plant Physiol 1233-1238) that PEPC plays a fundamental role in vivo in the cytosolic production of an important substrate (malate) for fatty acid biosynthesis by developing castor oil seed leucoplasts. Immediately following seed imbibition, PEPC activity and concentration increase in parallel, with the greatest levels attained by the third day of germination. It is suggested that during this early phase of seed germination PEPC has a critical function to build up cellular dicarboxylic acid pools required to initiate significant activities of both the tricarboxylic acid and glyoxylate cycles.

  14. Environmental Control of Phosphoenolpyruvate Carboxylase Induction in Mature Mesembryanthemum crystallinum L. 1

    PubMed Central

    Piepenbrock, Mechtild; Schmitt, Jürgen M.

    1991-01-01

    Mesembryanthemum crystallinum L. plants shift the mode of carbon assimilation from C3 to Crassulacean acid metabolism when stressed by high salinity. A prerequisite for Crassulacean acid metabolism induction is the synthesis of phosphoenolpyruvate carboxylase (PEPCase). A moderate increase in the abundance of PEPCase transcripts and activity is observed in 7-week-old, well-watered plants. This increase in PEPCase coincides in time with a decrease in the growth rate of the shoots. The steady-state level of PEPCase activity is uniform along the leaves of well-watered plants, as can be shown by comparing leaves of different age from individual 7-week-old plants. In contrast, the rate of induction in response to salt stress varies with the age of plants and to a lesser extent with the age of the leaves. Two-week-old seedlings induce PEPCase slowly under a moderate salt stress regimen, whereas older plants induce faster. When individual leaves from a seven-week-old plant are compared with respect to induction velocity, no clear-cut correlation with leaf age is apparent. The highest induction rate is observed in leaves from node five that are about 2 weeks old at the beginning of the experiment. PEPCase transcripts are readily down-regulated to minute levels when detached leaves are hydrated. The levels reached after 8 hours of rehydration are very similar, regardless of whether the leaves were cut from young or old plants or whether the plants were previously salt-stressed or well-watered. It is concluded that environmental rather than developmental factors are predominant in determining abundance of PEPCase activity and transcripts in leaves of mature M. crystallinum plants. ImagesFigure 1Figure 3Figure 5 PMID:16668542

  15. Two phosphoenolpyruvate carboxykinases coexist in the Crassulacean Acid Metabolism plant Ananas comosus. Isolation and characterization of the smaller 65 kDa form.

    PubMed

    Martín, Mariana; Rius, Sebastián Pablo; Podestá, Florencio Esteban

    2011-06-01

    Two phosphoenolpyruvate carboxykinase (PEPCK, EC 4.1.1.49) isoforms of 74 and 65 kDa were found to coexist in vivo in pineapple leaves, a constitutive Crassulacean Acid Metabolism plant. The 65 kDa form was not the result of proteolytic cleavage of the larger form since extraction methods reported to prevent PEPCK proteolysis in other plant tissues failed to yield a single immunoreactive PEPCK polypeptide in leaf extracts. In this work, the smaller form of 65 kDa was purified to homogeneity and physically and kinetically characterized and showed parameters compatible with a fully active enzyme. The specific activity was nearly twice higher for decarboxylation of oxaloacetate when compared to carboxylation of phosphoenolpyruvate. Kinetic parameters fell within the range of those estimated for other plant PEPCKs. Its activity was affected by several metabolites, as shown by inhibition by 3-phosphoglycerate, citrate, malate, fructose-1,6-bisphosphate, l-asparagine and activation of the decarboxylating activity by succinate. A break in the Arrhenius plot at about 30°C indicates that PEPCK structure is responsive to changes in temperature. The results indicate that pineapple leaves contain two PEPCK forms. The biochemical characterization of the smaller isoform performed in this work suggests that it could participate in both carbon and nitrogen metabolism in vivo by acting as a decarboxylase.

  16. Characterization of two functional phosphoenolpyruvate/phosphate translocator (PPT) genes in Arabidopsis--AtPPT1 may be involved in the provision of signals for correct mesophyll development.

    PubMed

    Knappe, Silke; Löttgert, Tanja; Schneider, Anja; Voll, Lars; Flügge, Ulf-Ingo; Fischer, Karsten

    2003-11-01

    The Arabidopsis thaliana chlorophyll a/b-binding protein underexpressed 1 (cue1) mutant shows a reticulate leaf phenotype and is defective in a plastidic phosphoenolpyruvate (PEP)/phosphate translocator (AtPPT1). A functional AtPPT1 providing plastids with PEP for the shikimate pathway is therefore essential for correct leaf development. The Arabidopsis genome contains a second PPT gene, AtPPT2. Both transporters share similar substrate specificities and are therefore able to transport PEP into plastids. The cue1 phenotype could partially be complemented by ectopic expression of AtPPT2 but obviously not by the endogeneous AtPPT2. Both genes are differentially expressed in most tissues: AtPPT1 is mainly expressed in the vasculature of leaves and roots, especially in xylem parenchyma cells, but not in leaf mesophyll cells, whereas AtPPT2 is expressed ubiquitously in leaves, but not in roots. The expression profiles are corroborated by tissue-specific transport data. As AtPPT1 expression is absent in mesophyll cells that are severely affected in the cue1 mutant, we propose that the vasculature-located AtPPT1 is involved in the generation of phenylpropanoid metabolism-derived signal molecules that trigger development in interveinal leaf regions. This signal probably originates from the root vasculature where only AtPPT1, but not AtPPT2, is present.

  17. Phosphoenolpyruvate carboxylase from pennywort (Umbilicus rupestris). Changes in properties after exposure to water stress.

    PubMed Central

    Daniel, P P; Bryant, J A; Woodward, F I

    1984-01-01

    Umbilicus rupestris (pennywort) switches from C3 photosynthesis to an incomplete form of crassulacean acid metabolism (referred to as 'CAM-idling') when exposed to water stress (drought). This switch is accompanied by an increase in the activity of phosphoenolpyruvate carboxylase. This enzyme also shows several changes in properties, including a marked decrease in sensitivity to acid pH, a lower Km for phosphoenolpyruvate, very much decreased sensitivity to the allosteric inhibitor malate, and increased responsiveness to the allosteric effector glucose 6-phosphate. The Mr of the enzyme remains unchanged, at approx. 185 000. These changes in properties of phosphoenolpyruvate carboxylase are discussed in relation to the roles of the enzyme in C3 and in CAM plants. Images Fig. 5. PMID:6712622

  18. Phosphoenolpyruvate carboxylase from pennywort (Umbilicus rupestris). Changes in properties after exposure to water stress.

    PubMed

    Daniel, P P; Bryant, J A; Woodward, F I

    1984-03-01

    Umbilicus rupestris (pennywort) switches from C3 photosynthesis to an incomplete form of crassulacean acid metabolism (referred to as 'CAM-idling') when exposed to water stress (drought). This switch is accompanied by an increase in the activity of phosphoenolpyruvate carboxylase. This enzyme also shows several changes in properties, including a marked decrease in sensitivity to acid pH, a lower Km for phosphoenolpyruvate, very much decreased sensitivity to the allosteric inhibitor malate, and increased responsiveness to the allosteric effector glucose 6-phosphate. The Mr of the enzyme remains unchanged, at approx. 185 000. These changes in properties of phosphoenolpyruvate carboxylase are discussed in relation to the roles of the enzyme in C3 and in CAM plants.

  19. Multiple isoforms of phosphoenolpyruvate carboxylase in the Orchidaceae (subtribe Oncidiinae): implications for the evolution of crassulacean acid metabolism

    PubMed Central

    Silvera, Katia; Winter, Klaus; Rodriguez, B. Leticia; Albion, Rebecca L.; Cushman, John C.

    2014-01-01

    Phosphoenolpyruvate carboxylase (PEPC) catalyses the initial fixation of atmospheric CO2 into oxaloacetate and subsequently malate. Nocturnal accumulation of malic acid within the vacuole of photosynthetic cells is a typical feature of plants that perform crassulacean acid metabolism (CAM). PEPC is a ubiquitous plant enzyme encoded by a small gene family, and each member encodes an isoform with specialized function. CAM-specific PEPC isoforms probably evolved from ancestral non-photosynthetic isoforms by gene duplication events and subsequent acquisition of transcriptional control elements that mediate increased leaf-specific or photosynthetic-tissue-specific mRNA expression. To understand the patterns of functional diversification related to the expression of CAM, ppc gene families and photosynthetic patterns were characterized in 11 closely related orchid species from the subtribe Oncidiinae with a range of photosynthetic pathways from C3 photosynthesis (Oncidium cheirophorum, Oncidium maduroi, Rossioglossum krameri, and Oncidium sotoanum) to weak CAM (Oncidium panamense, Oncidium sphacelatum, Gomesa flexuosa and Rossioglossum insleayi) and strong CAM (Rossioglossum ampliatum, Trichocentrum nanum, and Trichocentrum carthagenense). Phylogenetic analysis revealed the existence of two main ppc lineages in flowering plants, two main ppc lineages within the eudicots, and three ppc lineages within the Orchidaceae. Our results indicate that ppc gene family expansion within the Orchidaceae is likely to be the result of gene duplication events followed by adaptive sequence divergence. CAM-associated PEPC isoforms in the Orchidaceae probably evolved from several independent origins. PMID:24913627

  20. Multiple isoforms of phosphoenolpyruvate carboxylase in the Orchidaceae (subtribe Oncidiinae): implications for the evolution of crassulacean acid metabolism.

    PubMed

    Silvera, Katia; Winter, Klaus; Rodriguez, B Leticia; Albion, Rebecca L; Cushman, John C

    2014-07-01

    Phosphoenolpyruvate carboxylase (PEPC) catalyses the initial fixation of atmospheric CO2 into oxaloacetate and subsequently malate. Nocturnal accumulation of malic acid within the vacuole of photosynthetic cells is a typical feature of plants that perform crassulacean acid metabolism (CAM). PEPC is a ubiquitous plant enzyme encoded by a small gene family, and each member encodes an isoform with specialized function. CAM-specific PEPC isoforms probably evolved from ancestral non-photosynthetic isoforms by gene duplication events and subsequent acquisition of transcriptional control elements that mediate increased leaf-specific or photosynthetic-tissue-specific mRNA expression. To understand the patterns of functional diversification related to the expression of CAM, ppc gene families and photosynthetic patterns were characterized in 11 closely related orchid species from the subtribe Oncidiinae with a range of photosynthetic pathways from C3 photosynthesis (Oncidium cheirophorum, Oncidium maduroi, Rossioglossum krameri, and Oncidium sotoanum) to weak CAM (Oncidium panamense, Oncidium sphacelatum, Gomesa flexuosa and Rossioglossum insleayi) and strong CAM (Rossioglossum ampliatum, Trichocentrum nanum, and Trichocentrum carthagenense). Phylogenetic analysis revealed the existence of two main ppc lineages in flowering plants, two main ppc lineages within the eudicots, and three ppc lineages within the Orchidaceae. Our results indicate that ppc gene family expansion within the Orchidaceae is likely to be the result of gene duplication events followed by adaptive sequence divergence. CAM-associated PEPC isoforms in the Orchidaceae probably evolved from several independent origins. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  1. Photosynthetic and Other Phosphoenolpyruvate Carboxylase Isoforms in the Single-Cell, Facultative C4 System of Hydrilla verticillata1

    PubMed Central

    Rao, Srinath K.; Magnin, Noël C.; Reiskind, Julia B.; Bowes, George

    2002-01-01

    The submersed monocot Hydrilla verticillata (L.f.) Royle is a facultative C4 plant. It typically exhibits C3 photosynthetic characteristics, but exposure to low [CO2] induces a C4 system in which the C4 and Calvin cycles co-exist in the same cell and the initial fixation in the light is catalyzed by phosphoenolpyruvate carboxylase (PEPC). Three full-length cDNAs encoding PEPC were isolated from H. verticillata, two from leaves and one from root. The sequences were 95% to 99% identical and shared a 75% to 85% similarity with other plant PEPCs. Transcript studies revealed that one isoform, Hvpepc4, was exclusively expressed in leaves during C4 induction. This and enzyme kinetic data were consistent with it being the C4 photosynthesis isoform. However, the C4 signature serine of terrestrial plant C4 isoforms was absent in this and the other H. verticillata sequences. Instead, alanine, typical of C3 sequences, was present. Western analyses of C3 and C4 leaf extracts after anion-exchange chromatography showed similar dominant PEPC-specific bands at 110 kD. In phylogenetic analyses, the sequences grouped with C3, non-graminaceous C4, and Crassulacean acid metabolism PEPCs but not with the graminaceous C4, and formed a clade with a gymnosperm, which is consistent with H. verticillata PEPC predating that of other C4 angiosperms. PMID:12376652

  2. Homologous genes for the C4 isoform of phosphoenolpyruvate carboxylase in a C3 and a C4 Flaveria species.

    PubMed

    Hermans, J; Westhoff, P

    1992-08-01

    The C4 isoform of phosphoenolpyruvate carboxylase (PEPCase) in Flaveria trinervia is encoded by the ppcA subgroup of the PEPCase gene family and is abundantly expressed in the mesophyll cells of leaves. The homologous ppcA genes in the C3 plant F pringlei are only weakly expressed and their transcripts do not show the strictly leaf-specific accumulation pattern observed for the F. trinervia genes. Two representative members of the ppcA subfamilies of F. trinervia (C4) and F. pringeli (C3)-named ppcA1-were characterized by Southern blotting, nucleotide sequencing and primer extension analysis. Comparison of the deduced amino acid sequences reveals a close similarity between C4 and C3 isoforms. Only few C4-specific positions can be detected when all known plant PEPCases are included in the comparison. A regulatory domain involved in light-dependent phosphorylation/dephosphorylation of the C4 and crassulacean acid metabolism (CAM) isoforms is present in the ppcA1 gene products of both the C3 and C4 Flaveria. The 5' flanking regions are essentially homologous. The putative promoter regions share several identical sequence motifs (CCAAT, AT-1 and GT-1 box III/III* elements). Additionally, alterations in elements that could contribute to differences in expression rates and light regulation are found. The significance of these findings is discussed with respect to the molecular evolution of C4 photosynthesis in Flaveria.

  3. Does phosphoenolpyruvate carboxykinase have a role in both amino acid and carbohydrate metabolism?

    PubMed

    Lea, P J; Chen, Z H; Leegood, R C; Walker, R P

    2001-01-01

    Phosphoenolpyruvate carboxykinase (PEPCK) catalyses the reversible decarboxylation of oxaloacetate to yield phosphoenolpyruvate and CO2. The role of the enzyme in gluconeogenesis and anaplerotic reactions in a range of organisms is discussed, along with the important function in C4 and CAM photosynthesis in higher plants. In addition, new data are presented indicating that PEPCK may play a key role in amino acid metabolism. It is proposed that PEPCK is involved in the conversion of the carbon skeleton of asparagine/aspartate (oxaloacetate) to that of glutamate/glutamine (2-oxoglutarate). This metabolism is particularly important in the transport system, seeds and fruits of higher plants.

  4. Purification and characterization of a novel phosphoenolpyruvate carboxylase from banana fruit.

    PubMed Central

    Law, R D; Plaxton, W C

    1995-01-01

    Phosphoenolpyruvate carboxylase (PEPC) from ripened banana (Musa cavendishii L.) fruits has been purified 127-fold to apparent homogeneity and a final specific activity of 32 mumol of oxaloacetate produced/min per mg of protein. Non-denaturing PAGE of the final preparation resolved a single protein-staining band that co-migrated with PEPC activity. Polypeptides of 103 (alpha-subunit) and 100 (beta-subunit) kDa, which stain for protein with equal intensity and cross-react strongly with anti-(maize leaf PEPC) immune serum, were observed following SDS/PAGE of the final preparation. CNBr cleavage patterns of the two subunits were similar, but not identical, suggesting that these polypeptides are related, but distinct, proteins. The enzyme's native molecular mass was estimated to be about 425 kDa. These data indicate that in contrast to the homotetrameric PEPC from most other sources, the banana fruit enzyme exists as an alpha 2 beta 2 heterotetramer. Monospecific rabbit anti-(banana PEPC) immune serum effectively immunoprecipitated the activity of the purified enzyme. Immunoblotting studies established that the 100 kDa subunit did not arise via proteolysis of the 103 kDa subunit after tissue extraction, and that the subunit composition of banana PEPC remains uniform throughout the ripening process. PEPC displayed a typical pH activity profile with an alkaline optimum and activity rapidly decreasing below pH 7.0. Enzymic activity was absolutely dependent on the presence of a bivalent metal cation, with Mg2+ or Mn2+ fulfilling this requirement. The response of the PEPC activity to PEP concentration and to various effectors was greatly influenced by pH and glycerol addition to the assay. The enzyme was activated by hexose-monophosphates and potently inhibited by malate, succinate, aspartate and glutamate at pH 7.0, whereas the effect of these metabolites was considerably diminished or completely abolished at pH 8.0. The significance of metabolite regulation of PEPC is

  5. Molecular biology of C4 phosphoenolpyruvate carboxylase: Structure, regulation and genetic engineering.

    PubMed

    Rajagopalan, A V; Devi, M T; Raghavendra, A S

    1994-02-01

    Three to four families of nuclear genes encode different isoforms of phosphoenolpyruvate (PEP) carboxylase (PEPC): C4-specific, C3 or etiolated, CAM and root forms. C4 leaf PEPC is encoded by a single gene (ppc) in sorghum and maize, but multiple genes in the C4-dicot Flaveria trinervia. Selective expression of ppc in only C4-mesophyll cells is proposed to be due to nuclear factors, DNA methylation and a distinct gene promoter. Deduced amino acid sequences of C4-PEPC pinpoint the phosphorylatable serine near the N-terminus, C4-specific valine and serine residues near the C-terminus, conserved cysteine, lysine and histidine residues and PEP binding/catalytic sites. During the PEPC reaction, PEP and bicarbonate are first converted into carboxyphosphate and the enolate of pyruvate. Carboxyphosphate decomposes within the active site into Pi and CO2, the latter combining with the enolate to form oxalacetate. Besides carboxylation, PEPC catalyzes a HCO3 (-)-dependent hydrolysis of PEP to yield pyruvate and Pi. Post-translational regulation of PEPC occurs by a phosphorylation/dephosphorylation cascade in vivo and by reversible enzyme oligomerization in vitro. The interrelation between phosphorylation and oligomerization of the enzyme is not clear. PEPC-protein kinase (PEPC-PK), the enzyme responsible for phosphorylation of PEPC, has been studied extensively while only limited information is available on the protein phosphatase 2A capable of dephosphorylating PEPC. The C4 ppc was cloned and expressed in Escherichia coli as well as tobacco. The transformed E. coli produced a functional/phosphorylatable C4 PEPC and the transgenic tobacco plants expressed both C3 and C4 isoforms. Site-directed mutagenesis of ppc indicates the importance of His(138), His(579) and Arg(587) in catalysis and/or substrate-binding by the E. coli enzyme, Ser(8) in the regulation of sorghum PEPC. Important areas for further research on C4 PEPC are: mechanism of transduction of light signal during

  6. Carbon Dioxide Metabolism in Leaf Epidermal Tissue 1

    PubMed Central

    Willmer, C. M.; Pallas, J. E.; Black, C. C.

    1973-01-01

    A number of plant species were surveyed to obtain pure leaf epidermal tissue in quantity. Commelina communis L. and Tulipa gesnariana L. (tulip) were chosen for further work. Chlorophyll a/b ratios of epidermal tissues were 2.41 and 2.45 for C. communis and tulip, respectively. Phosphoenolpyruvate carboxylase, ribulose-1,5-diphosphate carboxylase, malic enzyme, and NAD+ and NADP+ malate dehydrogenases were assayed with epidermal tissue and leaf tissue minus epidermal tissue. In both species, there was less ribulose 1,5-diphosphate than phosphoenolpyruvate carboxylase activity in epidermal tissue whether expressed on a protein or chlorophyll basis whereas the reverse was true for leaf tissue minus epidermal tissue. In both species, malic enzyme activities were higher in epidermal tissue than in the remaining leaf tissue when expressed on a protein or chlorophyll basis. In both species, NAD+ and NADP+ malate dehydrogenase activities were higher in the epidermal tissue when expressed on a chlorophyll basis; however, on a protein basis, the converse was true. Microautoradiography of C. communis epidermis and histochemical tests for keto acids suggested that CO2 fixation occurred predominantly in the guard cells. The significance and possible location of the enzymes are discussed in relation to guard cell metabolism. Images PMID:16658581

  7. A simple enzymic method for the synthesis of [32P]phosphoenolpyruvate.

    PubMed

    Parra, F

    1982-09-01

    A rapid and simple enzymic method is described for the synthesis of [(32)P]phosphoenolpyruvate from [(32)P]P(i), with a reproducible yield of 74%. The final product was shown to be a good substrate for pyruvate kinase (EC 2.7.1.40).

  8. A simple enzymic method for the synthesis of [32P]phosphoenolpyruvate

    PubMed Central

    Parra, Francisco

    1982-01-01

    A rapid and simple enzymic method is described for the synthesis of [32P]phosphoenolpyruvate from [32P]Pi, with a reproducible yield of 74%. The final product was shown to be a good substrate for pyruvate kinase (EC 2.7.1.40). ImagesFig. 1. PMID:7150238

  9. Diurnal modulation of phosphoenolpyruvate carboxylation in pea leaves and roots as related to tissue malate concentrations and to the nitrogen source.

    PubMed

    Leport, Laurent; Kandlbinder, Andrea; Baur, Bernhard; Kaiser, Werner M

    1996-04-01

    Phosphoenolpyruvate (PEP) carboxylation was measured as dark (14)CO2 fixation in leaves and roots (in vivo) or as PEP carboxylase (PEPCase) activity in desalted leaf and roof extracts (in vitro) from Pisum sativum L. cv. Kleine Rheinländerin. Its relation to the malate content and to the nitrogen source (nitrate or ammonium) was investigated. In tissue from nitrate-grown plants, PEP carboxylation varied diurnally, showing an increase upon illumination and a decrease upon darkening. Diurnal variations in roots were much lower than in leaves. Fixation rates in leaves remained constantly low in continuous darkness or high in continuous light. Dark CO2 fixation of leaf slices also decreased when leaves were preilluminated for 1 h in CO2-free air, suggesting that the modulation of dark CO2 fixation was related to assimilate availability in leaves and roots. Phosphoenolpyruvate carboxylase activity was also measured in vitro. However, no difference in maximum enzyme activity was found in extracts from illuminated or darkened leaves, and the response to substrate and effectors (PEP, malate, glucose-6-phosphate, pH) was also identical. The serine/threonine protein kinase inhibitors K252b, H7 and staurosporine, and the protein phosphatase 2A inhibitors okadaic acid and cantharidin, fed through the leaf petiole, did not have the effects on dark CO2 fixation predicted by a regulatory system in which PEPCase is modulated via reversible protein phosphorylation. Therefore, it is suggested that the diurnal modulation of PEP carboxylation in vivo in leaves and roots of pea is not caused by protein phosphorylation, but rather by direct allosteric effects. Upon transfer of plants to ammonium-N or to an N-free nutrient solution, mean daily malate levels in leaves decreased drastically within 4-5 d. At that time, the diurnal oscillations of PEP carboxylation in vivo disappeared and rates remained at the high light-level. The coincidence of the two events suggests that PEPCase was de

  10. Tissue-specific expression and post-translational modifications of plant- and bacterial-type phosphoenolpyruvate carboxylase isozymes of the castor oil plant, Ricinus communis L.

    PubMed Central

    O’Leary, Brendan; Fedosejevs, Eric T.; Hill, Allyson T.; Bettridge, James; Park, Joonho; Rao, Srinath K.; Leach, Craig A.; Plaxton, William C.

    2011-01-01

    This study employs transcript profiling together with immunoblotting and co-immunopurification to assess the tissue-specific expression, protein:protein interactions, and post-translational modifications (PTMs) of plant- and bacterial-type phosphoenolpyruvate carboxylase (PEPC) isozymes (PTPC and BTPC, respectively) in the castor plant, Ricinus communis. Previous studies established that the Class-1 PEPC (PTPC homotetramer) of castor oil seeds (COS) is activated by phosphorylation at Ser-11 and inhibited by monoubiquitination at Lys-628 during endosperm development and germination, respectively. Elimination of photosynthate supply to developing COS by depodding caused the PTPC of the endosperm and cotyledon to be dephosphorylated, and then subsequently monoubiquitinated in vivo. PTPC monoubiquitination rather than phosphorylation is widespread throughout the castor plant and appears to be the predominant PTM of Class-1 PEPC that occurs in planta. The distinctive developmental patterns of PTPC phosphorylation versus monoubiquitination indicates that these two PTMs are mutually exclusive. By contrast, the BTPC: (i) is abundant in the inner integument, cotyledon, and endosperm of developing COS, but occurs at low levels in roots and cotyledons of germinated COS, (ii) shows a unique developmental pattern in leaves such that it is present in leaf buds and young expanding leaves, but undetectable in fully expanded leaves, and (iii) tightly interacts with co-expressed PTPC to form the novel and allosterically-desensitized Class-2 PEPC heteromeric complex. BTPC and thus Class-2 PEPC up-regulation appears to be a distinctive feature of rapidly growing and/or biosynthetically active tissues that require a large anaplerotic flux from phosphoenolpyruvate to replenish tricarboxylic acid cycle C-skeletons being withdrawn for anabolism. PMID:21841182

  11. Tissue-specific expression and post-translational modifications of plant- and bacterial-type phosphoenolpyruvate carboxylase isozymes of the castor oil plant, Ricinus communis L.

    PubMed

    O'Leary, Brendan; Fedosejevs, Eric T; Hill, Allyson T; Bettridge, James; Park, Joonho; Rao, Srinath K; Leach, Craig A; Plaxton, William C

    2011-11-01

    This study employs transcript profiling together with immunoblotting and co-immunopurification to assess the tissue-specific expression, protein:protein interactions, and post-translational modifications (PTMs) of plant- and bacterial-type phosphoenolpyruvate carboxylase (PEPC) isozymes (PTPC and BTPC, respectively) in the castor plant, Ricinus communis. Previous studies established that the Class-1 PEPC (PTPC homotetramer) of castor oil seeds (COS) is activated by phosphorylation at Ser-11 and inhibited by monoubiquitination at Lys-628 during endosperm development and germination, respectively. Elimination of photosynthate supply to developing COS by depodding caused the PTPC of the endosperm and cotyledon to be dephosphorylated, and then subsequently monoubiquitinated in vivo. PTPC monoubiquitination rather than phosphorylation is widespread throughout the castor plant and appears to be the predominant PTM of Class-1 PEPC that occurs in planta. The distinctive developmental patterns of PTPC phosphorylation versus monoubiquitination indicates that these two PTMs are mutually exclusive. By contrast, the BTPC: (i) is abundant in the inner integument, cotyledon, and endosperm of developing COS, but occurs at low levels in roots and cotyledons of germinated COS, (ii) shows a unique developmental pattern in leaves such that it is present in leaf buds and young expanding leaves, but undetectable in fully expanded leaves, and (iii) tightly interacts with co-expressed PTPC to form the novel and allosterically-desensitized Class-2 PEPC heteromeric complex. BTPC and thus Class-2 PEPC up-regulation appears to be a distinctive feature of rapidly growing and/or biosynthetically active tissues that require a large anaplerotic flux from phosphoenolpyruvate to replenish tricarboxylic acid cycle C-skeletons being withdrawn for anabolism.

  12. Enzymatic activity, gene expression and posttranslational modifications of photosynthetic and non-photosynthetic phosphoenolpyruvate carboxylase in ammonium-stressed sorghum plants.

    PubMed

    Arias-Baldrich, Cirenia; de la Osa, Clara; Bosch, Nadja; Ruiz-Ballesta, Isabel; Monreal, José A; García-Mauriño, Sofía

    2017-07-01

    Sorghum plants grown with 5mM (NH4)2SO4 showed symptoms of stress, such as reduced growth and photosynthesis, leaf chlorosis, and reddish roots. Phosphoenolpyruvate carboxylase (PEPC) activity, by supplying carbon skeletons for ammonium assimilation, plays a pivotal role in tolerance to ammonium stress. This work investigated the effect of ammonium nutrition on PPC and PPCK gene expression, on PEPC activity, and on post-translational modifications (PTMs) of PEPC in leaves and roots of sorghum plants. Ammonium increased PEPC kinase (PEPCk) activity and the phosphorylation state of PEPC in leaves, both in light and in the dark, due to increased PPCK1 expression in leaves. This result resembled the effect of salinity on sorghum leaf PEPC and PEPCk, which is thought to allow a better functioning of PEPC in conditions that limit the income of reduced C. In roots, ammonium increased PEPC activity and the amount of monoubiquitinated PEPC. The first effect was related to increased PPC3 expression in roots. These results highlight the relevance of this specific isoenzyme (PPC3) in sorghum responses to ammonium stress. Although the role of monoubiquitination is not fully understood, it also increased in germinating seeds along with massive mobilization of reserves, a process in which the anaplerotic function of PEPC is of major importance. Copyright © 2017 Elsevier GmbH. All rights reserved.

  13. Influence of NaCl on Growth, Proline, and Phosphoenolpyruvate Carboxylase Levels in Mesembryanthemum crystallinum Suspension Cultures 1

    PubMed Central

    Thomas, John C.; De Armond, Richard L.; Bohnert, Hans J.

    1992-01-01

    The facultative halophyte Mesembryanthemum crystallinum responds to salt stress by increasing the levels of phosphoenolpyruvate carboxylase (PEPCase) and other enzymes associated with Crassulacean acid metabolism. A more common response to salt stress in sensitive and tolerant species, including M. crystallinum, is the accumulation of proline. We have established M. crystallinum suspension cultures to investigate whether both these salt-induced responses occur at the cellular level. Leaf-and root-derived cultures maintain 5% of the total soluble amino acids as proline. Cell culture growth slows upon addition of 400 millimolar NaCl, and proline levels increase to 40% of the total soluble amino acids. These results suggest a functional salt-stress and response program in Mesembryanthemum cells. Suspension cultures grown with or without 400 millimolar NaCl have PEPCase levels that compare with those from roots and unstressed leaves. The predominant protein cross-reacting with an anti-PEPCase antibody corresponds to 105 kilodaltons (apparent molecular mass), whereas a second species of approximately 110 kilodaltons is present at low levels. In salt-stressed leaves, the 110 kilodalton protein is more prevalent. Levels of mRNA for both ppc1 (salt stress induced in leaves) and ppc2 (constitutive) genes in salt-treated suspensions cultures are equal to unstressed leaves, and only twice the levels found in untreated suspension cultures. Whereas cells accumulate proline in response to NaCl, PEPCase protein amounts remain similar in salt-treated and untreated cultures. The induction upon salt stress of the 110 kilodalton PEPCase protein and other Crassulacean acid metabolism enzymes in organized tissues is not observed in cell culture and may depend on tissue-dependent or photoautotrophy-dependent programs. ImagesFigure 4Figure 5 PMID:16668687

  14. Leaf Activities.

    ERIC Educational Resources Information Center

    Mingie, Walter

    Leaf activities can provide a means of using basic concepts of outdoor education to learn in elementary level subject areas. Equipment needed includes leaves, a clipboard with paper, and a pencil. A bag of leaves may be brought into the classroom if weather conditions or time do not permit going outdoors. Each student should pick a leaf, examine…

  15. [Functions of plant phosphoenolpyruvate carboxylase and its applications for genetic engineering].

    PubMed

    Wei, Shaowei; Li, Yin

    2011-12-01

    Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) is an important ubiquitous cytosol enzyme that fixes HCO3 together with phosphoenolpyruvate (PEP) and yields oxaloacetate that can be converted to intermediates of the citric acid cycle. In plant cells, PEPC participates in CO2 assimilation and other important metabolic pathways, and it has broad functions in different plant tissues. PEPC is also involved in the regulation of storage product synthesis and metabolism in seeds, such as affecting the metabolic fluxes from sugars/starch towards the synthesis of fatty acids or amino acids and proteins. In this review, we introduced the progress in classification, structure and regulation of PEPC in plant tissues. We discussed the potential applications of plant PEPCs in genetic engineering. The researches in functions and regulation mechanism of plant PEPCs will provide beneficial approaches to applications of plant PEPCs in high-yield crops breeding, energy crop and microbe genetic engineering.

  16. Metabolic engineering of Propionibacterium freudenreichii: effect of expressing phosphoenolpyruvate carboxylase on propionic acid production.

    PubMed

    Ammar, Ehab Mohamed; Jin, Ying; Wang, Zhongqiang; Yang, Shang-Tian

    2014-09-01

    Propionic acid is currently produced mainly via petrochemicals, but there is increasing interest in its fermentative production from renewable biomass. However, the current propionic acid fermentation process suffers from low product yield and productivity. In this work, the gene encoding phosphoenolpyruvate carboxylase (PPC) was cloned from Escherichia coli and expressed in Propionibacterium freudenreichii. PPC catalyzes the conversion of phosphoenolpyruvate to oxaloacetate with the fixation of one CO2. Its expression in P. freudenreichii showed profound effects on propionic acid fermentation. Compared to the wild type, the mutant expressing the ppc gene grew significantly faster, consumed more glycerol, and produced propionate to a higher final titer at a faster rate. The mutant also produced significantly more propionate from glucose under elevated CO2 partial pressure. These effects could be attributed to increased CO2 fixation and resulting changes in the flux distributions in the dicarboxylic acid pathway.

  17. Enzyme I facilitates reverse flux from pyruvate to phosphoenolpyruvate in Escherichia coli

    PubMed Central

    Long, Christopher P.; Au, Jennifer; Sandoval, Nicholas R.; Gebreselassie, Nikodimos A.; Antoniewicz, Maciek R.

    2017-01-01

    The bacterial phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) consists of cascading phosphotransferases that couple the simultaneous import and phosphorylation of a variety of sugars to the glycolytic conversion of phosphoenolpyruvate (PEP) to pyruvate. As the primary route of glucose uptake in E. coli, the PTS plays a key role in regulating central carbon metabolism and carbon catabolite repression, and is a frequent target of metabolic engineering interventions. Here we show that Enzyme I, the terminal phosphotransferase responsible for the conversion of PEP to pyruvate, is responsible for a significant in vivo flux in the reverse direction (pyruvate to PEP) during both gluconeogenic and glycolytic growth. We use 13C alanine tracers to quantify this back-flux in single and double knockouts of genes relating to PEP synthetase and PTS components. Our findings are relevant to metabolic engineering design and add to our understanding of gene-reaction connectivity in E. coli. PMID:28128209

  18. Crystallization and preliminary x-ray diffraction studies of C4-form phosphoenolpyruvate carboxylase from maize.

    PubMed

    Matsumura, H; Nagata, T; Terada, M; Shirakata, S; Inoue, T; Yoshinaga, T; Ueno, Y; Saze, H; Izui, K; Kai, Y

    1999-11-01

    Phosphoenolpyruvate carboxylase is a key enzyme in the fixation of atmospheric CO(2) in C(4) and crassulacean acid metabolism (CAM) plants. The enzyme catalyzes the irreversible carboxylation of phosphoenolpyruvate to form oxaloacetate and inorganic phosphate, the first committed step in the fixation of external CO(2) in these plants. The enzyme has been isolated from maize leaves and crystallized using the hanging-drop vapour-diffusion method with PEG 8000 as a precipitant at pH 7.5. The crystals belong to space group C222(1), with unit-cell dimensions a = 160.2, b = 175.6, c = 255.5 A, and diffract to 3.2 A resolution.

  19. Identification of a phosphoenolpyruvate:fructose 1-phosphotransferase system in Azospirillum brasilense.

    PubMed Central

    Gupta, K D; Ghosh, S

    1984-01-01

    An inducible phosphoenolpyruvate:fructose phosphotransferase system has been detected in Azospirillum brasilense, which requires a minimum of two components of the crude extracts for activity: (i) a soluble fraction (enzyme I) and (ii) a membrane fraction (enzyme II). The uninduced cells neither show any uptake of fructose nor express activity of either of these two enzyme fractions. C-1 of fructose is the site of phosphorylation. This phosphotransferase system does not accept glucose as a substrate for phosphorylation. PMID:6501230

  20. Phosphoenolpyruvate Phosphomutase Activity in an l-Phosphonoalanine-Mineralizing Strain of Burkholderia cepacia

    PubMed Central

    Ternan, Nigel G.; McGrath, John W.; Quinn, John P.

    1998-01-01

    A strain of Burkholderia cepacia isolated by enrichment culture utilized l-2-amino-3-phosphonopropionic acid (phosphonoalanine) at concentrations up to 20 mM as a carbon, nitrogen, and phosphorus source in a phosphate-insensitive manner. Cells contained phosphoenolpyruvate phosphomutase activity, presumed to be responsible for cleavage of the C—P bond of phosphonopyruvate, the transamination product of l-phosphonoalanine; this was inducible in the presence of phosphonoalanine. PMID:9603854

  1. CO2-fixing enzymes and phosphoenolpyruvate metabolism in the fish parasite Hysterothylacium aduncum (Ascaridoidea, Anisakidae).

    PubMed

    Malagón, David; Benítez, Rocio; Valero, Adela; Adroher, Francisco Javier

    2009-07-23

    CO2 stimulates the development of many of the intestinal helminths that are able to fix CO2 by means of phosphoenolpyruvate carboxykinase (PEPCK), such as Hysterothylacium aduncum. We determined the activity of CO2-fixing enzymes such as PEPCK and phosphoenolpyruvate carboxylase (PEPC), although no significant activity was detected for pyruvate carboxylase or carboxylating-malic enzyme. The former act on phosphoenolpyruvate (PEP) to yield oxalacetate. In the helminths studied, PEP has a vital role in glucidic metabolism. Consequently, we determined the activity of other enzymes involved in the crossroad of PEP, such as pyruvate kinase (PK), lactate dehydrogenase and malate dehydrogenase. All enzymes detected showed significant variations in activity during the in vitro development of the parasite from the third larval stage to mature adult. Fixing of CO2 by PEPCK decreased during development (from 228 to 115 nmol min(-1) mg(-1) protein), while that by PEPC increased (from 19 to 46 nmol min(-1) mg(-1) protein). This enzyme, which is rare in animals, could play a part in detecting levels of free phosphate, releasing it from PEP when required for processes such as glycogenolysis, glycolysis and adenosine 5'-triphosphate (ATP) synthesis. PK, which showed increasing activity during development up to immature adult (from 56 to 82 nmol min(-1) mg(-1) protein), could act in combination with PEPC to obtain energy in the cytosol (in the form of ATP) and in the mitochondria (possible destination of the pyruvate formed), compensating for the decrease in activity of PEPCK.

  2. Phosphorylation of streptozotocin during uptake via the phosphoenolpyruvate: sugar phosphotransferase system in Escherichia coli.

    PubMed Central

    Ammer, J; Brennenstuhl, M; Schindler, P; Höltje, J V; Zähner, H

    1979-01-01

    Mutants of Escherichia coli K-12, Staphylococcus aureus, and Bacillus subtilis defective in the general components (enzyme I, or HPr, or both) of the phosphoenolpyruvate:sugar phosphotransferase system are shown to be resistant to the antibiotic streptozotocin. It is shown here, employing 32P-labeled phosphoenolpyruvate, that wild-type cells of E. coli phosphorylate streptozotocin, whereas with a phosphotransferase system-defective mutant of E. coli the drug is recovered in an unaltered, free form. The internal accumulation of streptozotocin at the steady-state level was about 70 times that of the concentration in the external medium. The antibacterial action of streptozotocin, as well as the uptake of the drug, was inhibited by N-acetyl-D-glucosamine. The uptake of the antibiotic was extremely sensitive to p-chloromercuribenzoate. It is concluded that streptozotocin is taken up by E. coli via the phosphoenolpyruvate:sugar phosphotransferase system and consequently accumulates in the cell at first as streptozotocin-phosphate. PMID:161156

  3. Changes in hepatic messenger RNA for phosphoenolpyruvate carboxykinase (GTP) during development

    PubMed Central

    Ruiz, Josefa P. Garcia; Ingram, Robert; Hanson, Richard W.

    1978-01-01

    Phosphoenolpyruvate carboxykinase (GTP) [GTP;oxaloacetate carboxy-lyase(transphosphorylating); EC 4.1.1.32] is absent in rat liver cytosol during fetal life and is synthesized initially at birth. De novo synthesis of the enzyme can be induced prematurely by injection of dibutyryl cyclic AMP or glucagon into fetal animals in utero. In this study a wheat germ translation assay was used to quantitate the level of total functional mRNA for phosphoenolpyruvate carboxykinase in the liver of fetal rats at 21 days of pregnancy under different induction situations. The translatable mRNA for the enzyme was marginally detectable in fetal rat liver. Administration of either glucagon or dibutyryl cyclic AMP to fetal rats in utero caused a marked induction of functional mRNA for this enzyme. Three hours after administration of dibutyryl cyclic AMP, the level of translatable mRNA increased almost 23-fold, but by 6 hr the level dropped approximately 60%. Administration of actinomycin D prior to dibutyryl cyclic AMP in 21-day fetal rats prevented the appearance of newly synthesized poly(A)-containing RNA in the cytoplasm as well as the induction of translatable mRNA for phosphoenolpyruvate carboxykinase. In animals delivered prematurely and maintained for varying periods, the translatable mRNA for the enzyme accumulated in the liver at a rate comparable to that observed for enzyme synthesis. PMID:212740

  4. Characterization of Phosphoenolpyruvate Carboxykinase from Pineapple Leaves Ananas comosus (L.) Merr. 1

    PubMed Central

    Daley, Laurence S.; Ray, Thomas B.; Vines, H. Max; Black, Clanton C.

    1977-01-01

    Phosphoenolpyruvate carboxykinase has been partially purified from pineapple (Ananas comosus [L.]) leaves. Specific activities obtained show it to be a major activity in this tissue. Above 15 C, the respective activation energies for decarboxylation and carboxylation are 13 and 12 kcal/mol. Below 15 C, there are discontinuities in Arrhenius plots with an associated large increase in activation energy. The adenine nucleotides are preferred to other nucleotides as substrates. The apparent Km values in the carboxylation direction are: ADP 0.13 mm, HCO3- 3.4 mm, and phosphoenolpyruvate 5 mm. In the decarboxylation direction, the apparent Km values are: ATP 0.02 mm, ADP 0.05 mm, and oxaloacetate 0.4 mm. The decarboxylation activity had an almost equal velocity with either ADP or ATP. The pH optima are between 6.8 and 7. Inhibition of the carboxylation reaction by ATP, pyruvate, and carbonic anhydrase was demonstrated. Decarboxylase specific activities are over twice carboxylation activities. The data support a model in which phosphoenolpyruvate carboxykinase is of physiological significance only during the light period and then only as a decarboxylase. PMID:16659905

  5. High-Throughput Phenotyping of Maize Leaf Physiological and Biochemical Traits Using Hyperspectral Reflectance1[OPEN

    PubMed Central

    Yendrek, Craig R.; Tomaz, Tiago; Montes, Christopher M.; Cao, Youyuan; Morse, Alison M.; Brown, Patrick J.; McIntyre, Lauren M.; Leakey, Andrew D.B.

    2017-01-01

    High-throughput, noninvasive field phenotyping has revealed genetic variation in crop morphological, developmental, and agronomic traits, but rapid measurements of the underlying physiological and biochemical traits are needed to fully understand genetic variation in plant-environment interactions. This study tested the application of leaf hyperspectral reflectance (λ = 500–2,400 nm) as a high-throughput phenotyping approach for rapid and accurate assessment of leaf photosynthetic and biochemical traits in maize (Zea mays). Leaf traits were measured with standard wet-laboratory and gas-exchange approaches alongside measurements of leaf reflectance. Partial least-squares regression was used to develop a measure of leaf chlorophyll content, nitrogen content, sucrose content, specific leaf area, maximum rate of phosphoenolpyruvate carboxylation, [CO2]-saturated rate of photosynthesis, and leaf oxygen radical absorbance capacity from leaf reflectance spectra. Partial least-squares regression models accurately predicted five out of seven traits and were more accurate than previously used simple spectral indices for leaf chlorophyll, nitrogen content, and specific leaf area. Correlations among leaf traits and statistical inferences about differences among genotypes and treatments were similar for measured and modeled data. The hyperspectral reflectance approach to phenotyping was dramatically faster than traditional measurements, enabling over 1,000 rows to be phenotyped during midday hours over just 2 to 4 d, and offers a nondestructive method to accurately assess physiological and biochemical trait responses to environmental stress. PMID:28049858

  6. High-Throughput Phenotyping of Maize Leaf Physiological and Biochemical Traits Using Hyperspectral Reflectance.

    PubMed

    Yendrek, Craig R; Tomaz, Tiago; Montes, Christopher M; Cao, Youyuan; Morse, Alison M; Brown, Patrick J; McIntyre, Lauren M; Leakey, Andrew D B; Ainsworth, Elizabeth A

    2017-01-01

    High-throughput, noninvasive field phenotyping has revealed genetic variation in crop morphological, developmental, and agronomic traits, but rapid measurements of the underlying physiological and biochemical traits are needed to fully understand genetic variation in plant-environment interactions. This study tested the application of leaf hyperspectral reflectance (λ = 500-2,400 nm) as a high-throughput phenotyping approach for rapid and accurate assessment of leaf photosynthetic and biochemical traits in maize (Zea mays). Leaf traits were measured with standard wet-laboratory and gas-exchange approaches alongside measurements of leaf reflectance. Partial least-squares regression was used to develop a measure of leaf chlorophyll content, nitrogen content, sucrose content, specific leaf area, maximum rate of phosphoenolpyruvate carboxylation, [CO2]-saturated rate of photosynthesis, and leaf oxygen radical absorbance capacity from leaf reflectance spectra. Partial least-squares regression models accurately predicted five out of seven traits and were more accurate than previously used simple spectral indices for leaf chlorophyll, nitrogen content, and specific leaf area. Correlations among leaf traits and statistical inferences about differences among genotypes and treatments were similar for measured and modeled data. The hyperspectral reflectance approach to phenotyping was dramatically faster than traditional measurements, enabling over 1,000 rows to be phenotyped during midday hours over just 2 to 4 d, and offers a nondestructive method to accurately assess physiological and biochemical trait responses to environmental stress. © 2017 American Society of Plant Biologists. All Rights Reserved.

  7. Project LEAF

    EPA Pesticide Factsheets

    Project LEAF has a goal of educating farmworkers about how to reduce pesticide exposure to their families from pesticide residues they may be inadvertently taking home on their clothing, etc. Find outreach materials.

  8. Stimulation of phosphoenolpyruvate carboxykinase (guanosine triphosphate) activity by low concentrations of circulating glucose in perfused rat liver.

    PubMed Central

    Moreno, F J; Sánchez-Urrutia, L; Medina, J M; Sánchez-Medina, F; Mayor, F

    1975-01-01

    1. After nicotinic acid treatment, rat liver glycogen is depleted and phosphoenolpyruvate carboxykinase activity increased, to about twice the initial value. 2. The increase in phosphoenolpyruvate carboxykinase activity promoted by nicotinic acid is prevented by cycloheximide or actinomycin D, suggesting that this effect is produced by synthesis of the enzyme de novo. 3. Despite the enhancement of phosphoenolpyruvate carboxykinase activity and glycogen depletion, which occurs 5h after the injection of nicotinic acid, the gluconeogenic capacity of liver is low and considerably less than the values found in rats starved for 48h. 4. When the livers of well-fed rats are perfused in the presence of low concentrations of glucose, the activity of phosphoenolpyruvate carboxykinase significantly increases compared with the control. 5. This increase is not related to the glycogen content, but seems to be also the result of synthesis of the enzyme de novo, since this effect is counteracted by previous treatment with cycloheximide or actinomycin D. 6. Phosphoenolpyruvate carboxykinase activity is not increased in the presence of low concentrations of circulating glucose when 40 mM-imidazole (an activator of phosphodiesterase) is added to the perfusion medium. 7. Addition of dibutyryl cyclic AMP to the perfusion medium results in an increase in phosphoenolpyruvate carboxykinase activity, in spite of the presence of normal concentrations of circulating glucose. On the other hand, the concentration of cyclic AMP in the liver increases when that of glucose in the medium is low. 8. These results suggest that, in the absence of hormonal factors, the regulation of phosphoenolpyruvate carboxykinase can be accomplished by glucose itself, inadequate concentrations of it resulting in the induction of the enzyme. The mediator in this regulation, as in hormonal regulation, seems to be cyclic AMP. PMID:173301

  9. Light Moderates the Induction of Phosphoenolpyruvate Carboxylase by NaCl and Abscisic Acid in Mesembryanthemum crystallinum 1

    PubMed Central

    McElwain, Elizabeth F.; Bohnert, Hans J.; Thomas, John C.

    1992-01-01

    In Mesembryanthemum crystallinum, phosphoenolpyruvate carboxylase is synthesized de novo in response to osmotic stress, as part of the switch from C3-photosynthesis to Crassulacean acid metabolism. To better understand the environmental signals involved in this pathway, we have investigated the effects of light on the induced expression of phosphoenolpyruvate carboxylase mRNA and protein in response to stress by 400 millimolar NaCl or 10 micromolar abscisic acid in hydroponically grown plants. When plants were grown in high-intensity fluorescent or incandescent light (850 microeinsteins per square meter per second), NaCl and abscisic acid induced approximately an eightfold accumulation of phosphoenolpyruvate carboxylase mRNA when compared to untreated controls. Levels of phosphoenolpyruvate carboxylase protein were high in these abscisic acid- and NaCl-treated plants, and detectable in the unstressed control. Growth in high-intensity incandescent (red) light resulted in approximately twofold higher levels of phosphoenolpyruvate carboxylase mRNA in the untreated plants when compared to control plants grown in high-intensity fluorescent light. In low light (300 microeinsteins per square meter per second fluorescent), only NaCl induced mRNA levels significantly above the untreated controls. Low light grown abscisic acid- and NaCl-treated plants contained a small amount of phosphoenolpyruvate carboxylase protein, whereas the (untreated) control plants did not contain detectable amounts of phosphoenolpyruvate carboxylase. Environmental stimuli, such as light and osmotic stress, exert a combined effect on gene expression in this facultative halophyte. ImagesFigure 1Figure 2 PMID:16668999

  10. Leaf Development

    PubMed Central

    Tsukaya, Hirokazu

    2002-01-01

    The shoot system is the basic unit of development of seed plants and is composed of a leaf, a stem, and a lateral bud that differentiates into a lateral shoot. The most specialized organ in angiosperms, the flower, can be considered to be part of the same shoot system since floral organs, such as the sepal, petal, stamen, and carpel, are all modified leaves. Scales, bracts, and certain kinds of needle are also derived from leaves. Thus, an understanding of leaf development is critical to an understanding of shoot development. Moreover, leaves play important roles in photosynthesis, respiration and photoperception. Thus, a full understanding of leaves is directly related to a full understanding of seed plants. The details of leaf development remain unclear. The difficulties encountered in studies of leaf development, in particular in dicotyledonous plants such as Arabidopsis thaliana (L.) Henyn., are derived from the complex process of leaf development, during which the division and elongation of cells occur at the same time and in the same region of the leaf primordium (Maksymowych, 1963; Poethig and Sussex, 1985). Thus, we cannot divide the entire process into unit processes in accordance with the tenets of classical anatomy. Genetic approaches in Arabidopsis, a model plant (Meyerowitz and Pruitt, 1985), have provided a powerful tool for studies of mechanisms of leaf development in dicotyledonous plants, and various aspects of the mechanisms that control leaf development have been revealed in recent developmental and molecular genetic studies of Arabidopsis (for reviews, see Tsukaya, 1995 and 1998; Van Lijsebettens and Clarke, 1998; Sinha, 1999; Van Volkenburgh, 1999; Tsukaya, 2000; Byrne et al., 2001; Dengler and Kang, 2001; Dengler and Tsukaya, 2001; Tsukaya, 2001). In this review, we shall examine the information that is currently available about various mechanisms of leaf development in Arabidopsis. Vascular patterning is also an important factor in the

  11. Leaf Development

    PubMed Central

    2013-01-01

    Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

  12. Discovery of PPi-type Phosphoenolpyruvate Carboxykinase Genes in Eukaryotes and Bacteria.

    PubMed

    Chiba, Yoko; Kamikawa, Ryoma; Nakada-Tsukui, Kumiko; Saito-Nakano, Yumiko; Nozaki, Tomoyoshi

    2015-09-25

    Phosphoenolpyruvate carboxykinase (PEPCK) is one of the pivotal enzymes that regulates the carbon flow of the central metabolism by fixing CO2 to phosphoenolpyruvate (PEP) to produce oxaloacetate or vice versa. Whereas ATP- and GTP-type PEPCKs have been well studied, and their protein identities are established, inorganic pyrophosphate (PPi)-type PEPCK (PPi-PEPCK) is poorly characterized. Despite extensive enzymological studies, its protein identity and encoding gene remain unknown. In this study, PPi-PEPCK has been identified for the first time from a eukaryotic human parasite, Entamoeba histolytica, by conventional purification and mass spectrometric identification of the native enzyme, followed by demonstration of its enzymatic activity. A homolog of the amebic PPi-PEPCK from an anaerobic bacterium Propionibacterium freudenreichii subsp. shermanii also exhibited PPi-PEPCK activity. The primary structure of PPi-PEPCK has no similarity to the functional homologs ATP/GTP-PEPCKs and PEP carboxylase, strongly suggesting that PPi-PEPCK arose independently from the other functional homologues and very likely has unique catalytic sites. PPi-PEPCK homologs were found in a variety of bacteria and some eukaryotes but not in archaea. The molecular identification of this long forgotten enzyme shows us the diversity and functional redundancy of enzymes involved in the central metabolism and can help us to understand the central metabolism more deeply. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. Inhibition of Pig Phosphoenolpyruvate Carboxykinase Isoenzymes by 3-Mercaptopicolinic Acid and Novel Inhibitors.

    PubMed

    Hidalgo, Jorge; Latorre, Pedro; Carrodeguas, José Alberto; Velázquez-Campoy, Adrián; Sancho, Javier; López-Buesa, Pascual

    2016-01-01

    There exist two isoforms of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in pig populations that differ in a single amino acid (Met139Leu). The isoenzymes have different kinetic properties, affecting more strongly the Km and Vmax of nucleotides. They are associated to different phenotypes modifying traits of considerable economic interest. In this work we use inhibitors of phosphoenolpyruvate carboxykinase activity to search for further differences between these isoenzymes. On the one hand we have used the well-known inhibitor 3-mercaptopicolinic acid. Its inhibition patterns were the same for both isoenzymes: a three-fold decrease of the Ki values for GTP in 139Met and 139Leu (273 and 873 μM, respectively). On the other hand, through screening of a chemical library we have found two novel compounds with inhibitory effects of a similar magnitude to that of 3-mercaptopicolinic acid but with less solubility and specificity. One of these novel compounds, (N'1-({5-[1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-2-thienyl}methylidene)-2,4-dichlorobenzene-1-carbohydrazide), exhibited significantly different inhibitory effects on either isoenzyme: it enhanced threefold the apparent Km value for GTP in 139Met, whereas in 139Leu, it reduced it from 99 to 69 μM. The finding of those significant differences in the binding of GTP reinforces the hypothesis that the Met139Leu substitution affects strongly the nucleotide binding site of PEPCK-C.

  14. Inhibition of Pig Phosphoenolpyruvate Carboxykinase Isoenzymes by 3-Mercaptopicolinic Acid and Novel Inhibitors

    PubMed Central

    Hidalgo, Jorge; Latorre, Pedro; Carrodeguas, José Alberto; Velázquez-Campoy, Adrián; Sancho, Javier; López-Buesa, Pascual

    2016-01-01

    There exist two isoforms of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in pig populations that differ in a single amino acid (Met139Leu). The isoenzymes have different kinetic properties, affecting more strongly the Km and Vmax of nucleotides. They are associated to different phenotypes modifying traits of considerable economic interest. In this work we use inhibitors of phosphoenolpyruvate carboxykinase activity to search for further differences between these isoenzymes. On the one hand we have used the well-known inhibitor 3-mercaptopicolinic acid. Its inhibition patterns were the same for both isoenzymes: a three-fold decrease of the Ki values for GTP in 139Met and 139Leu (273 and 873 μM, respectively). On the other hand, through screening of a chemical library we have found two novel compounds with inhibitory effects of a similar magnitude to that of 3-mercaptopicolinic acid but with less solubility and specificity. One of these novel compounds, (N'1-({5-[1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-2-thienyl}methylidene)-2,4-dichlorobenzene-1-carbohydrazide), exhibited significantly different inhibitory effects on either isoenzyme: it enhanced threefold the apparent Km value for GTP in 139Met, whereas in 139Leu, it reduced it from 99 to 69 μM. The finding of those significant differences in the binding of GTP reinforces the hypothesis that the Met139Leu substitution affects strongly the nucleotide binding site of PEPCK-C. PMID:27391465

  15. Partitioning of Nitrogen among Ribulose-1,5-bisphosphate Carboxylase/Oxygenase, Phosphoenolpyruvate Carboxylase, and Pyruvate Orthophosphate Dikinase as Related to Biomass Productivity in Maize Seedlings 1

    PubMed Central

    Sugiyama, Tatsuo; Mizuno, Masuhiko; Hayashi, Masanori

    1984-01-01

    Maize (Zea mays L. cv Golden Cross Bantam T51) seedlings were grown under full sunlight or 50% sunlight in a temperature-controlled glasshouse at the temperatures of near optimum (30/25°C) and suboptimum (17/13°C) with seven levels of nitrate-N (0.4 to 12 millimolars). The contents of phosphoenolpyruvate carboxylase (PEPC), pyruvate orthophosphate dikinase (PPD), and ribulose-1,5-P2 carboxylase/oxygenase (RuBisCO) were immunochemically determined for each treatment with rabbit antibodies raised against the respective maize leaf proteins (anti-PEPC and anti-PPD) or spinach leaf protein (anti-RuBisCO). The content of each enzymic protein increased with increasing N and raised under reduced temperature. The positive effect of light intensity on their contents was evident only at near optimal temperature. The relative increase in PEPC and PPD content with increasing N was significantly greater than that of RuBisCO irrespective of growth conditions. These enzymic proteins comprised about 8, 6, and 35% of total soluble protein, respectively, at near optimal growth condition. In contrast to significant increase in the proportion of soluble protein allocated to PEPC and PPD seen under certain conditions, the proportion allocated to RuBisCO decreased reciprocally with an increased biomass yield by N supply. These results indicated that the levels of PEPC and PPD parallel to maize biomass more tightly than that of RuBisCO at least under near optimal growth condition. Images Fig. 2 PMID:16663684

  16. Expression of phosphoenolpyruvate carboxykinase linked to chemoradiation susceptibility of human colon cancer cells

    PubMed Central

    2014-01-01

    Background Resistance to 5-fluorouracil (5-FU) in patients with colorectal cancer prevents effective treatment and leads to unnecessary and burdensome chemotherapy. Therefore, prediction of 5-FU resistance is imperative. Methods To identify the proteins linked to 5-FU resistance, two-dimensional gel electrophoresis-based proteomics was performed using the human colon cancer cell line SNU-C4R with induced 5-FU resistance. Proteins showing altered expression in SNU-C4R were identified by matrix-associated laser desorption/ionization–time-of-flight analysis, and their roles in susceptibility to 5-FU or radiation were evaluated in various cell lines by transfection of specific siRNA or creation of overexpression constructs. Changes in cellular signaling and expression of mitochondrial apoptotic factors were investigated by Western Blot analysis. A mitochondrial membrane potential probe (JC-1 dye) and a flow cytometry system were employed to determine the mitochondrial membrane potential. Finally, protein levels were determined by Western Blot analysis in tissues from 122 patients with rectal cancer to clarify whether each identified protein is a useful predictor of a chemoradiation response. Results We identified mitochondrial phosphoenolpyruvate carboxykinase (mPEPCK) as a candidate predictor of 5-FU resistance. PEPCK was downregulated in SNU-C4R compared with its parent cell line SNU-C4. Overexpression of mPEPCK did not significantly alter the susceptibility to either 5-FU or radiation. Suppression of mPEPCK led to a decrease in both the cellular level of phosphoenolpyruvate and the susceptibility to 5-FU and radiation. Furthermore, the cellular levels of phosphoenolpyruvate (an end product of PEPCK and a substrate of pyruvate kinase), phosphorylated AKT, and phosphorylated 4EBP1 were decreased significantly secondary to the mPEPCK suppression in SNU-C4. However, mPEPCK siRNA transfection induced changes in neither the mitochondrial membrane potential nor the

  17. Evidence for a Phosphoenolpyruvate-Dependent Sugar Phosphotransferase in Mycoplasma Strain Y

    PubMed Central

    Van Demark, P. J.; Plackett, P.

    1972-01-01

    The uptake of 14C-α-methyl-d-glucoside (αMG) by washed cells of Mycoplasma strain Y was found to be dependent on the supply of metabolic energy. Glycerol or d-mannose, but not l-lactate, would serve as an energy source. Uptake was inhibited by fluoride, iodoacetate, and arsenate, but not by 2,4-dinitrophenol. d-Glucose was inhibitory, presumably by competing for the transport system. The initial product of accumulation had the properties of a phosphate ester of αMG. The proportion of free αMG in the cells increased with time, until a steady state was reached in which uptake was balanced by the efflux of free αMG from the cells. Broken-cell preparations catalyzed a phosphoenolpyruvate-dependent phosphorylation of αMG and of d-glucose. PMID:5053467

  18. The Phosphoenolpyruvate:Sugar Phosphotransferase System Is Involved in Sensitivity to the Glucosylated Bacteriocin Sublancin

    PubMed Central

    Garcia De Gonzalo, C. V.; Denham, E. L.; Mars, R. A. T.; Stülke, J.

    2015-01-01

    The mode of action of a group of glycosylated antimicrobial peptides known as glycocins remains to be elucidated. In the current study of one glycocin, sublancin, we identified the phosphoenolpyruvate:sugar phosphotransferase system (PTS) of Bacillus species as a key player in bacterial sensitivity. Sublancin kills several Gram-positive bacteria, such as Bacillus species and Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). Unlike other classes of bacteriocins for which the PTS is involved in their mechanism of action, we show that the addition of PTS-requiring sugars leads to increased resistance rather than increased sensitivity, suggesting that sublancin has a distinct mechanism of action. Collectively, our present mutagenesis and genomic studies demonstrate that the histidine-containing phosphocarrier protein (HPr) and domain A of enzyme II (PtsG) in particular are critical determinants for bacterial sensitivity to sublancin. PMID:26282429

  19. Location and characterization of two widely separated glucocorticoid response elements in the phosphoenolpyruvate carboxykinase gene

    SciTech Connect

    Petersen, D.D.; Magnuson, M.A.; Granner, D.K.

    1988-01-01

    Chimeric genes were constructed by fusion of various regions of the 5'-flanking sequence from the phosphoenolpyruvate carboxykinase (GTP) (PEPCK) gene to the chloramphenicol acetyltransferase-coding sequence and to simian virus 40 splice and polyadenylation sequences. These were used to demonstrate that two glucocorticoid regulatory elements (GREs) combine to confer glucocorticoid responsiveness upon the PEPCK gene in H4IIE hepatoma cells. Both elements, distal one whose 5' boundary is located between -1264 and -1111 base pairs and a proximal one located between -468 and -420 base pairs relative to the transcription initiation site, act independently, in various positions and orientations, and upon the heterologous thymidine kinase promoter. Each element accounts for half of the maximal response of the chimeric genes. Therefore, two widely separated enhancerlike elements contribute equally to the response of the PEPCK gene to glucocorticoid hormones. Neither of the PEPCK GREs contains the TGTTCT consensus sequence associated with most other GREs.

  20. Cloning, sequencing, and overexpression of the Anaerobiospirillum succiniciproducens phosphoenolpyruvate carboxykinase (pckA) gene.

    PubMed Central

    Laivenieks, M; Vieille, C; Zeikus, J G

    1997-01-01

    The phosphoenolpyruvate (PEP) carboxykinase-encoding gene from the anaerobic, CO2-fixing, succinate-producing bacterium Anaerobiospirillum succiniciproducens was cloned, sequenced, and expressed in Escherichia coli. The gene encoded a 532-residue polypeptide with a calculated molecular mass of 58.7 kDa. The sequence of the A. succiniciproducens PEP carboxykinase was similar to those of all known ATP/ADP-dependent PEP carboxykinases. In particular, the A. succiniciproducens enzyme was 67.3% identical and 79.2% similar to the E. coli enzyme. The A. succiniciproducens pckA transcription start site was determined, and putative promoter regions were identified. The recombinant enzyme was overexpressed in E. coli. The purified enzyme was indiscernible from the native enzyme by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had the same activity as the native enzyme. PMID:9172347

  1. Location and characterization of two widely separated glucocorticoid response elements in the phosphoenolpyruvate carboxykinase gene.

    PubMed Central

    Petersen, D D; Magnuson, M A; Granner, D K

    1988-01-01

    Chimeric genes were constructed by fusion of various regions of the 5'-flanking sequence from the phosphoenolpyruvate carboxykinase (GTP) (PEPCK) gene to the chloramphenicol acetyltransferase-coding sequence and to simian virus 40 splice and polyadenylation sequences. These were used to demonstrate that two glucocorticoid regulatory elements (GREs) combine to confer glucocorticoid responsiveness upon the PEPCK gene in H4IIE hepatoma cells. Both elements, a distal one whose 5' boundary is located between -1264 and -1111 base pairs and a proximal one located between -468 and -420 base pairs relative to the transcription initiation site, act independently, in various positions and orientations, and upon the heterologous thymidine kinase promoter. Each element accounts for half of the maximal response of the chimeric genes. Therefore, two widely separated enhancerlike elements contribute equally to the response of the PEPCK gene to glucocorticoid hormones. Neither of the PEPCK GREs contains the TGTTCT consensus sequence associated with most other GREs. Images PMID:3422101

  2. Reticulate leaves and stunted roots are independent phenotypes pointing at opposite roles of the phosphoenolpyruvate/phosphate translocator defective in cue1 in the plastids of both organs

    PubMed Central

    Staehr, Pia; Löttgert, Tanja; Christmann, Alexander; Krueger, Stephan; Rosar, Christian; Rolčík, Jakub; Novák, Ondřej; Strnad, Miroslav; Bell, Kirsten; Weber, Andreas P. M.; Flügge, Ulf-Ingo; Häusler, Rainer E.

    2014-01-01

    Phosphoenolpyruvate (PEP) serves not only as a high energy carbon compound in glycolysis, but it acts also as precursor for plastidial anabolic sequences like the shikimate pathway, which produces aromatic amino acids (AAA) and subsequently secondary plant products. After conversion to pyruvate, PEP can also enter de novo fatty acid biosynthesis, the synthesis of branched-chain amino acids, and the non-mevalonate way of isoprenoid production. As PEP cannot be generated by glycolysis in chloroplasts and a variety of non-green plastids, it has to be imported from the cytosol by a phosphate translocator (PT) specific for PEP (PPT). A loss of function of PPT1 in Arabidopsis thaliana results in the chlorophyll a/b binding protein underexpressed1 (cue1) mutant, which is characterized by reticulate leaves and stunted roots. Here we dissect the shoot- and root phenotypes, and also address the question whether or not long distance signaling by metabolites is involved in the perturbed mesophyll development of cue1. Reverse grafting experiments showed that the shoot- and root phenotypes develop independently from each other, ruling out long distance metabolite signaling. The leaf phenotype could be transiently modified even in mature leaves, e.g. by an inducible PPT1RNAi approach or by feeding AAA, the cytokinin trans-zeatin (tZ), or the putative signaling molecule dehydrodiconiferyl alcohol glucoside (DCG). Hormones, such as auxins, abscisic acid, gibberellic acid, ethylene, methyl jasmonate, and salicylic acid did not rescue the cue1 leaf phenotype. The low cell density1 (lcd1) mutant shares the reticulate leaf-, but not the stunted root phenotype with cue1. It could neither be rescued by AAA nor by tZ. In contrast, tZ and AAA further inhibited root growth both in cue1 and wild-type plants. Based on our results, we propose a model that PPT1 acts as a net importer of PEP into chloroplast, but as an overflow valve and hence exporter in root plastids. PMID:24782872

  3. Species having C4 single-cell-type photosynthesis in the Chenopodiaceae family evolved a photosynthetic phosphoenolpyruvate carboxylase like that of Kranz-type C4 species.

    PubMed

    Lara, María Valeria; Chuong, Simon D X; Akhani, Hossein; Andreo, Carlos Santiago; Edwards, Gerald E

    2006-10-01

    Spatial and temporal regulation of phosphoenolpyruvate carboxylase (PEPC) is critical to the function of C(4) photosynthesis. The photosynthetic isoform of PEPC in the cytosol of mesophyll cells in Kranz-type C(4) photosynthesis has distinctive kinetic and regulatory properties. Some species in the Chenopodiaceae family perform C(4) photosynthesis without Kranz anatomy by spatial separation of initial fixation of atmospheric CO(2) via PEPC from C(4) acid decarboxylation and CO(2) donation to Rubisco within individual chlorenchyma cells. We studied molecular and functional features of PEPC in two single-cell functioning C(4) species (Bienertia sinuspersici, Suaeda aralocaspica) as compared to Kranz type (Haloxylon persicum, Salsola richteri, Suaeda eltonica) and C(3) (Suaeda linifolia) chenopods. It was found that PEPC from both types of C(4) chenopods displays higher specific activity than that of the C(3) species and shows kinetic and regulatory characteristics similar to those of C(4) species in other families in that they are subject to light/dark regulation by phosphorylation and display differential malate sensitivity. Also, the deduced amino acid sequence from leaf cDNA indicates that the single-cell functioning C(4) species possesses a Kranz-type C(4) isoform with a Ser in the amino terminal. A phylogeny of PEPC shows that isoforms in the two single-cell functioning C(4) species are in a clade with the C(3) and Kranz C(4) Suaeda spp. with high sequence homology. Overall, this study indicates that B. sinuspersici and S. aralocaspica have a C(4)-type PEPC similar to that in Kranz C(4) plants, which likely is required for effective function of C(4) photosynthesis.

  4. Discrimination in the Dark. Resolving the Interplay between Metabolic and Physical Constraints to Phosphoenolpyruvate Carboxylase Activity during the Crassulacean Acid Metabolism Cycle1

    PubMed Central

    Griffiths, Howard; Cousins, Asaph B.; Badger, Murray R.; von Caemmerer, Susanne

    2007-01-01

    A model defining carbon isotope discrimination (Δ13C) for crassulacean acid metabolism (CAM) plants was experimentally validated using Kalanchoe daigremontiana. Simultaneous measurements of gas exchange and instantaneous CO2 discrimination (for 13C and 18O) were made from late photoperiod (phase IV of CAM), throughout the dark period (phase I), and into the light (phase II). Measurements of CO2 response curves throughout the dark period revealed changing phosphoenolpyruvate carboxylase (PEPC) capacity. These systematic changes in PEPC capacity were tracked by net CO2 uptake, stomatal conductance, and online Δ13C signal; all declined at the start of the dark period, then increased to a maximum 2 h before dawn. Measurements of Δ13C were higher than predicted from the ratio of intercellular to external CO2 (pi/pa) and fractionation associated with CO2 hydration and PEPC carboxylations alone, such that the dark period mesophyll conductance, gi, was 0.044 mol m−2 s−1 bar−1. A higher estimate of gi (0.085 mol m−2 s−1 bar−1) was needed to account for the modeled and measured Δ18O discrimination throughout the dark period. The differences in estimates of gi from the two isotope measurements, and an offset of −5.5‰ between the 18O content of source and transpired water, suggest spatial variations in either CO2 diffusion path length and/or carbonic anhydrase activity, either within individual cells or across a succulent leaf. Our measurements support the model predictions to show that internal CO2 diffusion limitations within CAM leaves increase Δ13C discrimination during nighttime CO2 fixation while reducing Δ13C during phase IV. When evaluating the phylogenetic distribution of CAM, carbon isotope composition will reflect these diffusive limitations as well as relative contributions from C3 and C4 biochemistry. PMID:17142488

  5. Discrimination in the dark. Resolving the interplay between metabolic and physical constraints to phosphoenolpyruvate carboxylase activity during the crassulacean acid metabolism cycle.

    PubMed

    Griffiths, Howard; Cousins, Asaph B; Badger, Murray R; von Caemmerer, Susanne

    2007-02-01

    A model defining carbon isotope discrimination (delta13C) for crassulacean acid metabolism (CAM) plants was experimentally validated using Kalanchoe daigremontiana. Simultaneous measurements of gas exchange and instantaneous CO2 discrimination (for 13C and 18O) were made from late photoperiod (phase IV of CAM), throughout the dark period (phase I), and into the light (phase II). Measurements of CO2 response curves throughout the dark period revealed changing phosphoenolpyruvate carboxylase (PEPC) capacity. These systematic changes in PEPC capacity were tracked by net CO2 uptake, stomatal conductance, and online delta13C signal; all declined at the start of the dark period, then increased to a maximum 2 h before dawn. Measurements of delta13C were higher than predicted from the ratio of intercellular to external CO2 (p(i)/p(a)) and fractionation associated with CO2 hydration and PEPC carboxylations alone, such that the dark period mesophyll conductance, g(i), was 0.044 mol m(-2) s(-1) bar(-1). A higher estimate of g(i) (0.085 mol m(-2) s(-1) bar(-1)) was needed to account for the modeled and measured delta18O discrimination throughout the dark period. The differences in estimates of g(i) from the two isotope measurements, and an offset of -5.5 per thousand between the 18O content of source and transpired water, suggest spatial variations in either CO2 diffusion path length and/or carbonic anhydrase activity, either within individual cells or across a succulent leaf. Our measurements support the model predictions to show that internal CO2 diffusion limitations within CAM leaves increase delta13C discrimination during nighttime CO2 fixation while reducing delta13C during phase IV. When evaluating the phylogenetic distribution of CAM, carbon isotope composition will reflect these diffusive limitations as well as relative contributions from C3 and C4 biochemistry.

  6. LCE: Leaf carbon exchange dataset for tropical, temperate, and boreal species of North and Central America.

    PubMed

    Smith, Nicholas G; Dukes, Jeffrey S

    2017-08-20

    Leaf canopy carbon exchange processes, such as photosynthesis and respiration, are substantial components of the global carbon cycle. Climate models base their simulations of photosynthesis and respiration on an empirical understanding of the underlying biochemical processes, and the responses of those processes to environmental drivers. As such, data spanning large spatial scales are needed to evaluate and parameterize these models. Here, we present data on four important biochemical parameters defining leaf carbon exchange processes from 626 individuals of 98 species at 12 North and Central American sites spanning ~53° of latitude. The four parameters are the maximum rate of Rubisco carboxylation (Vcmax ), the maximum rate of electron transport for the regeneration of Ribulose-1,5,-bisphosphate (Jmax ), the maximum rate of phosphoenolpyruvate carboxylase carboxylation (Vpmax ), and leaf dark respiration (Rd ). The raw net photosynthesis by intercellular CO2 (A/Ci ) data used to calculate Vcmax , Jmax , and Vpmax rates are also presented. Data were gathered on the same leaf of each individual (one leaf per individual), allowing for the examination of each parameter relative to others. Additionally, the dataset contains a number of covariates for the plants measured. Covariate data include (a) leaf-level traits (leaf mass, leaf area, leaf nitrogen and carbon content, predawn leaf water potential), (b) plant-level traits (plant height for herbaceous individuals and diameter at breast height for trees), (c) soil moisture at the time of measurement, (d) air temperature from nearby weather stations for the day of measurement and each of the 90 days prior to measurement, and (e) climate data (growing season mean temperature, precipitation, photosynthetically active radiation, vapor pressure deficit, and aridity index). We hope that the data will be useful for obtaining greater understanding of the abiotic and biotic determinants of these important biochemical

  7. A Metabolic Widget Adjusts the Phosphoenolpyruvate-Dependent Fructose Influx in Pseudomonas putida

    PubMed Central

    Chavarría, Max; Goñi-Moreno, Ángel

    2016-01-01

    ABSTRACT Fructose uptake in the soil bacterium Pseudomonas putida occurs through a canonical phosphoenolpyruvate (PEP)-dependent sugar transport system (PTSFru). The logic of the genetic circuit that rules its functioning is puzzling: the transcription of the fruBKA operon, encoding all the components of PTSFru, can escape the repression exerted by the catabolite repressor/activator protein Cra solely in the presence of intracellular fructose-1-P, an agonist formed only when fructose has been already transported. To study this apparently incongruous regulatory architecture, the changes in the transcriptome brought about by a seamless Δcra deletion in P. putida strain KT2440 were inspected under different culture conditions. The few genes found to be upregulated in the cra mutant unexpectedly included PP_3443, encoding a bona fide glyceraldehyde-3-P dehydrogenase. An in silico model was developed to explore emergent properties that could result from such connections between sugar uptake with Cra and PEP. Simulation of fructose transport revealed that sugar uptake called for an extra supply of PEP (obtained through the activity of PP_3443) that was kept (i.e., memorized) even when the carbohydrate disappeared from the medium. This feature was traced to the action of two sequential inverters that connect the availability of exogenous fructose to intracellular PEP levels via Cra/PP_3443. The loss of such memory caused a much longer lag phase in cells shifted from one growth condition to another. The term “metabolic widget” is proposed to describe a merged biochemical and regulatory patch that tailors a given node of the cell molecular network to suit species-specific physiological needs. IMPORTANCE The regulatory nodes that govern metabolic traffic in bacteria often show connectivities that could be deemed unnecessarily complex at a first glance. Being a soil dweller and plant colonizer, Pseudomonas putida frequently encounters fructose in the niches that it

  8. AMP-activated protein kinase counteracted the inhibitory effect of glucose on the phosphoenolpyruvate carboxykinase gene expression in rat hepatocytes.

    PubMed

    Hubert, A; Husson, A; Chédeville, A; Lavoinne, A

    2000-09-22

    The effect of AMP-activated protein kinase (AMPK) in the regulation of the phosphoenolpyruvate carboxykinase (PEPCK) gene expression was studied in isolated rat hepatocytes. Activation of AMPK by AICAR counteracted the inhibitory effect of glucose on the PEPCK gene expression, both at the mRNA and the transcriptional levels. It is proposed that a target for AMPK is involved in the inhibitory effect of glucose on PEPCK gene transcription.

  9. An assessment of the capacity for phosphoenolpyruvate carboxykinase to contribute to C4 photosynthesis.

    PubMed

    Koteyeva, Nuria K; Voznesenskaya, Elena V; Edwards, Gerald E

    2015-06-01

    Three C4 acid decarboxylases, phosphoenolpyruvate carboxykinase (PEPCK), NADP-malic enzyme (NADP-ME), and NAD-malic enzyme (NAD-ME) were recruited from C3 plants to support C4 photosynthesis. In Poaceae, there are established lineages having PEPCK type species, and some NADP-ME lineages in which PEPCK contributes to C4. Besides family Poaceae, recently PEPCK has been reported to function in C4 photosynthesis in eudicot species including Cleome gynandra (Cleomaceae), Trianthema portulacastrum and Zaleya pentandra (Aizoaceae). We evaluated PEPCK by enzyme assay and western blots in representatives of Poaceae, Aizoaceae, Cleomaceae, and Chenopodiaceae compared to that in the PEPCK type C4 grass Spartina anglica. Eragrostis nutans was identified as the first NAD-ME type C4 grass having substantial amounts of PEPCK. In the eudicots, including C. gynandra, Cleome angustifolia, T. portulacastrum, Z. pentandra, and nine C4 members of family Chenopodiaceae (which has the most C4 species and diversity in forms among eudicot families), amounts of PEPCK were generally very low (barely detectable up to 4% of that in S. anglica). Based on these results, C4 species can be classified biochemically according to the dominant decarboxylase recruited for C4 function; and, Poaceae remains the only family in which PEPCK is known to have a significant role in C4 photosynthesis.

  10. Metal Ion Interactions with Phosphoenolpyruvate Carboxylase from Crassula argentea and Zea mays1

    PubMed Central

    Nguyen, Tien T.; Ngam-ek, Apinya; Jenkins, Joane; Grover, Scott D.

    1988-01-01

    Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C4 plant Zea mays were kinetically analyzed. Fe2+ and Cd2+ were found to be active metal cofactors along with the previously known active metals Mg2+, Mn2+, and Co2+. In studies with the Crassula enzyme, Mg2+ yielded the highest Vmax value but also generated the highest values of Km(metal) and Km(pep). For these five active metals lower Km(metal) values tended to be associated with lower Km(pep) values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 Å. Ca2+, Sr2+, Ba2+, and Ni2+ inhibited competitively with respect to Mg2+, whereas Be2+, Cu2+, Zn2+, and Pd2+ showed mixed-type inhibition. Vmax trends with the five active metals were similar for the C. argentea and Z. mays enzymes except that Cd2+ was less effective with the maize enzyme. Km(metal) values were 10- to 60-fold higher in the enzyme from Z. mays. PMID:16665847

  11. Nur77 suppresses hepatocellular carcinoma via switching glucose metabolism toward gluconeogenesis through attenuating phosphoenolpyruvate carboxykinase sumoylation

    PubMed Central

    Bian, Xue-li; Chen, Hang-zi; Yang, Peng-bo; Li, Ying-ping; Zhang, Fen-na; Zhang, Jia-yuan; Wang, Wei-jia; Zhao, Wen-xiu; Zhang, Sheng; Chen, Qi-tao; Zheng, Yu; Sun, Xiao-yu; Wang, Xiao-min; Chien, Kun-Yi; Wu, Qiao

    2017-01-01

    Gluconeogenesis, an essential metabolic process for hepatocytes, is downregulated in hepatocellular carcinoma (HCC). Here we show that the nuclear receptor Nur77 is a tumour suppressor for HCC that regulates gluconeogenesis. Low Nur77 expression in clinical HCC samples correlates with poor prognosis, and a Nur77 deficiency in mice promotes HCC development. Nur77 interacts with phosphoenolpyruvate carboxykinase (PEPCK1), the rate-limiting enzyme in gluconeogenesis, to increase gluconeogenesis and suppress glycolysis, resulting in ATP depletion and cell growth arrest. However, PEPCK1 becomes labile after sumoylation and is degraded via ubiquitination, which is augmented by the p300 acetylation of ubiquitin-conjugating enzyme 9 (Ubc9). Although Nur77 attenuates sumoylation and stabilizes PEPCK1 via impairing p300 activity and preventing the Ubc9-PEPCK1 interaction, Nur77 is silenced in HCC samples due to Snail-mediated DNA methylation of the Nur77 promoter. Our study reveals a unique mechanism to suppress HCC by switching from glycolysis to gluconeogenesis through Nur77 antagonism of PEPCK1 degradation. PMID:28240261

  12. Characterization of lysine acetylation of a phosphoenolpyruvate carboxylase involved in glutamate overproduction in Corynebacterium glutamicum.

    PubMed

    Nagano-Shoji, Megumi; Hamamoto, Yuma; Mizuno, Yuta; Yamada, Ayuka; Kikuchi, Masaki; Shirouzu, Mikako; Umehara, Takashi; Yoshida, Minoru; Nishiyama, Makoto; Kosono, Saori

    2017-03-03

    Protein Nε-acylation is emerging as a ubiquitous post-translational modification. In Corynebacterium glutamicum, which is utilized for industrial production of L-glutamate, the levels of protein acetylation and succinylation change drastically under the conditions that induce glutamate overproduction. Here, we characterized the acylation of phosphoenolpyruvate carboxylase (PEPC), an anaplerotic enzyme that supplies oxaloacetate for glutamate overproduction. We showed that acetylation of PEPC at lysine 653 decreased enzymatic activity, leading to reduced glutamate production. An acetylation-mimic (KQ) mutant of K653 showed severely reduced glutamate production, while the corresponding KR mutant showed normal production levels. Using an acetyllysine-incorporated PEPC protein, we verified that K653-acetylation negatively regulates PEPC activity. In addition, NCgl0616, a sirtuin-type deacetylase, deacetylated K653-acetylated PEPC in vitro. Interestingly, the specific activity of PEPC was increased during glutamate overproduction, which was blocked by the K653R mutation or deletion of sirtuin-type deacetylase homologues. These findings suggested that deacetylation of K653 by NCgl0616 likely plays a role in the activation of PEPC, which maintains carbon flux under glutamate-producing conditions. PEPC deletion increased protein acetylation levels in cells under glutamate-producing conditions, supporting our hypothesis that PEPC is responsible for a large carbon flux change under glutamate-producing conditions. This article is protected by copyright. All rights reserved.

  13. Trypanosoma evansi contains two auxiliary enzymes of glycolytic metabolism: Phosphoenolpyruvate carboxykinase and pyruvate phosphate dikinase.

    PubMed

    Rivero, Luz Amira; Concepción, Juan Luis; Quintero-Troconis, Ender; Quiñones, Wilfredo; Michels, Paul A M; Acosta, Héctor

    2016-06-01

    Trypanosoma evansi is a monomorphic protist that can infect horses and other animal species of economic importance for man. Like the bloodstream form of the closely related species Trypanosoma brucei, T. evansi depends exclusively on glycolysis for its free-energy generation. In T. evansi as in other kinetoplastid organisms, the enzymes of the major part of the glycolytic pathway are present within organelles called glycosomes, which are authentic but specialized peroxisomes. Since T. evansi does not undergo stage-dependent differentiations, it occurs only as bloodstream forms, it has been assumed that the metabolic pattern of this parasite is identical to that of the bloodstream form of T. brucei. However, we report here the presence of two additional enzymes, phosphoenolpyruvate carboxykinase and PPi-dependent pyruvate phosphate dikinase in T. evansi glycosomes. Their colocalization with glycolytic enzymes within the glycosomes of this parasite has not been reported before. Both enzymes can make use of PEP for contributing to the production of ATP within the organelles. The activity of these enzymes in T. evansi glycosomes drastically changes the model assumed for the oxidation of glucose by this parasite. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Molecular and biochemical characterization of phosphoenolpyruvate carboxykinase in the ruminal bacterium Ruminococcus albus.

    PubMed

    Asanuma, Narito; Yoshizawa, Kimio; Kanada, Kazuhiro; Hino, Tsuneo

    2009-05-01

    Molecular properties and transcriptional control of phosphoenolpyruvate carboxykinase (PCK; EC 4.1.1.32) in Ruminococcus albus were examined. The putative 537-amino acid PCK polypeptide has a predicted mass of 59.4 kDa and an isoelectric point of 4.82. RT-PCR and Northern blot analyses of pck mRNA suggest that the transcript is monocistronic and that pck transcription is not affected by changes in sugar sources present in growth medium. PCK enzymatic activity requires either Mg(2+) or Mn(2+) and an optimal pH of 7.0. R. albus PCK phosphorylated ADP more readily than GDP. Apparent K ( m ) values of PCK for PEP and ADP were considerably lower than those for OAA and ATP, suggesting that the reaction from PEP to OAA is favored in R. albus. The enzyme properties of PCK in R. albus appear to be more similar to Selenomonas ruminantium PCK than to Ruminococcus flavefacience, although R. albus and R. flavefacience belong to the same genus. The specific activity of PCK, representing the amount of enzyme per cell, in R. albus was much lower than that in S. ruminantium. The amount of succinate produced in R. albus from one unit of cellobiose was also much lower than the sum of succinate and propionate produced in S. ruminantium. Based on these results, we propose enhancement of PCK activity by stimulating PCK transcription as a method to decrease R. albus H(2) production without suppressing growth.

  15. Improvement of the phosphoenolpyruvate carboxylase activity of Phaeodactylum tricornutum PEPCase 1 through protein engineering.

    PubMed

    Chang, Kwang Suk; Jeon, Hancheol; Seo, Seungbeom; Lee, Yew; Jin, EonSeon

    2014-06-10

    In order to mitigate CO2 accumulation and decrease the rate of global warming and climate change, we previously presented a strategy for the development of an efficient CO2 capture and utilization system. The system employs two recombinant enzymes, carbonic anhydrase and phosphoenolpyruvate carboxylase, which were originated from microalgae. Although utilization of this integrated system would require a large quantity of high quality PEPCase protein, such quantities could be produced by increasing the solubility of the Phaeodactylum tricornutum PEPCase 1 (PtPEPCase 1) protein in the Escherichia coli heterologous expression system. We first expressed the putative mitochondria targeting peptide- and chloroplast transit peptide-truncated proteins of PtPEPCase 1, mPtPEPCase 1 and cPtPEPCase 1, respectively, in E. coli. After affinity chromatography, the amount of purified PEPCase protein from 500mL of E. coli culture was greatest for cPtPEPCase 1 (1.99mg), followed by mPtPEPCase 1 (0.82mg) and PtPEPCase 1 (0.61mg). Furthermore, the enzymatic activity of mPtPEPCase 1 and cPtPEPCase 1 showed approximately 1.6-fold (32.19 units/mg) and 3-fold (59.48 units/mg) increases, respectively. Therefore, cPtPEPCase 1 purified using the E. coli heterogeneous expression system could be a strong candidate for a platform technology to capture CO2 and produce value-added four-carbon platform chemicals.

  16. Ketogenic diet-fed rats have increased fat mass and phosphoenolpyruvate carboxykinase activity.

    PubMed

    Ribeiro, Letícia C; Chittó, Ana L; Müller, Alexandre P; Rocha, Juliana K; Castro da Silva, Mariane; Quincozes-Santos, André; Nardin, Patrícia; Rotta, Liane N; Ziegler, Denize R; Gonçalves, Carlos-Alberto; Da Silva, Roselis S M; Perry, Marcos L S; Gottfried, Carmem

    2008-11-01

    The ketogenic diet (KD), characterized by high fat and low carbohydrate and protein contents, has been proposed to be beneficial in children with epilepsy disorders not helped by conventional anti-epileptic drug treatment. Weight loss and inadequate growth is an important drawback of this diet and metabolic causes are not well characterized. The aim of this study was to examine body weight variation during KD feeding for 6 wk of Wistar rats; fat mass and adipocyte cytosolic phosphoenolpyruvate carboxykinase (PEPCK) activity were also observed. PEPCK activity was determined based on the [H(14)CO(3) (-)]-oxaloacetate exchange reaction. KD-fed rats gained weight at a less rapid rate than normal-fed rats, but with a significant increment in fat mass. The fat mass/body weight ratio already differed between ketogenic and control rats after the first week of treatment, and was 2.4 x higher in ketogenic rats. The visceral lipogenesis was supported by an increment in adipocyte PEPCK, aiming to provide glycerol 3-phosphate to triacylglycerol synthesis and this fat accumulation was accompanied by glucose intolerance. These data contribute to our understanding of the metabolic effects of the KD in adipose tissue and liver and suggest some potential risks of this diet, particularly visceral fat accumulation.

  17. Inhibition of triosephosphate isomerase by phosphoenolpyruvate in the feedback-regulation of glycolysis.

    PubMed

    Grüning, Nana-Maria; Du, Dijun; Keller, Markus A; Luisi, Ben F; Ralser, Markus

    2014-03-05

    The inhibition of triosephosphate isomerase (TPI) in glycolysis by the pyruvate kinase (PK) substrate phosphoenolpyruvate (PEP) results in a newly discovered feedback loop that counters oxidative stress in cancer and actively respiring cells. The mechanism underlying this inhibition is illuminated by the co-crystal structure of TPI with bound PEP at 1.6 Å resolution, and by mutational studies guided by the crystallographic results. PEP is bound to the catalytic pocket of TPI and occludes substrate, which accounts for the observation that PEP competitively inhibits the interconversion of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Replacing an isoleucine residue located in the catalytic pocket of TPI with valine or threonine altered binding of substrates and PEP, reducing TPI activity in vitro and in vivo. Confirming a TPI-mediated activation of the pentose phosphate pathway (PPP), transgenic yeast cells expressing these TPI mutations accumulate greater levels of PPP intermediates and have altered stress resistance, mimicking the activation of the PK-TPI feedback loop. These results support a model in which glycolytic regulation requires direct catalytic inhibition of TPI by the pyruvate kinase substrate PEP, mediating a protective metabolic self-reconfiguration of central metabolism under conditions of oxidative stress.

  18. The Role of Cysteine Residues in Catalysis of Phosphoenolpyruvate Carboxykinase from Mycobacterium tuberculosis

    PubMed Central

    Machová, Iva; Hubálek, Martin; Lepšík, Martin; Bednárová, Lucie; Pazderková, Markéta; Kopecký, Vladimír; Snášel, Jan; Dostál, Jiří; Pichová, Iva

    2017-01-01

    Mycobacterium tuberculosis (MTb), the causative agent of tuberculosis, can persist in macrophages for decades, maintaining its basic metabolic activities. Phosphoenolpyruvate carboxykinase (Pck; EC 4.1.1.32) is a key player in central carbon metabolism regulation. In replicating MTb, Pck is associated with gluconeogenesis, but in non-replicating MTb, it also catalyzes the reverse anaplerotic reaction. Here, we explored the role of selected cysteine residues in function of MTb Pck under different redox conditions. Using mass spectrometry analysis we confirmed formation of S–S bridge between cysteines C391 and C397 localized in the C-terminal subdomain. Molecular dynamics simulations of C391-C397 bridged model indicated local conformation changes needed for formation of the disulfide. Further, we used circular dichroism and Raman spectroscopy to analyze the influence of C391 and C397 mutations on Pck secondary and tertiary structures, and on enzyme activity and specificity. We demonstrate the regulatory role of C391 and C397 that form the S–S bridge and in the reduced form stabilize Pck tertiary structure and conformation for gluconeogenic and anaplerotic reactions. PMID:28135343

  19. Epigenetic modification of fetal baboon hepatic phosphoenolpyruvate carboxykinase following exposure to moderately reduced nutrient availability.

    PubMed

    Nijland, Mark J; Mitsuya, Kozoh; Li, Cun; Ford, Stephen; McDonald, Thomas J; Nathanielsz, Peter W; Cox, Laura A

    2010-04-15

    Decreased maternal nutrient availability during pregnancy induces compensatory fetal metabolic and endocrine responses. Knowledge of cellular changes involved is critical to understanding normal and abnormal development. Several studies in rodents and sheep report increased fetal plasma cortisol and associated increased gluconeogenesis in response to maternal nutrient reduction (MNR) but observations in primates are lacking. We determined MNR effects on fetal liver phosphoenolpyruvate carboxykinase 1 (protein, PEPCK1; gene, PCK1 orthologous/homologous human chromosomal region 20q13.31) at 0.9 gestation (G). Female baboon social groups were fed ad libitum (control, CTR) or 70% CTR (MNR) from 0.16 to 0.9G when fetuses were delivered by caesarean section under general anaesthesia. Plasma cortisol was elevated in fetuses of MNR mothers (P < 0.05). Immunoreactive PEPCK1 protein was located around the liver lobule central vein and was low in CTR fetuses but rose to 63% of adult levels in MNR fetuses. PCK1 mRNA measured by QRT-PCR increased in MNR (2.3-fold; P < 0.05) while the 25% rise in protein by Western blot analysis was not significant. PCK1 promoter methylation analysis using bisulfite sequencing was significantly reduced in six out of nine CpG-dinucleotides evaluated in MNR compared with CTR liver samples. In conclusion, these are the first data from a fetal non-human primate indicating hypomethylation of the PCK1 promoter in the liver following moderate maternal nutrient reduction.

  20. Cell volume regulates liver phosphoenolpyruvate carboxykinase and fructose-1,6-bisphosphatase genes.

    PubMed

    Kaiser, S

    1998-03-01

    Hypertonic-induced cell shrinkage increases glucose release in H-4-II-E rat hepatoma cells. This is paralleled by a concomitant increase in the mRNA levels of the rate-limiting enzymes of the pathway of gluconeogenesis, phosphoenolpyruvate carboxykinase (PCK) and fructose-1,6-bisphosphatase (FBP), of seven- and fivefold, respectively. In contrast, hypotonic-induced swelling of the cells results in a transient decrease in PCK and FBP mRNAs to 15% and 39% of control levels. The antagonistic effects of hyper- and hypotonicity mimic the counteracting effects of adenosine 3',5'-cyclic monophosphate (cAMP) and insulin on PCK and FBP mRNA levels. The hypertonic-induced increase in mRNA levels is due to an enhanced transcriptional rate, whereas the decrease in mRNAs caused by hypotonicity results from a decrease in transcription as well as mRNA stability. The inductive effect of hypertonicity does not require ongoing protein synthesis and acts independently of the cAMP-dependent protein kinase and protein kinase C pathways. These results suggest that cell volume changes in liver cells may play an important role in regulating hepatic glucose metabolism by altered gene expression.

  1. Control of Transposon-mediated Directed Mutation by the Escherichia coli Phosphoenolpyruvate:Sugar Phosphotransferase System

    PubMed Central

    Saier, Milton H.; Zhang, Zhongge

    2015-01-01

    The phosphoenolpyruvate:sugar phosphotransferase system (PTS) has been shown to control transport, cell metabolism and gene expression. We here present results supporting the novel suggestion that in certain instances, it also regulates mutation rate. Directed mutations are defined as mutations that occur at higher frequencies when beneficial than when neutral or detrimental. To date, the occurrence of directed point mutations has not been documented and confirmed, but a few examples of transposon-mediated directed mutation have been reported. Here we focus on the first and best-studied example of directed mutation, which involves the regulation of Insertion Sequence-5 (IS5) hopping into a specific site upstream of the glpFK glycerol utilization operon in Escherichia coli. This insertional event specifically activates expression of the glpFK operon, allowing growth of wild type cells with glycerol as a carbon source in the presence of non-metabolizable glucose analogues which normally block glycerol utilization. The sugar transporting PTS controls this process by regulating levels of cytoplasmic glycerol-3-phosphate and cyclic AMP as established in previous publications. Direct involvement of the glycerol repressor, GlpR, and the cyclic AMP receptor protein, Crp, in the regulation of transposon-mediated directed mutation has been demonstrated. PMID:26159081

  2. Nur77 suppresses hepatocellular carcinoma via switching glucose metabolism toward gluconeogenesis through attenuating phosphoenolpyruvate carboxykinase sumoylation.

    PubMed

    Bian, Xue-Li; Chen, Hang-Zi; Yang, Peng-Bo; Li, Ying-Ping; Zhang, Fen-Na; Zhang, Jia-Yuan; Wang, Wei-Jia; Zhao, Wen-Xiu; Zhang, Sheng; Chen, Qi-Tao; Zheng, Yu; Sun, Xiao-Yu; Wang, Xiao-Min; Chien, Kun-Yi; Wu, Qiao

    2017-02-27

    Gluconeogenesis, an essential metabolic process for hepatocytes, is downregulated in hepatocellular carcinoma (HCC). Here we show that the nuclear receptor Nur77 is a tumour suppressor for HCC that regulates gluconeogenesis. Low Nur77 expression in clinical HCC samples correlates with poor prognosis, and a Nur77 deficiency in mice promotes HCC development. Nur77 interacts with phosphoenolpyruvate carboxykinase (PEPCK1), the rate-limiting enzyme in gluconeogenesis, to increase gluconeogenesis and suppress glycolysis, resulting in ATP depletion and cell growth arrest. However, PEPCK1 becomes labile after sumoylation and is degraded via ubiquitination, which is augmented by the p300 acetylation of ubiquitin-conjugating enzyme 9 (Ubc9). Although Nur77 attenuates sumoylation and stabilizes PEPCK1 via impairing p300 activity and preventing the Ubc9-PEPCK1 interaction, Nur77 is silenced in HCC samples due to Snail-mediated DNA methylation of the Nur77 promoter. Our study reveals a unique mechanism to suppress HCC by switching from glycolysis to gluconeogenesis through Nur77 antagonism of PEPCK1 degradation.

  3. Influence of endotoxin treatment on dexamethasone induction of hepatic phosphoenolpyruvate carboxykinase.

    PubMed Central

    McCallum, R E; Seale, T W; Stith, R D

    1983-01-01

    Decreased glucocorticoid binding has been observed at a time after endotoxin (3 to 6 h) when imparied liver enzyme induction is known to occur. This study was undertaken to characterize the early time course of hypoglycemia and decreased liver phosphoenolpyruvate carboxykinase (PEPCK) activity in intact and adrenalectomized mice given endotoxin. In addition, altered steroid induction of hepatic PEPCK was examined in adrenalectomized mice given dexamethasone at intervals before and after a median lethal dose of endotoxin. Intact mice demonstrated a dramatic hyperglycemia at 1 h after endotoxin treatment, a response absent in adrenalectomized mice. Plasma glucose levels were significantly reduced from control values at 3 and 6 h posttreatment, with the most pronounced endotoxin-induced hypoglycemia seen in adrenalectomized mice. Hepatic PEPCK activity in intact mice given endotoxin was decreased at 3 and 6 h after treatment, although no change from basal, noninduced levels was seen in poisoned adrenalectomized mice. The increased increment in hepatic PEPCK activity due to fasting of intact control mice was reproduced in adrenalectomized control mice by the administration of dexamethasone. Furthermore, the induction of hepatic PEPCK by dexamethasone was inhibited by 1 h after endotoxin treatment, with enzyme activity falling to basal, noninduced levels by 6 h posttreatment. At these same time intervals after endotoxin treatment, no evidence of histopathology in the liver or adrenal glands was seen. These results coincide with changes in steroid binding seen previously and indicate that endotoxin treatment produces significant alterations in glucocorticoid action at the subcellular or molecular level. PMID:6822414

  4. Inflammation inhibits the expression of phosphoenolpyruvate carboxykinase in liver and adipose tissue.

    PubMed

    Feingold, Kenneth R; Moser, Arthur; Shigenaga, Judy K; Grunfeld, Carl

    2012-04-01

    Inhibition of adipocyte triglyceride biosynthesis is required for fatty acid mobilization during inflammation. Triglyceride biosynthesis requires glycerol 3-phosphate and phosphoenolpyruvate carboxykinase (PEPCK) plays a key role. We demonstrate that LPS, zymosan, and TNF-α decrease PEPCK in liver and fat. Turpentine decreases PEPCK in liver, but not in fat. The LPS-induced decrease in PEPCK does not occur in TLR4 deficient animals, indicating that this receptor is required. The LPS-induced decrease in hepatic PEPCK does not occur in TNF receptor/IL-1 receptor knockout mice, but occurs in fat, indicating that TNF-α/IL-1 is essential for the decrease in liver but not fat. In 3T3-L1 adipocytes TNF-α, IL-1, IL-6, and IFNγ inhibit PEPCK indicating that there are multiple pathways by which PEPCK is decreased in adipocytes. The binding of PPARγ and RXRα to the PPARγ response element in the PEPCK promoter is markedly decreased in adipose tissue nuclear extracts from LPS treated animals. Lipopolysaccharide and zymosan reduce PPARγ and RXRα expression in fat, suggesting that a decrease in PPARγ and RXRα accounts for the decrease in PEPCK. Thus, there are multiple cytokine pathways by which inflammation inhibits PEPCK expression in adipose tissue which could contribute to the increased mobilization of fatty acids during inflammation.

  5. Transport of Phosphoenolpyruvate by Chloroplasts from Mesembryanthemum crystallinum L. Exhibiting Crassulacean Acid Metabolism 1

    PubMed Central

    Neuhaus, H. Ekkehard; Holtum, Joseph A. M.; Latzko, Erwin

    1988-01-01

    Chloroplasts from CAM-Mesembryanthemum crystallinum can transport phosphoenolpyruvate (PEP) across the envelope. The initial velocities of PEP uptake in the dark at 4°C exhibited saturation kinetics with increasing external PEP concentration. PEP uptake had a Vmax of 6.46 (±0.05) micromoles per milligram chlorophyll per hour and an apparent Kmpep of 0.148 (±0.004) millimolar. The uptake was competitively inhibited by Pi (apparent Ki = 0.19 millimolar), by glycerate 3-phosphate (apparent Ki = 0.13 millimolar), and by dihydroxyacetone phosphate, but malate and pyruvate were without effect. The chloroplasts were able to synthesize PEP when presented with pyruvate. PEP synthesis was light dependent. The prolonged synthesis and export of PEP from the chloroplasts required the presence of Pi or glycerate 3-phosphate in the external medium. It is suggested that the transport of pyruvate and PEP across the chloroplasts envelope is required during the gluconeogenic conversion of carbon from malate to storage carbohydrate in the light. PMID:16666128

  6. Structure of phosphorylated enzyme I, the phosphoenolpyruvate:sugar phosphotransferase system sugar translocation signal protein.

    PubMed

    Teplyakov, Alexey; Lim, Kap; Zhu, Peng-Peng; Kapadia, Geeta; Chen, Celia C H; Schwartz, Jennifer; Howard, Andrew; Reddy, Prasad T; Peterkofsky, Alan; Herzberg, Osnat

    2006-10-31

    Bacterial transport of many sugars, coupled to their phosphorylation, is carried out by the phosphoenolpyruvate (PEP):sugar phosphotransferase system and involves five phosphoryl group transfer reactions. Sugar translocation initiates with the Mg(2+)-dependent phosphorylation of enzyme I (EI) by PEP. Crystals of Escherichia coli EI were obtained by mixing the protein with Mg(2+) and PEP, followed by oxalate, an EI inhibitor. The crystal structure reveals a dimeric protein where each subunit comprises three domains: a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr; a domain that carries the phosphorylated histidine residue, His-189; and a PEP-binding domain. The PEP-binding site is occupied by Mg(2+) and oxalate, and the phosphorylated His-189 is in-line for phosphotransfer to/from the ligand. Thus, the structure represents an enzyme intermediate just after phosphotransfer from PEP and before a conformational transition that brings His-189 approximately P in proximity to the phosphoryl group acceptor, His-15 of HPr. A model of this conformational transition is proposed whereby swiveling around an alpha-helical linker disengages the His domain from the PEP-binding domain. Assuming that HPr binds to the HPr-binding domain as observed by NMR spectroscopy of an EI fragment, a rotation around two linker segments orients the His domain relative to the HPr-binding domain so that His-189 approximately P and His-15 are appropriately stationed for an in-line phosphotransfer reaction.

  7. Regulatory Tasks of the Phosphoenolpyruvate-Phosphotransferase System of Pseudomonas putida in Central Carbon Metabolism

    PubMed Central

    Chavarría, Max; Kleijn, Roelco J.; Sauer, Uwe; Pflüger-Grau, Katharina; de Lorenzo, Víctor

    2012-01-01

    ABSTRACT Two branches of the phosphoenolpyruvate-phosphotransferase system (PTS) operate in the soil bacterium Pseudomonas putida KT2440. One branch encompasses a complete set of enzymes for fructose intake (PTSFru), while the other (N-related PTS, or PTSNtr) controls various cellular functions unrelated to the transport of carbohydrates. The potential of these two systems for regulating central carbon catabolism has been investigated by measuring the metabolic fluxes of isogenic strains bearing nonpolar mutations in PTSFru or PTSNtr genes and grown on either fructose (a PTS substrate) or glucose, the transport of which is not governed by the PTS in this bacterium. The flow of carbon from each sugar was distinctly split between the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways in a ratio that was maintained in each of the PTS mutants examined. However, strains lacking PtsN (EIIANtr) displayed significantly higher fluxes in the reactions of the pyruvate shunt, which bypasses malate dehydrogenase in the TCA cycle. This was consistent with the increased activity of the malic enzyme and the pyruvate carboxylase found in the corresponding PTS mutants. Genetic evidence suggested that such a metabolic effect of PtsN required the transfer of high-energy phosphate through the system. The EIIANtr protein of the PTSNtr thus helps adjust central metabolic fluxes to satisfy the anabolic and energetic demands of the overall cell physiology. PMID:22434849

  8. Phosphoenolpyruvate-supply module in Escherichia coli improves N-acetyl-D-neuraminic acid biocatalysis.

    PubMed

    Zhu, Deqiang; Wu, Jianrong; Zhan, Xiaobei; Zhu, Li; Zheng, Zhiyong; Gao, Minjie

    2017-02-01

    N-Acetyl-D-neuraminic acid (Neu5Ac) is often synthesized from exogenous N-acetylglucosamine (GlcNAc) and excess pyruvate. We have previously constructed a recombinant Escherichia coli strain for Neu5Ac production using GlcNAc and intracellular phosphoenolpyruvate (PEP) as substrates (Zhu et al. Biotechnol Lett 38:1-9, 2016). PEP synthesis-related genes, pck and ppsA, were overexpressed within different modes to construct PEP-supply modules, and their effects on Neu5Ac production were investigated. All the PEP-supply modules enhanced Neu5Ac production. For the best module, pCDF-pck-ppsA increased Neu5Ac production to 8.6 ± 0.15 g l(-1), compared with 3.6 ± 0.15 g l(-1) of the original strain. Neu5Ac production was further increased to 15 ± 0.33 g l(-1) in a 1 l fermenter. The PEP-supply module can improve the intracellular PEP supply and enhance Neu5Ac production, which benefited industrial Neu5Ac production.

  9. Stability of Escherichia coli phosphoenolpyruvate carboxykinase against urea-induced unfolding and ligand effects.

    PubMed

    Encinas, M V; Evangelio, J A; Andreu, J M; Goldie, H; Cardemil, E

    1998-07-15

    The urea-induced unfolding at pH 7.5 of Escherichia coli phosphoenolpyruvate (P-pyruvate) carboxykinase was studied by monitoring the enzyme activity, intrinsic protein fluorescence, circular dichroism spectra, and 1-anilino-8-naphthalenesulfonate binding. These studies were performed in the absence and presence of substrates and ligands. ATP or P-pyruvate plus MnCl2, or of the combined presence of ATP plus MnCl2 and oxalate, conferred great protection against urea-induced denaturation. The unfolding process showed the presence of at least one stable intermediate which is notably shifted to higher urea concentrations in the presence of substrates. This intermediate protein structure was inactive, contained less tertiary structure than the native protein and retained most of the original secondary structure. Hydrophobic surfaces were more exposed in the intermediate than in the native or unfolded species. Refolding experiments indicated that the secondary structure was completely recovered. Total recovery of tertiary structure and activity was obtained only from samples denatured at urea concentrations lower than those where the intermediate accumulates.

  10. Stereochemical course of the reactions catalyzed by the bacterial phosphoenolpyruvate: Mannitol phosphotransferase system

    SciTech Connect

    Mueller, E.G.; Knowles, J.R. ); Khandekar, S.S.; Jacobson, G.R. )

    1990-07-24

    The authors have determined the overall stereochemical course of the reactions leading to the phosphorylation of D-mannitol by mannitol-specific enzyme II (EII{sup Mtl}) of the Escherichia coli phosphoenolpyruvate- (PEP) dependent phosphotransferase system (PTS). In the presence of enzyme I and HPr of the PTS, and of membranes containing EII{sup Mtl}, the phospho group from ((R)-{sup 16}O, {sup 17}O, {sup 18}O)PEP was transferred to D-mannitol to form mannitol 1-phosphate with overall inversion of the configuration at phosphorus with respect to that of PEP. Since in the course of these reactions enzyme I and HPr are each covalently phosphorylated at a single site and inversion of the chiral phospho group from PEP indicates an odd number of transfer steps overall, transfer from phospho-HPr to mannitol via EII{sup Mtl} must also occur in an odd number of steps. Taken together with the fact that catalytically important phospho-EII{sup Mtl} intermediates have been demonstrated biochemically, the results imply that EII{sup Mtl} is sequentially phosphorylated at two different sites during phospho transfer from phospho-HPr to mannitol. This conclusion is consistent with the available evidence on phospho-EII{sup Mtl} intermediates and in particular with the recent report that two different phospho peptides can be isolated from the fully phosphorylated protein.

  11. Allosteric Inhibition of Phosphoenolpyruvate Carboxylases is Determined by a Single Amino Acid Residue in Cyanobacteria

    PubMed Central

    Takeya, Masahiro; Hirai, Masami Yokota; Osanai, Takashi

    2017-01-01

    Phosphoenolpyruvate carboxylase (PEPC) is an important enzyme for CO2 fixation and primary metabolism in photosynthetic organisms including cyanobacteria. The kinetics and allosteric regulation of PEPCs have been studied in many organisms, but the biochemical properties of PEPC in the unicellular, non-nitrogen-fixing cyanobacterium Synechocystis sp. PCC 6803 have not been clarified. In this study, biochemical analysis revealed that the optimum pH and temperature of Synechocystis 6803 PEPC proteins were 7.3 and 30 °C, respectively. Synechocystis 6803 PEPC was found to be tolerant to allosteric inhibition by several metabolic effectors such as malate, aspartate, and fumarate compared with other cyanobacterial PEPCs. Comparative sequence and biochemical analysis showed that substitution of the glutamate residue at position 954 with lysine altered the enzyme so that it was inhibited by malate, aspartate, and fumarate. PEPC of the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 was purified, and its activity was inhibited in the presence of malate. Substitution of the lysine at position 946 (equivalent to position 954 in Synechocystis 6803) with glutamate made Anabaena 7120 PEPC tolerant to malate. These results demonstrate that the allosteric regulation of PEPC in cyanobacteria is determined by a single amino acid residue, a characteristic that is conserved in different orders. PMID:28117365

  12. Phosphoenolpyruvate Carboxykinase and Glucose-6-phosphatase Are Required for Steroidogenesis in Testicular Leydig Cells*

    PubMed Central

    Ahn, Seung Won; Gang, Gil-Tae; Tadi, Surendar; Nedumaran, Balachandar; Kim, Yong Deuk; Park, Ji Hoon; Kweon, Gi Ryang; Koo, Seung-Hoi; Lee, Keesook; Ahn, Ryun-Sup; Yim, Yong-Hyeon; Lee, Chul-Ho; Harris, Robert A.; Choi, Hueng-Sik

    2012-01-01

    Cyclic AMP (cAMP) induces steroidogenic enzyme gene expression and stimulates testosterone production in Leydig cells. Phosphoenolpyruvate carboxykinase (PEPCK) is expressed in Leydig cells, but its role has not been defined. In this study, we found that PEPCK and glucose-6-phosphatase (Glc-6-Pase) are increased significantly following cAMP treatment of mouse Leydig cells. Moreover, cAMP treatment increased recruitment of the cAMP-response element-binding transcription factor and decreased recruitment of the corepressor DAX-1 on the pepck promoter. Furthermore, cAMP induced an increase in ATP that correlated with a decrease in phospho-AMP-activated protein kinase (AMPK). In contrast, knockdown or inhibition of PEPCK decreased ATP and increased phospho-AMPK. Treatment with an AMPK activator or overexpression of the constitutively active form of AMPK inhibited cAMP-induced steroidogenic enzyme promoter activities and gene expression. Liver receptor homolog-1 (LRH-1) was involved in cAMP-induced steroidogenic enzyme gene expression but was inhibited by AMPK activation in Leydig cells. Additionally, inhibition or knockdown of PEPCK and Glc-6-Pase decreased cAMP-mediated induction of steroidogenic enzyme gene expression and steroidogenesis. Finally, pubertal mouse (8-week-old) testes and human chorionic gonadotropin-induced prepubertal mouse testes showed increased PEPCK and Glc-6-Pase gene expression. Taken together, these results suggest that induction of PEPCK and Glc-6-Pase by cAMP plays an important role in Leydig cell steroidogenesis. PMID:23074219

  13. Control of Transposon-Mediated Directed Mutation by the Escherichia coli Phosphoenolpyruvate:Sugar Phosphotransferase System.

    PubMed

    Saier, Milton H; Zhang, Zhongge

    2015-01-01

    The phosphoenolpyruvate:sugar phosphotransferase system (PTS) has been shown to control transport, cell metabolism and gene expression. We here present results supporting the novel suggestion that in certain instances it also regulates the mutation rate. Directed mutations are defined as mutations that occur at higher frequencies when beneficial than when neutral or detrimental. To date, the occurrence of directed point mutations has not been documented and confirmed, but a few examples of transposon-mediated directed mutations have been reported. Here we focus on the first and best-studied example of directed mutation, which involves the regulation of insertion sequence-5 hopping into a specific site upstream of the glpFK glycerol utilization operon in Escherichia coli. This insertional event specifically activates expression of the glpFK operon, allowing the growth of wild-type cells with glycerol as a carbon source in the presence of nonmetabolizable glucose analogues which normally block glycerol utilization. The sugar-transporting PTS controls this process by regulating levels of cytoplasmic glycerol-3-phosphate and cyclic (c)AMP as established in previous publications. Direct involvement of the glycerol repressor, GlpR, and the cAMP receptor protein, Crp, in the regulation of transposon-mediated directed mutation has been demonstrated.

  14. Liver-specific expression of a phosphoenolpyruvate carboxykinase-neo gene in genetically modified chickens.

    PubMed

    Cook, R F; Cook, S J; Savon, S; McGrane, M; Hartitz, M; Hanson, R W; Hodgson, C P

    1993-03-01

    In order to investigate the potential of the avian liver for the expression of recombinant proteins in vivo, replication-competent retroviral vectors were used to introduce a recombinant rat phosphoenolpyruvate carboxykinase promoter-driven neomycin resistance gene (PEPCKneo) into early Line 11 Leghorn embryos. After hatching, these birds possessed apparently intact PEPCKneo sequences in most tissues examined, however, the neo protein was expressed preferentially in the liver (up to .45% of total cellular protein). Therefore, the tissue specificity of the PEPCK promoter from the rat was retained in the chicken, although hormone responsiveness was not observed. Retroviral vectors used to transmit the genes were more stable during passage in either fibroblast cells or in the animal if the inserted genes were oriented in the same (sense) direction as the viral genome. After Geneticin drug selection in cultured cells, PEPCKneo mRNA was the predominant recombinant species observed on Northern blots, whereas embryos expressed mostly the RNA species originating in the retroviral long terminal repeats. The results demonstrate the potential usefulness of liver-specific gene expression in chickens, as well as the transcriptional effects observed when a foreign promoter is introduced into the replication-competent vector.

  15. Abiotic stresses affecting water balance induce phosphoenolpyruvate carboxylase expression in roots of wheat seedlings.

    PubMed

    González, María-Cruz; Sánchez, Rosario; Cejudo, Francisco J

    2003-04-01

    Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) plays an important role in CO(2) fixation in C4 and CAM plants. In C3 plants, PEPC is widely expressed in most organs; however, its function is not yet clearly established. With the aim of providing clues on the function of PEPC in C3 plants, we have analyzed its pattern of expression in wheat ( Triticum aestivum L.) seedlings. Roots showed almost double the level of PEPC activity of shoots. Further analysis of PEPC expression in roots by in situ localization techniques showed a high accumulation of PEPC transcripts and polypeptides in meristematic cells, whereas in the rest of the root PEPC localized preferentially to the vascular tissue. Treatment with NaCl and LiCl induced PEPC expression in roots. Similarly, other abiotic stresses affecting water status, such as drought or cold, induced PEPC expression. Induction was root-specific except for the cold treatment, which also induced PEPC in shoots, although to a lesser extent. In contrast, hypoxia, which does not affect water balance, did not promote any induction of PEPC expression. These results suggest an important role for this enzyme in the adaptation of plants to environmental changes.

  16. Mutants of Salmonella typhimurium Lacking Phosphoenolpyruvate Carboxykinase and α-Ketoglutarate Dehydrogenase Activities

    PubMed Central

    Carrillo-Castañeda, Guillermo; Ortega, Manuel V.

    1970-01-01

    Two auxotrophic mutants (SM16 and SM51) of Salmonella typhimurium, which for aerobic growth, with hexoses as carbon source, required lysine and methionine (SM51 required also nicotinic acid), were isolated and characterized. The requirement for the amino acids disappeared in anaerobiosis. Neither lipoate nor 4-hydroxybenzoate was effective in supporting aerobic growth of the mutants. The lysine and methionine requirement for aerobic growth was due to the absence in the mutants of the enzymatic activities of the α-ketoglutarate dehydrogenase complex. The mutants could not use succinate as carbon source even after enrichment of the growth medium with acid-hydrolyzed casein and yeast extract. No phosphoenolpyruvate carboxykinase activity was found in the mutants, a phenomenon which explained their inability to use succinate. By interrupted conjugation and by transduction experiments, the positions of the three affected loci, pck, suc, and Nic, were located at approximately 17 to 19 min of the S. typhimurium chromosome; they were found to be closely linked. From different criteria, it appears as if the genetic lesions present in both mutants are due to deletion of a small chromosome fragment. PMID:4911543

  17. Sophisticated Regulation of Transcriptional Factors by the Bacterial Phosphoenolpyruvate: Sugar Phosphotransferase System.

    PubMed

    Galinier, Anne; Deutscher, Josef

    2017-03-24

    The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is a carbohydrate transport and phosphorylation system present in bacteria of all different phyla and in archaea. It is usually composed of three proteins or protein complexes, enzyme I, HPr, and enzyme II, which are phosphorylated at histidine or cysteine residues. However, in many bacteria, HPr can also be phosphorylated at a serine residue. The PTS not only functions as a carbohydrate transporter but also regulates numerous cellular processes either by phosphorylating its target proteins or by interacting with them in a phosphorylation-dependent manner. The target proteins can be catabolic enzymes, transporters, and signal transduction proteins but are most frequently transcriptional regulators. In this review, we will describe how PTS components interact with or phosphorylate proteins to regulate directly or indirectly the activity of transcriptional repressors, activators, or antiterminators. We will briefly summarize the well-studied mechanism of carbon catabolite repression in firmicutes, where the transcriptional regulator catabolite control protein A needs to interact with seryl-phosphorylated HPr in order to be functional. We will present new results related to transcriptional activators and antiterminators containing specific PTS regulation domains, which are the phosphorylation targets for three different types of PTS components. Moreover, we will discuss how the phosphorylation level of the PTS components precisely regulates the activity of target transcriptional regulators or antiterminators, with or without PTS regulation domain, and how the availability of PTS substrates and thus the metabolic status of the cell are connected with various cellular processes, such as biofilm formation or virulence of certain pathogens.

  18. Towards efficient photosynthesis: overexpression of Zea mays phosphoenolpyruvate carboxylase in Arabidopsis thaliana.

    PubMed

    Kandoi, Deepika; Mohanty, Sasmita; Govindjee; Tripathy, Baishnab C

    2016-12-01

    Plants with C4 photosynthesis are efficient in carbon assimilation and have an advantage over C3 photosynthesis. In C4 photosynthesis, the primary CO2 fixation is catalyzed by phosphoenolpyruvate carboxylase (PEPC). Here, we show that overexpression of Zea mays PEPC cDNA, under the control of (35)S promoter, in Arabidopsis thaliana resulted in ~7-10 fold higher protein abundance and ~7-10 fold increase in PEPC activity in the transgenic lines than that in the vector control. We suggest that overexpression of PEPC played an anaplerotic role to increase the supply of 4-carbon carboxylic acids, which provided carbon skeletons for increased amino acid and protein synthesis. Higher protein content must have been responsible for increased metabolic processes including chlorophyll biosynthesis, photosynthesis, and respiration. Consequently, the PEPC-overexpressed transgenic plants had higher chlorophyll content, enhanced electron transport rate (ETR), lower non-photochemical quenching (NPQ) of chlorophyll a fluorescence, and a higher performance index (PI) than the vector control. Consistent with these observations, the rate of CO2 assimilation, the starch content, and the dry weight of PEPC-overexpressed plants increased by 14-18 %, 10-18 %, and 6.5-16 %, respectively. Significantly, transgenics were tolerant to salt stress as they had increased ability to synthesize amino acids, including the osmolyte proline. NaCl (150 mM)-treated transgenic plants had higher variable to maximum Chl a fluorescence (F v/F m) ratio, higher PI, higher ETR, and lower NPQ than the salt-treated vector controls. These results suggest that expression of C4 photosynthesis enzyme(s) in a C3 plant can improve its photosynthetic capacity with enhanced tolerance to salinity stress.

  19. Functional analysis of putative phosphoenolpyruvate transporters localized to the Golgi apparatus in Schizosaccharomyces pombe.

    PubMed

    Yoritsune, Ken-ichi; Higuchi, Yujiro; Matsuzawa, Tomohiko; Takegawa, Kaoru

    2014-11-01

    The cell surface of Schizosaccharomyces pombe is negatively charged due to the presence of pyruvylated oligosaccharides, which is important for cell-cell recognition. However, the mechanism of pyruvate supply to oligosaccharides is not clearly understood. Here, we analyzed three putative phosphoenolpyruvate (PEP) transporter genes (pet1(+) , pet2(+) , and pet3(+) ) in S. pombe, identified by sequence homology search against the Arabidopsis thaliana PEP transporter AtPPT1. Schizosaccharomyces pombe strain carrying a disruption in pet1(+) (pet1Δ) or in pet2(+) (pet2Δ), but not the strain carrying a disruption in pet3(+) (pet3Δ), showed reduced pyruvate level on the cell surface. This reduction in pyruvate level was restored to the control level by expressing green fluorescent protein (GFP)-tagged Pet1p and Pet2p in respective disruptants. Fluorescence microscope studies revealed that GFP-tagged Pet1p and Pet2p were localized to the Golgi apparatus. Although expression of neither AtPPT1 nor AtPPT2 suppressed the pet1Δ phenotype, that of chimeric constructs, where the N-terminal regions of AtPPT1 and AtPPT2 were replaced by the N-terminal region of Pet1p, partially suppressed the pet1Δ phenotype. Furthermore, the reduction in cell surface negative charge in pet1Δ cells was restored by incubating these cells with recombinant Pvg1p and PEP. Thus, Pet1p and Pet2p are likely involved in transporting PEP from the cytoplasm into the Golgi.

  20. Phosphoenolpyruvate Phosphotransferase System Components Modulate Gene Transcription and Virulence of Borrelia burgdorferi.

    PubMed

    Khajanchi, Bijay K; Odeh, Evelyn; Gao, Lihui; Jacobs, Mary B; Philipp, Mario T; Lin, Tao; Norris, Steven J

    2015-12-28

    The phosphoenolpyruvate phosphotransferase system (PEP-PTS) and adenylate cyclase (AC) IV (encoded by BB0723 [cyaB]) are well conserved in different species of Borrelia. However, the functional roles of PEP-PTS and AC in the infectious cycle of Borrelia have not been characterized previously. We examined 12 PEP-PTS transporter component mutants by needle inoculation of mice to assess their ability to cause mouse infection. Transposon mutants with mutations in the EIIBC components (ptsG) (BB0645, thought to be involved in glucose-specific transport) were unable to cause infection in mice, while all other tested PEP-PTS mutants retained infectivity. Infectivity was partially restored in an in trans-complemented strain of the ptsG mutant. While the ptsG mutant survived normally in unfed as well as fed ticks, it was unable to cause infection in mice by tick transmission, suggesting that the function of ptsG is essential to establish infection by either needle inoculation or tick transmission. In Gram-negative organisms, the regulatory effects of the PEP-PTS are mediated by adenylate cyclase and cyclic AMP (cAMP) levels. A recombinant protein encoded by B. burgdorferi BB0723 (a putative cyaB homolog) was shown to have adenylate cyclase activity in vitro; however, mutants with mutations in this gene were fully infectious in the tick-mouse infection cycle, indicating that its function is not required in this process. By transcriptome analysis, we demonstrated that the ptsG gene may directly or indirectly modulate gene expression of Borrelia burgdorferi. Overall, the PEP-PTS glucose transporter PtsG appears to play important roles in the pathogenesis of B. burgdorferi that extend beyond its transport functions.

  1. In vivo monoubiquitination of anaplerotic phosphoenolpyruvate carboxylase occurs at Lys624 in germinating sorghum seeds

    PubMed Central

    Echevarría, Cristina

    2014-01-01

    Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) is an important cytosolic regulatory enzyme that plays a pivotal role in numerous physiological processes in plants, including seed development and germination. Previous studies demonstrated the occurrence of immunoreactive PEPC polypeptides of ~110kDa and 107kDa (p110 and p107, respectively) on immunoblots of clarified extracts of germinating sorghum (Sorghum bicolor) seeds. In order to establish the biochemical basis for this observation, a 460kDa PEPC heterotetramer composed of an equivalent ratio of p110 and p107 subunits was purified to near homogeneity from the germinated seeds. Mass spectrometry established that p110 and p107 are both encoded by the same plant-type PEPC gene (CP21), but that p107 was in vivo monoubiquitinated at Lys624 to form p110. This residue is absolutely conserved in vascular plant PEPCs and is proximal to a PEP-binding/catalytic domain. Anti-ubiquitin IgG immunodetected p110 but not p107, whereas incubation with a deubiquitinating enzyme (USP-2 core) efficiently converted p110 into p107, while relieving the enzyme’s feedback inhibition by l-malate. Partial PEPC monoubiquitination was also detected during sorghum seed development. It is apparent that monoubiquitination at Lys624 is opposed to phosphorylation at Ser7 in terms of regulating the catalytic activity of sorghum seed PEPC. PEPC monoubiquitination is hypothesized to fine-tune anaplerotic carbon flux according to the cell’s immediate physiological requirements for tricarboxylic acid cycle intermediates needed in support of biosynthesis and carbon–nitrogen interactions. PMID:24288181

  2. Phosphoenolpyruvate Phosphotransferase System Components Modulate Gene Transcription and Virulence of Borrelia burgdorferi

    PubMed Central

    Odeh, Evelyn; Gao, Lihui; Jacobs, Mary B.; Philipp, Mario T.; Lin, Tao

    2015-01-01

    The phosphoenolpyruvate phosphotransferase system (PEP-PTS) and adenylate cyclase (AC) IV (encoded by BB0723 [cyaB]) are well conserved in different species of Borrelia. However, the functional roles of PEP-PTS and AC in the infectious cycle of Borrelia have not been characterized previously. We examined 12 PEP-PTS transporter component mutants by needle inoculation of mice to assess their ability to cause mouse infection. Transposon mutants with mutations in the EIIBC components (ptsG) (BB0645, thought to be involved in glucose-specific transport) were unable to cause infection in mice, while all other tested PEP-PTS mutants retained infectivity. Infectivity was partially restored in an in trans-complemented strain of the ptsG mutant. While the ptsG mutant survived normally in unfed as well as fed ticks, it was unable to cause infection in mice by tick transmission, suggesting that the function of ptsG is essential to establish infection by either needle inoculation or tick transmission. In Gram-negative organisms, the regulatory effects of the PEP-PTS are mediated by adenylate cyclase and cyclic AMP (cAMP) levels. A recombinant protein encoded by B. burgdorferi BB0723 (a putative cyaB homolog) was shown to have adenylate cyclase activity in vitro; however, mutants with mutations in this gene were fully infectious in the tick-mouse infection cycle, indicating that its function is not required in this process. By transcriptome analysis, we demonstrated that the ptsG gene may directly or indirectly modulate gene expression of Borrelia burgdorferi. Overall, the PEP-PTS glucose transporter PtsG appears to play important roles in the pathogenesis of B. burgdorferi that extend beyond its transport functions. PMID:26712207

  3. Bovine somatotropin increases hepatic phosphoenolpyruvate carboxykinase mRNA in lactating dairy cows.

    PubMed

    Velez, J C; Donkin, S S

    2004-05-01

    Somatotropin (ST) increases milk production and through coordinated changes in hepatic glucose synthesis and amino acid metabolism in dairy cows. The objective of this study was to determine the effects of ST on hepatic mRNA expression for phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC), enzymes that are critical to the synthesis of glucose in liver and hepatic mRNA expression for carbamylphosphate synthetase I (CPS-I), argininosuccinate synthetase (AS), and ornithine transcarbamylase (OTC), critical enzymes of the urea cycle. Eighteen cows were randomly allocated to 2 treatment groups and received either recombinant bovine ST (Posilac; Monsanto, St. Louis, MO) or saline injections at 14-d intervals during a 42-d period. Expression of mRNA was determined using Northern blot analysis. Nuclei, isolated from liver biopsy samples, were used to determine effects of ST on transcription rate of PEPCK. Milk production was increased with ST (37.3 vs. 35.1+/-0.6 kg/ d). Plasma NEFA was increased with ST (299 vs. 156+/-34 microM). There were no differences in the expression of CPS-I, AS, and OTC mRNA with ST. Expression of PEPCK and IGF-I mRNA were increased with ST but PC mRNA was unchanged. The data indicate increased PEPCK mRNA in cows given ST and indicates a greater capacity for gluconeogenesis from gluconeogenic precursors that form oxaloacetate. The effects of ST to elevate PEPCK mRNA expression require chronic administration and involve increased transcription of the PEPCK gene.

  4. The Ω-loop lid domain of phosphoenolpyruvate carboxykinase is essential for catalytic function

    PubMed Central

    Johnson, Troy A.; Holyoak, Todd

    2012-01-01

    Phosphoenolpyruvate carboxykinase (PEPCK) is an essential metabolic enzyme operating in the gluconeogenesis and glyceroneogenesis pathways. Recent studies have demonstrated that the enzyme contains a mobile active site lid domain that transitions between an open/disorded conformation to a closed/ordered conformation as the enzyme progresses through the catalytic cycle. The understanding of how this mobile domain functions in catalysis is incomplete. Previous studies show that the closure of the lid domain stabilizes the reaction intermediate and protects the reactive intermediate from spurious protonation and thus contributes to the fidelity of the enzyme. In order to more fully investigate the roles of the lid domain in PEPCK function we created three mutations that replaced the 11-residue lid domain with one, two or three glycine residues. Kinetic analysis of the mutant enzymes demonstrates that none of the enzyme constructs exhibit any measurable kinetic activity resulting in a decrease in the catalytic parameters by at least 106. Structural characterization of the mutants in complexes representing the catalytic cycle suggest that the inactivity is due to a role for the lid domain in the formation of the fully closed state of the enzyme that is required for catalytic function. In the absence of the lid domain, the enzyme is unable to achieve the fully closed state and is rendered inactive despite possessing all of the residues and substrates required for catalytic function. This work demonstrates how enzyme catalytic function can be abolished through the alteration of conformational equilibria despite all elements required for chemical conversion of substrates to products remaining intact. PMID:23127136

  5. Effects of phosphoenolpyruvate carboxylase desensitization on glutamic acid production in Corynebacterium glutamicum ATCC 13032.

    PubMed

    Wada, Masaru; Sawada, Kazunori; Ogura, Kotaro; Shimono, Yuta; Hagiwara, Takuya; Sugimoto, Masakazu; Onuki, Akiko; Yokota, Atsushi

    2016-02-01

    Phosphoenolpyruvate carboxylase (PEPC) in Corynebacterium glutamicum ATCC13032, a glutamic-acid producing actinobacterium, is subject to feedback inhibition by metabolic intermediates such as aspartic acid and 2-oxoglutaric acid, which implies the importance of PEPC in replenishing oxaloacetic acid into the TCA cycle. Here, we investigated the effects of feedback-insensitive PEPC on glutamic acid production. A single amino-acid substitution in PEPC, D299N, was found to relieve the feedback control by aspartic acid, but not by 2-oxoglutaric acid. A simple mutant, strain R1, having the D299N substitution in PEPC was constructed from ATCC 13032 using the double-crossover chromosome replacement technique. Strain R1 produced glutamic acid at a concentration of 31.0 g/L from 100 g/L glucose in a jar fermentor culture under biotin-limited conditions, which was significantly higher than that of the parent, 26.0 g/L (1.19-fold), indicative of the positive effect of desensitized PEPC on glutamic acid production. Another mutant, strain DR1, having both desensitized PEPC and PYK-gene deleted mutations, was constructed in a similar manner using strain D1 with a PYK-gene deleted mutation as the parent. This mutation had been shown to enhance glutamic acid production in our previous study. Although marginal, strain D1 produced higher glutamic acid, 28.8 g/L, than ATCC13032 (1.11-fold). In contrast, glutamic acid production by strain DR-1 was elevated up to 36.9 g/L, which was 1.42-fold higher than ATCC13032 and significantly higher than the other three strains. The results showed a synergistic effect of these two mutations on glutamic acid production in C. glutamicum. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  6. Phosphoenolpyruvate- and ATP-dependent dihydroxyacetone kinases: covalent substrate-binding and kinetic mechanism.

    PubMed

    Garcia-Alles, Luis F; Siebold, Christian; Nyffeler, Therese Lüthi; Flükiger-Brühwiler, Karin; Schneider, Philipp; Bürgi, Hans-Beat; Baumann, Ulrich; Erni, Bernhard

    2004-10-19

    Dihydroxyacetone (Dha) kinases are a sequence-conserved family of enzymes, which utilize two different phosphoryldonors, ATP in animals, plants, and some bacteria, and a multiphosphoprotein of the phosphoenolpyruvate carbohydrate phosphotransferase system (PTS) in most bacteria. Here, we compare the PTS-dependent kinase of Escherichia coli and the ATP-dependent kinase of Citrobacter freundii. They display 30% sequence identity. The binding constants of the E. coli kinase for eleven short-chain carbonyl compounds were determined by acetone precipitation of the enzyme-substrate complexes. They are 3.4 microM for Dha, 780 microM for Dha-phosphate (DhaP), 50 microM for D,L-glyceraldehyde (GA), and 90 microM for D,L-glyceraldehyde-3-phosphate. The k(cat) for Dha of the PTS-dependent kinase is 290 min(-1), and that of the ATP-dependent kinase is 1050 min(-1). The Km for Dha of both kinases is <6 microM. The X-ray structures of the enzyme-GA and the enzyme-DhaP complex show that substrates as well as products are bound in hemiaminal linkage to an active-site histidine. Quantum-mechanical calculations offer no indication for activation of the reacting hydroxyl group by the formation of the hemiaminal. However, the formation of the hemiaminal bond allows selection for short-chain carbonyl compounds and discrimination against structurally similar polyols. The Dha kinase remains fully active in the presence of 2 M glycerol, and phosphorylates trace impurities of carbonyl compounds present in glycerol.

  7. O-GlcNAcylation mediates the control of cytosolic phosphoenolpyruvate carboxykinase activity via Pgc1α

    PubMed Central

    Latorre, Pedro; Varona, Luis; Burgos, Carmen; López-Buesa, Pascual

    2017-01-01

    PGC1α is a coactivator of many transcription factors and cytosolic phosphoenolpyruvate carboxykinase (PCK1) is a key enzyme for gluconeogenesis. PGC1α interacts with the transcription factor PPARγ to stimulate PCK1 expression and thus de novo glucose synthesis. These proteins are not only important for central energy metabolism but also for supplying intermediates for other metabolic pathways, including lipidogenesis and protein synthesis and might therefore be important factors in the ethiopathogenesis of metabolic disorders like diabetes but also in other pathologies like cancer. Since polymorphisms in these proteins have been related to some phenotypic traits in animals like pigs and PGC1α G482S polymorphism increases fat deposition in humans, we have investigated the molecular basis of such effects focusing on a commonly studied polymorphism in pig Pgc1α, which changes a cysteine at position 430 (WT) of the protein to a serine (C430S). Biochemical analyses show that Pgc1α WT stimulates higher expression of human PCK1 in HEK293T and HepG2 cells. Paradoxically, Pgc1α WT is less stable than Pgc1α p.C430S in HEK293T cells. However, the study of different post-translational modifications shows a higher O-GlcNAcylation level of Pgc1α p.C430S. This higher O-GlcNAcylation level significantly decreases the interaction between Pgc1α and PPARγ demonstrating the importance of post-translational glycosylation of PGC1α in the regulation of PCK1 activity. This, furthermore, could explain at least in part the observed epistatic effects between PGC1α and PCK1 in pigs. PMID:28644880

  8. In vivo monoubiquitination of anaplerotic phosphoenolpyruvate carboxylase occurs at Lys624 in germinating sorghum seeds.

    PubMed

    Ruiz-Ballesta, Isabel; Feria, Ana-Belén; Ni, Hong; She, Yi-Min; Plaxton, William Charles; Echevarría, Cristina

    2014-02-01

    Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) is an important cytosolic regulatory enzyme that plays a pivotal role in numerous physiological processes in plants, including seed development and germination. Previous studies demonstrated the occurrence of immunoreactive PEPC polypeptides of ~110 kDa and 107 kDa (p110 and p107, respectively) on immunoblots of clarified extracts of germinating sorghum (Sorghum bicolor) seeds. In order to establish the biochemical basis for this observation, a 460 kDa PEPC heterotetramer composed of an equivalent ratio of p110 and p107 subunits was purified to near homogeneity from the germinated seeds. Mass spectrometry established that p110 and p107 are both encoded by the same plant-type PEPC gene (CP21), but that p107 was in vivo monoubiquitinated at Lys624 to form p110. This residue is absolutely conserved in vascular plant PEPCs and is proximal to a PEP-binding/catalytic domain. Anti-ubiquitin IgG immunodetected p110 but not p107, whereas incubation with a deubiquitinating enzyme (USP-2 core) efficiently converted p110 into p107, while relieving the enzyme's feedback inhibition by L-malate. Partial PEPC monoubiquitination was also detected during sorghum seed development. It is apparent that monoubiquitination at Lys624 is opposed to phosphorylation at Ser7 in terms of regulating the catalytic activity of sorghum seed PEPC. PEPC monoubiquitination is hypothesized to fine-tune anaplerotic carbon flux according to the cell's immediate physiological requirements for tricarboxylic acid cycle intermediates needed in support of biosynthesis and carbon-nitrogen interactions.

  9. Phosphoenolpyruvate Carboxylase in Arabidopsis Leaves Plays a Crucial Role in Carbon and Nitrogen Metabolism.

    PubMed

    Shi, Jianghua; Yi, Keke; Liu, Yu; Xie, Li; Zhou, Zhongjing; Chen, Yue; Hu, Zhanghua; Zheng, Tao; Liu, Renhu; Chen, Yunlong; Chen, Jinqing

    2015-03-01

    Phosphoenolpyruvate carboxylase (PEPC) is a crucial enzyme that catalyzes an irreversible primary metabolic reaction in plants.Previous studies have used transgenic plants expressing ectopic PEPC forms with diminished feedback inhibition to examine the role of PEPC in carbon and nitrogen metabolism. To date, the in vivo role of PEPC in carbon and nitrogen metabolism has not been analyzed in plants. In this study, we examined the role of PEPC in plants, demonstrating that PPC1 and PPC2 were highly expressed genes encoding PEPC in Arabidopsis (Arabidopsis thaliana) leaves and that PPC1 and PPC2 accounted for approximately 93% of total PEPC activity in the leaves. A double mutant, ppc1/ppc2, was constructed that exhibited a severe growth-arrest phenotype. The ppc1/ppc2 mutant accumulated more starch and sucrose than wild-type plants when seedlings were grown under normal conditions. Physiological and metabolic analysis revealed that decreased PEPC activity in the ppc1/ppc2 mutant greatly reduced the synthesis of malate and citrate and severely suppressed ammonium assimilation. Furthermore, nitrate levels in the ppc1/ppc2 mutant were significantly lower than those in wild-type plants due to the suppression of ammonium assimilation. Interestingly, starch and sucrose accumulation could be prevented and nitrate levels could be maintained by supplying the ppc1/ppc2 mutant with exogenous malate and glutamate, suggesting that low nitrogen status resulted in the alteration of carbon metabolism and prompted the accumulation of starch and sucrose in the ppc1/ppc2 mutant. Our results demonstrate that PEPC in leaves plays a crucial role in modulating the balance of carbon and nitrogen metabolism in Arabidopsis.

  10. Characterization of a complex glucocorticoid response unit in the phosphoenolpyruvate carboxykinase gene.

    PubMed Central

    Imai, E; Stromstedt, P E; Quinn, P G; Carlstedt-Duke, J; Gustafsson, J A; Granner, D K

    1990-01-01

    The minimal DNA sequence required for glucocorticoid induction of the phosphoenolpyruvate carboxykinase (PEPCK) gene in H4IIE rat hepatoma cells was defined. This novel glucocorticoid response unit (GRU) spans about 110 base pairs (bp) and includes two receptor-binding elements plus two accessory factor-binding elements. Purified glucocorticoid receptor bound to two regions (GR1 and GR2) between -395 and -349 bp relative to the transcription start site. Factors in crude rat liver nuclear extract bound to DNA in the regions -455 to -431 and -420 to -403 bp, which are designated accessory factor 1 (AF1) and accessory factor 2 (AF2) elements, respectively. Gel retardation analysis revealed that at least two proteins bound to AF1 and that they were distinct from the protein(s) that bound to AF2. Various combinations of GR1, GR2, AF1, and AF2 were fused to the chloramphenicol acetyltransferase (CAT) reporter gene and cotransfected with a glucocorticoid receptor expression plasmid (pSVGR1) into H4IIE cells to identify the functional GRU. Neither the glucocorticoid receptor binding region nor the accessory factor binding region alone was sufficient to confer glucocorticoid responsiveness. The two components of the glucocorticoid receptor binding region functioned independently, and each accounted for half of the maximal response, provided the accessory factor elements were present. Similarly, deletion of either AF1 or AF2 diminished glucocorticoid induction of the PEPCK gene to approximately half of the maximum. We propose that the complex PEPCK gene GRU provides the stringent regulation required of this critical enzyme in liver. Images PMID:2388623

  11. Regulatory tasks of the phosphoenolpyruvate-phosphotransferase system of Pseudomonas putida in central carbon metabolism.

    PubMed

    Chavarría, Max; Kleijn, Roelco J; Sauer, Uwe; Pflüger-Grau, Katharina; de Lorenzo, Víctor

    2012-01-01

    Two branches of the phosphoenolpyruvate-phosphotransferase system (PTS) operate in the soil bacterium Pseudomonas putida KT2440. One branch encompasses a complete set of enzymes for fructose intake (PTS(Fru)), while the other (N-related PTS, or PTS(Ntr)) controls various cellular functions unrelated to the transport of carbohydrates. The potential of these two systems for regulating central carbon catabolism has been investigated by measuring the metabolic fluxes of isogenic strains bearing nonpolar mutations in PTS(Fru) or PTS(Ntr) genes and grown on either fructose (a PTS substrate) or glucose, the transport of which is not governed by the PTS in this bacterium. The flow of carbon from each sugar was distinctly split between the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways in a ratio that was maintained in each of the PTS mutants examined. However, strains lacking PtsN (EIIA(Ntr)) displayed significantly higher fluxes in the reactions of the pyruvate shunt, which bypasses malate dehydrogenase in the TCA cycle. This was consistent with the increased activity of the malic enzyme and the pyruvate carboxylase found in the corresponding PTS mutants. Genetic evidence suggested that such a metabolic effect of PtsN required the transfer of high-energy phosphate through the system. The EIIA(Ntr) protein of the PTS(Ntr) thus helps adjust central metabolic fluxes to satisfy the anabolic and energetic demands of the overall cell physiology. This study demonstrates that EIIA(Ntr) influences the biochemical reactions that deliver carbon between the upper and lower central metabolic domains for the consumption of sugars by P. putida. These findings indicate that the EIIA(Ntr) protein is a key player for orchestrating the fate of carbon in various physiological destinations in this bacterium. Additionally, these results highlight the importance of the posttranslational regulation of extant enzymatic complexes for increasing the robustness of the

  12. O-GlcNAcylation mediates the control of cytosolic phosphoenolpyruvate carboxykinase activity via Pgc1α.

    PubMed

    Latorre, Pedro; Varona, Luis; Burgos, Carmen; Carrodeguas, José A; López-Buesa, Pascual

    2017-01-01

    PGC1α is a coactivator of many transcription factors and cytosolic phosphoenolpyruvate carboxykinase (PCK1) is a key enzyme for gluconeogenesis. PGC1α interacts with the transcription factor PPARγ to stimulate PCK1 expression and thus de novo glucose synthesis. These proteins are not only important for central energy metabolism but also for supplying intermediates for other metabolic pathways, including lipidogenesis and protein synthesis and might therefore be important factors in the ethiopathogenesis of metabolic disorders like diabetes but also in other pathologies like cancer. Since polymorphisms in these proteins have been related to some phenotypic traits in animals like pigs and PGC1α G482S polymorphism increases fat deposition in humans, we have investigated the molecular basis of such effects focusing on a commonly studied polymorphism in pig Pgc1α, which changes a cysteine at position 430 (WT) of the protein to a serine (C430S). Biochemical analyses show that Pgc1α WT stimulates higher expression of human PCK1 in HEK293T and HepG2 cells. Paradoxically, Pgc1α WT is less stable than Pgc1α p.C430S in HEK293T cells. However, the study of different post-translational modifications shows a higher O-GlcNAcylation level of Pgc1α p.C430S. This higher O-GlcNAcylation level significantly decreases the interaction between Pgc1α and PPARγ demonstrating the importance of post-translational glycosylation of PGC1α in the regulation of PCK1 activity. This, furthermore, could explain at least in part the observed epistatic effects between PGC1α and PCK1 in pigs.

  13. The Ω-loop lid domain of phosphoenolpyruvate carboxykinase is essential for catalytic function.

    PubMed

    Johnson, Troy A; Holyoak, Todd

    2012-11-27

    Phosphoenolpyruvate carboxykinase (PEPCK) is an essential metabolic enzyme operating in the gluconeogenesis and glyceroneogenesis pathways. Recent studies have demonstrated that the enzyme contains a mobile active site lid domain that undergoes a transition between an open, disorded conformation and a closed, ordered conformation as the enzyme progresses through the catalytic cycle. The understanding of how this mobile domain functions in catalysis is incomplete. Previous studies showed that the closure of the lid domain stabilizes the reaction intermediate and protects the reactive intermediate from spurious protonation and thus contributes to the fidelity of the enzyme. To more fully investigate the roles of the lid domain in PEPCK function, we introduced three mutations that replaced the 11-residue lid domain with one, two, and three glycine residues. Kinetic analysis of the mutant enzymes demonstrates that none of the enzyme constructs exhibit any measurable kinetic activity, resulting in a decrease in the catalytic parameters of at least 10(6). Structural characterization of the mutants in complexes representing the catalytic cycle suggests that the inactivity is due to a role for the lid domain in the formation of the fully closed state of the enzyme that is required for catalytic function. In the absence of the lid domain, the enzyme is unable to achieve the fully closed state and is rendered inactive despite possessing all of the residues and substrates required for catalytic function. This work demonstrates how enzyme catalytic function can be abolished through the alteration of conformational equilibria despite all the elements required for chemical conversion of substrates to products remaining intact.

  14. Metal ion interactions with phosphoenolpyruvate carboxylase from Crassula argentea and Zea mays

    SciTech Connect

    Nguyen, T.T.; Ngam-ek, A.; Jenkins, J.; Grover, S.D.

    1988-01-01

    Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C/sub 4/ plant Zea mays were kinetically analyzed. Fe/sup 2 +/ and Cd/sup 2 +/ were found to be active metal cofactors along with the previously known active metals Mg/sup 2 +/, Mn/sup 2 +/, and Co/sup 2 +/. In studies with the Crassula enzyme, Mg/sup 2 +/ yielded the highest V/sub max/ value but also generated the highest values of K/sub m(metal)/ and K/sub m(PEP)/. For these five active metals lower K/sub m(metal)/ values tended to be associated with lower K/sub m(PEP)/ values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 A. Ca/sup 2 +/, Sr/sup 2 +/, Ba/sup 2 +/, and Ni/sup 2 +/ inhibited competitively with respect to Mg/sup 2 +/, whereas Be/sup 2 +/, Cu/sup 2 +/, Zn/sup 2 +/, and Pd/sup 2 +/ showed mixed-type inhibition. V/sub max/ trends with the five active metals were similar for the C. argenta and Z. mays enzymes except that Cd/sup 2 +/ was less effective with the maize enzyme. K/sub m(metal)/ values were 10- to 60-fold higher in the enzyme from Z. mays.

  15. Key role of hydrazine to the interaction between oxaloacetic against phosphoenolpyruvic carboxykinase (PEPCK): ONIOM calculations.

    PubMed

    Prajongtat, Pongthep; Phromyothin, Darinee Sae-Tang; Hannongbua, Supa

    2013-08-01

    The interactions between oxaloacetic (OAA) and phosphoenolpyruvic carboxykinase (PEPCK) binding pocket in the presence and absence of hydrazine were carried out using quantum chemical calculations, based on the two-layered ONIOM (ONIOM2) approach. The complexes were partially optimized by ONIOM2 (B3LYP/6-31G(d):PM6) method while the interaction energies between OAA and individual residues surrounding the pocket were performed at the MP2/6-31G(d,p) level of theory. The calculated interaction energies (INT) indicated that Arg87, Gly237, Ser286, and Arg405 are key residues for binding to OAA with the INT values of -1.93, -2.06, -2.47, and -3.16 kcal mol(-1), respectively. The interactions are mainly due to the formation of hydrogen bonding interactions with OAA. Moreover, using ONIOM2 (B3LYP/6-31G(d):PM6) applied on the PEPCKHS complex, two proton transfers were observed; first, the proton was transferred from the carboxylic group of OAA to hydrazine while the second one was from Asp311 to Lys244. Such reactions cause the generation of binding strength of OAA to the pocket via electrostatic interaction. The orientations of Lys243, Lys244, His264, Asp311, Phe333, and Arg405 were greatly deviated after hydrazine incorporation. These indicate that hydrazine plays an important role in terms of not only changing the conformation of the binding pocket, but is also tightly bound to OAA resulting in its conformation change in the pocket. The understanding of such interaction can be useful for the design of hydrazine-based inhibitor for antichachexia agents.

  16. Novel phosphoenolpyruvate-dependent futile cycle in Streptococcus lactis: 2-deoxy-D-glucose uncouples energy production from growth.

    PubMed Central

    Thompson, J; Chassy, B M

    1982-01-01

    The addition of 2-deoxy-D-glucose to cultures of Streptococcus lactis 133 that were growing exponentially on sucrose or lactose reduced the growth rate by ca. 95%. Inhibition did not occur with glucose or mannose as the growth sugar. The reduction in growth rate was concomitant with rapid accumulation of the analog in phosphorylated form (2-deoxy-D-glucose 6-phosphate) via the phosphoenolpyruvate-dependent mannose:phosphotransferase system. Within 5 min the intracellular 2-deoxy-D-glucose 6-phosphate concentration reached a steady-state level of greater than 100 mM. After maximum accumulation of the sugar phosphate, the rate of sucrose metabolism (glycolysis) decreased by only 30%, but the cells were depleted of fructose-1,6-diphosphate. The addition of glucose to 2-deoxy-D-glucose 6-phosphate preloaded cells caused expulsion of 2-deoxy-D-glucose and a resumption of normal growth. S. lactis 133 contained an intracellular Mg2+-dependent, fluoride-sensitive phosphatase which hydrolyzed 2-deoxy-D-glucose 6-phosphate (and glucose 6-phosphate) to free sugar and inorganic phosphate. Because of continued dephosphorylation and efflux of the non-metabolizable analog, the maintenance of the intracellular 2-deoxy-D-glucose 6-phosphate pool during growth stasis was dependent upon continued glycolysis. This steady-state condition represented a dynamic equilibrium of: (i) phosphoenolpyruvate-dependent accumulation of 2-deoxy-D-glucose 6-phosphate, (ii) intracellular dephosphorylation, and (iii) efflux of free 2-deoxy-D-glucose. This sequence of events constitutes a futile cycle which promotes the dissipation of phosphoenolpyruvate. We conclude that 2-deoxy-D-glucose functions as an uncoupler by dissociating energy production from growth in S. lactis 133. Images PMID:6286601

  17. Physiological studies on regulation of glycerol utilization by the phosphoenolpyruvate:sugar phosphotransferase system in Enterococcus faecalis.

    PubMed Central

    Romano, A H; Saier, M H; Harriott, O T; Reizer, J

    1990-01-01

    In vitro studies with purified glycerol kinase from Enterococcus faecalis have established that this enzyme is activated by phosphorylation of a histidyl residue in the protein, catalyzed by the phosphoenolpyruvate-dependent phosphotransferase system (PTS), but the physiological significance of this observation is not known. In the present study, the regulation of glycerol uptake was examined in a wild-type strain of E. faecalis as well as in tight and leaky ptsI mutants, altered with respect to their levels of enzyme I of the PTS. Glycerol kinase was shown to be weakly repressible by lactose and strongly repressible by glucose in the wild-type strain. Greatly reduced levels of glycerol kinase activity were also observed in the ptsI mutants. Uptake of glycerol into intact wild-type and mutant cells paralleled the glycerol kinase activities in extracts. Glycerol uptake in the leaky ptsI mutant was hypersensitive to inhibition by low concentrations of 2-deoxyglucose or glucose even though the rates and extent of 2-deoxyglucose uptake were greatly reduced. These observations provide strong support for the involvement of reversible PTS-mediated phosphorylation of glycerol kinase in the regulation of glycerol uptake in response to the presence or absence of a sugar substrate of the PTS in the medium. Glucose and 2-deoxyglucose were shown to elicit rapid efflux of cytoplasmic [14C]lactate derived from [14C]glycerol. This phenomenon was distinct from the inhibition of glycerol uptake and was due to phosphorylation of the incoming sugar by cytoplasmic phosphoenolpyruvate. Lactate appeared to be generated by sequential dephosphorylation and reduction of cytoplasmic phosphoenolpyruvate present in high concentrations in resting cells.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2123855

  18. Peach leaf curl disease shifts sugar metabolism in severely infected leaves from source to sink.

    PubMed

    Moscatello, Stefano; Proietti, Simona; Buonaurio, Roberto; Famiani, Franco; Raggi, Vittorio; Walker, Robert P; Battistelli, Alberto

    2017-03-01

    Peach leaf curl is a disease that affects the leaves of peach trees, and in severe cases all of the leaf can be similarly affected. This study investigated some effects of this disease on the metabolism of peach leaves in which all parts of the leaf were infected. These diseased leaves contained very little chlorophyll and performed little or no photosynthesis. Compared to uninfected leaves, diseased leaves possessed higher contents of fructose and especially glucose, but lowered contents of sucrose, sorbitol and especially starch. The activities of soluble acid invertase, neutral invertase, sorbitol dehydrogenase and sucrose synthase were all higher in diseased leaves, whereas, those of aldose-6-phosphate reductase and sucrose phosphate synthase were lower. The activities of hexokinase and fructokinase were little changed. In addition, immunblots showed that the contents of Rubisco and ADP-glucose phosphorylase were reduced in diseased leaves, whereas, the content of phosphoenolpyruvate carboxylase was increased. The results show that certain aspects of the metabolism of diseased leaves are similar to immature sink leaves. That is photosynthetic function is reduced, the leaf imports rather than exports sugars, and the contents of non-structural carbohydrates and enzymes involved in their metabolism are similar to sink leaves. Further, the effects of peach leaf curl on the metabolism of peach leaves are comparable to the effects of some other diseases on the metabolism of photosynthetic organs of other plant species. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  19. Hepatic Subcellular Compartmentation of Cytoplasmic Phosphoenolpyruvate Carboxykinase Determined by Immunogold Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Gao, Kuixiong; Cardell, Emma Lou; Morris, Randal E.; Giffin, Bruce F.; Cardell, Robert R.

    1995-08-01

    Phosphoenolpyruvate carboxykinase (PEPCK) is the rate-limiting gluconeogenic enzyme and in liver occurs in a lobular gradient from periportal to pericentral regions. The subcellular distribution of cytoplasmic PEPCK molecules within hepatocytes and its relationship to organelles have not been determined previously. In this study, we have used immunogold electron microscopy to evaluate the subcellar distribution of the enzyme, in addition to brightfield and epipolarized light microscopy. Cryosections (10 [mu]m) of perfusion-fixed rat liver were collected on silanated slides and immunostained using goat anti-rat PEPCK followed by 5-nm gold-labeled secondary and tertiary antibodies. Additionally, free-floating vibratome sections (25, 50, and 100 [mu]m) of perfusion-immersion-fixed rat liver were immunogold stained using goat anti-rat PEPCK and 5-nm gold-labeled secondary antibody, with and without silver enhancement. The immunogold labeled sections from both procedures were embedded in epoxy resin for the preparation of thin sections for electron microscopy. The results showed that the gold-labeled antibodies penetrated the entire thickness of cryosections, resulting in a high signal for PEPCK, but membranes in general, the smooth endoplasmic reticulum in particular, were not identifiable as electron dense unit membranes. On the other hand, the vibratome sections of well-fixed tissue allowed good visualization of the ultrastructure of cellular organelles, with the smooth endoplasmic reticulum appearing as vesicles and tubules with electron dense unit membranes; however, the penetration of the gold-labeled antibody was limited to cells at the surface of the vibratome sections. In both procedures, PEPCK, as indicated by gold particles, is predominantly in the glycogen areas of the cytosome and not in mitochondria, nuclei, Golgi apparatus, or other cell organelles. Hepatocytes in periportal regions have a compact subcellular distribution of PEPCK shown by gold particles

  20. A GTP-dependent Phosphoenolpyruvate Carboxykinase from Crassostrea gigas Involved in Immune Recognition.

    PubMed

    Lv, Zhao; Qiu, Limei; Wang, Weilin; Liu, Zhaoqun; Xue, Zhuang; Yu, Zichao; Song, Xiaorui; Chen, Hao; Wang, Lingling; Song, Linsheng

    2017-12-01

    Phosphoenolpyruvate carboxykinase (PEPCK) is well known as a key enzyme involved in the metabolic pathway of gluconeogenesis in organisms, but the information about its involvement in immune response is still very limited. In the present study, a novel PEPCK homolog named CgPEPCK was identified from oyster Crassostrea gigas. The deduced amino acid sequence of CgPEPCK shared 52%-74% similarities with those from other known PEPCKs. There were one conserved guanosine triphosphate (GTP) binding site, one substrate binding site, one metal binding site and one active site in CgPEPCK. The mRNA transcripts of CgPEPCK were constitutively expressed in all the tested tissues including hemolymph, mantle, gill, muscle, gonad and hepatopancreas. CgPEPCK proteins were mainly distributed in adductor muscle, gonad, gill and mantle, and rarely detected in hepatopancreas by using immunohistochemical analysis. After the stimulations with lipopolysaccharide (LPS), peptidoglycan (PGN), Vibrio splendidus and V. anguillarum, CgPEPCK transcripts in hemocytes were significantly up-regulated and peaked at 6 h (LPS, 9.62-fold, p < 0.01), 9 h (PGN, 4.25-fold, p < 0.01), 12 h (V. splendidus, 5.72-fold, p < 0.01), 3 h (V. anguillarum, 2.87-fold, p < 0.01), respectively. The recombinant CgPEPCK protein (rCgPEPCK) exhibited Mn(2+)/Mg(2+) dependent GTP binding activity, and the activities to bind LPS and PGN, but not β-1,3-glucan (GLU), lipoteichoic acid (LTA), mannan (MAN) nor polyinosinic-polycytidylic (Poly I: C). It could also bind Escherichia coli, Staphylococcus aureus, Micrococcus luteus and significantly inhibit their growth. All these results collectively suggested that CgPEPCK could not only exert GTP binding activity involved in gluconeogenesis, but also mediate the bacteria recognition and clearance in immune response of oysters. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Increased Phosphoenolpyruvate Carboxykinase Gene Expression and Steatosis during Hepatitis C Virus Subgenome Replication

    PubMed Central

    Qadri, Ishtiaq; Choudhury, Mahua; Rahman, Shaikh Mizanoor; Knotts, Trina A.; Janssen, Rachel C.; Schaack, Jerome; Iwahashi, Mieko; Puljak, Livia; Simon, Francis R.; Kilic, Gordan; Fitz, J. Gregory; Friedman, Jacob E.

    2012-01-01

    Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression

  2. Studies on the degradative mechanism of phosphoenolpyruvate carboxykinase from yeast Saccharomyces cerevisiae.

    PubMed

    Burlini, N; Morandi, S; Pellegrini, R; Tortora, P; Guerritore, A

    1989-11-20

    Previous work carried out in our laboratory (Burlini, N., Lamponi S., Radrizzani, M., Monti, E. and Tortora P. (1987) Biochim. Biophys. Acta 930, 220-229) led to the immunological identification of a yeast 65-kDa phosphoprotein as a modified form of phosphoenolpyruvate carboxykinase; moreover the appearance of this phospho form was proven to be independent of cAMP, whereas the glucose-induced inactivation of the native enzyme is cAMP-dependent. Here, we report further investigations on the mechanism of the glucose-triggered degradation of the enzyme which led to the following results: (a) the aforementioned phospho form displayed a binding pattern to 5 AMP-Sepharose 4B quite similar to that of native enzyme, although it did not retain its oligomeric structure, nor was it catalytically active; (b) its phosphate content was of about two residues per monomer; (c) its isoelectric point was slightly higher than that of native enzyme, this shows that the enzyme undergoes additional modifications besides phosphorylation; (d) it represented about 4% of the native enzyme in glucose-depressed cells; (e) other forms immunologically cross-reactive with the native enzyme were also isolated, whose molecular mass was in the range of 60-62 kDa, and they are probable candidates as degradation products of the phospho form; (f) time courses of the native and phospho forms in the presence and the absence of glucose provided data consistent with a kinetic model involving a strong stimulation of the decay of both forms effected by the sugar; (g) in the mutant ABYS1 (Achstetter, T., Emter, O., Ehmann, C. and Wolf, D.H. (1984) J. Biol. Chem. 259, 13334-13343) which is devoid of the four major vacuolar proteinases, the decay pattern was essentially the same as in wild-type; (h) effectors lowering intracellular ATP also retarded the first step of enzyme degradation; this points to an ATP-dependence of this step. Based on these results we propose a degradation mechanism consisting of an

  3. The activity of phosphoenolpyruvate carboxykinase in rat tissues. Assay techniques and effects of dietary and hormonal changes

    PubMed Central

    Pogson, Christopher I.; Smith, Stephen A.

    1975-01-01

    1. Phosphoenolpyruvate carboxykinase was assayed by three methods: (i) incorporation of H14CO3− into oxaloacetate: (ii) conversion of oxaloacetate into phosphoenolpyruvate, subsequently assayed enzymically; and (iii) transfer of 32P from [γ-32P]GTP to oxaloacetate. 2. Enzyme activity is increased in liver and epididymal adipose tissue in alloxan-diabetes and starvation, and in kidney in starved, acidotic and steroid-treated animals. 3. The ratios of the `back' to the `forward' reactions in liver, kidney and epididymal adipose tissue are different and characteristic of each tissue; they differ markedly from values reported for the purified mitochondrial enzyme. 4. The ratio of the `back' to `forward' reaction in any one tissue is constant in adrenalectomized, diabetic, acidotic and steroid-treated animals. 5. In starved animals, the ratio is increased in liver and kidney, but decreased in epididymal adipose tissue. 6. Administration of l-tryptophan results in an acute (1h) increase in activity measured in the `forward' direction alone in liver and epididymal adipose tissue, but not in kidney. PMID:1220693

  4. Re-examination of the roles of PEP and Mg2+ in the reaction catalysed by the phosphorylated and non-phosphorylated forms of phosphoenolpyruvate carboxylase from leaves of Zea mays. Effects of the activators glucose 6-phosphate and glycine.

    PubMed Central

    Tovar-Méndez, A; Rodríguez-Sotres, R; López-Valentín, D M; Muñoz-Clares, R A

    1998-01-01

    To study the effects of phosphoenolpyruvate (PEP) and Mg2+ on the activity of the non-phosphorylated and phosphorylated forms of phosphoenolpyruvate carboxylase (PEPC) from Zea mays leaves, steady-state measurements have been carried out with the free forms of PEP (fPEP) and Mg2+ (fMg2+), both in a near-physiological concentration range. At pH 7.3, in the absence of activators, the initial velocity data obtained with both forms of the enzyme are consistent with the exclusive binding of MgPEP to the active site and of fPEP to an activating allosteric site. At pH 8.3, and in the presence of saturating concentrations of glucose 6-phosphate (Glc6P) or Gly, the free species also combined with the active site in the free enzyme, but with dissociation constants at least 35-fold that estimated for MgPEP. The latter dissociation constant was lowered to the same extent by saturating Glc6P and Gly, to approx. one-tenth and one-sixteenth in the non-phosphorylated and phosphorylated enzymes respectively. When Glc6P is present, fPEP binds to the active site in the free enzyme better than fMg2+, whereas the metal ion binds better in the presence of Gly. Saturation of the enzyme with Glc6P abolished the activation by fPEP, consistent with a common binding site, whereas saturation with Gly increased the affinity of the allosteric site for fPEP. Under all the conditions tested, our results suggest that fPEP is not able to combine with the allosteric site in the free enzyme, i.e. it cannot combine until after MgPEP, fPEP or fMg2+ are bound at the active site. The physiological role of Mg2+ in the regulation of the enzyme is only that of a substrate, mainly as part of the MgPEP complex. The kinetic properties of maize leaf PEPC reported here are consistent with the enzyme being well below saturation under the physiological concentrations of fMg2+ and PEP, particularly during the dark period; it is therefore suggested that the basal PEPC activity in vivo is very low, but highly

  5. Activation of SIRT1 by resveratrol represses transcription of the gene for the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) by deacetylating hepatic nuclear factor 4alpha

    USDA-ARS?s Scientific Manuscript database

    The cytosolic isoform of phosphoenolpyruvate carboxykinase (GTP) (PEPCK-C) is a key enzyme of gluconeogenesis and glyceroneogenesis. While this enzyme is often over-expressed in diabetes and obesity, studies showed that decrease in its expression results in lessening the diseases condition in animal...

  6. Enhancement of porcine intramuscular fat content by overexpression of the cytosolic form of phosphoenolpyruvate carboxykinase in skeletal muscle

    PubMed Central

    Ren, Zijian; Wang, Ying; Ren, Yuanyuan; Zhang, Zhengwei; Gu, Weiwang; Wu, Zhaoting; Chen, Lingyi; Mou, Lisha; Li, Rongfeng; Yang, Haiyuan; Dai, Yifan

    2017-01-01

    Intramuscular fat (IMF) content has been generally recognized as a desirable trait in pork meat because of its positive effect on eating quality. An effective approach to enhance IMF content in pork is the generation of transgenic pigs. In this study, we used somatic cell nuclear transfer (SCNT) to generate cloned pigs exhibiting ectopic expression of phosphoenolpyruvate carboxykinase (PEPCK-C) driven by an α-skeletal-actin gene promoter, which was specifically expressed in skeletal muscle. Using qRT-PCR and Western blot analysis, we demonstrated that PEPCK-C was functionally expressed and had a significant effect on total fatty acid content in the skeletal muscle of the transgenic pigs, while the n-6/n-3 polyunsaturated fatty acid (PUFA) ratio showed no difference between transgenic and control pigs. Thus, genetically engineered PEPCK-Cmus pigs may be an effective solution for the production of IMF-enriched pork. PMID:28252054

  7. Control of phosphoenolpyruvate-dependent phosphotransferase-mediated sugar transport in Escherichia coli by energization of the cell membrane.

    PubMed Central

    Reider, E; Wagner, E F; Schweiger, M

    1979-01-01

    The phosphoenolpyruvate-dependent phosphotransferase-mediated sugar transport in Escherichia coli is inhibited by the energized of the membrane. This was shown in intact cells as well as in membrane vesicles. Relaxation of the proton gradient by uncouplers stimulated the uptake of sugars via the phosphotransferase system in aerobically cultured cells. No such effect was seen in anaerobic cells, apparently because the cell membrane of these cells is poorly energized. Energization by respiration of D-lactate or ascorbate inhibited the phosphotransferase uptake system in membrane vesicles. This inhibition was reversed by the addition of cyanide. Oxamate, a specific inhibitor of lactate dehydrogenase, prevented the inhibitory effect of D-lactate. Membrane vesicles prepared from a cytochrome-less mutant were not energized by D-lactate oxidation and the phosphotransferase uptake system was not inhibited. PMID:392504

  8. Cytosolic Phosphoenolpyruvate Carboxykinase Does Not Solely Control the Rate of Hepatic Gluconeogenesis in the Intact Mouse Liver

    PubMed Central

    Burgess, Shawn C.; He, Tian Teng; Yan, Zheng; Lindner, Jill; Sherry, A. Dean; Malloy, Craig R.; Browning, Jeffrey D.; Magnuson, Mark A.

    2009-01-01

    SUMMARY When dietary carbohydrate is unavailable, glucose required to support metabolism in vital tissues is generated via gluconeogenesis in the liver. Expression of phosphoenolpyruvate carboxykinase (PEPCK), commonly considered the control point for liver gluconeogenesis, is normally regulated by circulating hormones to match systemic glucose demand. However, this regulation fails in diabetes. Because other molecular and metabolic factors can also influence gluconeogenesis, the explicit role of PEPCK protein content in the control of gluconeogenesis was unclear. In this study, metabolic control of liver gluconeogenesis was quantified in groups of mice with varying PEPCK protein content. Surprisingly, livers with a 90% reduction in PEPCK content showed only a ~40% reduction in gluconeogenic flux, indicating a lower than expected capacity for PEPCK protein content to control gluconeogenesis. However, PEPCK flux correlated tightly with TCA cycle activity, suggesting that under some conditions in mice, PEPCK expression must coordinate with hepatic energy metabolism to control gluconeogenesis. PMID:17403375

  9. Purification and comparison of phosphoenolpyruvate carboxykinase from the liver and kidney of the Arabian camel (Camelus dromedarius).

    PubMed

    Al-Ali, A K; Al-Husayni, H; Power, D M

    1988-01-01

    1. Phosphoenolpyruvate carboxykinase was partially purified from camel liver and kidney by ammonium sulphate fractionation, gel filtration and ion-exchange chromatography. 2. The specific activity of the purified preparation from liver was 39.2 mumol/min per mg protein. 3. When isolated from the kidney the specific activity of the enzyme was very much higher 155.5 mumol/min per mg protein. 4. The enzyme from the two sources were similar in their pH optimum which was approx. 7.2 and their relative stability to thermal inactivation at 60 degrees C. 5. The mol. wt of the enzyme from both organs was estimated at 80,000 +/- 5000.

  10. Enhancement of porcine intramuscular fat content by overexpression of the cytosolic form of phosphoenolpyruvate carboxykinase in skeletal muscle.

    PubMed

    Ren, Zijian; Wang, Ying; Ren, Yuanyuan; Zhang, Zhengwei; Gu, Weiwang; Wu, Zhaoting; Chen, Lingyi; Mou, Lisha; Li, Rongfeng; Yang, Haiyuan; Dai, Yifan

    2017-03-02

    Intramuscular fat (IMF) content has been generally recognized as a desirable trait in pork meat because of its positive effect on eating quality. An effective approach to enhance IMF content in pork is the generation of transgenic pigs. In this study, we used somatic cell nuclear transfer (SCNT) to generate cloned pigs exhibiting ectopic expression of phosphoenolpyruvate carboxykinase (PEPCK-C) driven by an α-skeletal-actin gene promoter, which was specifically expressed in skeletal muscle. Using qRT-PCR and Western blot analysis, we demonstrated that PEPCK-C was functionally expressed and had a significant effect on total fatty acid content in the skeletal muscle of the transgenic pigs, while the n-6/n-3 polyunsaturated fatty acid (PUFA) ratio showed no difference between transgenic and control pigs. Thus, genetically engineered PEPCK-C(mus) pigs may be an effective solution for the production of IMF-enriched pork.

  11. Increased incorporation of gaseous CO2 into succinate by Escherichia coli overexpressing carbonic anhydrase and phosphoenolpyruvate carboxylase genes.

    PubMed

    Park, Soohyun; Lee, Jae-Ung; Cho, Sukhyeong; Kim, Hyeonsoo; Oh, Han Bin; Pack, Seung Pil; Lee, Jinwon

    2017-01-10

    Carbon dioxide (CO2) is an abundant and cheap carbon source that is partly responsible for global warming in the atmosphere. The objective of this study was to construct a recombinant E. coli strain that can show enhanced production of succinate derived from CO2. In this study, we confirmed the enhancement of utilization by analyzing succinate containing one carbon-13 ((13)C) derived from (13)CO2. Firstly, the carbonic anhydrase gene (SP(-)HCCA) derived from Hahella chejuensis KCTC 2396 was over-expressed to enhance carbon flux toward bicarbonate ion (HCO3(-)) synthesis in E. coli. The phosphoenolpyruvate carboxylase gene (ppc) was over-expressed to enhance the production of oxaloacetate by enhancing the carbon flux. Compared with the control strain, the percentage of the succinate containing one (13)C (succinate(119)) to total succinate was enhanced by approximately 2.80-fold and the amount of succinate(119) also increased by approximately 4.09-fold in SGJS120. Secondly, the lactate dehydrogenase gene (ldhA) was deleted to re-direct the utilization of the carbon source from glucose to enhance succinate production in SGJS120. However, ldhA deletion did not increase CO2 utilization in SJGS120. Finally, the phosphotransferase system gene (ptsG) and pyruvate kinase F gene (pykF) were deleted to increase the amount of phosphoenolpyruvate (PEP). SGJS126 (pykF deletion strain) showed the highest increase, which was 6.05-fold higher than the control strain. From the results, SP(-)HCCA overexpression and pykF deletion may be useful for enhancing CO2 utilization in E. coli. Additionally, engineered strains showed the potential to reduce the cost of succinate production by using an industrially cheaper carbon source such as CO2 and converting CO2 to a valuable chemical. Copyright © 2016. Published by Elsevier B.V.

  12. Evolution of the Phosphoenolpyruvate Carboxylase Protein Kinase Family in C3 and C4 Flaveria spp.1[W][OPEN

    PubMed Central

    Aldous, Sophia H.; Weise, Sean E.; Sharkey, Thomas D.; Waldera-Lupa, Daniel M.; Stühler, Kai; Mallmann, Julia; Groth, Georg; Gowik, Udo; Westhoff, Peter; Arsova, Borjana

    2014-01-01

    The key enzyme for C4 photosynthesis, Phosphoenolpyruvate Carboxylase (PEPC), evolved from nonphotosynthetic PEPC found in C3 ancestors. In all plants, PEPC is phosphorylated by Phosphoenolpyruvate Carboxylase Protein Kinase (PPCK). However, differences in the phosphorylation pattern exist among plants with these photosynthetic types, and it is still not clear if they are due to interspecies differences or depend on photosynthetic type. The genus Flaveria contains closely related C3, C3-C4 intermediate, and C4 species, which are evolutionarily young and thus well suited for comparative analysis. To characterize the evolutionary differences in PPCK between plants with C3 and C4 photosynthesis, transcriptome libraries from nine Flaveria spp. were used, and a two-member PPCK family (PPCKA and PPCKB) was identified. Sequence analysis identified a number of C3- and C4-specific residues with various occurrences in the intermediates. Quantitative analysis of transcriptome data revealed that PPCKA and PPCKB exhibit inverse diel expression patterns and that C3 and C4 Flaveria spp. differ in the expression levels of these genes. PPCKA has maximal expression levels during the day, whereas PPCKB has maximal expression during the night. Phosphorylation patterns of PEPC varied among C3 and C4 Flaveria spp. too, with PEPC from the C4 species being predominantly phosphorylated throughout the day, while in the C3 species the phosphorylation level was maintained during the entire 24 h. Since C4 Flaveria spp. evolved from C3 ancestors, this work links the evolutionary changes in sequence, PPCK expression, and phosphorylation pattern to an evolutionary phase shift of kinase activity from a C3 to a C4 mode. PMID:24850859

  13. Leaf Size in Swietenia

    Treesearch

    Charles B. Briscoe; F. Bruce. Lamb

    1962-01-01

    A study was made of the putative hybrid of bigleaf and small-leaf mahoganies. Initial measurements indicated that bigleaf mahogany can be distinguished from small-leaf mahogany by gross measurements of leaflets. Isolated mother trees yield typical progeny. Typical mother trees in mixed stands yield like progeny plus, usually, mediumleaf progeny. Mediumleaf mother trees...

  14. Leaf growth is conformal

    NASA Astrophysics Data System (ADS)

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I.; Boudaoud, Arezki

    2016-10-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour.

  15. Increased Phosphoenolpyruvate Carboxykinase (PEPCK) Gene Expression and Steatosis During Hepatitis C Virus (HCV) Subgenome Replication: Role of Nonstructural Component-5A (NS5A) and CCAAT/Enhancer Binding Protein ß (C/EBPß)

    USDA-ARS?s Scientific Manuscript database

    Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated tra...

  16. Project LEAF Documents

    EPA Pesticide Factsheets

    Project LEAF has a goal of educating farmworkers about how to reduce pesticide exposure to their families from pesticide residues they may be inadvertently taking home on their clothing, etc. Find outreach materials.

  17. A kinetic study of the effects of phosphate and organic phosphates on the activity of phosphoenolpyruvate carboxylase from Crassula argentea.

    PubMed

    Meyer, C R; Rustin, P; Wedding, R T

    1989-05-15

    The effects of phosphate and several phosphate-containing compounds on the activity of purified phosphoenolpyruvate carboxylase (PEPC) from the crassulacean acid metabolism plant, Crassula argentea, were investigated. When assayed at subsaturating phosphoenolpyruvate (PEP) concentrations, low concentrations of most of the compounds tested were found to stimulate PEPC activity. This activation, variable in extent, was found in all cases to be competitive with glucose 6-phosphate (Glc-6-P) stimulation, suggesting that these effectors bind to the Glc-6-P site. At higher concentrations, depending upon the effector molecule studied, deactivation, inhibition, or no response was observed. More detailed studies were performed with Glc-6-P, AMP, phosphoglycolate, and phosphate. AMP had previously been shown to be a specific ligand for the Glc-6-P site. The main effect of Glc-6-P and AMP on the kinetic parameters was to decrease the apparent Km and increase Vmax/Km. AMP also caused a decrease in the Vmax of the reaction. In contrast, phosphoglycolate acted essentially as a competitive inhibitor increasing the apparent Km for PEP and decreasing Vmax/Km. Inorganic phosphate had a biphasic effect on the kinetic parameters, resulting in a transient decrease in Km followed by an increase of the apparent Km for PEP with increasing concentration of phosphate. The Vmax also was decreased with increasing phosphate concentrations. Further, the enzyme appeared to respond to the complex of phosphate with magnesium. In the presence of a saturating concentration of AMP, no activation but rather inhibition was observed with increasing phosphate concentration. This is consistent with the binding of phosphate to two separate sites--the Glc-6-P activation site and an inhibitory site, a phenomenon that may be occurring with other phosphate containing compounds. High concentrations of phosphate with magnesium were found to protect enzyme activity when PEPC, previously shown to contain an

  18. Deer predation on leaf miners via leaf abscission

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  19. Deer predation on leaf miners via leaf abscission.

    PubMed

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer (Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  20. Phosphoenolpyruvate carboxykinase (GTP): Characterization of the human PCK1 gene and localization distal to MODY on chromosome 20

    SciTech Connect

    Ting, Chao Nan; Burgess, D.L.; Chamberlain, J.S.; Meisler, M.H. ); Keith, T.P.; Falls, K. )

    1993-06-01

    The human PCK 1 gene encoding phosphoenolpyruvate carboxykinase (GTP) (PEPCK) was isolated and sequenced. There is 91% amino acid sequence identity (567/622 residues) between the human and the rat proteins, with conservation of intron/exon borders. A polymorphic dinucleotide microsatellite with the structure (CA)[sub 16](TA)[sub 5](CA) was identified in the 3[prime] untranslated region of the cloned human PCK1 gene. This highly informative genetic marker has an estimated PIC value of 0.79 and heterozygosity of 0.81. Analysis of the RW pedigree demonstrated recombination between PCK1 and the MODY gene on chromosome 20. Multipoint linkage analysis of the reference pedigrees of the Centre d'Etude du Polymorphisme Humain localized PCK1 on the genetic map of chromosome 20 at a position distal to markers that are closely linked to MODY. PCK1 is part of a conserved linkage group on mouse Chromosome 2 with identical gene order but expanded length in the human genome. 34ref., 7 figs., 1 tab.

  1. A Genome-Wide Screen Reveals that the Vibrio cholerae Phosphoenolpyruvate Phosphotransferase System Modulates Virulence Gene Expression

    PubMed Central

    Millet, Yves A.; Chao, Michael C.; Sasabe, Jumpei; Davis, Brigid M.

    2015-01-01

    Diverse environmental stimuli and a complex network of regulatory factors are known to modulate expression of Vibrio cholerae's principal virulence factors. However, there is relatively little known about how metabolic factors impinge upon the pathogen's well-characterized cascade of transcription factors that induce expression of cholera toxin and the toxin-coregulated pilus (TCP). Here, we used a transposon insertion site (TIS) sequencing-based strategy to identify new factors required for expression of tcpA, which encodes the major subunit of TCP, the organism's chief intestinal colonization factor. Besides identifying most of the genes known to modulate tcpA expression, the screen yielded ptsI and ptsH, which encode the enzyme I (EI) and Hpr components of the V. cholerae phosphoenolpyruvate phosphotransferase system (PTS). In addition to reduced expression of TcpA, strains lacking EI, Hpr, or the associated EIIAGlc protein produced less cholera toxin (CT) and had a diminished capacity to colonize the infant mouse intestine. The PTS modulates virulence gene expression by regulating expression of tcpPH and aphAB, which themselves control expression of toxT, the central activator of virulence gene expression. One mechanism by which PTS promotes virulence gene expression appears to be by modulating the amounts of intracellular cyclic AMP (cAMP). Our findings reveal that the V. cholerae PTS is an additional modulator of the ToxT regulon and demonstrate the potency of loss-of-function TIS sequencing screens for defining regulatory networks. PMID:26056384

  2. Promotion of photosynthesis in transgenic rice over-expressing of maize C4 phosphoenolpyruvate carboxylase gene by nitric oxide donors.

    PubMed

    Chen, Pingbo; Li, Xia; Huo, Kai; Wei, Xiaodong; Dai, Chuanchao; Lv, Chuangen

    2014-03-15

    We determined the effects of exogenous nitric oxide on photosynthesis and gene expression in transgenic rice plants (PC) over-expressing the maize C4pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC). Seedlings were subjected to treatments with NO donors, an NO scavenger, phospholipase inhibitors, a Ca(2+) chelator, a Ca(2+) channel inhibitor, and a hydrogen peroxide (H2O2) inhibitor, individually and in various combinations. The NO donors significantly increased the net photosynthetic rate (PN) of PC and wild-type (WT), especially that of PC. Treatment with an NO scavenger did inhibit the PN of rice plants. The treatments with phospholipase inhibitors and a Ca(2+) chelator decreased the PN of WT and PC, and photosynthesis was more strongly inhibited in WT than in PC. Further analyses showed that the NO donors increased endogenous levels of NO and PLD activity, but decreased endogenous levels of Ca(2+) both WT and PC. However, there was a greater increase in NO in WT and a greater increase in PLD activity and Ca(2+) level in PC. The NO donors also increased both PEPC activity and pepc gene expression in PC. PEPC activity can be increased by SNP alone. But the expression of its encoding gene in PC might be regulated by SNP, together with PA and Ca(2+).

  3. Insulinotropic effect of cinnamaldehyde on transcriptional regulation of pyruvate kinase, phosphoenolpyruvate carboxykinase, and GLUT4 translocation in experimental diabetic rats.

    PubMed

    Anand, Prachi; Murali, K Y; Tandon, Vibha; Murthy, P S; Chandra, Ramesh

    2010-06-07

    Diabetes mellitus is a chronic metabolic disorder affecting about 6% of population worldwide with its complications and is rapidly reaching epidemic scale. Cinnamomum zeylanicum is widely used in alternative system of medicine for treatment of diabetes. In the present study, we have performed bioassay guided fractionation of chloroform extract of C. zeylaniucm and identified cinnamaldehyde (CND) as an active principle against diabetes. In continuation to it, a detailed study was undertaken to elucidate its mode of antidiabetic action in STZ induced diabetic rats. Oral administration of CND (20 mg/kg bw) to diabetic rats for 2 months showed significant improvement (p<0.001) in muscle and hepatic glycogen content. In vitro incubation of pancreatic islets with CND enhanced the insulin release compared to glibenclamide. The insulinotropic effect of CND was found to increase the glucose uptake through glucose transporter (GLUT4) translocation in peripheral tissues. The treatment also showed a significant improvement in altered enzyme activities of pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) and their mRNA expression levels. Furthermore, the median lethal dose (LD(50)) of CND could not be obtained even at 20 times (0.4 g/kg bw) of its effective dose. With the high margin of safety of CND, it can be developed as a potential therapeutic candidate for the treatment of diabetes.

  4. Constitutive and dark-induced expression of Solanum tuberosum phosphoenolpyruvate carboxylase enhances stomatal opening and photosynthetic performance of Arabidopsis thaliana.

    PubMed

    Kebeish, Rashad; Niessen, Markus; Oksaksin, Mehtap; Blume, Christian; Peterhaensel, Christoph

    2012-02-01

    The effect of constitutive and dark-induced expression of Solanum tuberosum phosphoenolpyruvate carboxylase (PEPC) on the opening state of stomata and photosynthetic performance in Arabidopsis thaliana plants was studied. Transcript accumulation analyses of the A. thaliana dark-induced (Din10 and Din6) and the Pisum sativum asparagine synthetase 2 promoters (Asn2) in transiently transformed tobacco leaves showed that Din10 promoter induced more DsRed accumulation in the dark compared to the other din genes. Overexpression of PEPC under the control of the constitutive enhanced CaMV 35S (p35SS) and dark-induced Din10 promoter in stably transformed A. thaliana plants increased the number of opened stomata in dark adapted leaves. Gas exchange measurements using A. thaliana plants transgenic for p35SS-PEPC and Din10-PEPC revealed a marked increase in stomatal conductance, transpiration, and dark respiration rates measured in the dark compared to wild-type plants. Moreover, measurement of CO(2) assimilation rates at different external CO(2) concentrations (C(a) ) and different light intensities shows an increase in the CO(2) assimilation rates in transgenic Arabidopsis lines compared to wild-type plants. This is considered as first step towards transferring the aspects of Crassulacean acid metabolism-like photosynthetic mechanism into C3 plants.

  5. Reaction of wild-type C365S, and C458S saccharomyces cerevisiae phosphoenolpyruvate carboxykinases with fluorescent iodoacetamide derivatives.

    PubMed

    Krautwurst, H; Berti, M; Encinas, M V; Frey, P A

    1996-03-01

    The reactivities of Cys365 and Cys458 of ATP-dependent Saccharomyces cerevisiae phosphoenolpyruvate (PEP) carboxykinase against a range of sulfhydryl reagents have been investigated. The effect of pH on the second order reaction constants of N-(1-pyrenyl)maleimide with mutant C458S and C365S PEP carboxykinases allowed the determination of pKa values of 9.4 and 9.1 for Cys365 and Cys458, respectively. The analysis of the inactivation rates of C458S and C365S mutant enzymes by several sulfhydryl reagents of different hydrophobicity showed that the microenvironment of these residues is rather polar. Anisotrophy measurements and acrylamide quenching experiments carried out with N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine-labeled mutant enzymes indicated a higher rotational freedom and solvent exposure for the probe linked to Cys458 than to Cys365. These findings point to differences in the protein microenvironments around Cys365 and Cys458 in S. cerevisiae PEP carboxykinase. A comparison of the results obtained with published data for GTP-dependent PEP carboxykinases, suggest significant differences for the protein region around the reactive cysteinyl residues in these enzymes.

  6. Localization and hormonal control of serine dehydratase during metabolic acidosis differ markedly from those of phosphoenolpyruvate carboxykinase in rat kidney.

    PubMed

    Masuda, Tohru; Ogawa, Hirofumi; Matsushima, Takako; Kawamata, Seiichi; Sasahara, Masakiyo; Kuroda, Kazunari; Suzuki, Yasuhiro; Takata, Yoshimi; Yamazaki, Mitsuaki; Takusagawa, Fusao; Pitot, Henry C

    2003-08-01

    Serine dehydratase (SDH) is abundant in the rat liver but scarce in the kidney. When administrated with dexamethasone, the renal SDH activity was augmented 20-fold, whereas the hepatic SDH activity was affected little. In situ hybridization and immunohistochemistry revealed that SDH was localized to the proximal straight tubule of the nephron. To address the role of this hormone, rats were made acidotic by gavage of NH(4)Cl. Twenty-two hours later, the SDH activity was increased three-fold along with a six-fold increment in the phosphoenolpyruvate carboxykinase (PEPCK) activity, a rate-limiting enzyme of gluconeogenesis. PEPCK, which is localized to the proximal tubules under the normal condition, spreads throughout the entire cortex to the outer medullary rays by acidosis, whereas SDH does not change regardless of treatment with dexamethasone or NH(4)Cl. When NH(4)Cl was given to adrenalectomized rats, in contrast to the SDH activity no longer increasing, the PEPCK activity responded to acidosis to the same extent as in the intact rats. A simultaneous administration of dexamethasone and NH(4)Cl into the adrenalectomized rats fully restored the SDH activity, demonstrating that the rise in the SDH activity during acidosis is primarily controlled by glucocorticoids. The present findings clearly indicate that the localization of SDH and its hormonal regulation during acidosis are strikingly different from those of PEPCK.

  7. ppc, the gene for phosphoenolpyruvate carboxylase from an extremely thermophilic bacterium, Rhodothermus obamensis: cloning, sequencing and overexpression in Escherichia coli.

    PubMed

    Takai, K; Sako, Y; Uchida, A

    1998-05-01

    The ppc gene, which encodes phosphoenolpyruvate carboxylase (PEPC) of an extremely thermophilic bacterium, Rhodothermus obamensis, was directly sequenced by the thermal asymmetric interlaced (TAIL) PCR method. An ORF for a 937 amino acid polypeptide was found in the gene. The ppc gene had a high G+C content (66.2 mol%) and the third position of the codon exhibited strong preference for G or C usage (85.0 mol%). The calculated molecular mass was 107,848 Da, which was consistent with the molecular mass of the enzyme as determined by SDS-PAGE (100 kDa). The amino acid sequence of R. obamensis PEPC was closely related to that of PEPC from another thermophile, a Thermus sp., and from a mesophile, Corynebacterium glutamicum, exhibiting 45.3% or 37.7% identity and 61.5% or 56.5% similarity, respectively. By Southern analysis, the ppc gene was found to be present in a single copy in the genomic DNA of this organism. The cloned gene was expressed in Escherichia coli using a pET expression vector system and a thermostable recombinant PEPC was obtained. Comparison of the deduced amino acid sequences of the thermophilic and mesophilic PEPCs revealed distinct or common preferences for specific amino acid composition and substitutions in the two thermophilic enzymes.

  8. Metabolic analysis of Escherichia coli in the presence and absence of the carboxylating enzymes phosphoenolpyruvate carboxylase and pyruvate carboxylase

    SciTech Connect

    Gokarn, R.R.; Eiteman, M.A.; Altman, E.

    2000-05-01

    Fermentation patterns of Escherichia coli with and without the phosphoenolpyruvate carboxylase (PPC) and pyruvate carboxylase (PYC) enzymes were compared under anaerobic conditions with glucose as a carbon source. Time profiles of glucose and fermentation product concentrations were determined and used to calculate metabolic fluxes through central carbon pathways during exponential cell growth. The presence of the Rhizobium etli pyc gene in E. coli (JCL1242/pTrc99A-pyc) restored the succinate producing ability of E. coli ppc null mutants (JCL1242), with PYC competing favorably with both pyruvate formate lyase and lactate dehydrogenase. Succinate formation was slightly greater by JCL1242/pTrc99a-pyc than by cells which overproduced PPC(JCL1242/pPC201, ppc{sup +}), even though PPC activity in cell extracts of JCL1242/pPC201 (ppc{sup +}) was 40-fold greater than PYC activity in extracts of JCL1242/pTrc99a-pyc. Flux calculations indicate that during anaerobic metabolism the pyc{sup +} strain had a 34% greater specific glucose consumption rate, a 37% greater specific rate of ATP formation, and a 6% greater specific growth rate compared to the ppc{sup +} strain. In light of the important position of pyruvate at the juncture of NADH-generating pathways and NADH-dissimilating branches, the results show that when PPC or PYC is expressed, the metabolic network adapts by altering the flux to lactate and the molar ratio of ethanol to acetate formation.

  9. Hormonal regulation of phosphoenolpyruvate carboxykinase gene expression is mediated through modulation of an already disrupted chromatin structure

    SciTech Connect

    Ip, Y.T.; Granner, D.K.; Chalkley, R. . School of Medicine)

    1989-03-01

    The authors used indirect end labeling to identify a series of five hypersensitive (HS) sites in the phosphoenolpyruvate carboxykinase (PEPCK) gene in H4IIE rat hepatoma cells. These sites were found at -4800 base pairs (bp) (site A), at -1300 bp (site B), over a broad domain between -400 and -30 bp (site C), at +4650 bp (site D), and at +6200 bp (site E). Sites A to D were detected only in cells capable of expressing the PEPCK gene, whereas site E was present in all of the cells examined thus far. The HS sites were present in H4IIE cells even when transcriptional activity was reduced to a minimum by treatment with insulin. Stimulation of transcription by a cyclic AMP analog to a 40-fold increase over the insulin-repressed level did not affect the main features of the HS sites. Furthermore, increased transcription did not disrupt the nucleosomal arrangement of the coding region of the gene, nor did it affect the immediate 5' region (site C), which is always nucleosome-free. In HTC cells, a rat hepatoma line that is hormonally responsive but unable to synthesize PEPCK mRNA, the four expression-specific HS sites were totally absent. The authors experimental results also showed that, although there is a general correlation between lack of DNA methylation and transcriptional competence of the PEPCK gene, the role, if any, of methylation in the regulation of PEPCK gene activity is likely to be exerted at very specific sites.

  10. Phenobarbital reduces blood glucose and gluconeogenesis through down-regulation of phosphoenolpyruvate carboxykinase (GTP) gene expression in rats.

    PubMed

    Oda, Hiroaki; Okuda, Yuji; Yoshida, Yukiko; Kimura, Noriko; Kakinuma, Atsushi

    2015-10-23

    The regulatory mechanism of phosphoenolpyruvate carboykinase (GTP) (EC 4.1.1.32) (PEPCK) gene expression and gluconeogenesis by phenobarbital (PB), which is known to induce drug-metabolizing enzymes, was investigated. Higher level of PEPCK mRNA was observed in spherical rat primary hepatocytes on EHS-gel than monolayer hepatocytes on TIC (type I collagen). We found that PB directly suppressed PEPCK gene expression in spherical hepatocytes on EHS-gel, but not in those on TIC. PB strongly suppressed cAMP-dependent induction of PEPCK gene expression. Tyrosine aminotransferase (TAT), another gluconeogenic enzyme, was induced by cAMP, but not suppressed by PB. Chronic administration of PB reduced hepatic PEPCK mRNA in streptozotocin-induced diabetic and nondiabetic rats, and PB reduced blood glucose level in diabetic rats. Increased TAT mRNA in diabetic rats was not suppressed by PB. These results indicated that PB-dependent reduction is specific to PEPCK. From pyrvate challenge test, PB suppressed the increased gluconeogenesis in diabetic rats. PEPCK gene promoter activity was suppressed by PB in HepG2 cells. In conclusion, we found that spherical hepatocytes cultured on EHS-gel are capable to respond to PB to suppress PEPCK gene expression. Moreover, our results indicate that hypoglycemic action of PB result from transcriptional repression of PEPCK gene and subsequent suppression of gluconeogenesis. Copyright © 2015. Published by Elsevier Inc.

  11. Amylin impairment of insulin effects on glycogen synthesis and phosphoenolpyruvate carboxykinase gene expression in rat primary cultured hepatocytes.

    PubMed Central

    Baqué, S; Guinovart, J J; Gómez-Foix, A M

    1994-01-01

    The ability of amylin to impair hepatic insulin action is controversial. We have found that the effect of amylin in primary cultured hepatocytes is strongly dependent on the culture conditions. Only in hepatocytes preincubated in the presence of fetal serum did amylin, at concentrations ranging from 1 to 100 nM, reduce insulin-stimulated glycogen synthesis rate and glycogen accumulation without showing direct effects. Neither basal glycogen synthase nor glycogen phosphorylase activity was modified by amylin treatment. Nevertheless, amylin (100 nM) blocked the activation of glycogen synthase by insulin. Amylin also proved capable of opposing the reduction in the expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene induced by insulin, whereas the basal mRNA level of PEPCK was unaffected by amylin treatment. Thus, these results show that, in cultured rat hepatocytes, amylin is indeed able to interfere with insulin regulation of glycogenesis and PEPCK gene expression, favouring the hypothesis that amylin may modulate liver sensitivity to insulin. Images Figure 3 PMID:7998979

  12. Cloning and expression of phosphoenolpyruvate carboxykinase from a cestode parasite and its solubilization from inclusion bodies using l-arginine.

    PubMed

    Dutta, Asim K; Ramnath; Dkhar, Barilin; Tandon, Veena; Das, Bidyadhar

    2016-09-01

    Phosphoenolpyruvate carboxykinase is an essential regulatory enzyme of glycolysis in the cestode parasite, Raillietina echinobothrida, and is considered a potential target for anthelmintic action because of its differential activity from that of its avian host. However, due to the unavailability of its structure, the mechanism of regulation of PEPCK from R. echinobothrida (rePEPCK) and its interaction with possible modulators remain unclear. Hence, in this study, the rePEPCK gene was cloned into pGEX-4T-3 and overexpressed for its characterization. On being induced by IPTG, the recombinant rePEPCK was expressed as inclusion bodies (IBs); hence, various agents, like different inducer concentrations, temperature, time, host cell types, culture media, pH, and additives, were used to bring the protein to soluble form. Finally, a significant amount (∼46%) of rePEPCK was solubilized from IBs by adding 2M l-arginine. Near-UV circular dichroism spectra analysis indicated that l-arginine (2M) had no effect on the conformation of the protein. In this study, we have reported a yield of ∼73mg of purified rePEPCK per 1L of culture. The purified rePEPCK retained its biological activity, and Km of the enzyme for its substrate was determined and discussed. The availability of recombinant rePEPCK may help in biochemical- and biophysical-studies to explore its molecular mechanisms and regulations. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Genome-wide Analysis of Phosphoenolpyruvate Carboxylase Gene Family and Their Response to Abiotic Stresses in Soybean

    PubMed Central

    Wang, Ning; Zhong, Xiujuan; Cong, Yahui; Wang, Tingting; Yang, Songnan; Li, Yan; Gai, Junyi

    2016-01-01

    Phosphoenolpyruvate carboxylase (PEPC) plays an important role in assimilating atmospheric CO2 during C4 and crassulacean acid metabolism photosynthesis, and also participates in various non-photosynthetic processes, including fruit ripening, stomatal opening, supporting carbon–nitrogen interactions, seed formation and germination, and regulation of plant tolerance to stresses. However, a comprehensive analysis of PEPC family in Glycine max has not been reported. Here, a total of ten PEPC genes were identified in soybean and denominated as GmPEPC1-GmPEPC10. Based on the phylogenetic analysis of the PEPC proteins from 13 higher plant species including soybean, PEPC family could be classified into two subfamilies, which was further supported by analyses of their conserved motifs and gene structures. Nineteen cis-regulatory elements related to phytohormones, abiotic and biotic stresses were identified in the promoter regions of GmPEPC genes, indicating their roles in soybean development and stress responses. GmPEPC genes were expressed in various soybean tissues and most of them responded to the exogenously applied phytohormones. GmPEPC6, GmPEPC8 and GmPEPC9 were significantly induced by aluminum toxicity, cold, osmotic and salt stresses. In addition, the enzyme activities of soybean PEPCs were also up-regulated by these treatments, suggesting their potential roles in soybean response to abiotic stresses. PMID:27924923

  14. Phosphoenolpyruvate carboxykinase (PEPCK) deficiency affects the germination, growth and fruit sugar content in tomato (Solanum lycopersicum L.).

    PubMed

    Huang, Yong-Xing; Yin, Yong-Gen; Sanuki, Atsuko; Fukuda, Naoya; Ezura, Hiroshi; Matsukura, Chiaki

    2015-11-01

    Phosphoenolpyruvate carboxykinase (PEPCK) is a key regulatory enzyme and is utilized in the gluconeogenesis pathway in plants. Although, its catalytic and regulatory properties are quite well understood, there are uncertainties regarding its physiological role in many plants tissues such as the flesh of developing fruits. To further understand the function of PEPCK in fruits and other tissues, RNAi transgenic tomato plants in which SlPEPCK transcription was down-regulated by either CaMV 35S constitutive promoter or the fruit-specific E8 promoter were generated and characterized on the basis of their phenotypic and metabolic aspects. In the PEPCK-deficient lines, prominent growth suppression of germinated seedlings was observed and other vegetative suppression appeared during the early stage of plant growth in the 35S promoter-driven lines. In particular, root elongation was most obviously suppressed in the germinated seedlings, indicating that the gluconeogenesis pathway is involved in the root growth of seedlings. Regarding the primary metabolism in fruit, the soluble sugar content tended to decrease, whereas the malate content tended to increase in ripening fruits of the RNAi lines compared with the wild type. These results indicate that activation of the gluconeogenesis pathway from organic acids to sugars occurs during ripening but is suppressed by the knocking down of the PEPCK gene, suggesting that PEPCK participates in determining the sugar/acid ratio in ripening fruit. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  15. Cloning and Molecular Analysis of a Mannitol Operon of Phosphoenolpyruvate-dependent Phosphotransferase (PTS) type From Vibrio cholerae O395

    PubMed Central

    Kumar, Sanath; Smith, Kenneth P.; Floyd, Jody L.; Varela, Manuel F.

    2010-01-01

    A putative mannitol operon of the phosphoenolpyruvate phosphotransferase (PTS) type was cloned from Vibrio cholerae O395 and its activity studied in Escherichia coli. The 3.9 kb operon comprising of three genes is organized as mtlADR. Based on the sequence analysis, these were identified as genes encoding a putative mannitol-specific enzyme IICBA (EIIMtl) component (MtlA), a mannitol-1-phosphate dehydrogenase (MtlD) and a mannitol operon repressor (MtlR). The transport of [3H]mannitol by the cloned mannitol operon in E. coli was 13.8±1.4 nmol/min/mg protein. The insertional inactivation of EIIMtl abolished mannitol and sorbitol transport in V. cholerae O395. Comparison of the mannitol utilization apparatus of V. cholerae with those of Gram-negative and Gram positive bacteria suggests highly conserved nature of the system. MtlA and MtlD exhibit 75% similarity with corresponding sequences of E. coli mannitol operon genes, while MtlR has 63% similarity with MtlR of E. coli. The cloning of V. cholerae mannitol utilization system in an E. coli background will help in elucidating the functional properties of this operon. PMID:21184218

  16. Drought tolerance and proteomics studies of transgenic wheat containing the maize C4 phosphoenolpyruvate carboxylase (PEPC) gene.

    PubMed

    Qin, Na; Xu, Weigang; Hu, Lin; Li, Yan; Wang, Huiwei; Qi, Xueli; Fang, Yuhui; Hua, Xia

    2016-11-01

    Enhancing drought tolerance of crops has been a great challenge in crop improvement. Here, we report the maize phosphoenolpyruvate carboxylase (PEPC) gene was able to confer drought tolerance and increase grain yield in transgenic wheat (Triticum aestivum L.) plants. The improved of drought tolerance was associated with higher levels of proline, soluble sugar, soluble protein, and higher water use efficiency. The transgenic wheat plants had also a more extensive root system as well as increased photosynthetic capacity during stress treatments. The increased grain yield of the transgenic wheat was contributed by improved biomass, larger spike and grain numbers, and heavier 1000-grain weight under drought-stress conditions. Under non-stressed conditions, there were no significant increases in these of the measured traits except for photosynthetic rate when compared with parental wheat. Proteomic research showed that the expression levels of some proteins, including chlorophyll A-B binding protein and pyruvate, phosphate dikinase, which are related to photosynthesis, PAP fibrillin, which is involved in cytoskeleton synthesis, S-adenosylmethionine synthetase, which catalyzes methionine synthesis, were induced in the transgenic wheat under drought stress. Additionally, the expression of glutamine synthetase, which is involved in ammonia assimilation, was induced by drought stress in the wheat. Our study shows that PEPC can improve both stress tolerance and grain yield in wheat, demonstrating the efficacy of PEPC in crop improvement.

  17. Characterization of mutant histidine-containing proteins of the phosphoenolpyruvate:sugar phosphotransferase system of Escherichia coli and Salmonella typhimurium

    SciTech Connect

    Waygood, E.B.; Reiche, B.; Hengstenberg, W.; Lee, J.S.

    1987-06-01

    Histidine-containing phosphocarrier protein (HPr) is common to all of the phosphoenolpyruvate:sugar phosphotransferase systems (PTS) in Escherichia coli and Salmonella typhimurium, except the fructose-specific PTS. Strains which lack HPr activity (ptsH) have been characterized in the past, and it has proved difficult to delineate between tight and leaky mutants. In this study four different parameters of ptsH strains were measured: in vitro sugar phosphorylation activity of the mutant HPr; detection of /sup 32/P-labeled P-HPr; ability of monoclonal antibodies to bind mutant HPr; and sensitivity of ptsH strains to fosfomycin. Tight ptsH strains could be defined; they were fosfomycin resistant and produced no HPr protein or completely inactive mutant HPr. All leaky ptsH strains were fosfomycin sensitive, Usually produced normal amounts of mutant HPr protein, and had low but measurable activity, and HPr was detectable as a phosphoprotein. This indicates that the regulatory functions of the PTS require a very low level of HPr activity (about 1%). The antibodies used to detect mutant HPr in crude extracts were two monoclonal immunoglobulin G antibodies Jel42 and Jel44. Both antibodies, which have different pIs, inhibited PTS sugar phosphorylation assays, but the antibody-JPr complex could still be phosphorylated by enzyme I. Preliminary evidence suggests that the antibodies bind to two different epitopes which are in part located in a ..beta..-sheet structure.

  18. Regulated high-level expression of the mannitol permease of the phosphoenolpyruvate-dependent sugar phosphotransferase system in Escherichia coli.

    PubMed Central

    van Weeghel, R P; Keck, W; Robillard, G T

    1990-01-01

    The structural gene (mtlA) of the Escherichia coli phosphoenolpyruvate-dependent mannitol-transport protein (EIImtl) and its upstream promoter region (Pmtl) were subcloned approximately 150 base pairs downstream of a lambda PR promoter on a multicopy mutagenesis/expression vector and used to transform a mutant (MtlA-) E. coli strain. Induction at 42 degrees C led to 50 to 100-fold overproduction of EIImtl (5-10 mg/g of cell wet weight) relative to mannitol-induced levels in a wild-type (Mtl+) strain. Most of the overproduced protein was sequestered as an inactive form in inclusion bodies and cytoplasmic membranous structures. The protein could be extracted in an active form by rupturing the cells with lysozyme and sonication or with a passage through a French pressure cell and incubating the inclusion bodies and membranous structures with detergent (Lubrol PX or deoxycholate) in the presence of Q or S Sepharose ion-exchange resin for several hours. This procedure resulted in a 20- to 25-fold overproduction of active EIImtl compared with mannitol-induced wild-type levels. Images PMID:2181442

  19. Reciprocal Changes in Phosphoenolpyruvate Carboxykinase and Pyruvate Kinase with Age Are a Determinant of Aging in Caenorhabditis elegans*

    PubMed Central

    Yuan, Yiyuan; Hakimi, Parvin; Kao, Clara; Kao, Allison; Liu, Ruifu; Janocha, Allison; Boyd-Tressler, Andrea; Hang, Xi; Alhoraibi, Hanna; Slater, Erin; Xia, Kevin; Cao, Pengxiu; Shue, Quinn; Ching, Tsui-Ting; Hsu, Ao-Lin; Erzurum, Serpil C.; Dubyak, George R.; Berger, Nathan A.; Hanson, Richard W.; Feng, Zhaoyang

    2016-01-01

    Aging involves progressive loss of cellular function and integrity, presumably caused by accumulated stochastic damage to cells. Alterations in energy metabolism contribute to aging, but how energy metabolism changes with age, how these changes affect aging, and whether they can be modified to modulate aging remain unclear. In locomotory muscle of post-fertile Caenorhabditis elegans, we identified a progressive decrease in cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), a longevity-associated metabolic enzyme, and a reciprocal increase in glycolytic pyruvate kinase (PK) that were necessary and sufficient to limit lifespan. Decline in PEPCK-C with age also led to loss of cellular function and integrity including muscle activity, and cellular senescence. Genetic and pharmacologic interventions of PEPCK-C, muscle activity, and AMPK signaling demonstrate that declines in PEPCK-C and muscle function with age interacted to limit reproductive life and lifespan via disrupted energy homeostasis. Quantifications of metabolic flux show that reciprocal changes in PEPCK-C and PK with age shunted energy metabolism toward glycolysis, reducing mitochondrial bioenergetics. Last, calorie restriction countered changes in PEPCK-C and PK with age to elicit anti-aging effects via TOR inhibition. Thus, a programmed metabolic event involving PEPCK-C and PK is a determinant of aging that can be modified to modulate aging. PMID:26631730

  20. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  1. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  2. Comparative leaf development in angiosperms.

    PubMed

    Tsukaya, Hirokazu

    2014-02-01

    Recent accumulation of our knowledge on basic leaf development mechanisms in model angiosperm species has allowed us to pursue evolutionary development (evo/devo) studies of various kinds of leaf development. As a result, unexpected findings and clues have been unearthed aiding our understanding of the mechanisms involved in the diversity of leaf morphology, although the covered remain limited. In this review, we highlight recent findings of diversified leaf development in angiosperms.

  3. Maple Leaf Outdoor Centre.

    ERIC Educational Resources Information Center

    Maguire, Molly; Gunton, Ric

    2000-01-01

    Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

  4. Bacterial leaf spot

    USDA-ARS?s Scientific Manuscript database

    Bacterial leaf spot has been reported in Australia (Queensland), Egypt, El Salvador, India, Japan, Nicaragua, Sudan, and the United States (Florida, Iowa, Kansas, Maryland, and Wisconsin). It occasionally causes locally severe defoliation and post-emergence damping-off and stunting. The disease is...

  5. Cucumber leaf spot virus

    USDA-ARS?s Scientific Manuscript database

    Cucumber leaf spot virus (CLSV) was originally identified from cucumber (Cucumis sativus) in Germany, but has since been found in various parts of Europe, the UK, and the Middle East, including Jordan, Saudi Arabia, Bulgaria, Poland, and Spain. CLSV is known to cause symptoms ranging from chloroti...

  6. Positive selection of Kranz and non-Kranz C4 phosphoenolpyruvate carboxylase amino acids in Suaedoideae (Chenopodiaceae).

    PubMed

    Rosnow, Josh J; Edwards, Gerald E; Roalson, Eric H

    2014-07-01

    In subfamily Suaedoideae, four independent gains of C4 photosynthesis are proposed, which includes two parallel origins of Kranz anatomy (sections Salsina and Schoberia) and two independent origins of single-cell C4 anatomy (Bienertia and Suaeda aralocaspica). Additional phylogenetic support for this hypothesis was generated from sequence data of the C-terminal portion of the phosphoenolpyruvate carboxylase (PEPC) gene used in C4 photosynthesis (ppc-1) in combination with previous sequence data. ppc-1 sequence was generated for 20 species in Suaedoideae and two outgroup Salsola species that included all types of C4 anatomies as well as two types of C3 anatomies. A branch-site test for positively selected codons was performed using the software package PAML. From labelling of the four branches where C4 is hypothesized to have developed (foreground branches), residue 733 (maize numbering) was identified to be under positive selection with a posterior probability >0.99 and residue 868 at the >0.95 interval using Bayes empirical Bayes (BEB). When labelling all the branches within C4 clades, the branch-site test identified 13 codons to be under selection with a posterior probability >0.95 by BEB; this is discussed considering current information on functional residues. The signature C4 substitution of an alanine for a serine at position 780 in the C-terminal end (which is considered a major determinant of affinity for PEP) was only found in four of the C4 species sampled, while eight of the C4 species and all the C3 species have an alanine residue; indicating that this substitution is not a requirement for C4 function.

  7. Phosphoenolpyruvate Carboxykinase 1 Gene (Pck1) Displays Parallel Evolution between Old World and New World Fruit Bats

    PubMed Central

    Irwin, David M.; Zhang, Shuyi

    2015-01-01

    Bats are an ideal mammalian group for exploring adaptations to fasting due to their large variety of diets and because fasting is a regular part of their life cycle. Mammals fed on a carbohydrate-rich diet experience a rapid decrease in blood glucose levels during a fast, thus, the development of mechanisms to resist the consequences of regular fasts, experienced on a daily basis, must have been crucial in the evolution of frugivorous bats. Phosphoenolpyruvate carboxykinase 1 (PEPCK1, encoded by the Pck1 gene) is the rate-limiting enzyme in gluconeogenesis and is largely responsible for the maintenance of glucose homeostasis during fasting in fruit-eating bats. To test whether Pck1 has experienced adaptive evolution in frugivorous bats, we obtained Pck1 coding sequence from 20 species of bats, including five Old World fruit bats (OWFBs) (Pteropodidae) and two New World fruit bats (NWFBs) (Phyllostomidae). Our molecular evolutionary analyses of these sequences revealed that Pck1 was under purifying selection in both Old World and New World fruit bats with no evidence of positive selection detected in either ancestral branch leading to fruit bats. Interestingly, however, six specific amino acid substitutions were detected on the ancestral lineage of OWFBs. In addition, we found considerable evidence for parallel evolution, at the amino acid level, between the PEPCK1 sequences of Old World fruit bats and New World fruit bats. Test for parallel evolution showed that four parallel substitutions (Q276R, R503H, I558V and Q593R) were driven by natural selection. Our study provides evidence that Pck1 underwent parallel evolution between Old World and New World fruit bats, two lineages of mammals that feed on a carbohydrate-rich diet and experience regular periods of fasting as part of their life cycle. PMID:25807515

  8. Phosphoenolpyruvate carboxykinase 1 gene (Pck1) displays parallel evolution between Old World and New World fruit bats.

    PubMed

    Zhu, Lei; Yin, Qiuyuan; Irwin, David M; Zhang, Shuyi

    2015-01-01

    Bats are an ideal mammalian group for exploring adaptations to fasting due to their large variety of diets and because fasting is a regular part of their life cycle. Mammals fed on a carbohydrate-rich diet experience a rapid decrease in blood glucose levels during a fast, thus, the development of mechanisms to resist the consequences of regular fasts, experienced on a daily basis, must have been crucial in the evolution of frugivorous bats. Phosphoenolpyruvate carboxykinase 1 (PEPCK1, encoded by the Pck1 gene) is the rate-limiting enzyme in gluconeogenesis and is largely responsible for the maintenance of glucose homeostasis during fasting in fruit-eating bats. To test whether Pck1 has experienced adaptive evolution in frugivorous bats, we obtained Pck1 coding sequence from 20 species of bats, including five Old World fruit bats (OWFBs) (Pteropodidae) and two New World fruit bats (NWFBs) (Phyllostomidae). Our molecular evolutionary analyses of these sequences revealed that Pck1 was under purifying selection in both Old World and New World fruit bats with no evidence of positive selection detected in either ancestral branch leading to fruit bats. Interestingly, however, six specific amino acid substitutions were detected on the ancestral lineage of OWFBs. In addition, we found considerable evidence for parallel evolution, at the amino acid level, between the PEPCK1 sequences of Old World fruit bats and New World fruit bats. Test for parallel evolution showed that four parallel substitutions (Q276R, R503H, I558V and Q593R) were driven by natural selection. Our study provides evidence that Pck1 underwent parallel evolution between Old World and New World fruit bats, two lineages of mammals that feed on a carbohydrate-rich diet and experience regular periods of fasting as part of their life cycle.

  9. The pepper phosphoenolpyruvate carboxykinase CaPEPCK1 is involved in plant immunity against bacterial and oomycete pathogens.

    PubMed

    Choi, Du Seok; Kim, Nak Hyun; Hwang, Byung Kook

    2015-09-01

    Phosphoenolpyruvate carboxykinase, a member of the lyase family, is involved in the metabolic pathway of gluconeogenesis in organisms. Although the major function of PEPCK in gluconeogenesis is well established, it is unclear whether this enzyme is involved in plant immunity. Here, we isolated and identified the pepper (Capsicum annuum) PEPCK (CaPEPCK1) gene from pepper leaves infected with Xanthomonas campestris pv. vesicatoria (Xcv). CaPEPCK1 was strongly expressed in pepper leaves during the incompatible interaction with avirulent Xcv and in response to environmental stresses, especially salicylic acid (SA) treatment. PEPCK activity was low in healthy leaves but dramatically increased in avirulent Xcv-infected leaves. Knock-down expression of CaPEPCK1 by virus-induced gene silencing resulted in high levels of susceptibility to both virulent and avirulent Xcv infection. CaPEPCK1 silencing in pepper compromised induction of the basal defense-marker genes CaPR1 (pathogenesis-related 1 protein), CaPR10 (pathogenesis-related 10 protein) and CaDEF1 (defensin) during Xcv infection. SA accumulation was also significantly suppressed in the CaPEPCK1-silenced pepper leaves infected with Xcv. CaPEPCK1 in an Arabidopsis overexpression (OX) line inhibited the proliferation of Pseudomonas syringae pv. tomato (Pst) and Hyaloperonospora arabidopsidis (Hpa). CaPEPCK1-OX plants developed more rapidly, with enlarged leaves, compared to wild-type plants. The T-DNA insertion Arabidopsis orthologous mutants pck1-3 and pck1-4 were more susceptible to the bacterial Pst and oomycete Hpa pathogens than the wild type. Taken together, these results suggest that CaPEPCK positively contributes to plant innate immunity against hemibiotrophic bacterial and obligate biotrophic oomycete pathogens.

  10. Induction of Phosphoenolpyruvate Carboxykinase (PEPCK) during Acute Acidosis and Its Role in Acid Secretion by V-ATPase-Expressing Ionocytes

    PubMed Central

    Furukawa, Fumiya; Tseng, Yung-Che; Liu, Sian-Tai; Chou, Yi-Ling; Lin, Ching-Chun; Sung, Po-Hsuan; Uchida, Katsuhisa; Lin, Li-Yih; Hwang, Pung-Pung

    2015-01-01

    Vacuolar-Type H+-ATPase (V-ATPase) takes the central role in pumping H+ through cell membranes of diverse organisms, which is essential for surviving acid-base fluctuating lifestyles or environments. In mammals, although glucose is believed to be an important energy source to drive V-ATPase, and phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme for gluconeogenesis, is known to be activated in response to acidosis, the link between acid secretion and PEPCK activation remains unclear. In the present study, we used zebrafish larva as an in vivo model to show the role of acid-inducible PEPCK activity in glucose production to support higher rate of H+ secretion via V-ATPase, by utilizing gene knockdown, glucose supplementation, and non-invasive scanning ion-selective electrode technique (SIET). Zebrafish larvae increased V-ATPase-mediated acid secretion and transiently expression of Pck1, a zebrafish homolog of PEPCK, in response to acid stress. When pck1 gene was knocked down by specific morpholino, the H+ secretion via V-ATPase decreased, but this effect was rescued by supplementation of glucose into the yolk. By assessing changes in amino acid content and gene expression of respective enzymes, glutamine and glutamate appeared to be the major source for replenishment of Krebs cycle intermediates, which are subtracted by Pck1 activity. Unexpectedly, pck1 knockdown did not affect glutamine/glutamate catalysis, which implies that Pck1 does not necessarily drive this process. The present study provides the first in vivo evidence that acid-induced PEPCK provides glucose for acid-base homeostasis at an individual level, which is supported by rapid pumping of H+ via V-ATPase at the cellular level. PMID:25999794

  11. Induction of Phosphoenolpyruvate Carboxykinase (PEPCK) during Acute Acidosis and Its Role in Acid Secretion by V-ATPase-Expressing Ionocytes.

    PubMed

    Furukawa, Fumiya; Tseng, Yung-Che; Liu, Sian-Tai; Chou, Yi-Ling; Lin, Ching-Chun; Sung, Po-Hsuan; Uchida, Katsuhisa; Lin, Li-Yih; Hwang, Pung-Pung

    2015-01-01

    Vacuolar-Type H(+)-ATPase (V-ATPase) takes the central role in pumping H(+) through cell membranes of diverse organisms, which is essential for surviving acid-base fluctuating lifestyles or environments. In mammals, although glucose is believed to be an important energy source to drive V-ATPase, and phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme for gluconeogenesis, is known to be activated in response to acidosis, the link between acid secretion and PEPCK activation remains unclear. In the present study, we used zebrafish larva as an in vivo model to show the role of acid-inducible PEPCK activity in glucose production to support higher rate of H(+) secretion via V-ATPase, by utilizing gene knockdown, glucose supplementation, and non-invasive scanning ion-selective electrode technique (SIET). Zebrafish larvae increased V-ATPase-mediated acid secretion and transiently expression of Pck1, a zebrafish homolog of PEPCK, in response to acid stress. When pck1 gene was knocked down by specific morpholino, the H(+) secretion via V-ATPase decreased, but this effect was rescued by supplementation of glucose into the yolk. By assessing changes in amino acid content and gene expression of respective enzymes, glutamine and glutamate appeared to be the major source for replenishment of Krebs cycle intermediates, which are subtracted by Pck1 activity. Unexpectedly, pck1 knockdown did not affect glutamine/glutamate catalysis, which implies that Pck1 does not necessarily drive this process. The present study provides the first in vivo evidence that acid-induced PEPCK provides glucose for acid-base homeostasis at an individual level, which is supported by rapid pumping of H(+) via V-ATPase at the cellular level.

  12. The effects of stress and injury on the activity of phosphoenolpyruvate carboxykinase in the liver of the rat.

    PubMed Central

    Rose, J G; Heath, D F

    1986-01-01

    The effects of stress (diethyl ether anaesthesia for 4-8 min, or intravenous injection of 0.05 ml of a dimethyl sulphoxide/water mixture) and of a scald injury given under ether anaesthesia on hepatic PEPCK (phosphoenolpyruvate carboxykinase, EC 4.1.1.32) were studied in the post-absorptive rat. Injury raised PEPCK activity by about 70% in 2 h and by over 100% in 4 h, over three times as fast as in animals that had only been handled (controls). The two stresses, both of types commonly imposed in animal experiments, had almost as much effect as injury for the first 2 h, although much less thereafter. The roles of sympathetic stimulation and corticosterone in mediating these rises were studied by using alpha beta-blockers and trilostane respectively as inhibitors. (Trilostane only decreased corticosterone concentrations to a little above control values.) The ether-induced increase was somewhat decreased by alpha beta-blockade, but was only eliminated by combined alpha beta-blockade and trilostane. After injury, however, PEPCK synthesis was unaffected by either alpha beta-blockade or trilostane, although it was decreased by their combined action; and it seems that either corticosterone or sympathetic stimulation was sufficient to stimulate PEPCK synthesis maximally. Stimulation by corticosterone was much greater than reported previously by others, for reasons that are discussed. Sympathetic stimulation may have been mediated by glucagon and cyclic AMP, since injury raised portal glucagon concentrations, and stress and injury raised those of hepatic cyclic AMP. PEPCK synthesis was, however, stimulated despite increases in portal insulin concentration, and was not related to the [insulin]/[glucagon] ratio. Thus stress and injury over-rode normal control mechanisms. PMID:3006659

  13. Glucose transport by a mutant of Streptococcus mutans unable to accumulate sugars via the phosphoenolpyruvate phosphotransferase system.

    PubMed Central

    Cvitkovitch, D G; Boyd, D A; Thevenot, T; Hamilton, I R

    1995-01-01

    Streptococcus mutans transports glucose via the phosphoenolpyruvate (PEP)-dependent sugar phosphotransferase system (PTS). Earlier studies indicated that an alternate glucose transport system functions in this organism under conditions of high growth rates, low pH, or excess glucose. To identify this system, S. mutans BM71 was transformed with integration vector pDC-5 to generate a mutant, DC10, defective in the general PTS protein enzyme I (EI). This mutant expressed a defective EI that had been truncated by approximately 150 amino acids at the carboxyl terminus as revealed by Western blot (immunoblot) analysis with anti-EI antibody and Southern hybridizations with a fragment of the wild-type EI gene as a probe. Phosphotransfer assays utilizing 32P-PEP indicated that DC10 was incapable of phosphorylating HPr and EIIAMan, indicating a nonfunctional PTS. This was confirmed by the fact that DC10 was able to ferment glucose but not a variety of other PTS substrates and phosphorylated glucose with ATP and not PEP. Kinetic assays indicated that the non-PTS system exhibited an apparent Ks of 125 microM for glucose and a Vmax of 0.87 nmol mg (dry weight) of cells-1 min-1. Sugar competition experiments with DC10 indicated that the non-PTS transport system had high specificity for glucose since glucose transport was not significantly by a 100-fold molar excess of several competing sugar substrates, including 2-deoxyglucose and alpha-methylglucoside. These results demonstrate that S. mutans possesses a glucose transport system that can function independently of the PEP PTS. PMID:7730250

  14. Novel listerial glycerol dehydrogenase- and phosphoenolpyruvate-dependent dihydroxyacetone kinase system connected to the pentose phosphate pathway.

    PubMed

    Monniot, Céline; Zébré, Arthur Constant; Aké, Francine Moussan Désirée; Deutscher, Josef; Milohanic, Eliane

    2012-09-01

    Several bacteria use glycerol dehydrogenase to transform glycerol into dihydroxyacetone (Dha). Dha is subsequently converted into Dha phosphate (Dha-P) by an ATP- or phosphoenolpyruvate (PEP)-dependent Dha kinase. Listeria innocua possesses two potential PEP-dependent Dha kinases. One is encoded by 3 of the 11 genes forming the glycerol (gol) operon. This operon also contains golD (lin0362), which codes for a new type of Dha-forming NAD(+)-dependent glycerol dehydrogenase. The subsequent metabolism of Dha requires its phosphorylation via the PEP:sugar phosphotransferase system components enzyme I, HPr, and EIIA(Dha)-2 (Lin0369). P∼EIIA(Dha)-2 transfers its phosphoryl group to DhaL-2, which phosphorylates Dha bound to DhaK-2. The resulting Dha-P is probably metabolized mainly via the pentose phosphate pathway, because two genes of the gol operon encode proteins resembling transketolases and transaldolases. In addition, purified Lin0363 and Lin0364 exhibit ribose-5-P isomerase (RipB) and triosephosphate isomerase activities, respectively. The latter enzyme converts part of the Dha-P into glyceraldehyde-3-P, which, together with Dha-P, is metabolized via gluconeogenesis to form fructose-6-P. Together with another glyceraldehyde-3-P molecule, the transketolase transforms fructose-6-P into intermediates of the pentose phosphate pathway. The gol operon is preceded by golR, transcribed in the opposite orientation and encoding a DeoR-type repressor. Its inactivation causes the constitutive but glucose-repressible expression of the entire gol operon, including the last gene, encoding a pediocin immunity-like (PedB-like) protein. Its elevated level of synthesis in the golR mutant causes slightly increased immunity against pediocin PA-1 compared to the wild-type strain or a pedB-like deletion mutant.

  15. Phosphoenolpyruvate carboxykinase from the moderate halophile Vibrio costicola. Purification, physicochemical properties and the effect of univalent-cation salts.

    PubMed Central

    Salvarrey, M S; Cannata, J J; Cazzulo, J J

    1989-01-01

    Phosphoenolpyruvate carboxykinase (PEPCK) was purified to homogeneity from the moderately halophilic bacterium Vibrio costicola. The enzyme is monomeric, with an Mr of 62,000, as determined by the Svedberg equation, by using values of s0(20,w) 4.4 x 10(-13) s, D20,w 6.13 x 10(-7) cm2.s-1 and v 0.719 cm3.g-1. Compared with other, non-halophilic, PEPCKs, the enzyme from V. costicola had a significantly lower total content of hydrophobic amino acids. The contents of glycine and serine were higher in the V. costicola enzyme (16.7 and 10.22% respectively) than in the non-halophilic PEPCKs (6.8-9.6% and 4.67-6.28% respectively). These results resemble those obtained by De Médicis & Rossignol [(1979) Experientia 35, 1546-1547] with the pyruvate kinase from V. costicola, and agree with the proposal by Lanyi [(1974) Bacteriol. Rev. 38, 272-290] of partial replacement of hydrophobic amino acids by glycine and serine to maintain the balance between hydrophobic and hydrophilic forces in halophilic enzymes. In agreement with this 'halophilic' characteristic, the PEPCK was somewhat stabilized by 1 M-KCl or -NaCl and by 20% (v/v) glycerol, and its oxaloacetate-decarboxylation and 14CO2-oxaloacetate-exchange reactions were activated by KCl and NaCl up to 1 M, whereas the fixation of CO2 on PEP had a maximum at 0.025-0.05 M salt. These facts suggest that the salts, at concentrations probably physiological for the bacterium, increase the formation of the complex of oxaloacetate and ATP with the enzyme, and the liberation of the products, PEP and ADP, thus favouring PEP synthesis. Images Fig. 1. PMID:2775185

  16. Identification of tumor necrosis factor as a transcriptional regulator of the phosphoenolpyruvate carboxykinase gene following endotoxin treatment of mice.

    PubMed Central

    Hill, M R; McCallum, R E

    1992-01-01

    The decreased synthesis of hepatic phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme of gluconeogenesis, that occurs during endotoxemia was shown previously in rats to occur at the transcriptional level. In the current study, the exogenous administration of human recombinant tumor necrosis factor (TNF), a proximal mediator of endotoxic shock, reduced the PEPCK transcription rate, mRNAPEPCK levels, and PEPCK enzyme activity in a time- and dose-dependent manner in CD-1 mice. Comparable amounts of circulating TNF were measured in mice 2 h after injection of human recombinant TNF (10(5) U) or a 50% lethal dose of Escherichia coli endotoxin (20 mg/kg). Direct action of TNF to decrease the PEPCK transcription rate was confirmed in vitro with H-4-II-E Reuber hepatoma cells, in which a dose-dependent inhibition of PEPCK transcription was observed with 1 to 100 U of TNF per ml. A role for TNF-elicited changes in PEPCK gene expression during endotoxemia was confirmed by the protective effect of rabbit polyclonal antibodies to recombinant murine TNF. C57BL/6 mice passively immunized with anti-TNF 4 h prior to endotoxin challenge exhibited normal PEPCK enzyme activity. Neutralization of circulating TNF with anti-TNF failed, however, to prevent the hypoglycemia commonly observed during endotoxemia, suggesting the participation of other mediators. Anti-TNF treatment reduced circulating interleukins 1 and 6 at 3 and 6 h after endotoxin treatment, respectively. These results suggest that during endotoxemia, the development of hypoglycemia is multifaceted and that several cytokines are most likely involved. The findings from the Reuber hepatoma cell model afford an opportunity in future work to map putative cytokine response elements in the PEPCK promoter responsible for perturbed hormonal regulation of the gene during endotoxemia. PMID:1398916

  17. Breed-dependent transcriptional regulation of phosphoenolpyruvate carboxylase, cytosolic form, expression in the liver of broiler chickens.

    PubMed

    Guo, Feng; Zhang, Yanhong; Su, Lanli; Ahmed, Abdelkareem A; Ni, Yingdong; Zhao, Ruqian

    2013-10-01

    Hepatic gluconeogenesis is the main source of glucose during chicken embryonic development, and it plays a major role in glucose homeostasis for developing embryos. Phosphoenolpyruvate carboxylase (PEPCK) catalyzes the rate-limiting step of gluconeogenesis, yet how hepatic PEPCK expression is differentially regulated between chicken breeds remains elusive. In this study, fertile eggs from a slow-growing Chinese Yellow Feathered Chicken and a fast-growing White Recessive Rock Chicken were incubated under the same standard conditions, and serum and liver samples were collected on embryonic d 18 (18E). The fast-growing breed had a significantly higher fetal weight (P < 0.01) and serum glucose concentration (P < 0.05) compared with the slow-growing breed. The fast-growing breed also had significantly higher hepatic mRNA expression levels of the cystolic form of PEPCK (PEPCK-c; P < 0.05) and significantly higher hepatic mRNA and protein expression levels of cAMP response element binding protein 1 (CREB-1; P < 0.05). Moreover, the binding of phosphorylated CREB-1 to the PEPCK-c promoter tended to be higher in the fast-growing breed (P = 0.08). Breed-specific epigenetic modifications of the PEPCK-c promoter were also observed; the fast-growing breed demonstrated lower CpG methylation (P < 0.05) and histone H3 (P < 0.05) levels but more histone H3 acetylation (H3ac) and histone H3 lysine 27 trimethylation (H3K27me3; P < 0.05) compared with the slow-growing breed. Our results suggest that hepatic PEPCK-c expression is transcriptionally regulated in a breed-specific manner and that fast- and slow-growing broiler chicken fetuses exhibit different epigenetic modifications on their PEPCK-c promoter regions.

  18. The Bacterial Phosphoenolpyruvate:Carbohydrate Phosphotransferase System: Regulation by Protein Phosphorylation and Phosphorylation-Dependent Protein-Protein Interactions

    PubMed Central

    Aké, Francine Moussan Désirée; Derkaoui, Meriem; Zébré, Arthur Constant; Cao, Thanh Nguyen; Bouraoui, Houda; Kentache, Takfarinas; Mokhtari, Abdelhamid; Milohanic, Eliane; Joyet, Philippe

    2014-01-01

    SUMMARY The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) carries out both catalytic and regulatory functions. It catalyzes the transport and phosphorylation of a variety of sugars and sugar derivatives but also carries out numerous regulatory functions related to carbon, nitrogen, and phosphate metabolism, to chemotaxis, to potassium transport, and to the virulence of certain pathogens. For these different regulatory processes, the signal is provided by the phosphorylation state of the PTS components, which varies according to the availability of PTS substrates and the metabolic state of the cell. PEP acts as phosphoryl donor for enzyme I (EI), which, together with HPr and one of several EIIA and EIIB pairs, forms a phosphorylation cascade which allows phosphorylation of the cognate carbohydrate bound to the membrane-spanning EIIC. HPr of firmicutes and numerous proteobacteria is also phosphorylated in an ATP-dependent reaction catalyzed by the bifunctional HPr kinase/phosphorylase. PTS-mediated regulatory mechanisms are based either on direct phosphorylation of the target protein or on phosphorylation-dependent interactions. For regulation by PTS-mediated phosphorylation, the target proteins either acquired a PTS domain by fusing it to their N or C termini or integrated a specific, conserved PTS regulation domain (PRD) or, alternatively, developed their own specific sites for PTS-mediated phosphorylation. Protein-protein interactions can occur with either phosphorylated or unphosphorylated PTS components and can either stimulate or inhibit the function of the target proteins. This large variety of signal transduction mechanisms allows the PTS to regulate numerous proteins and to form a vast regulatory network responding to the phosphorylation state of various PTS components. PMID:24847021

  19. Novel Listerial Glycerol Dehydrogenase- and Phosphoenolpyruvate-Dependent Dihydroxyacetone Kinase System Connected to the Pentose Phosphate Pathway

    PubMed Central

    Monniot, Céline; Zébré, Arthur Constant; Aké, Francine Moussan Désirée; Milohanic, Eliane

    2012-01-01

    Several bacteria use glycerol dehydrogenase to transform glycerol into dihydroxyacetone (Dha). Dha is subsequently converted into Dha phosphate (Dha-P) by an ATP- or phosphoenolpyruvate (PEP)-dependent Dha kinase. Listeria innocua possesses two potential PEP-dependent Dha kinases. One is encoded by 3 of the 11 genes forming the glycerol (gol) operon. This operon also contains golD (lin0362), which codes for a new type of Dha-forming NAD+-dependent glycerol dehydrogenase. The subsequent metabolism of Dha requires its phosphorylation via the PEP:sugar phosphotransferase system components enzyme I, HPr, and EIIADha-2 (Lin0369). P∼EIIADha-2 transfers its phosphoryl group to DhaL-2, which phosphorylates Dha bound to DhaK-2. The resulting Dha-P is probably metabolized mainly via the pentose phosphate pathway, because two genes of the gol operon encode proteins resembling transketolases and transaldolases. In addition, purified Lin0363 and Lin0364 exhibit ribose-5-P isomerase (RipB) and triosephosphate isomerase activities, respectively. The latter enzyme converts part of the Dha-P into glyceraldehyde-3-P, which, together with Dha-P, is metabolized via gluconeogenesis to form fructose-6-P. Together with another glyceraldehyde-3-P molecule, the transketolase transforms fructose-6-P into intermediates of the pentose phosphate pathway. The gol operon is preceded by golR, transcribed in the opposite orientation and encoding a DeoR-type repressor. Its inactivation causes the constitutive but glucose-repressible expression of the entire gol operon, including the last gene, encoding a pediocin immunity-like (PedB-like) protein. Its elevated level of synthesis in the golR mutant causes slightly increased immunity against pediocin PA-1 compared to the wild-type strain or a pedB-like deletion mutant. PMID:22773791

  20. Phosphoenolpyruvate carboxylase protein kinase from developing castor oil seeds: partial purification, characterization, and reversible control by photosynthate supply.

    PubMed

    Murmu, Jhadeswar; Plaxton, William C

    2007-10-01

    Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) protein kinase (PPCK) was purified approximately 1,500-fold from developing castor oil seeds (COS). Gel filtration and immunoblotting with anti-(rice PPCK2)-immune serum indicated that this Ca2+-insensitive PPCK exists as a 31-kDa monomer. COS PPCK-mediated rephosphorylation of the 107-kDa subunit (p107) of COS PEPC1 (Km = 2.2 microM) activated PEPC1 by approximately 80% when assayed under suboptimal conditions (pH 7.3, 0.2 mM PEP, and 0.125 mM malate). COS PPCK displayed remarkable selectivity for phosphorylating COS PEPC1 (relative to tobacco, sorghum, or maize PEPCs), exhibited a broad pH-activity optima of approximately pH 8.5, and at pH 7.3 was activated 40-65% by 1 mM PEP, or 10 mM Gln or Asn, but inhibited 65% by 10 mM L-malate. The possible control of COS PPCK by disulfide-dithiol interconversion was suggested by its rapid inactivation and subsequent reactivation when incubated with oxidized glutathione and then dithiothreitol. In vitro PPCK activity correlated with in vivo p107 phosphorylation status, with both peaking in mid-cotyledon to full-cotyledon developing COS. Notably, PPCK activity and p107 phosphorylation of developing COS were eliminated following pod excision or prolonged darkness of intact plants. Both effects were fully reversed 12 h following reillumination of darkened plants. These results implicate a direct relationship between the up-regulation of COS PPCK and p107 phosphorylation during the recommencement of photosynthate delivery from illuminated leaves to the non-photosynthetic COS. Overall, the results support the hypothesis that PEPC and PPCK participate in the control of photosynthate partitioning into C-skeletons needed as precursors for key biosynthetic pathways of developing COS.

  1. Increasing the conformational entropy of the Omega-loop lid domain in phosphoenolpyruvate carboxykinase impairs catalysis and decreases catalytic fidelity .

    PubMed

    Johnson, Troy A; Holyoak, Todd

    2010-06-29

    Many studies have shown that the dynamic motions of individual protein segments can play an important role in enzyme function. Recent structural studies of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) demonstrate that PEPCK contains a 10-residue Omega-loop domain that acts as an active site lid. On the basis of these structural studies, we have previously proposed a model for the mechanism of PEPCK catalysis in which the conformation of this mobile lid domain is energetically coupled to ligand binding, resulting in the closed conformation of the lid, necessary for correct substrate positioning, becoming more energetically favorable as ligands associate with the enzyme. Here we test this model by introducing a point mutation (A467G) into the center of the Omega-loop lid that is designed to increase the entropic penalty for lid closure. Structural and kinetic characterization of this mutant enzyme demonstrates that the mutation has decreased the favorability of the enzyme adapting the closed lid conformation. As a consequence of this shift in the equilibrium defining the conformation of the active site lid, the enzyme's ability to stabilize the reaction intermediate is weakened, resulting in catalytic defect. This stabilization is initially surprising, as the lid domain makes no direct contacts with the enolate intermediate formed during the reaction. Furthermore, during the conversion of OAA to PEP, the destabilization of the lid-closed conformation results in the reaction becoming decoupled as the enolate intermediate is protonated rather than phosphorylated, resulting in the formation of pyruvate. Taken together, the structural and kinetic characterization of A467G-PEPCK supports our model of the role of the active site lid in catalytic function and demonstrates that the shift in the lowest-energy conformation between open and closed lid states is a function of the free energy available to the enzyme through ligand binding and the entropic

  2. Positive selection of Kranz and non-Kranz C4 phosphoenolpyruvate carboxylase amino acids in Suaedoideae (Chenopodiaceae)

    PubMed Central

    Rosnow, Josh J.; Edwards, Gerald E.; Roalson, Eric H.

    2014-01-01

    In subfamily Suaedoideae, four independent gains of C4 photosynthesis are proposed, which includes two parallel origins of Kranz anatomy (sections Salsina and Schoberia) and two independent origins of single-cell C4 anatomy (Bienertia and Suaeda aralocaspica). Additional phylogenetic support for this hypothesis was generated from sequence data of the C-terminal portion of the phosphoenolpyruvate carboxylase (PEPC) gene used in C4 photosynthesis (ppc-1) in combination with previous sequence data. ppc-1 sequence was generated for 20 species in Suaedoideae and two outgroup Salsola species that included all types of C4 anatomies as well as two types of C3 anatomies. A branch-site test for positively selected codons was performed using the software package PAML. From labelling of the four branches where C4 is hypothesized to have developed (foreground branches), residue 733 (maize numbering) was identified to be under positive selection with a posterior probability >0.99 and residue 868 at the >0.95 interval using Bayes empirical Bayes (BEB). When labelling all the branches within C4 clades, the branch-site test identified 13 codons to be under selection with a posterior probability >0.95 by BEB; this is discussed considering current information on functional residues. The signature C4 substitution of an alanine for a serine at position 780 in the C-terminal end (which is considered a major determinant of affinity for PEP) was only found in four of the C4 species sampled, while eight of the C4 species and all the C3 species have an alanine residue; indicating that this substitution is not a requirement for C4 function. PMID:24600021

  3. Functional reconstitution of the purified phosphoenolpyruvate-dependent mannitol-specific transport system of Escherichia coli in phospholipid vesicles: coupling between transport and phosphorylation.

    PubMed Central

    Elferink, M G; Driessen, A J; Robillard, G T

    1990-01-01

    Purified mannitol-specific enzyme II (EII) from Escherichia coli was reconstituted into phospholipid vesicles with the aid of a detergent-dialysis procedure followed by a freeze-thaw sonication step. The orientation of EII in the proteoliposomes was random. The cytoplasmic moiety of the inverted EII could be removed with trypsin without effecting the integrity of the liposomal membrane. This enabled us to study the two different EII orientations independently. The population of inverted EII molecules was monitored by measuring active extrusion of mannitol after the addition of phosphoenolpyruvate, EI, and histidine-containing phosphocarrier protein (HPr) at the outside of the vesicles. The population of correctly oriented EII molecules was monitored by measuring active uptake of mannitol with internal phosphoenolpyruvate, EI, and HPr. A low rate of facilitated diffusion of mannitol via the unphosphorylated carrier could be measured. On the other hand, a high phosphorylation activity without translocation was observed at the outside of the liposomes. The kinetics of the phosphoenolpyruvate-dependent transport reaction and the nonvectorial phosphorylation reaction were compared. Transport of mannitol into the liposomes via the correctly oriented EII molecules occurred with a high affinity (Km, lower than 10 microM) and with a relatively low Vmax. Phosphorylation at the outside of the liposomes catalyzed by the inverted EII molecules occurred with a low affinity (Km of about 66 microM), while the maximal velocity was about 10 times faster than the transport reaction. The latter observation is kinetic proof for the lack of strict coupling between transport and phosphorylation in these enzymes. Images PMID:2123863

  4. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  5. [Effect of preparations exhibiting cytokinin-like activity on the specific density of leaf in grasses].

    PubMed

    Cherniad'ev, I I

    2002-01-01

    The effects of synthetic preparations exhibiting cytokinin-like activity (6-benzylaminopurine, Thidiazuron, and kartolin-2) on the specific leaf area (SLA) were studied in plants of the family Gramineae (wheat, Triticum aestivum L.; meadow fescue, Festuca pratensis Huds.; and reed fescue, F. arindinacea Schreb.). At the early stages of ontogeny (until the leaf area reached 50-60% of the maximum value), treatment of plants of the three species with cytokinin-like preparations caused an increase in SLA. The SLA value in these plants was correlated with the rate of photosynthetic assimilation of carbon dioxide and activities of carbon metabolism enzymes: ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), NAD-malate dehydrogenase (EC 1.1.1.37), and NADP-glyceraldehydrophosphate dehydrogenase complex, which includes phosphoglycerate kinase (EC 2.7.2.3) and glyceraldehydrophosphate dehydrogenase (EC 1.2.1.13). However, there was no correlation of SLA with the activity of phospho(enol)pyruvate carboxylase (EC 4.1.1.31), an anaplerotic carboxylation enzyme of grasses. SLA is suggested to reflect the state and activity of the photosynthetic apparatus and can be recommended as a characteristic of photosynthesis variability (e.g., caused by cytokinin-like preparations).

  6. Rapid Metabolic Changes in the Wounding Response of Leaf Discs following Excision

    PubMed Central

    Macnicol, Peter K.

    1976-01-01

    The dark respiration rate of discs from fully expanded tobacco leaves (Nicotiana tabacum) increased linearly with decreasing diameter, the relative increase being independent of leaf age. The wound respiration responsible for this situation reached a plateau within 15 minutes of excision. Metabolite analysis gave evidence for two independent effects, also unrelated to age. The first was a forward crossover between phosphoenolpyruvate and pyruvate which was found as early as 1 minute after excision and persisted for up to 40 minutes. It was attributed to activation of pyruvate kinase by a changed ionic balance resulting from membrane damage, was accompanied by a reverse crossover between triose phosphates and 3-phosphoglycerate, and was localized in the outer region of the discs. The second effect was a rapid rise in hexose monophosphate and ATP levels throughout the discs. After 1 to 10 minutes the ATP/ADP ratio rose strongly for at least 3 hours; after 20 to 40 minutes there was net synthesis of adenine nucleotide as ATP. These results indicate that extrapolation from leaf discs to intact leaves is highly inadvisable. PMID:16659430

  7. In vivo regulatory phosphorylation of the phosphoenolpyruvate carboxylase AtPPC1 in phosphate-starved Arabidopsis thaliana

    PubMed Central

    Gregory, Allison L.; Hurley, Brenden A.; Tran, Hue T.; Valentine, Alexander J.; She, Yi-Min; Knowles, Vicki L.; Plaxton, William C.

    2009-01-01

    PEPC [PEP(phosphoenolpyruvate) carboxylase] is a tightly controlled cytosolic enzyme situated at a major branchpoint in plant metabolism. Accumulating evidence indicates important functions for PEPC and PPCK (PEPC kinase) in plant acclimation to nutritional Pi deprivation. However, little is known about the genetic origin or phosphorylation status of native PEPCs from −Pi (Pi-deficient) plants. The transfer of Arabidopsis suspension cells or seedlings to −Pi growth media resulted in: (i) the marked transcriptional upregulation of genes encoding the PEPC isoenzyme AtPPC1 (Arabidopsis thaliana PEPC1), and PPCK isoenzymes AtPPCK1 and AtPPCK2; (ii) >2-fold increases in PEPC specific activity and in the amount of an immunoreactive 107-kDa PEPC polypeptide (p107); and (iii) In vivo p107 phosphorylation as revealed by immunoblotting of clarified extracts with phosphosite-specific antibodies to Ser-11 (which could be reversed following Pi resupply). Approx. 1.3 mg of PEPC was purified 660-fold from −Pi suspension cells to apparent homogeneity with a specific activity of 22.3 units · mg−1 of protein. Gel filtration, SDS/PAGE and immunoblotting demonstrated that purified PEPC exists as a 440-kDa homotetramer composed of identical p107 subunits. Sequencing of p107 tryptic and Asp-N peptides by tandem MS established that this PEPC is encoded by AtPPC1. Pi-affinity PAGE coupled with immunoblotting indicated stoichiometric phosphorylation of the p107 subunits of AtPPC1 at its conserved Ser-11 phosphorylation site. Phosphorylation activated AtPPC1 at pH 7.3 by lowering its Km(PEP) and its sensitivity to inhibition by L-malate and L-aspartate, while enhancing activation by glucose 6-phosphate. Our results indicate that the simultaneous induction and In vivo phosphorylation activation of AtPPC1 contribute to the metabolic adaptations of −Pi Arabidopsis. PMID:19228119

  8. A plant/fungal-type phosphoenolpyruvate carboxykinase located in the parasite mitochondrion ensures glucose-independent survival of Toxoplasma gondii.

    PubMed

    Nitzsche, Richard; Günay-Esiyok, Özlem; Tischer, Maximilian; Zagoriy, Vyacheslav; Gupta, Nishith

    2017-09-15

    Toxoplasma gondii is considered to be one of the most successful intracellular pathogens, because it can reproduce in varied nutritional milieus, encountered in diverse host cell types of essentially any warm-blooded organism. Our earlier work demonstrated that the acute (tachyzoite) stage of T. gondii depends on cooperativity of glucose and glutamine catabolism to meet biosynthetic demands. Either of these two nutrients can sustain the parasite survival; however, what determines the metabolic plasticity has not yet been resolved. Here, we reveal two discrete phosphoenolpyruvate carboxykinase (PEPCK) enzymes in the parasite, one of which resides in the mitochondrion (TgPEPCKmt), whereas the other protein is not expressed in tachyzoites (TgPEPCKnet). Parasites with an intact glycolysis can tolerate genetic deletions of TgPEPCKmt as well as of TgPEPCKnet, indicating their nonessential roles for tachyzoite survival. TgPEPCKnet can also be ablated in a glycolysis-deficient mutant, while TgPEPCKmt is refractory to deletion. Consistent with this, the lytic cycle of a conditional mutant of TgPEPCKmt in the glycolysis-impaired strain was aborted upon induced repression of the mitochondrial isoform, demonstrating its essential role for the glucose-independent survival of parasites. Isotope-resolved metabolomics of the conditional mutant revealed defective flux of glutamine-derived carbon into RNA-bound ribose sugar as well as metabolites associated with gluconeogenesis, entailing a critical nodal role of PEPCKmt in linking catabolism of glucose and glutamine with anabolic pathways. Our data also suggest a homeostatic function ofTgPEPCKmt in cohesive operation of glycolysis and the tricarboxylic acid cycle in a normal glucose-replete milieu. Conversely, we found that the otherwise integrative enzyme pyruvate carboxylase (TgPyC) is dispensable not only in glycolysis-competent but also in glycolysis-deficient tachyzoites despite a mitochondrial localization. Last but not least

  9. Physiological and Transcriptional Characterization of Escherichia Coli Strains Lacking Interconversion of Phosphoenolpyruvate and Pyruvate When Glucose and Acetate are Coutilized

    PubMed Central

    Sabido, Andrea; Sigala, Juan Carlos; Hernández-Chávez, Georgina; Flores, Noemí; Gosset, Guillermo; Bolívar, Francisco

    2013-01-01

    Phosphoenolpyruvate (PEP) is a precursor involved in the biosynthesis of aromatics and other valuable compounds in Escherichia coli. The PEP:carbohydrate phosphotransferase system (PTS) is the major glucose transport system and the largest PEP consumer. To increase intracellular PEP availability for aromatics production purposes, mutant strains of E. coli JM101 devoid of the ptsHIcrr operon (PB11 strain) have been previously generated. In this derivative, transport and growth rate on glucose decreased significantly. A laboratory evolved strain derived from PB11 that partially recovered its growth capacity on glucose was named PB12. In the present study, we blocked carbon skeletons interchange between PEP and pyruvate (PYR) in these ptsHIcrr− strains by deleting the pykA, pykF, and ppsA genes. The PB11 pykAF− ppsA− strain exhibited no growth on glucose or acetate alone, but it was viable when both substrates were consumed simultaneously. In contrast, the PB12 pykAF− ppsA− strain displayed a low growth rate on glucose or acetate alone, but in the mixture, growth was significantly improved. RT-qPCR expression analysis of PB11 pykAF− ppsA− growing with both carbon sources showed a downregulation of all central metabolic pathways compared with its parental PB11 strain. Under the same conditions, transcription of most of the genes in PB12 pykAF− ppsA− did not change, and few like aceBAK, sfcA, and poxB were overexpressed compared with PB12. We explored the aromatics production capabilities of both ptsHIcrr− pykAF− ppsA− strains and the engineered PB12 pykAF− ppsA− tyrR− pheAev2+/pJLBaroGfbrtktA enhanced the yield of aromatic compounds when coutilizing glucose and acetate compared with the control strain PB12 tyrR− pheAev2+/pJLBaroGfbrtktA. Biotechnol. Bioeng. 2014;111: 1150–1160. © 2013 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. PMID:24375081

  10. Metabolic engineering for the production of shikimic acid in an evolved Escherichia coli strain lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system

    PubMed Central

    2010-01-01

    Background Shikimic acid (SA) is utilized in the synthesis of oseltamivir-phosphate, an anti-influenza drug. In this work, metabolic engineering approaches were employed to produce SA in Escherichia coli strains derived from an evolved strain (PB12) lacking the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS-) but with capacity to grow on glucose. Derivatives of PB12 strain were constructed to determine the effects of inactivating aroK, aroL, pykF or pykA and the expression of plasmid-coded genes aroGfbr, tktA, aroB and aroE, on SA synthesis. Results Batch cultures were performed to evaluate the effects of genetic modifications on growth, glucose consumption, and aromatic intermediate production. All derivatives showed a two-phase growth behavior with initial high specific growth rate (μ) and specific glucose consumption rate (qs), but low level production of aromatic intermediates. During the second growth phase the μ decreased, whereas aromatic intermediate production reached its maximum. The double aroK- aroL- mutant expressing plasmid-coded genes (strain PB12.SA22) accumulated SA up to 7 g/L with a yield of SA on glucose of 0.29 mol/mol and a total aromatic compound yield (TACY) of 0.38 mol/mol. Single inactivation of pykF or pykA was performed in PB12.SA22 strain. Inactivation of pykF caused a decrease in μ, qs, SA production, and yield; whereas TACY increased by 33% (0.5 mol/mol). Conclusions The effect of increased availability of carbon metabolites, their channeling into the synthesis of aromatic intermediates, and disruption of the SA pathway on SA production was studied. Inactivation of both aroK and aroL, and transformation with plasmid-coded genes resulted in the accumulation of SA up to 7 g/L with a yield on glucose of 0.29 mol/mol PB12.SA22, which represents the highest reported yield. The pykF and pykA genes were inactivated in strain PB12.SA22 to increase the production of aromatic compounds in the PTS- background. Results

  11. Developmental Physiology of Cluster-Root Carboxylate Synthesis and Exudation in Harsh Hakea. Expression of Phosphoenolpyruvate Carboxylase and the Alternative Oxidase1

    PubMed Central

    Shane, Michael W.; Cramer, Michael D.; Funayama-Noguchi, Sachiko; Cawthray, Gregory R.; Millar, A. Harvey; Day, David A.; Lambers, Hans

    2004-01-01

    Harsh hakea (Hakea prostrata R.Br.) is a member of the Proteaceae family, which is highly represented on the extremely nutrient-impoverished soils in southwest Australia. When phosphorus is limiting, harsh hakea develops proteoid or cluster roots that release carboxylates that mobilize sparingly soluble phosphate in the rhizosphere. To investigate the physiology underlying the synthesis and exudation of carboxylates from cluster roots in Proteaceae, we measured O2 consumption, CO2 release, internal carboxylate concentrations and carboxylate exudation, and the abundance of the enzymes phosphoenolpyruvate carboxylase and alternative oxidase (AOX) over a 3-week time course of cluster-root development. Peak rates of citrate and malate exudation were observed from 12- to 13-d-old cluster roots, preceded by a reduction in cluster-root total protein levels and a reduced rate of O2 consumption. In harsh hakea, phosphoenolpyruvate carboxylase expression was relatively constant in cluster roots, regardless of developmental stage. During cluster-root maturation, however, the expression of AOX protein increased prior to the time when citrate and malate exudation peaked. This increase in AOX protein levels is presumably needed to allow a greater flow of electrons through the mitochondrial electron transport chain in the absence of rapid ATP turnover. Citrate and isocitrate synthesis and accumulation contributed in a major way to the subsequent burst of citrate and malate exudation. Phosphorus accumulated by harsh hakea cluster roots was remobilized during senescence as part of their efficient P cycling strategy for growth on nutrient impoverished soils. PMID:15122030

  12. Biological significance of phosphoenolpyruvate carboxykinase in a cestode parasite, Raillietina echinobothrida and effect of phytoestrogens on the enzyme from the parasite and its host, Gallus domesticus.

    PubMed

    Ramnath; Dutta, Asim Kumar; Dkhar, Barilin; Tandon, Veena; DAS, Bidyadhar

    2017-08-01

    Phosphoenolpyruvate carboxykinase (PEPCK) is involved in glycolysis in the cestode parasite, Raillietina echinobothrida; whereas, it executes a gluconeogenic role in its host, Gallus domesticus. Because of its differing primary function in the cestode parasite and its host, this enzyme is regarded as a plausible anthelmintic target. Hence, the biological significance of PEPCK in the parasite was analysed using siRNA against PEPCK from R. echinobothrida (RePEPCK). In order to find out the functional differences between RePEPCK and GdPEPCK (PEPCK from its host, G. domesticus), PEPCK genes from both sources were cloned, over-expressed, characterized, and some properties of the purified enzymes were compared. RePEPCK and GdPEPCK showed a standard Michaelis-Menten kinetics with K mapp of 46.9 and 22.9 µ m, respectively, for phosphoenolpyruvate and K mapp of 15.4 µ m for oxaloacetate in GdPEPCK decarboxylation reaction. Here, we report antagonist behaviours of recombinant PEPCKs derived from the parasite and its host. In search of possible modulators for PEPCK, few phytoestrogens were examined on the purified enzymes and their inhibitory constants were determined and discussed. This study stresses the potential of these findings to validate PEPCK as the anthelmintic drug target for parasitism management.

  13. The worldwide leaf economics spectrum.

    PubMed

    Wright, Ian J; Reich, Peter B; Westoby, Mark; Ackerly, David D; Baruch, Zdravko; Bongers, Frans; Cavender-Bares, Jeannine; Chapin, Terry; Cornelissen, Johannes H C; Diemer, Matthias; Flexas, Jaume; Garnier, Eric; Groom, Philip K; Gulias, Javier; Hikosaka, Kouki; Lamont, Byron B; Lee, Tali; Lee, William; Lusk, Christopher; Midgley, Jeremy J; Navas, Marie-Laure; Niinemets, Ulo; Oleksyn, Jacek; Osada, Noriyuki; Poorter, Hendrik; Poot, Pieter; Prior, Lynda; Pyankov, Vladimir I; Roumet, Catherine; Thomas, Sean C; Tjoelker, Mark G; Veneklaas, Erik J; Villar, Rafael

    2004-04-22

    Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

  14. Leaf development: a cellular perspective

    PubMed Central

    Kalve, Shweta; De Vos, Dirk; Beemster, Gerrit T. S.

    2014-01-01

    Through its photosynthetic capacity the leaf provides the basis for growth of the whole plant. In order to improve crops for higher productivity and resistance for future climate scenarios, it is important to obtain a mechanistic understanding of leaf growth and development and the effect of genetic and environmental factors on the process. Cells are both the basic building blocks of the leaf and the regulatory units that integrate genetic and environmental information into the developmental program. Therefore, to fundamentally understand leaf development, one needs to be able to reconstruct the developmental pathway of individual cells (and their progeny) from the stem cell niche to their final position in the mature leaf. To build the basis for such understanding, we review current knowledge on the spatial and temporal regulation mechanisms operating on cells, contributing to the formation of a leaf. We focus on the molecular networks that control exit from stem cell fate, leaf initiation, polarity, cytoplasmic growth, cell division, endoreduplication, transition between division and expansion, expansion and differentiation and their regulation by intercellular signaling molecules, including plant hormones, sugars, peptides, proteins, and microRNAs. We discuss to what extent the knowledge available in the literature is suitable to be applied in systems biology approaches to model the process of leaf growth, in order to better understand and predict leaf growth starting with the model species Arabidopsis thaliana. PMID:25132838

  15. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  16. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  17. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  18. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  19. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  20. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  1. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  2. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  3. 7 CFR 29.3033 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.3033 Section 29.3033 Agriculture Regulations... Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16758, Apr. 20, 1984] ...

  4. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  5. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  6. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  7. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  8. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  9. 7 CFR 29.3525 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.3525 Section 29.3525 Agriculture Regulations... Type 95) § 29.3525 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16759, Apr. 20, 1984] ...

  10. 7 CFR 29.1028 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.1028 Section 29.1028 Agriculture Regulations... Type 92) § 29.1028 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16755, Apr. 20, 1984. Redesignated at 51 FR 25027, July...

  11. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ...

  12. Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups

    Treesearch

    Peter B. Reich; Michael B. Walters; David S. Ellsworth; [and others; [Editor’s note: James M.. Vose is the SRS co-author for this publication.

    1998-01-01

    Based on prior evidence of coordinated multiple leaf trait scaling, the authors hypothesized that variation among species in leaf dark respiration rate (Rd) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (Amax). However, it is not known whether such scaling, if it exists, is...

  13. The artificial leaf.

    PubMed

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a

  14. Leaf Extract from Lithocarpus polystachyus Rehd. Promote Glycogen Synthesis in T2DM Mice

    PubMed Central

    Chen, Yingying; Vanegas, Diana; McLamore, Eric Scott; Shen, Yingbai

    2016-01-01

    The purpose of this study was to investigate the effects of leaf extract from Lithocarpus polystachyus Rehd. on type II diabetes mellitus (T2DM) and the active ingredients of this effect. In addition, this study determined, for the first time, the underlying molecular and pharmacological mechanisms of the extracts on hyperglycemia using long-term double high diet-fed and streptozotocin (STZ) induced type II diabetic mice. In the present study, leaf extract, phloridzin and trilobatin were assessed in vivo (gavage) and in vitro (non-invasive micro-test technique, NMT) in experimental T2DM mice. The biochemical parameters were measured including blood glucose and blood lipid level, liver biochemical indexes, and hepatic glycogen. The relative expression of glycometabolism-related genes was detected. The effect of leaf extracts on physiological glucose flux in liver tissue from control and T2DM mice was also investigated. Body weight of experimental T2DM mice increased significantly after the first week, but stabilized over the subsequent three weeks; body weight of all other groups did not change during the four weeks’ study. After four weeks, all treatment groups decreased blood glucose, and treatment with leaf extract had numerous positive effects: a) promoted in glucose uptake in liver, b) increased synthesis of liver glycogen, c) reduced oxidative stress, d) up-regulation of glucokinase (GK), glucose transporter 2 (GLUT2), insulin receptor (IR) and insulin receptor substrate (IRS) expression in liver, e) down-regulation of glucose-6-phosphatase (G-6-P) expression, and f) ameliorated blood lipid levels. Both treatment with trilobatin or phloridzin accelerated liver glycogen synthesis, decreased oxidative stress and increased expression of GK. IRS and phosphoenolpyruvate carboxykinase (PEPCK) were both up-regulated after treatment with trilobatin. Expression of GLUT2, PEPCK and G-6-P were also increased in liver tissue after treatment with phloridzin. Our data

  15. Glucose-Specific Enzyme IIA of the Phosphoenolpyruvate:Carbohydrate Phosphotransferase System Modulates Chitin Signaling Pathways in Vibrio cholerae.

    PubMed

    Yamamoto, Shouji; Ohnishi, Makoto

    2017-09-15

    In Vibrio cholerae, the genes required for chitin utilization and natural competence are governed by the chitin-responsive two-component system (TCS) sensor kinase ChiS. In the classical TCS paradigm, a sensor kinase specifically phosphorylates a cognate response regulator to activate gene expression. However, our previous genetic study suggested that ChiS stimulates the non-TCS transcriptional regulator TfoS by using mechanisms distinct from classical phosphorylation reactions (S. Yamamoto, J. Mitobe, T. Ishikawa, S. N. Wai, M. Ohnishi, H. Watanabe, and H. Izumiya, Mol Microbiol 91:326-347, 2014, https://doi.org/10.1111/mmi.12462). TfoS specifically activates the transcription of tfoR, encoding a small regulatory RNA essential for competence gene expression. Whether ChiS and TfoS interact directly remains unknown. To determine if other factors mediate the communication between ChiS and TfoS, we isolated transposon mutants that turned off tfoR::lacZ expression but possessed intact chiS and tfoS genes. We demonstrated an unexpected association of chitin-induced signaling pathways with the glucose-specific enzyme IIA (EIIA(glc)) of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) for carbohydrate uptake and catabolite control of gene expression. Genetic and physiological analyses revealed that dephosphorylated EIIA(glc) inactivated natural competence and tfoR transcription. Chitin-induced expression of the chb operon, which is required for chitin transport and catabolism, was also repressed by dephosphorylated EIIA(glc) Furthermore, the regulation of tfoR and chb expression by EIIA(glc) was dependent on ChiS and intracellular levels of ChiS were not affected by disruption of the gene encoding EIIA(glc) These results define a previously unknown connection between the PTS and chitin signaling pathways in V. cholerae and suggest a strategy whereby this bacterium can physiologically adapt to the existing nutrient status.IMPORTANCE The EIIA

  16. How to pattern a leaf

    USDA-ARS?s Scientific Manuscript database

    Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, an...

  17. Exserohilum Leaf Spot on Tigergrass

    USDA-ARS?s Scientific Manuscript database

    Tigergrass (Thysanolaena maxima (Roxb.) Kuntze ) is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tigergrass in the landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated, cha...

  18. Evolution of C4 phosphoenolpyruvate carboxylase in Flaveria, a conserved serine residue in the carboxyl-terminal part of the enzyme is a major determinant for C4-specific characteristics.

    PubMed

    Bläsing, O E; Westhoff, P; Svensson, P

    2000-09-08

    C4 phosphoenolpyruvate carboxylases have evolved from ancestral C3 isoforms during the evolution of angiosperms and gained distinct kinetic and regulatory properties compared with the C3 isozymes. To identify amino acid residues and/or domains responsible for these C4-specific properties the C4 phosphoenolpyruvate carboxylase of Flaveria trinervia (C4) was compared with its orthologue in the closely related C3 plant Flaveria pringlei. Reciprocal enzyme chimera were constructed and the kinetic constants, K(0.5) and k(cat), as well as the Hill coefficient, h, were determined for the substrate phosphoenolpyruvate both in the presence and absence of the activator glucose 6-phosphate. By this approach two regions were identified which determined most of the kinetic differences of the C4 and C3 ppcA phosphoenolpyruvate carboxylases with respect to the substrate PEP. In addition, the experiments suggest that the two regions do not act additively but interact with each other. The region between amino acids 296 and 437 is essential for activation by glucose 6-phosphate. The carboxyl-terminal segment between amino acids 645 and 966 contains a C4 conserved serine or a C3 invariant alanine at position 774 in the respective enzyme isoform. Site-directed mutagenesis shows that this position is a key determinant for the kinetic properties of the two isozymes.

  19. Sequence of the pckA gene of Escherichia coli K-12: relevance to genetic and allosteric regulation and homology of E. coli phosphoenolpyruvate carboxykinase with the enzymes from Trypanosoma brucei and Saccharomyces cerevisiae.

    PubMed

    Medina, V; Pontarollo, R; Glaeske, D; Tabel, H; Goldie, H

    1990-12-01

    The sequence of the pckA gene coding for phosphoenolpyruvate carboxykinase in Escherichia coli K-12 and previous molecular weight determinations indicate that this allosteric enzyme is a monomer of Mr 51,316. The protein is homologous to ATP-dependent phosphoenolpyruvate carboxykinases from Trypanosoma brucei and Saccharomyces cerevisiae. A potential ATP binding site was conserved in all three sequences. A potential binding site for the allosteric activator, calcium, identified in the E. coli enzyme, was only partially conserved in T. brucei and S. cerevisiae, consistent with the observation that the enzymes from the latter organisms were not activated by calcium. The published sequence of the ompR and envZ genes from Salmonella typhimurium is followed by a partial sequence that is highly homologous to pckA from E. coli. The order of these genes and the direction of transcription of the presumptive S. typhimurium pckA gene are the same as those in E. coli. The potential calcium binding site of the E. coli enzyme is conserved in the partial predicted sequence of the S. typhimurium phosphoenolpyruvate carboxykinase, consistent with the observation that calcium activation of the S. typhimurium phosphoenolpyruvate carboxykinase is very similar to that observed for the E. coli enzyme. A pckA mRNA transcript was observed in stationary-phase cells but not in logarithmically growing cells. The mRNA start site was mapped relative to the sequence of the pckA structural gene.

  20. Integration of Lupinus angustifolius L. (narrow-leafed lupin) genome maps and comparative mapping within legumes.

    PubMed

    Wyrwa, Katarzyna; Książkiewicz, Michał; Szczepaniak, Anna; Susek, Karolina; Podkowiński, Jan; Naganowska, Barbara

    2016-09-01

    Narrow-leafed lupin (Lupinus angustifolius L.) has recently been considered a reference genome for the Lupinus genus. In the present work, genetic and cytogenetic maps of L. angustifolius were supplemented with 30 new molecular markers representing lupin genome regions, harboring genes involved in nitrogen fixation during the symbiotic interaction of legumes and soil bacteria (Rhizobiaceae). Our studies resulted in the precise localization of bacterial artificial chromosomes (BACs) carrying sequence variants for early nodulin 40, nodulin 26, nodulin 45, aspartate aminotransferase P2, asparagine synthetase, cytosolic glutamine synthetase, and phosphoenolpyruvate carboxylase. Together with previously mapped chromosomes, the integrated L. angustifolius map encompasses 73 chromosome markers, including 5S ribosomal DNA (rDNA) and 45S rDNA, and anchors 20 L. angustifolius linkage groups to corresponding chromosomes. Chromosomal identification using BAC fluorescence in situ hybridization identified two BAC clones as narrow-leafed lupin centromere-specific markers, which served as templates for preliminary studies of centromere composition within the genus. Bioinformatic analysis of these two BACs revealed that centromeric/pericentromeric regions of narrow-leafed lupin chromosomes consisted of simple sequence repeats ordered into tandem repeats containing the trinucleotide and pentanucleotide simple sequence repeats AGG and GATAC, structured into long arrays. Moreover, cross-genus microsynteny analysis revealed syntenic patterns of 31 single-locus BAC clones among several legume species. The gene and chromosome level findings provide evidence of ancient duplication events that must have occurred very early in the divergence of papilionoid lineages. This work provides a strong foundation for future comparative mapping among legumes and may facilitate understanding of mechanisms involved in shaping legume chromosomes.

  1. NMR-restrained docking of a peptidic inhibitor to the N-terminal domain of the phosphoenolpyruvate:sugar phosphotransferase enzyme I

    NASA Astrophysics Data System (ADS)

    Rognan, Didier; Mukhija, Seema; Folkers, Gerd; Zerbe, Oliver

    2001-02-01

    Starting from the NMR structure of the binary complex between the N-terminal domain of the unphosphorylated enzyme I (EIN) of the phosphoenolpyruvate:sugar phosphotransferase (PTS) and the histidine-containing phosphocarrier protein (HPr), a molecular model of the phosphorylated transition state of the related complex was established using constrained simulated annealing. The coordinates of the phosphorylated EIN enzyme were then used in a second step for flexible docking of a decapeptide inhibitor of EIN whose enzyme-bound conformation itself was determined by NMR using transferred nuclear Overhauser effects. Two phosphorylation models of the peptide inhibitor were investigated and shown to be both functional. Interestingly, one model is very similar to that of the complex between EIN and its natural substrate HPr. The present study demonstrates that NMR-guided flexible docking constitutes an interesting tool for docking highly flexible peptide ligands and facilitates the upcoming protein-based design of nonpeptide EIN inhibitors for discovering new antibiotics.

  2. Cloning, expression, purification and physical and kinetic characterization of the phosphoenolpyruvate carboxylase from orange (Citrus sinensis osbeck var. Valencia) fruit juice sacs.

    PubMed

    Perotti, Valeria E; Figueroa, Carlos M; Andreo, Carlos S; Iglesias, Alberto A; Podestá, Florencio E

    2010-11-01

    Phosphoenolpyruvate (PEP) carboxylase (PEPCase) from orange fruit juice sacs has been cloned and heterogously expressed in high yield. The purified recombinant enzyme displays properties typical of plant PEPCase, including activation by sugar phosphates and inhibition by malate and citrate. Malate inhibition is weak in the physiological pH range, and the enzyme is also poorly affected by Glu and Asp, known inhibitors of C(3) plants PEPCases. However, it is strongly inhibited by citrate. Orange fruit PEPCase phosphorylation by mammalian protein kinase A decreased inhibition by malate. The enzyme presents an unusual high molecular mass in the absence of PEP, while in its presence it displays a more common tetrameric arrangement. The overall properties of the enzyme suggest that it is suited for organic acid synthesis and NADH reoxidation in the mature fruit. The present study provides the first analysis of a recombinant fruit PEPCase.

  3. Establishment of an effective TLC bioautographic method for the detection of Mycobacterium tuberculosis H37Ra phosphoglucose isomerase inhibition by phosphoenolpyruvate.

    PubMed

    Paradowska, Katarzyna; Polak, Beata; Chomicki, Adam; Ginalska, Grażyna

    2016-12-01

    A bioautographic assay based on thin layer chromatography was developed for phosphoenolpyruvate (PEP) detecting as a known but rarely studied inhibitor of phosphoglucose isomerase (PGI). The protocol with NADP(+)/NBT/PMS (β-nicotinamide adenine dinucleotide phosphate/nitrotetrazolium blue chloride/phenazine methosulfate) staining was capable of detecting Mycobacterium tuberculosis H37Ra PGI inhibition using PEP. According to this method, visibly brighter spots (zones) against purple background are observed in the area of inhibition of the above-mentioned enzyme activity. The detection limit for PEP as an inhibitor of Mycobacterium tuberculosis H37Ra PGI was 226 μg per spot/zone. Noteworthy is that we are the first authors to have successfully used a bioautographic assay to detect Mycobacterium tuberculosis H37Ra PGI inhibition by PEP.

  4. Induction of mRNA for Phosphoenolpyruvate Carboxylase Is Correlated with a Decrease in Shoot Water Content in Well-Irrigated Mesembryanthemum crystallinum 1

    PubMed Central

    Schmitt, Jürgen M.; Piepenbrock, Mechtild

    1992-01-01

    The abundance of mRNA specific for phosphoenolpyruvate carboxylase (PEPCase) was measured in leaves from well-watered plants of Mesembryanthemum crystallinum. Plants grown side by side in pots of four different volumes (0.16, 0.74, 2.6, 6.5 liters) were compared. The time of increase in the steady-state level of PEPCase mRNA in well-watered plants was dependent on soil volume. The larger the pot, the later PEPCase transcripts were increased. PEPCase mRNA induction started when shoot water content decreased to well below 4000% of dry weight. No positive correlation with the developmental status of the plants could be found. The data indicate that PEPCase mRNA induction in well-watered plants up to 10 weeks of age is controlled environmentally rather than developmentally. ImagesFigure 2 PMID:16668951

  5. The bacterial-type phosphoenolpyruvate carboxylase isozyme from developing castor oil seeds is subject to in vivo regulatory phosphorylation at serine-451.

    PubMed

    Dalziel, Katie J; O'Leary, Brendan; Brikis, Carolyne; Rao, Srinath K; She, Yi-Min; Cyr, Terry; Plaxton, William C

    2012-04-05

    Phosphoenolpyruvate carboxylase (PEPC) is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate-metabolism. In developing castor oil seeds (COS) a novel allosterically-densensitized 910-kDa Class-2 PEPC hetero-octameric complex arises from a tight interaction between 107-kDa plant-type PEPC and 118-kDa bacterial-type PEPC (BTPC) subunits. Mass spectrometry and immunoblotting with anti-phosphoSer451 specific antibodies established that COS BTPC is in vivo phosphorylated at Ser451, a highly conserved target residue that occurs within an intrinsically disordered region. This phosphorylation was enhanced during COS development or in response to depodding. Kinetic characterization of a phosphomimetic (S451D) mutant indicated that Ser451 phosphorylation inhibits the catalytic activity of BTPC subunits within the Class-2 PEPC complex.

  6. Isolation of a cDNA for a phosphoenolpyruvate carboxylase from a monocot CAM-plant, Aloe arborescens: structure and its gene expression.

    PubMed

    Honda, H; Okamoto, T; Shimada, H

    1996-09-01

    A phosphoenolpyruvate carboxylase (PEPCase) cDNA was isolated from Aloe arborescens, a monocot CAM plant. Northern analysis of the PEPCase transcript indicated that it is specifically expressed in green leaves, strongly suggesting its involvement in CAM photosynthesis. No diurnal change in expression level was evident. Western blot analysis also showed no alteration of the amount of the PEPCase protein. These results suggest that circadian rhythm in PEPCase activity may be regulated post-translationally. The representative cDNA clone contained an ORF encoding 964 amino acid residues. Deduced amino acid sequence of the aloe PEPCase is highly conserved as compared with other PEPCases. The phosphorylation site which may be modified by PEPC-kinase was conserved. An evolutional map with known PEPCases suggested that CAM-type PEPCases were located between C4 and housekeeping PEPCases.

  7. Recombinant thermoactive phosphoenolpyruvate carboxylase (PEPC) from Thermosynechococcus elongatus and its coupling with mesophilic/thermophilic bacterial carbonic anhydrases (CAs) for the conversion of CO2 to oxaloacetate.

    PubMed

    Del Prete, Sonia; De Luca, Viviana; Capasso, Clemente; Supuran, Claudiu T; Carginale, Vincenzo

    2016-01-15

    With the continuous increase of atmospheric CO2 in the last decades, efficient methods for carbon capture, sequestration, and utilization are urgently required. The possibility of converting CO2 into useful chemicals could be a good strategy to both decreasing the CO2 concentration and for achieving an efficient exploitation of this cheap carbon source. Recently, several single- and multi-enzyme systems for the catalytic conversion of CO2 mainly to bicarbonate have been implemented. In order to design and construct a catalytic system for the conversion of CO2 to organic molecules, we implemented an in vitro multienzyme system using mesophilic and thermophilic enzymes. The system, in fact, was constituted by a recombinant phosphoenolpyruvate carboxylase (PEPC) from the thermophilic cyanobacterium Thermosynechococcus elongatus, in combination with mesophilic/thermophilic bacterial carbonic anhydrases (CAs), for converting CO2 into oxaloacetate, a compound of potential utility in industrial processes. The catalytic procedure is in two steps: the conversion of CO2 into bicarbonate by CA, followed by the carboxylation of phosphoenolpyruvate with bicarbonate, catalyzed by PEPC, with formation of oxaloacetate (OAA). All tested CAs, belonging to α-, β-, and γ-CA classes, were able to increase OAA production compared to procedures when only PEPC was used. Interestingly, the efficiency of the CAs tested in OAA production was in good agreement with the kinetic parameters for the CO2 hydration reaction of these enzymes. This PEPC also revealed to be thermoactive and thermostable, and when coupled with the extremely thermostable CA from Sulphurhydrogenibium azorense (SazCA) the production of OAA was achieved even if the two enzymes were exposed to temperatures up to 60 °C, suggesting a possible role of the two coupled enzymes in biotechnological processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Unraveling the evolutionary history of the phosphoryl-transfer chain of the phosphoenolpyruvate:phosphotransferase system through phylogenetic analyses and genome context

    PubMed Central

    2008-01-01

    Background The phosphoenolpyruvate phosphotransferase system (PTS) plays a major role in sugar transport and in the regulation of essential physiological processes in many bacteria. The PTS couples solute transport to its phosphorylation at the expense of phosphoenolpyruvate (PEP) and it consists of general cytoplasmic phosphoryl transfer proteins and specific enzyme II complexes which catalyze the uptake and phosphorylation of solutes. Previous studies have suggested that the evolution of the constituents of the enzyme II complexes has been driven largely by horizontal gene transfer whereas vertical inheritance has been prevalent in the general phosphoryl transfer proteins in some bacterial groups. The aim of this work is to test this hypothesis by studying the evolution of the phosphoryl transfer proteins of the PTS. Results We have analyzed the evolutionary history of the PTS phosphoryl transfer chain (PTS-ptc) components in 222 complete genomes by combining phylogenetic methods and analysis of genomic context. Phylogenetic analyses alone were not conclusive for the deepest nodes but when complemented with analyses of genomic context and functional information, the main evolutionary trends of this system could be depicted. Conclusion The PTS-ptc evolved in bacteria after the divergence of early lineages such as Aquificales, Thermotogales and Thermus/Deinococcus. The subsequent evolutionary history of the PTS-ptc varied in different bacterial lineages: vertical inheritance and lineage-specific gene losses mainly explain the current situation in Actinobacteria and Firmicutes whereas horizontal gene transfer (HGT) also played a major role in Proteobacteria. Most remarkably, we have identified a HGT event from Firmicutes or Fusobacteria to the last common ancestor of the Enterobacteriaceae, Pasteurellaceae, Shewanellaceae and Vibrionaceae. This transfer led to extensive changes in the metabolic and regulatory networks of these bacteria including the development of a

  9. Coutilization of glucose and glycerol enhances the production of aromatic compounds in an Escherichia coli strain lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system

    PubMed Central

    Martínez, Karla; de Anda, Ramón; Hernández, Georgina; Escalante, Adelfo; Gosset, Guillermo; Ramírez, Octavio T; Bolívar, Francisco G

    2008-01-01

    Background Escherichia coli strains lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS) are capable of coutilizing glucose and other carbon sources due to the absence of catabolite repression by glucose. In these strains, the lack of this important regulatory and transport system allows the coexistence of glycolytic and gluconeogenic pathways. Strains lacking PTS have been constructed with the goal of canalizing part of the phosphoenolpyruvate (PEP) not consumed in glucose transport to the aromatic pathway. The deletion of the ptsHIcrr operon inactivates PTS causing poor growth on this sugar; nonetheless, fast growing mutants on glucose have been isolated (PB12 strain). However, there are no reported studies concerning the growth potential of a PTS- strain in mixtures of different carbon sources to enhance the production of aromatics compounds. Results PB12 strain is capable of coutilizing mixtures of glucose-arabinose, glucose-gluconate and glucose-glycerol. This capacity increases its specific growth rate (μ) given that this strain metabolizes more moles of carbon source per unit time. The presence of plasmids pRW300aroGfbr and pCLtktA reduces the μ of strain PB12 in all mixtures of carbon sources, but enhances the productivity and yield of aromatic compounds, especially in the glucose-glycerol mixture, as compared to glucose or glycerol cultures. No acetate was detected in the glycerol and the glucose-glycerol batch fermentations. Conclusion Due to the lack of catabolite repression, PB12 strain carrying multicopy plasmids containing tktA and aroGfbr genes is capable of coutilizing glucose and other carbon sources; this capacity, reduces its μ but increases the production of aromatic compounds. PMID:18211716

  10. New insights into the post-translational modification of multiple phosphoenolpyruvate carboxylase isoenzymes by phosphorylation and monoubiquitination during sorghum seed development and germination

    PubMed Central

    Ruiz-Ballesta, Isabel; Baena, Guillermo; Gandullo, Jacinto; Wang, Liqun; She, Yi-Min; Plaxton, William Charles; Echevarría, Cristina

    2016-01-01

    Phosphoenolpyruvate carboxylase (PEPC; E.C. 4.1.1.31) was characterized in developing and germinating sorghum seeds, focusing on the transcript and polypeptide abundance of multiple plant-type phosphoenolpyruvate carboxylase (PTPC) genes, and the post-translational modification of each isoenzyme by phosphorylation versus monoubiquitination during germination. We observed high levels of SbPPC4 (Sb07g014960) transcripts during early development (stage I), and extensive transcript abundance of SbPPC2 (Sb02g021090) and SbPPC3 (Sb04g008720) throughout the entire life cycle of the seed. Although tandem mass spectrometry (MS) analysis of immunopurified PTPC indicated that four different PTPC isoenzymes were expressed in the developing and germinating seeds, SbPPC3 was the most abundant isozyme of the developing seed, and of the embryo and the aleurone layer of germinating seeds. In vivo phosphorylation of the different PTPC isoenzymes at their conserved N-terminal seryl phosphorylation site during germination was also established by MS/MS analysis. Furthermore, three of the four isoenzymes were partially monoubiquitinated, with MS/MS pinpointing SbPPC2 and SbPPC3 monoubiquitination at the conserved Lys-630 and Lys-624 residues, respectively. Our results demonstrate that monoubiquitination and phosphorylation simultaneously occur in vivo with different PTPC isozymes during seed germination. In addition, we show that PTPC monoubiquitination in germinating sorghum seeds always increases at stage II (emergence of the radicle), is maintained during the aerobic period of rapid cell division and reserve mobilization, and remains relatively constant until stage IV–V when coleoptiles initiate the formation of the photosynthetic tissues. PMID:27194739

  11. Coimmunopurification of phosphorylated bacterial- and plant-type phosphoenolpyruvate carboxylases with the plastidial pyruvate dehydrogenase complex from developing castor oil seeds.

    PubMed

    Uhrig, R Glen; O'Leary, Brendan; Spang, H Elizabeth; MacDonald, Justin A; She, Yi-Min; Plaxton, William C

    2008-03-01

    The phosphoenolpyruvate carboxylase (PEPC) interactome of developing castor oil seed (COS; Ricinus communis) endosperm was assessed using coimmunopurification (co-IP) followed by proteomic analysis. Earlier studies suggested that immunologically unrelated 107-kD plant-type PEPCs (p107/PTPC) and 118-kD bacterial-type PEPCs (p118/BTPC) are subunits of an unusual 910-kD hetero-octameric class 2 PEPC complex of developing COS. The current results confirm that a tight physical interaction occurs between p118 and p107 because p118 quantitatively coimmunopurified with p107 following elution of COS extracts through an anti-p107-IgG immunoaffinity column. No PEPC activity or immunoreactive PEPC polypeptides were detected in the corresponding flow-through fractions. Although BTPCs lack the N-terminal phosphorylation motif characteristic of PTPCs, Pro-Q Diamond phosphoprotein staining, immunoblotting with phospho-serine (Ser)/threonine Akt substrate IgG, and phosphate-affinity PAGE established that coimmunopurified p118 was multiphosphorylated at unique Ser and/or threonine residues. Tandem mass spectrometric analysis of an endoproteinase Lys-C p118 peptide digest demonstrated that Ser-425 is subject to in vivo proline-directed phosphorylation. The co-IP of p118 with p107 did not appear to be influenced by their phosphorylation status. Because p118 phosphorylation was unchanged 48 h following elimination of photosynthate supply due to COS depodding, the signaling mechanisms responsible for photosynthate-dependent p107 phosphorylation differ from those controlling p118's in vivo phosphorylation. A 110-kD PTPC coimmunopurified with p118 and p107 when depodded COS was used. The plastidial pyruvate dehydrogenase complex (PDC(pl)) was identified as a novel PEPC interactor. Thus, a putative metabolon involving PEPC and PDC(pl) could function to channel carbon from phosphoenolpyruvate to acetyl-coenzyme A and/or to recycle CO(2) from PDC(pl) to PEPC.

  12. Leaf hydraulics II: vascularized tissues.

    PubMed

    Rockwell, Fulton E; Holbrook, N Michele; Stroock, Abraham D

    2014-01-07

    Current models of leaf hydration employ an Ohm's law analogy of the leaf as an ideal capacitor, neglecting the resistance to flow between cells, or treat the leaf as a plane sheet with a source of water at fixed potential filling the mid-plane, neglecting the discrete placement of veins as well as their resistance. We develop a model of leaf hydration that considers the average conductance of the vascular network to a representative areole (region bounded by the vascular network), and represent the volume of tissue within the areole as a poroelastic composite of cells and air spaces. Solutions to the 3D flow problem are found by numerical simulation, and these results are then compared to 1D models with exact solutions for a range of leaf geometries, based on a survey of temperate woody plants. We then show that the hydration times given by these solutions are well approximated by a sum of the ideal capacitor and plane sheet times, representing the time for transport through the vasculature and tissue respectively. We then develop scaling factors relating this approximate solution to the 3D model, and examine the dependence of these scaling factors on leaf geometry. Finally, we apply a similar strategy to reduce the dimensions of the steady state problem, in the context of peristomatal transpiration, and consider the relation of transpirational gradients to equilibrium leaf water potential measurements. © 2013 Published by Elsevier Ltd. All rights reserved.

  13. Subcellular Localization of a UDP-Glucose:Aldehyde Cyanohydrin β-Glucosyl Transferase in Epidermal Plastids of Sorghum Leaf Blades 1

    PubMed Central

    Wurtele, Eve Syrkin; Thayer, Susan S.; Conn, Eric E.

    1982-01-01

    Epidermal and mesophyll protoplasts, prepared from leaf blades of 6-day-old light-grown Sorghum bicolor seedlings were separated by differential sedimentation and assayed for a number of enzymes. The epidermal protoplasts contained higher levels of NADPH-cytochrome c reductase (EC 1.6.2.4), triose phosphate isomerase (EC 5.3.1.1), phosphoenolpyruvate carboxylase (EC 4.1.1.31), and a UDP-glucose:cyanohydrin β-glucosyl transferase (EC 2.4.1.85), but lower levels of NADP+ triosephosphate dehydrogenase (EC 1.2.1.13) than did mesophyll protoplasts. When protoplast preparations were lysed and applied to linear sucrose density gradients, triosephosphate isomerase was found to be present in epidermal plastids. A significant fraction (41%) of the glucosyl transferase activity was also associated with the epidermal plastids. Images Fig. 2 PMID:16662753

  14. Maize YABBY genes drooping leaf1 and drooping leaf2 affect agronomic traits by regulating leaf architecture

    USDA-ARS?s Scientific Manuscript database

    Leaf architectural traits, such as length, width and angle, directly influence canopy structure and light penetration, photosynthate production and overall yield. We discovered and characterized a maize (Zea mays) mutant with aberrant leaf architecture we named drooping leaf1 (drl1), as leaf blades ...

  15. Active suppression of a leaf meristem orchestrates determinate leaf growth.

    PubMed

    Alvarez, John Paul; Furumizu, Chihiro; Efroni, Idan; Eshed, Yuval; Bowman, John L

    2016-10-06

    Leaves are flat determinate organs derived from indeterminate shoot apical meristems. The presence of a specific leaf meristem is debated, as anatomical features typical of meristems are not present in leaves. Here we demonstrate that multiple NGATHA (NGA) and CINCINNATA-class-TCP (CIN-TCP) transcription factors act redundantly, shortly after leaf initiation, to gradually restrict the activity of a leaf meristem in Arabidopsis thaliana to marginal and basal domains, and that their absence confers persistent marginal growth to leaves, cotyledons and floral organs. Following primordia initiation, the restriction of the broadly acting leaf meristem to the margins is mediated by the juxtaposition of adaxial and abaxial domains and maintained by WOX homeobox transcription factors, whereas other marginal elaboration genes are dispensable for its maintenance. This genetic framework parallels the morphogenetic program of shoot apical meristems and may represent a relic of an ancestral shoot system from which seed plant leaves evolved.

  16. Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.

  17. Leaf chlorophyll content as a proxy for leaf photosynthetic capacity.

    PubMed

    Croft, Holly; Chen, Jing M; Luo, Xiangzhong; Bartlett, Paul; Chen, Bin; Staebler, Ralf M

    2017-09-01

    Improving the accuracy of estimates of forest carbon exchange is a central priority for understanding ecosystem response to increased atmospheric CO2 levels and improving carbon cycle modelling. However, the spatially continuous parameterization of photosynthetic capacity (Vcmax) at global scales and appropriate temporal intervals within terrestrial biosphere models (TBMs) remains unresolved. This research investigates the use of biochemical parameters for modelling leaf photosynthetic capacity within a deciduous forest. Particular attention is given to the impacts of seasonality on both leaf biophysical variables and physiological processes, and their interdependent relationships. Four deciduous tree species were sampled across three growing seasons (2013-2015), approximately every 10 days for leaf chlorophyll content (ChlLeaf ) and canopy structure. Leaf nitrogen (NArea ) was also measured during 2014. Leaf photosynthesis was measured during 2014-2015 using a Li-6400 gas-exchange system, with A-Ci curves to model Vcmax. Results showed that seasonality and variations between species resulted in weak relationships between Vcmax normalized to 25°C (Vcmax25) and NArea (R(2)  = 0.62, P < 0.001), whereas ChlLeaf demonstrated a much stronger correlation with Vcmax25 (R(2)  = 0.78, P < 0.001). The relationship between ChlLeaf and NArea was also weak (R(2)  = 0.47, P < 0.001), possibly due to the dynamic partitioning of nitrogen, between and within photosynthetic and nonphotosynthetic fractions. The spatial and temporal variability of Vcmax25 was mapped using Landsat TM/ETM satellite data across the forest site, using physical models to derive ChlLeaf . TBMs largely treat photosynthetic parameters as either fixed constants or varying according to leaf nitrogen content. This research challenges assumptions that simple NArea -Vcmax25 relationships can reliably be used to constrain photosynthetic capacity in TBMs, even within the same plant functional type. It

  18. Leaf fall as a source of leaf miner mortality.

    PubMed

    Pritchard, I M; James, R

    1984-09-01

    Leaf miner deaths resulting from the death of their leaves were assessd by collecting falling leaves of holm oak and beech. The Phyllonorycter mines thus captured were examined to ascertain the cause of death. For both mining species the mortality from leaf shedding accounted for less than 2.8% of the mining cohorts. It is argued that the level of mortality is insufficient for population regulation, as has been previously suggested.

  19. Differentiation of C4 photosynthesis along a leaf developmental gradient in two Cleome species having different forms of Kranz anatomy

    PubMed Central

    Koteyeva, Nuria K.; Voznesenskaya, Elena V.; Cousins, Asaph B.; Edwards, Gerald E.

    2014-01-01

    In family Cleomaceae there are NAD-malic enzyme-type C4 species having different forms of leaf anatomy. Leaves of Cleome angustifolia have Glossocardioid-type anatomy with a single complex Kranz unit which surrounds all the veins, while C. gynandra has Atriplicoid anatomy with multiple Kranz units, each surrounding an individual vein. Biochemical and ultrastructural differentiation of mesophyll (M) and bundle sheath (BS) cells were studied along a developmental gradient, from the leaf base (youngest) to the tip (mature). Initially, there is cell-specific expression of certain photosynthetic enzymes, which subsequently increase along with structural differentiation. At the base of the leaf, following division of ground tissue to form M and BS cells which are structurally similar, there is selective localization of Rubisco and glycine decarboxylase to BS cells. Thus, a biochemical C3 default stage, with Rubisco expression in both cell types, does not occur. Additionally, phosphoenolpyruvate carboxylase (PEPC) is selectively expressed in M cells near the base. Surprisingly, in both species, an additional layer of spongy M cells on the abaxial side of the leaf has the same differentiation with PEPC, even though it is not in contact with BS cells. During development along the longitudinal gradient there is structural differentiation of the cells, chloroplasts, and mitochondria, resulting in complete formation of Kranz anatomy. In both species, development of the C4 system occurs similarly, irrespective of having very different types of Kranz anatomy, different ontogenetic origins of BS and M, and independent evolutionary origins of C4 photosynthesis. PMID:24550438

  20. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  1. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  2. Diffuse and specular characteristics of leaf reflectance

    NASA Technical Reports Server (NTRS)

    Grant, Lois

    1987-01-01

    In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

  3. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  4. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  5. 7 CFR 29.3036 - Leaf surface.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf surface. 29.3036 Section 29.3036 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf surface. The smoothness or roughness of the web or lamina of a tobacco leaf. Leaf surface is...

  6. Experiments in Whole Leaf Photosynthesis

    ERIC Educational Resources Information Center

    Stewart, J. C.; And Others

    1974-01-01

    Described is a simple experimental system, which uses radioactive carbon dioxide to study whole leaf photosynthesis under a variety of conditions. Other experiments and simple apparatus for the experiments are also described. (Author/RH)

  7. Near infrared leaf reflectance modeling

    NASA Technical Reports Server (NTRS)

    Parrish, J. B.

    1985-01-01

    Near infrared leaf reflectance modeling using Fresnel's equation (Kumar and Silva, 1973) and Snell's Law successfully approximated the spectral curve for a 0.25-mm turgid oak leaf lying on a Halon background. Calculations were made for ten interfaces, air-wax, wax-cellulose, cellulose-water, cellulose-air, air-water, and their inverses. A water path of 0.5 mm yielded acceptable results, and it was found that assignment of more weight to those interfaces involving air versus water or cellulose, and less to those involving wax, decreased the standard deviation of the error for all wavelengths. Data suggest that the air-cell interface is not the only important contributor to the overall reflectance of a leaf. Results also argue against the assertion that the near infrared plateau is a function of cell structure within the leaf.

  8. Hormonal Regulation of Leaf Abscission

    PubMed Central

    Jacobs, William P.

    1968-01-01

    A review is given of the progress made during the last 6 years in elucidating the nature, locus of action, and transport properties of the endogenous hormones that control leaf abscission. PMID:16657014

  9. Experiments in Whole Leaf Photosynthesis

    ERIC Educational Resources Information Center

    Stewart, J. C.; And Others

    1974-01-01

    Described is a simple experimental system, which uses radioactive carbon dioxide to study whole leaf photosynthesis under a variety of conditions. Other experiments and simple apparatus for the experiments are also described. (Author/RH)

  10. Why do leaf-tying caterpillars abandon their leaf ties?

    PubMed Central

    Sliwinski, Michelle

    2013-01-01

    Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm2 leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf

  11. Why do leaf-tying caterpillars abandon their leaf ties?

    PubMed

    Sliwinski, Michelle; Sigmon, Elisha

    2013-01-01

    Leaf-tying caterpillars act as ecosystem engineers by building shelters between overlapping leaves, which are inhabited by other arthropods. Leaf-tiers have been observed to leave their ties and create new shelters (and thus additional microhabitats), but the ecological factors affecting shelter fidelity are poorly known. For this study, we explored the effects of resource limitation and occupant density on shelter fidelity and assessed the consequences of shelter abandonment. We first quantified the area of leaf material required for a caterpillar to fully develop for two of the most common leaf-tiers that feed on white oak, Quercus alba. On average, Psilocorsis spp. caterpillars consumed 21.65 ± 0.67 cm(2) leaf material to complete development. We also measured the area of natural leaf ties found in a Maryland forest, to determine the distribution of resources available to caterpillars in situ. Of 158 natural leaf ties examined, 47% were too small to sustain an average Psilocorsis spp. caterpillar for the entirety of its development. We also manipulated caterpillar densities within experimental ties on potted trees to determine the effects of cohabitants on the likelihood of a caterpillar to leave its tie. We placed 1, 2, or 4 caterpillars in ties of a standard size and monitored the caterpillars twice daily to track their movement. In ties with more than one occupant, caterpillars showed a significantly greater propensity to leave their tie, and left sooner and at a faster rate than those in ties as single occupants. To understand the consequences of leaf tie abandonment, we observed caterpillars searching a tree for a site to build a shelter in the field. This is a risky behavior, as 17% of the caterpillars observed died while searching for a shelter site. Caterpillars that successfully built a shelter traveled 110 ± 20 cm and took 28 ± 7 min to find a suitable site to build a shelter. In conclusion, leaf-tying caterpillars must frequently abandon their leaf

  12. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf.

    PubMed

    Simonin, Kevin A; Burns, Emily; Choat, Brendan; Barbour, Margaret M; Dawson, Todd E; Franks, Peter J

    2015-03-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem-leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO₂ concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO₂ concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO₂ on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem-leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO₂ assimilation rate over the diurnal course of evaporative demand.

  13. Increasing leaf hydraulic conductance with transpiration rate minimizes the water potential drawdown from stem to leaf

    PubMed Central

    Simonin, Kevin A.; Burns, Emily; Choat, Brendan; Barbour, Margaret M.; Dawson, Todd E.; Franks, Peter J.

    2015-01-01

    Leaf hydraulic conductance (k leaf) is a central element in the regulation of leaf water balance but the properties of k leaf remain uncertain. Here, the evidence for the following two models for k leaf in well-hydrated plants is evaluated: (i) k leaf is constant or (ii) k leaf increases as transpiration rate (E) increases. The difference between stem and leaf water potential (ΔΨstem–leaf), stomatal conductance (g s), k leaf, and E over a diurnal cycle for three angiosperm and gymnosperm tree species growing in a common garden, and for Helianthus annuus plants grown under sub-ambient, ambient, and elevated atmospheric CO2 concentration were evaluated. Results show that for well-watered plants k leaf is positively dependent on E. Here, this property is termed the dynamic conductance, k leaf(E), which incorporates the inherent k leaf at zero E, which is distinguished as the static conductance, k leaf(0). Growth under different CO2 concentrations maintained the same relationship between k leaf and E, resulting in similar k leaf(0), while operating along different regions of the curve owing to the influence of CO2 on g s. The positive relationship between k leaf and E minimized variation in ΔΨstem–leaf. This enables leaves to minimize variation in Ψleaf and maximize g s and CO2 assimilation rate over the diurnal course of evaporative demand. PMID:25547915

  14. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  15. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  16. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture Regulations...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. [49 FR 16757, Apr. 20...

  17. Leaf proteomic analysis of three rice heritable mutants after seed space flight

    NASA Astrophysics Data System (ADS)

    Wang, W.; Gu, D. P.; Zheng, Q.; Sun, Y. Q.

    2008-09-01

    To explore the proteomic changes of heritable variant rice plants induced by space environment, three mutants were selected after seed space flight by comparing the phenotypes with their on-ground controls. R955 grew more tillers and became dwarf, 971-5 acquired higher grain yield and better stress resistance, 974-5 matured earlier. Leaf proteins were extracted during the tiller development and analyzed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). More than 300 proteins were detected as reproducible Coomassie Brilliant Blue stained spots with p I values from around 4.0 to 7.0. Five proteins that changed significantly over the controls were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The main functions of these proteins were photosynthesis, stress defense and metabolism including RuBisCO activase, glycine rich RNA binding protein, peroxidase, triosephosphate isomerase and phosphoenolpyruvate carboxylase, which might be probably associated with the altered phenotypes. Quantitative analyses were also applied: less total protein spots and more down-regulated protein spots were detected in the mutants, indicating there might be a major loss of protein in heritable variant rice plants after seed space flight. These results may provide new insights to understand the biological effects of space environment to rice.

  18. Barley leaf transcriptome and metabolite analysis reveals new aspects of compatibility and Piriformospora indica-mediated systemic induced resistance to powdery mildew.

    PubMed

    Molitor, Alexandra; Zajic, Doreen; Voll, Lars M; Pons-K Hnemann, Jorn; Samans, Birgit; Kogel, Karl-Heinz; Waller, Frank

    2011-12-01

    Colonization of barley roots with the basidiomycete fungus Piriformospora indica (Sebacinales) induces systemic resistance against the biotrophic leaf pathogen Blumeria graminis f. sp. hordei (B. graminis). To identify genes involved in this mycorrhiza-induced systemic resistance, we compared the leaf transcriptome of P. indica-colonized and noncolonized barley plants 12, 24, and 96 h after challenge with a virulent race of B. graminis. The leaf pathogen induced specific gene sets (e.g., LRR receptor kinases and WRKY transcription factors) at 12 h postinoculation (hpi) (prepenetration phase) and vesicle-localized gene products 24 hpi (haustorium establishment). Metabolic analysis revealed a progressing shift of steady state contents of the intermediates glucose-1-phosphate, uridinediphosphate-glucose, and phosphoenolpyruvate 24 and 96 hpi, indicating that B. graminis shifts central carbohydrate metabolism in favor of sucrose biosynthesis. Both B. graminis and P. indica increased glutamine and alanine contents, whereas substrates for starch and nitrogen assimilation (adenosinediphosphate- glucose and oxoglutarate) decreased. In plants that were more B. graminis resistant due to P. indica root colonization, 22 transcripts, including those of pathogenesis-related genes and genes encoding heat-shock proteins, were differentially expressed ?twofold in leaves after B. graminis inoculation compared with non-mycorrhized plants. Detailed expression analysis revealed a faster induction after B. graminis inoculation between 8 and 16 hpi, suggesting that priming of these genes is an important mechanism of P. indica-induced systemic disease resistance.

  19. Functional relationships of leafing intensity to plant height, growth form and leaf habit

    NASA Astrophysics Data System (ADS)

    Yan, En-Rong; Milla, Rubén; Aarssen, Lonnie W.; Wang, Xi-Hua

    2012-05-01

    Leafing intensity, i.e. the number of leaves per unit of stem volume or mass, is a common developmental correlate of leaf size. However, the ecological significance and the functional implications of variation in leafing intensity, other than its relation to leaf size, are unknown. Here, we explore its relationships with plant height, growth form, leaf size, and leaf habit to test a series of corollaries derived from the leafing intensity premium hypothesis. Volume-based leafing intensities and plant heights were recorded for 109 woody species from the subtropical evergreen broadleaf forests of eastern China. In addition, we compiled leafing intensity data from published literature, and combined it with our data to form a 398 species dataset, to test for differences of leafing intensity between plant growth forms (i.e. herbaceous and woody) and leaf habits (i.e. deciduous and evergreens). Leafing intensity was negatively correlated with plant height and individual leaf mass. Volume-based leafing intensities were significantly higher in herbaceous species than in woody species, and also higher in deciduous than in evergreen woody species. In conclusion, leafing intensity relates strongly to plant height, growth form, leaf size, and leaf habit in directions generally in accordance to the leafing intensity premium hypothesis. These results can be interpreted in terms of the evolution of adaptive strategies involving response to herbivory, competitive ability for light and reproductive economy.

  20. Salt induction and the partial purification/characterization of phosphoenolpyruvate carboxylase protein-serine kinase from an inducible crassulacean-acid-metabolism (CAM) plant, Mesembryanthemum crystallinum L.

    PubMed

    Li, B; Chollet, R

    1994-10-01

    Treatment of the common ice plant (Mesembryanthemum crystallinum) with high salinity caused the well-documented increase in phosphoenolpyruvate carboxylase (PEPC) protein and a concomitant rise in the activity of a Ca(2+)-independent PEPC-kinase (PEPC-PK). When the plants were irrigated with 0.5 M NaCl, PEPC protein level and PEPC-PK activity started to increase after 2 days of treatment and continued to rise for the next 8 days, attaining about a 14- and 8-fold total increase, respectively. This salt-induced PEPC-kinase activity was detected only in leaves harvested from the stressed plants at night. This highly regulated protein kinase was partially purified about 3500-fold from these darkened, salt-stressed plants by sequential fast-protein liquid chromatography on phenyl-Sepharose, blue dextran-agarose, and Superdex 75. The gel-filtration data indicated that the native PEPC-kinase has a molecular weight around 33,000. Complementary analysis by denaturing electrophoresis and subsequent in situ renaturation and assay of PEPC-kinase activity revealed two major PEPC-PK polypeptides with approximate molecular masses of 39 and 32 kDa. The partially purified M. crystallinum PEPC-kinase readily phosphorylated PEPCs purified from maize, M. crystallinum, and tobacco leaves and a recombinant sorghum enzyme. In contrast, this Ca(2+)-independent protein kinase phosphorylated neither a recombinant sorghum mutant PEPC in which the target residue (Ser-8) was changed by site-directed mutagenesis to Asp nor histone III-S, casein, and bovine serum albumin. The optimal pH for PEPC-PK activity was pH 8.0 and this activity was affected by both the substrate (phosphoenolpyruvate) and the negative allosteric effector (L-malate) of PEPC in a pH-dependent manner. Overall, the molecular properties of this highly regulated PEPC-kinase from M. crystallinum are strikingly similar to those reported recently by this laboratory for the reversibly light-activated C4 enzyme from maize (Arch

  1. Biophysical control of leaf temperature

    NASA Astrophysics Data System (ADS)

    Dong, N.; Prentice, I. C.; Wright, I. J.

    2014-12-01

    In principle sunlit leaves can maintain their temperatures within a narrower range than ambient temperatures. This is an important and long-known (but now overlooked) prediction of energy balance theory. Net radiation at leaf surface in steady state (which is reached rapidly) must be equal to the combination of sensible and latent heat exchanges with surrounding air, the former being proportional to leaf-to-air temperature difference (ΔT), the latter to the transpiration rate. We present field measurements of ΔT which confirm the existence of a 'crossover temperature' in the 25-30˚C range for species in a tropical savanna and a tropical rainforest environment. This finding is consistent with a simple representation of transpiration as a function of net radiation and temperature (Priestley-Taylor relationship) assuming an entrainment factor (ω) somewhat greater than the canonical value of 0.26. The fact that leaves in tropical forests are typically cooler than surrounding air, often already by solar noon, is consistent with a recently published comparison of MODIS day-time land-surface temperatures with air temperatures. Theory further predicts a strong dependence of leaf size (which is inversely related to leaf boundary-layer conductance, and therefore to absolute magnitude of ΔT) on moisture availability. Theoretically, leaf size should be determined by either night-time constraints (risk of frost damage to active leaves) or day-time constraints (risk of heat stress damage),with the former likely to predominate - thereby restricting the occurrence of large leaves - at high latitudes. In low latitudes, daytime maximum leaf size is predicted to increase with temperature, provided that water is plentiful. If water is restricted, however, transpiration cannot proceed at the Priestley-Taylor rate, and it quickly becomes advantageous for plants to have small leaves, which do not heat up much above the temperature of their surroundings. The difference between leaf

  2. Active suppression of a leaf meristem orchestrates determinate leaf growth

    PubMed Central

    Alvarez, John Paul; Furumizu, Chihiro; Efroni, Idan; Eshed, Yuval; Bowman, John L

    2016-01-01

    Leaves are flat determinate organs derived from indeterminate shoot apical meristems. The presence of a specific leaf meristem is debated, as anatomical features typical of meristems are not present in leaves. Here we demonstrate that multiple NGATHA (NGA) and CINCINNATA-class-TCP (CIN-TCP) transcription factors act redundantly, shortly after leaf initiation, to gradually restrict the activity of a leaf meristem in Arabidopsis thaliana to marginal and basal domains, and that their absence confers persistent marginal growth to leaves, cotyledons and floral organs. Following primordia initiation, the restriction of the broadly acting leaf meristem to the margins is mediated by the juxtaposition of adaxial and abaxial domains and maintained by WOX homeobox transcription factors, whereas other marginal elaboration genes are dispensable for its maintenance. This genetic framework parallels the morphogenetic program of shoot apical meristems and may represent a relic of an ancestral shoot system from which seed plant leaves evolved. DOI: http://dx.doi.org/10.7554/eLife.15023.001 PMID:27710768

  3. Xanthone derivatives could be potential antibiotics: virtual screening for the inhibitors of enzyme I of bacterial phosphoenolpyruvate-dependent phosphotransferase system.

    PubMed

    Huang, Kuo-Jien; Lin, Shih-Hung; Lin, Meei-Ru; Ku, Hao; Szkaradek, Natalia; Marona, Henryk; Hsu, Alvin; Shiuan, David

    2013-08-01

    The phosphoenolpyruvate phosphotransferase system (PTS) is ubiquitous in eubacteria and absent from eukaryotes. The system consists of two phosphoryl carriers, enzyme I (EI) and the histidine-containing phosphoryl carrier protein (HPr), and several PTS transporters, catalyzing the concomitant uptake and phosphorylation of several carbohydrates. Since a deficiency of EI in bacterial mutants lead to severe growth defects, EI could be a drug target to develop antimicrobial agents. We used the 3D structure PDB 1ZYM of Escherichia coli EI as the target to virtually screen the potential tight binders from NPPEDIA (Natural Product Encyclopedia), ZINC and Super Natural databases. These databases were screened using the docking tools of Discovery Studio 2.0 and the Integrated Drug Design System IDDS. Among the many interesting hits, xanthone derivatives with reasonably high Dock scores received more attentions. Two of the xanthone derivatives were obtained to examine their capabilities to inhibit cell growth of both Gram-positive and Gram-negative bacterial strains. The results indicate that they may exert the inhibition effects by blocking the EI activities. We have demonstrated for the first time that the xanthone derivatives have high potential to be developed as future antibiotics.

  4. Acclimation of two tomato species to high atmospheric CO sub 2 : II. Ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase

    SciTech Connect

    Yelle, S.; Beeson, R.C. Jr.; Trudel, M.J.; Gosselin, A. )

    1989-08-01

    Lycopersicon esculentum Mill. cv Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO{sub 2} concentrations for 10 weeks. The elevated CO{sub 2} concentrations increased the initial ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity of both species for the first 5 weeks of treatment but the difference did not persist during the last 5 weeks. The activity of Mg{sup 2+}-CO{sub 2}-activated Rubisco was higher in 900 microliters per liter for the first 2 weeks but declined sharply thereafter. After 10 weeks, leaves grown at 330 microliters per liter CO{sub 2} had about twice the Rubisco activity compared with those grown at 900 microliters per liter CO{sub 2}. The two species showed the same trend to Rubisco declines under high CO{sub 2} concentrations. The percent activation of Rubisco was always higher under high CO{sub 2}. The phosphoenolpyruvate carboxylase (PEPCase) activity measured in tomato leaves averaged 7.9% of the total Rubisco. PEPCase showed a similar trend with time as the initial Rubisco but with no significant difference between nonenriched and CO{sub 2}-enriched plants. Long-term exposure of tomato plants to high CO{sub 2} was previously shown to induce a decline of photosynthetic efficiency. Based on the current study and on previous results, we propose that the decline of activated Rubisco is the main cause of the acclimation of tomato plants to high CO{sub 2} concentrations.

  5. Phosphoenolpyruvate Carboxykinase, a Key Enzyme That Controls Blood Glucose, Is a Target of Retinoic Acid Receptor-Related Orphan Receptor α

    PubMed Central

    Matsuoka, Hiroshi; Shima, Akiho; Kuramoto, Daisuke; Kikumoto, Daisuke; Matsui, Takashi; Michihara, Akihiro

    2015-01-01

    Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes a committed and rate-limiting step in hepatic gluconeogenesis, and its activity is tightly regulated to maintain blood glucose levels within normal limits. PEPCK activity is primarily regulated through hormonal control of gene transcription. Transcription is additionally regulated via a cAMP response unit, which includes a cAMP response element and four binding sites for CCAAT/enhancer-binding protein (C/EBP). Notably, the cAMP response unit also contains a putative response element for retinoic acid receptor-related orphan receptor α (RORα). In this paper, we characterize the effect of the RORα response element on cAMP-induced transcription. Electrophoresis mobility shift assay indicates that RORα binds this response element in a sequence-specific manner. Furthermore, luciferase reporter assays indicate that RORα interacts with C/EBP at the PEPCK promoter to synergistically enhance transcription. We also found that cAMP-induced transcription depends in part on RORα and its response element. In addition, we show that suppression of RORα by siRNA significantly decreased PEPCK transcription. Finally, we found that a RORα antagonist inhibits hepatic gluconeogenesis in an in vitro glucose production assay. Taken together, the data strongly suggest that PEPCK is a direct RORα target. These results define possible new roles for RORα in hepatic gluconeogenesis. PMID:26383638

  6. Interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP) in the isolated perfused rat liver. Effects of cordycepin and cycloheximide.

    PubMed

    Krone, W; Marquardt, W; Seitz, H J; Tarnowski, W

    1976-11-18

    The mechanism of the interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP: oxalocetate carboxylase, transphosphorylating, EC 4.1.1.32) was investigated in the isolated perfused rat liver using inhibitors of transcription or translation. Dibutyryl cyclic AMP produced a rapid increase in P-enolpyruvate carboxykinase activity. The response of the enzyme to the cyclic nucleotide ceased however, at 4 h, but was restored by dexamethasone. The dibutyryl cyclic AMP-induced increase in P-enolpyruvate carboxykinase activity was completely blocked by cycloheximide, but not not by cordycepin. However, cordycepin totalaly suppressed the "permissive" effect of dexamethasone on the response of the enzyme to dibutyryl cyclic AMP. Preperfusion of the livers with dexamethasone and cycloheximide, following by perfusion without the steroid hormone and the inhibitor, resulted in a rapid rise in P-enolpyruvate carbosykinase activity, which was not affect by cordycepin. If livers were preperfused with cordycepin for different time-periods, followed by dibutyryl cyclic AMP stimulation of P-enolpyruvate carboxykinase synthesis, the response of the enzyme to the cyclic nucleotide was progressively reduced, achieving 50% inhibition after 1.5 h of preperfusion. These results suggest that the induction of hepatic P-enolpyruvate carboxykinase to maximum values, brought about by cyclic AMP at the level of translation, depends on the supply of newly synthetized mRNA provided by the transcriptional action of glucocorticoids.

  7. Cloning of cellobiose phosphoenolpyruvate-dependent phosphotransferase genes: Functional expression in recombinant Escherichia coli and identification of a putative binding region for disaccharides

    SciTech Connect

    Lai, Xiaokuang; Davis, F.C.; Ingram, L.O.; Hespell, R.B.

    1997-02-01

    Genomic libraries from nine cellobiose-metabolizing bacteria were screened for cellobiose utilization. Positive clones were recovered from six libraries, all of which encode phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) proteins. Clones from Bacillus subtilis, Butyrivibrio fibrisolvens, and Klebsiella oxytoca allowed the growth of recombinant Escherichia coli in cellobiose-M9 minimal medium. The K. oxytoca clone, pLOI1906, exhibited an unusually broad substrate range (cellobiose, arbutin, salicin, and methylumbelliferyl derivatives of glucose, cellobiose, mannose, and xylose) and was sequenced. The insert in this plasmid encoded the carboxy-terminal region of a putative regulatory protein, cellobiose permease (single polypeptide), and phospho-{beta}-glucosidase, which appear to form an operon (casRAB). Subclones allowed both casA and casB to be expressed independently, as evidenced by in vitro complementation. An analysis of the translated sequences from the EIIC domains of cellobiose, aryl-{beta}-glucoside, and other disaccharide permeases allowed the identification of a 50-amino-acid conserved region. A disaccharide consensus sequence is proposed for the most conserved segment (13 amino acids), which may represent part of the EIIC active site for binding and phosphorylation. 63 refs., 4 figs., 4 tabs.

  8. Cloning of cellobiose phosphoenolpyruvate-dependent phosphotransferase genes: functional expression in recombinant Escherichia coli and identification of a putative binding region for disaccharides.

    PubMed Central

    Lai, X; Davis, F C; Hespell, R B; Ingram, L O

    1997-01-01

    Genomic libraries from nine cellobiose-metabolizing bacteria were screened for cellobiose utilization. Positive clones were recovered from six libraries, all of which encode phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) proteins. Clones from Bacillus subtilis, Butyrivibrio fibrisolvens, and Klebsiella oxytoca allowed the growth of recombinant Escherichia coli in cellobiose-M9 minimal medium. The K. oxytoca clone, pLOI1906, exhibited an unusually broad substrate range (cellobiose, arbutin, salicin, and methylumbelliferyl derivatives of glucose, cellobiose, mannose, and xylose) and was sequenced. The insert in this plasmid encoded the carboxy-terminal region of a putative regulatory protein, cellobiose permease (single polypeptide), and phospho-beta-glucosidase, which appear to form an operon (casRAB). Subclones allowed both casA and casB to be expressed independently, as evidenced by in vitro complementation. An analysis of the translated sequences from the EIIC domains of cellobiose, aryl-beta-glucoside, and other disaccharide permeases allowed the identification of a 50-amino-acid conserved region. A disaccharide consensus sequence is proposed for the most conserved segment (13 amino acids), which may represent part of the EIIC active site for binding and phosphorylation. PMID:9023916

  9. Evidence for the presence of heat-stable protein (HPr) and ATP-dependent HPr kinase in heterofermentative lactobacilli lacking phosphoenolpyruvate:glycose phosphotransferase activity.

    PubMed Central

    Reizer, J; Peterkofsky, A; Romano, A H

    1988-01-01

    An analysis of the biochemical basis for the lack of phosphoenolpyruvate:glycose phosphotransferase activity in heterofermentative lactobacilli was carried out. Extracts of Lactobacillus brevis and Lactobacillus buchneri failed to reconstitute phosphotransferase activity of extracts of Staphylococcus aureus mutants impaired in the phosphotransferase system due to the absence of enzyme I, enzyme IILac, or enzyme IIILac activity, suggesting that these lactobacilli lack those phosphotransferase system components. In contrast, complementation tests with an extract of a S. aureus mutant deficient in heat-stable protein (HPr) indicated the presence of HPr activity in heterofermentative lactobacilli. The HPr of L. brevis was purified and shown to have properties similar to those of a typical HPr. In addition, L. brevis possesses an ATP-dependent protein kinase that phosphorylates a serine residue of the endogenous HPr as well as other HPrs of Gram-positive origin. The kinase activity is markedly stimulated by phosphorylated compounds related to sugar metabolism and is negatively modulated by orthophosphate, pyrophosphate, or arsenate and by a low molecular weight endogenous factor. In keeping with the idea of a regulatory role for the phosphorylation of HPr in lactobacilli, a HPr[Ser(P)] phosphatase activity in L. brevis was also demonstrated. On the basis of the finding of HPr and a system for its reversible covalent modification in an organism devoid of a functional phosphotransferase system we propose that, in lactobacilli, HPr has a role in the regulation of pathways other than the phosphotransferase system. Images PMID:2832843

  10. Phosphoenolpyruvate carboxykinase (Pck1) helps regulate the triglyceride/fatty acid cycle and development of insulin resistance in mice[S

    PubMed Central

    Millward, Carrie A.; DeSantis, David; Hsieh, Chang-Wen; Heaney, Jason D.; Pisano, Sorana; Olswang, Yael; Reshef, Lea; Beidelschies, Michelle; Puchowicz, Michelle; Croniger, Colleen M.

    2010-01-01

    The aim of this study was to investigate the role of the cytosolic form of phosphoenolpyruvate carboxykinase (Pck1) in the development of insulin resistance. Previous studies have shown that the roles of Pck1 in white adipose tissue (WAT) in glyceroneogenesis and reesterification of free fatty acids (FFA) to generate triglyceride are vital for the prevention of diabetes. We hypothesized that insulin resistance develops when dysregulation of Pck1 occurs in the triglyceride/fatty acid cycle, which regulates lipid synthesis and transport between adipose tissue and the liver. We examined this by analyzing mice with a deletion of the PPARγ binding site in the promoter of Pck1 (PPARE−/−). This mutation reduced the fasting Pck1 mRNA expression in WAT in brown adipose tissue (BAT). To analyze insulin resistance, we performed hyperinsulinemic-euglycemic glucose clamp analyses. PPARE−/− mice were profoundly insulin resistant and had more FFA and glycerol released during the hyperinsulinemic-euglycemic clamp compared with wild-type mice (WT). Finally, we analyzed insulin secretion in isolated islets. We found a 2-fold increase in insulin secretion in the PPARE−/− mice at 16.7 mM glucose. Thus, the PPARE site in the Pck1 promoter is essential for maintenance of lipid metabolism and glucose homeostasis and disease prevention. PMID:20124556

  11. Correlation between depression of catabolite control of xylose metabolism and a defect in the phosphoenolpyruvate:mannose phosphotransferase system in Pediococcus halophilus.

    PubMed Central

    Abe, K; Uchida, K

    1989-01-01

    Pediococcus halophilus X-160 which lacks catabolite control by glucose was isolated from nature (soy moromi mash). Wild-type strains, in xylose-glucose medium, utilized glucose preferentially over xylose and showed diauxic growth. With wild-type strain I-13, xylose isomerase activity was not induced until glucose was consumed from the medium. Strain X-160, however, utilized xylose concurrently with glucose and did not show diauxic growth. In this strain, xylose isomerase was induced even in the presence of glucose. Glucose transport activity in intact cells of strain X-160 was less than 10% of that assayed in strain I-13. Determinations of glycolytic enzymes did not show any difference responsible for the unique behavior of strain X-160, but the rate of glucose-6-phosphate formation with phosphoenolpyruvate (PEP) as a phosphoryl donor in permeabilized cells was less than 10% of that observed in the wild type. Starved P. halophilus I-13 cells contained the glycolytic intermediates 3-phosphoglycerate, 2-phosphoglycerate, and PEP (PEP pool). These were consumed concomitantly with glucose or 2-deoxyglucose uptake but were not consumed with xylose uptake. The glucose transport system in P. halophilus was identified as a PEP:mannose phosphotransferase system on the basis of the substrate specificity of PEP pool-starved cells. It is concluded that, in P. halophilus, this system is functional as a main glucose transport system and that defects in this system may be responsible for the depression of glucose-mediated catabolite control. Images PMID:2703460

  12. Novel homozygous PCK1 mutation causing cytosolic phosphoenolpyruvate carboxykinase deficiency presenting as childhood hypoglycemia, an abnormal pattern of urine metabolites and liver dysfunction.

    PubMed

    Vieira, Päivi; Cameron, Jessie; Rahikkala, Elisa; Keski-Filppula, Riikka; Zhang, Lin-Hua; Santra, Saikat; Matthews, Allison; Myllynen, Päivi; Nuutinen, Matti; Moilanen, Jukka S; Rodenburg, Richard J; Rolfs, Arndt; Uusimaa, Johanna; van Karnebeek, Clara D M

    2017-04-01

    Clinical and laboratory data were collected from three Finnish patients including a sibling pair and another unrelated child with unexplained childhood hypoglycemia. Transient elevation of alanine transaminase, lactate and tricarboxylic acid cycle intermediates, especially fumarate, were noticed in urine organic acid analysis. Exome sequencing was performed for the patients and their parents. A novel homozygous PCK1 c.925G>A (p.G309R) mutation was detected in all affected individuals. COS-1 cells transfected with mutant PCK1 transcripts were used to study the pathogenic nature of the detected variant. The COS-1 transfected cells showed the mutant gene to be incapable of producing a normally functioning cytosolic phosphoenolpyruvate carboxykinase (PEPCK) enzyme. This report further delineates the clinical phenotype of isolated cytosolic PEPCK deficiency and offers a metabolic pattern helping to recognize these patients. Cytosolic PEPCK deficiency should be considered in the differential diagnosis of children presenting with hypoglycemia, hepatic dysfunction and elevated tricarboxylic acid intermediates in urinary organic acid analysis. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Relationship between NH(4) Assimilation Rate and in Vivo Phosphoenolpyruvate Carboxylase Activity : Regulation of Anaplerotic Carbon Flow in the Green Alga Selenastrum minutum.

    PubMed

    Vanlerberghe, G C; Schuller, K A; Smith, R G; Feil, R; Plaxton, W C; Turpin, D H

    1990-09-01

    The rate of NH(4) (+) assimilation by N-limited Selenastrum minutum (Naeg.) Collins cells in the dark was set as an independent variable and the relationship between NH(4) (+) assimilation rate and in vivo activity of phosphoenolpyruvate carboxylase (PEPC) was determined. In vivo activity of PEPC was measured by following the incorporation of H(14)CO(-) (3) into acid stable products. A linear relationship of 0.3 moles C fixed via PEPC per mole N assimilated was observed. This value agrees extremely well with the PEPC requirement for the synthesis of the amino acids found in total cellular protein. Determinations of metabolite levels in vivo at different rates of N assimilation indicated that the known metabolite effectors of S. minutum PEPC in vitro (KA Schuller, WC Plaxton, DH Turpin, [1990] Plant Physiol 93: 1303-1311) are important regulators of this enzyme during N assimilation. As PEPC activity increased in response to increasing rates of N assimilation, there was a corresponding decline in the level of PEPC inhibitors (2-oxoglutarate, malate), an increase in the level of PEPC activators (glutamine, dihydroxyacetone phosphate), and an increase in the Gln/Glu ratio. Treatment of N-limited cells with azaserine caused an increase in the Gln/Glu ratio resulting in increased PEPC activity in the absence of N assimilation. We suggest glutamate and glutamine play a key role in regulating the anaplerotic function of PEPC in this C(3) organism.

  14. Stimulation of dihydroxyacetone and glycerol kinase activity in Streptococcus faecalis by phosphoenolpyruvate-dependent phosphorylation catalyzed by enzyme I and HPr of the phosphotransferase system.

    PubMed

    Deutscher, J; Sauerwald, H

    1986-06-01

    Recently we reported the phosphoenolpyruvate (PEP)-dependent phosphorylation of a 55-kilodalton protein of Streptococcus faecalis catalyzed by enzyme I and histidine-containing protein (HPr) of the phosphotransferase system (J. Deutscher, FEMS Microbiol. Lett. 29:237-243, 1985). The purified 55-kilodalton protein was found to exhibit dihydroxyacetone kinase activity. Glycerol was six times more slowly phosphorylated than dihydroxyacetone. The Kms were found to be 0.7 mM for ATP, 0.45 mM for dihydroxyacetone, and 0.9 mM for glycerol. PEP-dependent phosphorylation of dihydroxyacetone kinase stimulated phosphorylation of both substrates about 10-fold. Fructose 1,6-diphosphate at concentrations higher than 2 mM inhibited the activity of phosphorylated and unphosphorylated dihydroxyacetone kinase in a noncompetitive manner. The rate of PEP-dependent phosphorylation of dihydroxyacetone kinase was about 200-fold slower than the phosphorylation rate of III proteins (also called enzyme III or factor III), which so far have been considered the only phosphoryl acceptors of histidyl-phosphorylated HPr. P-Dihydroxyacetone kinase was found to be able to transfer its phosphoryl group in a backward reaction to HPr. Following [32P]PEP-dependent phosphorylation and tryptic digestion of dihydroxyacetone kinase, we isolated a labeled peptide composed of 37 amino acids, as determined by amino acid analysis. The single histidyl residue of this peptide most likely carries the phosphoryl group in phosphorylated dihydroxyacetone kinase.

  15. CO2 reduction and organic compounds production by photosynthetic bacteria with surface displayed carbonic anhydrase and inducible expression of phosphoenolpyruvate carboxylase.

    PubMed

    Park, Ju-Yong; Kim, Yang-Hoon; Min, Jiho

    2017-01-01

    In Rhodobacter sphaeroides, carbonic anhydrase (CA; EC 4.2.1.1) is a zinc-containing metalloenzyme that catalyzes the reversible hydration of CO2 to HCO3(-) while phosphoenolpyruvate carboxylase (PEPC; 4.1.1.31), an enzyme involved in the carbon metabolism that catalyzed the fixation of CO2 to PEP, is a key factor for biological fixation of CO2 and enhances the production of organic compounds. In this study, the recombinant R. sphaeroides with highly-expressed CA was developed based on a surface displayed system of CA (pJY-OmpCA) on the outer membrane of R. sphaeroides using outer membrane protein (Omp) in R. sphaeroides, Finally, two more different recombinant R. sphaeroides were developed, which transformed with a two-vector system harboring cytosolic expressed CA (pJY-OmpCA-CA)or PEPC (pJY-OMPCA-PEPC) in R. sphaeroides with surface displayed CA on the outer membrane. In case of recombinant R. sphaeroides with the pJY-OmpCA-PEPC, it has shown the highest CO2 reduction efficiency and the production of several organic compounds (carotenoids, polyhydroxybutyrate, malic acid, succinic acid). It means that the surface displayed CA on the R. sphaeroides would accelerate the CO2-bicabonate conversion on the bacterial outer membrane. Moreover, inducible over-expression of PEPC with surface-displayed CA was successfully used to facilitate a rapider CO2 reduction and quicker production of organic compounds.

  16. Phosphorylation of phosphoenolpyruvate carboxykinase in plants. Studies in plants with C4 photosynthesis and Crassulacean acid metabolism and in germinating seeds.

    PubMed

    Walker, R P; Leegood, R C

    1996-08-01

    We have previously shown that phosphoenolpyruvate carboxykinase (PEPCK) is phosphorylated in vivo in the cotyledons of darkened cucumber seedlings and that phosphorylation is reversed by light [Walker and Leegood (1995) FEBS Lett. 362, 70-74]. In this study the molecular mass of PEPCK was estimated in a range of gluconeogenic seedlings and in leaves of C4 plants and plants with Crassulacean acid metabolism (CAM). Phosphorylation of PEPCK was studied in these plants by feeding tissues with [32P]Pi and assessing phosphorylation by SDS/PAGE and autoradiography of either total proteins or of immunoprecipitated protein. In gluconeogenic seedlings and most CAM plants PEPCK had a molecular mass of 74 kDa, whereas in C4 grasses the molecular mass of PEPCK was always smaller and varied from 67-71 kDa. In all gluconeogenic seedlings and leaves of CAM plants PEPCK was phosphorylated, but it was not phosphorylated in all species of C4 grasses studied. In CAM plants, phosphorylation of PEPCK occurred at night and dephosphorylation occurred during the day. In C4 grasses phosphorylation occurred when leaves were darkened and the enzyme was dephosphorylated following illumination, but it was only phosphorylated in those plants with larger (71 kDa) molecular mass forms of PEPCK.

  17. Spectral reflectance relationships to leaf water stress

    NASA Technical Reports Server (NTRS)

    Ripple, William J.

    1986-01-01

    Spectral reflectance data were collected from detached snapbean leaves in the laboratory with a multiband radiometer. Four experiments were designed to study the spectral response resulting from changes in leaf cover, relative water content of leaves, and leaf water potential. Spectral regions included in the analysis were red (630-690 nm), NIR (760-900 nm), and mid-IR (2.08-2.35 microns). The red and mid-IR bands showed sensitivity to changes in both leaf cover and relative water content of leaves. The NIR was only highly sensitive to changes in leaf cover. Results provided evidence that mid-IR reflectance was governed primarily by leaf moisture content, although soil reflectance was an important factor when leaf cover was less than 100 percent. High correlations between leaf water potentials and reflectance were attributed to covariances with relative water content of leaves and leaf cover.

  18. Spectral reflectance relationships to leaf water stress

    NASA Technical Reports Server (NTRS)

    Ripple, William J.

    1986-01-01

    Spectral reflectance data were collected from detached snapbean leaves in the laboratory with a multiband radiometer. Four experiments were designed to study the spectral response resulting from changes in leaf cover, relative water content of leaves, and leaf water potential. Spectral regions included in the analysis were red (630-690 nm), NIR (760-900 nm), and mid-IR (2.08-2.35 microns). The red and mid-IR bands showed sensitivity to changes in both leaf cover and relative water content of leaves. The NIR was only highly sensitive to changes in leaf cover. Results provided evidence that mid-IR reflectance was governed primarily by leaf moisture content, although soil reflectance was an important factor when leaf cover was less than 100 percent. High correlations between leaf water potentials and reflectance were attributed to covariances with relative water content of leaves and leaf cover.

  19. Behavior of Leaf Meristems and Their Modification

    PubMed Central

    Ichihashi, Yasunori; Tsukaya, Hirokazu

    2015-01-01

    A major source of diversity in flowering plant form is the extensive variability of leaf shape and size. Leaf formation is initiated by recruitment of a handful of cells flanking the shoot apical meristem (SAM) to develop into a complex three-dimensional structure. Leaf organogenesis depends on activities of several distinct meristems that are established and spatiotemporally differentiated after the initiation of leaf primordia. Here, we review recent findings in the gene regulatory networks that orchestrate leaf meristem activities in a model plant Arabidopsis thaliana. We then discuss recent key studies investigating the natural variation in leaf morphology to understand how the gene regulatory networks modulate leaf meristems to yield a substantial diversity of leaf forms during the course of evolution. PMID:26648955

  20. LEAF: A Microcomputer Program for Constructing the Tukey Stem and Leaf Graph.

    ERIC Educational Resources Information Center

    Pascale, Pietro J.; Smith, Joseph

    1986-01-01

    This paper presents a BASIC microcomputer program that constructs the Tukey (1977) stem and leaf graph. Options within the LEAF program include a modified stem and leaf where the stem is split and a parallel stem and leaf graph where two separate sets of data are displayed from a common stem. (Author)

  1. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  2. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  3. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  4. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  5. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  6. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  7. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  8. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  9. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  10. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  11. 7 CFR 29.3035 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Leaf structure. The cell development of a leaf as indicated by its porosity or solidity. (See Elements... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.3035 Section 29.3035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  12. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  13. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  14. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  15. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  16. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  17. 7 CFR 29.3527 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Type 95) § 29.3527 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.3527 Section 29.3527 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  18. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  19. 7 CFR 29.1030 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Type 92) § 29.1030 Leaf structure. The cell development of a leaf as indicated by its porosity. (See... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.1030 Section 29.1030 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  20. 7 CFR 29.6023 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... INSPECTION Standards Definitions § 29.6023 Leaf structure. The cell development of a leaf as indicated by its... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.6023 Section 29.6023 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  1. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf surface. 29.3528 Section 29.3528 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf...

  2. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf surface. 29.3528 Section 29.3528 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco leaf...

  3. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or...

  4. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  5. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or...

  6. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  7. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. [30 FR 9207, July 23, 1965...

  8. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  9. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. [24 FR 8771, Oct. 29, 1959. Redesignated at 49 FR...

  10. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists...

  11. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or...

  12. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists...

  13. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2277 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists...

  14. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  15. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  16. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  17. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or broken leaves. ...

  18. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and...

  19. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling...

  20. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results...

  1. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or...

  2. 7 CFR 29.3034 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.3034 Section 29.3034 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Leaf scrap. A by-product of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and...

  3. 7 CFR 29.2529 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.2529 Section 29.2529 Agriculture...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2529 Leaf scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists of loose and tangled whole or...

  4. 7 CFR 29.3526 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.3526 Section 29.3526 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 95) § 29.3526 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results from handling...

  5. 7 CFR 29.6022 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.6022 Section 29.6022 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Definitions § 29.6022 Leaf scrap. A byproduct of unstemmed tobacco Leaf scrap results...

  6. Comparison of half and full-leaf shape feature extraction for leaf classification

    NASA Astrophysics Data System (ADS)

    Sainin, Mohd Shamrie; Ahmad, Faudziah; Alfred, Rayner

    2016-08-01

    Shape is the main information for leaf feature that most of the current literatures in leaf identification utilize the whole leaf for feature extraction and to be used in the leaf identification process. In this paper, study of half-leaf features extraction for leaf identification is carried out and the results are compared with the results obtained from the leaf identification based on a full-leaf features extraction. Identification and classification is based on shape features that are represented as cosines and sinus angles. Six single classifiers obtained from WEKA and seven ensemble methods are used to compare their performance accuracies over this data. The classifiers were trained using 65 leaves in order to classify 5 different species of preliminary collection of Malaysian medicinal plants. The result shows that half-leaf features extraction can be used for leaf identification without decreasing the predictive accuracy.

  7. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color intensity...

  8. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color intensity...

  9. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color intensity...

  10. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color intensity...

  11. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... tolerance. C4L Fair Quality Light-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in oil... tolerance. C5L Low Quality Light-brown Thin Leaf Underripe, thin, close leaf structure, rough, lean in oil... tolerance. C4F Fair Quality Medium-brown Thin Leaf. Mature, thin, close leaf structure, rough, lean in oil...

  12. 7 CFR 29.1162 - Leaf (B Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Specifications, and Tolerances B1L—Choice Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil... percent. B2L—Fine Quality Lemon Leaf Ripe, firm leaf structure, medium body, rich in oil, deep color.... B3L—Good Quality Lemon Leaf Ripe, firm leaf structure, medium body, oily, strong color intensity...

  13. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C1F Choice Quality Medium-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, rich in oil...

  14. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C1F Choice Quality Medium-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, rich in oil...

  15. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... specifications, and tolerances C1L Choice Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth... injury tolerance. C2L Fine Quality Light-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, oily... tolerance. C1F Choice Quality Medium-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, rich in oil...

  16. Leafing patterns and leaf traits of four evergreen shrubs in the Patagonian Monte, Argentina

    NASA Astrophysics Data System (ADS)

    Campanella, María Victoria; Bertiller, Mónica B.

    2009-11-01

    We assessed leafing patterns (rate, timing, and duration of leafing) and leaf traits (leaf longevity, leaf mass per area and leaf-chemistry) in four co-occurring evergreen shrubs of the genus Larrea and Chuquiraga (each having two species) in the arid Patagonian Monte of Argentina. We asked whether species with leaves well-defended against water shortage (high LMA, leaf longevity, and lignin concentration, and low N concentration) have lower leaf production, duration of the leafing period, and inter-annual variation of leafing than species with the opposite traits. We observed two distinctive leafing patterns each related to one genus. Chuquiraga species produced new leaves concentrated in a massive short leafing event (5-48 days) while new leaves of Larrea species emerged gradually (128-258 days). Observed leafing patterns were consistent with simultaneous and successive leafing types previously described for woody plants. The peak of leaf production occurred earlier in Chuquiraga species (mid September) than in Larrea species (mid October-late November). Moreover, Chuquiraga species displayed leaves with the longest leaf lifespan, while leaves of Larrea species had the lowest LMA and the highest N and soluble phenolics concentrations. We also observed that only the leaf production of Larrea species increased in humid years. We concluded that co-occurring evergreen species in the Patagonian Monte displayed different leafing patterns, which were associated with some relevant leaf traits acting as plant defenses against water stress and herbivores. Differences in leafing patterns could provide evidence of ecological differentiation among coexisting species of the same life form.

  17. Leaf area dynamics of conifer forests

    SciTech Connect

    Margolis, H.; Oren, R.; Whitehead, D.; Kaufmann, M.R.

    1995-07-01

    Estimating the surface area of foliage supported by a coniferous forest canopy is critical for modeling its biological properties. Leaf area represents the surface area available for the interception of energy, the absorption of carbon dioxide, and the diffusion of water from the leaf to the atmosphere. The concept of leaf area is pertinent to the physiological and ecological dynamics of conifers at a wide range of spatial scales, from individual leaves to entire biomes. In fact, the leaf area of vegetation at a global level can be thought of as a carbon-absorbing, water-emitting membrane of variable thickness, which can have an important influence on the dynamics and chemistry of the Earth`s atmosphere over both the short and the long term. Unless otherwise specified, references to leaf area herein refer to projected leaf area, i.e., the vertical projection of needles placed on a flat plane. Total leaf surface area is generally from 2.0 to 3.14 times that of projected leaf area for conifers. It has recently been suggested that hemisurface leaf area, i.e., one-half of the total surface area of a leaf, a more useful basis for expressing leaf area than is projected area. This chapter is concerned with the dynamics of coniferous forest leaf area at different spatial and temporal scales. In the first part, we consider various hypotheses related to the control of leaf area development, ranging from simple allometric relations with tree size to more complex mechanistic models that consider the movement of water and nutrients to tree canopies. In the second part, we consider various aspects of leaf area dynamics at varying spatial and temporal scales, including responses to perturbation, seasonal dynamics, genetic variation in crown architecture, the responses to silvicultural treatments, the causes and consequences of senescence, and the direct measurement of coniferous leaf area at large spatial scales using remote sensing.

  18. SPAD-based leaf nitrogen estimation is impacted by environmental factors and crop leaf characteristics

    PubMed Central

    Xiong, Dongliang; Chen, Jia; Yu, Tingting; Gao, Wanlin; Ling, Xiaoxia; Li, Yong; Peng, Shaobing; Huang, Jianliang

    2015-01-01

    Chlorophyll meters are widely used to guide nitrogen (N) management by monitoring leaf N status in agricultural systems, but the effects of environmental factors and leaf characteristics on leaf N estimations are still unclear. In the present study, we estimated the relationships among SPAD readings, chlorophyll content and leaf N content per leaf area for seven species grown in multiple environments. There were similar relationships between SPAD readings and chlorophyll content per leaf area for the species groups, but the relationship between chlorophyll content and leaf N content per leaf area, and the relationship between SPAD readings and leaf N content per leaf area varied widely among the species groups. A significant impact of light-dependent chloroplast movement on SPAD readings was observed under low leaf N supplementation in both rice and soybean but not under high N supplementation. Furthermore, the allocation of leaf N to chlorophyll was strongly influenced by short-term changes in growth light. We demonstrate that the relationship between SPAD readings and leaf N content per leaf area is profoundly affected by environmental factors and leaf features of crop species, which should be accounted for when using a chlorophyll meter to guide N management in agricultural systems. PMID:26303807

  19. Habitat Complexity of Stream Leaf Packs: Effects on Benthic Macroinvertebrates and Leaf Litter Breakdown

    NASA Astrophysics Data System (ADS)

    Ruetz, C. R.; Vanhaitsma, D. L.; Breen, M. J.

    2005-05-01

    We investigated two attributes of leaf-pack complexity (i.e., leaf-pack mass and leaf surface area) on fish predation, colonization of benthic macroinvertebrates, and leaf breakdown rates in a coldwater Michigan stream. We manipulated three factors using a factorial design: fish (exclusion or control cage), leaf-pack mass (1, 3, or 5 g dry mass), and leaf surface area (<7, 7-10, or >10 cm leaf width). Acer leaves were fastened into leaf packs. Exclusion cages had mesh on all sides; control cages lacked mesh on two sides to provide access to fishes. Two replicate leaf packs were randomly collected after 25-31 d from two sections of the stream (n = 4). Common shredders were Gammarus, Pycnopsyche, and Lepidostoma. We did not detect a significant effect of fish predation on benthic macroinvertebrates or leaf breakdown (i.e., mass loss). Colonization of benthic macroinvertebrates appeared proportional to leaf-pack mass but was unaffected by the surface area of leaves. Leaf breakdown was more rapid among leaf packs with fewer leaves (i.e., leaves with large surface area and leaf packs with low mass) and greater numbers of shredders. We suspect that physical fragmentation is the primary mechanism for higher breakdown rates among leaf packs with fewer leaves.

  20. Leaf physiognomy and climate: A multivariate analysis

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Taylor, S. E.

    1980-11-01

    Research has demonstrated that leaf physiognomy is representative of the local or microclimate conditions under which plants grow. The physiognomy of leaf samples from Oregon, Michigan, Missouri, Tennessee, and the Panama Canal Zone has been related to the microclimate using Walter diagrams and Thornthwaite water-budget data. A technique to aid paleoclimatologists in identifying the nature of the microclimate from leaf physiognomy utilizes statistical procedures to classify leaf samples into one of six microclimate regimes based on leaf physiognomy information available from fossilized samples.

  1. Hormonal regulation of leaf senescence in Lilium.

    PubMed

    Arrom, Laia; Munné-Bosch, Sergi

    2012-10-15

    In addition to floral senescence and longevity, the control of leaf senescence is a major factor determining the quality of several cut flowers, including Lilium, in the commercial market. To better understand the physiological process underlying leaf senescence in this species, we evaluated: (i) endogenous variation in the levels of phytohormones during leaf senescence, (ii) the effects of leaf darkening in senescence and associated changes in phytohormones, and (iii) the effects of spray applications of abscisic acid (ABA) and pyrabactin on leaf senescence. Results showed that while gibberellin 4 (GA(4)) and salicylic acid (SA) contents decreased, that of ABA increased during the progression of leaf senescence. However, dark-induced senescence increased ABA levels, but did not affect GA(4) and SA levels, which appeared to correlate more with changes in air temperature and/or photoperiod than with the induction of leaf senescence. Furthermore, spray applications of pyrabactin delayed the progression of leaf senescence in cut flowers. Thus, we conclude that (i) ABA plays a major role in the regulation of leaf senescence in Lilium, (ii) darkness promotes leaf senescence and increases ABA levels, and (iii) exogenous applications of pyrabactin inhibit leaf senescence in Lilium, therefore suggesting that it acts as an antagonist of ABA in senescing leaves of cut lily flowers.

  2. Global climatic drivers of leaf size.

    PubMed

    Wright, Ian J; Dong, Ning; Maire, Vincent; Prentice, I Colin; Westoby, Mark; Díaz, Sandra; Gallagher, Rachael V; Jacobs, Bonnie F; Kooyman, Robert; Law, Elizabeth A; Leishman, Michelle R; Niinemets, Ülo; Reich, Peter B; Sack, Lawren; Villar, Rafael; Wang, Han; Wilf, Peter

    2017-09-01

    Leaf size varies by over a 100,000-fold among species worldwide. Although 19th-century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal gradient of leaf size has not been well quantified nor the key climatic drivers convincingly identified. Here, we characterize worldwide patterns in leaf size. Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations. By modeling the balance of leaf energy inputs and outputs, we show that daytime and nighttime leaf-to-air temperature differences are key to geographic gradients in leaf size. This knowledge can enrich "next-generation" vegetation models in which leaf temperature and water use during photosynthesis play key roles. Copyright © 2017, American Association for the Advancement of Science.

  3. Size-dependent leaf area ratio in plant twigs: implication for leaf size optimization

    PubMed Central

    Yang, Dongmei; Niklas, Karl J.; Xiang, Shuang; Sun, Shucun

    2010-01-01

    Background and Aims Although many hypotheses have been proposed to explain variation in leaf size, the mechanism underlying the variation remains not fully understood. To help understand leaf size variation, the cost/benefit of twig size was analysed, since, according to Corner's rule, twig size is positively correlated with the size of appendages the twig bears. Methods An extensive survey of twig functional traits, including twig (current-year shoots including one stem and few leaves) and leaf size (individual leaf area and mass), was conducted for 234 species from four broadleaved forests. The scaling relationship between twig mass and leaf area was determined using standardized major axis regression and phylogenetic independent comparative analyses. Key Results Leaf area was found to scale positively and allometrically with both stem and twig mass (stem mass plus leaf mass) with slopes significantly smaller than 1·0, independent of life form and habitat type. Thus, the leaf area ratio (the ratio of total leaf area to stem or twig mass) decreases with increasing twig size. Moreover, the leaf area ratio correlated negatively with individual leaf mass. The results of phylogenetic independent comparativeanalyses were consistent with the correlations. Based on the above results, a simple model for twig size optimization was constructed, from which it is postulated that large leaf size–twig size may be favoured when leaf photosynthetic capacity is high and/or when leaf life span and/or stem longevity are long. The model's predictions are consistent with leaf size variation among habitats, in which leaf size tends to be small in poor habitats with a low primary productivity. The model also explains large variations in leaf size within habitats for which leaf longevity and stem longevity serve as important determinants. Conclusions The diminishing returns in the scaling of total leaf area with twig size can be explained in terms of a very simple model on twig size

  4. The relationship of leaf photosynthetic traits V cmax and Jmax - to leaf nitrogen, leaf phosphorus, and specific leaf area: A meta-analysis and modeling study

    SciTech Connect

    Walker, Anthony P.; Beckerman, Andrew P.; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A.; Domingues, Tomas F.; Scales, Joanna C.; Wohlfahrt, Georg; Wullschleger, Stan D.; Woodward, F. Ian

    2014-07-25

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm 2), increasing leaf P from 0.05 to 0.22 gm 2 nearly doubled assimilation rates. Lastly, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting.

  5. The relationship of leaf photosynthetic traits V cmax and Jmax - to leaf nitrogen, leaf phosphorus, and specific leaf area: A meta-analysis and modeling study

    DOE PAGES

    Walker, Anthony P.; Beckerman, Andrew P.; Gu, Lianhong; ...

    2014-07-25

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derivedmore » from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm 2), increasing leaf P from 0.05 to 0.22 gm 2 nearly doubled assimilation rates. Lastly, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting.« less

  6. The relationship of leaf photosynthetic traits - V cmax and J max - to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study.

    PubMed

    Walker, Anthony P; Beckerman, Andrew P; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A; Domingues, Tomas F; Scales, Joanna C; Wohlfahrt, Georg; Wullschleger, Stan D; Woodward, F Ian

    2014-08-01

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (V cmax) and the maximum rate of electron transport (J max). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between V cmax and J max and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between V cmax and J max and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of V cmax and J max with leaf N, P, and SLA. V cmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of V cmax to leaf N. J max was strongly related to V cmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm(-2)), increasing leaf P from 0.05 to 0.22 gm(-2) nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of J max to V cmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting.

  7. The relationship of leaf photosynthetic traits – Vcmax and Jmax – to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta-analysis and modeling study

    PubMed Central

    Walker, Anthony P; Beckerman, Andrew P; Gu, Lianhong; Kattge, Jens; Cernusak, Lucas A; Domingues, Tomas F; Scales, Joanna C; Wohlfahrt, Georg; Wullschleger, Stan D; Woodward, F Ian

    2014-01-01

    Great uncertainty exists in the global exchange of carbon between the atmosphere and the terrestrial biosphere. An important source of this uncertainty lies in the dependency of photosynthesis on the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax). Understanding and making accurate prediction of C fluxes thus requires accurate characterization of these rates and their relationship with plant nutrient status over large geographic scales. Plant nutrient status is indicated by the traits: leaf nitrogen (N), leaf phosphorus (P), and specific leaf area (SLA). Correlations between Vcmax and Jmax and leaf nitrogen (N) are typically derived from local to global scales, while correlations with leaf phosphorus (P) and specific leaf area (SLA) have typically been derived at a local scale. Thus, there is no global-scale relationship between Vcmax and Jmax and P or SLA limiting the ability of global-scale carbon flux models do not account for P or SLA. We gathered published data from 24 studies to reveal global relationships of Vcmax and Jmax with leaf N, P, and SLA. Vcmax was strongly related to leaf N, and increasing leaf P substantially increased the sensitivity of Vcmax to leaf N. Jmax was strongly related to Vcmax, and neither leaf N, P, or SLA had a substantial impact on the relationship. Although more data are needed to expand the applicability of the relationship, we show leaf P is a globally important determinant of photosynthetic rates. In a model of photosynthesis, we showed that at high leaf N (3 gm−2), increasing leaf P from 0.05 to 0.22 gm−2 nearly doubled assimilation rates. Finally, we show that plants may employ a conservative strategy of Jmax to Vcmax coordination that restricts photoinhibition when carboxylation is limiting at the expense of maximizing photosynthetic rates when light is limiting. PMID:25473475

  8. Enhanced drought tolerance in transgenic rice over-expressing of maize C4 phosphoenolpyruvate carboxylase gene via NO and Ca(2+).

    PubMed

    Qian, Baoyun; Li, Xia; Liu, Xiaolong; Chen, Pingbo; Ren, Chengang; Dai, Chuanchao

    2015-03-01

    We determined the effects of endogenous nitric oxide and Ca(2+) on photosynthesis and gene expression in transgenic rice plants (PC) over-expressing the maize C4pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC) under drought. In this study, seedlings were subjected to PEG 6000 treatments using PC and wild type (WT; Kitaake). The results showed that, compared with WT, PC had higher relative water content (RWC) and net photosynthetic rate (Pn) under drought. During a 2-day re-watering treatment, Pn recovered faster in PC than in WT. Further analyses showed that, under the drought treatment, the amount of endogenous hydrogen peroxide (H2O2) increased in WT mainly via NADPH oxidase. While in PC, the endogenous nitric oxide (NO) content increased via nitrate reductase and nitric oxide synthase on day 2 of the drought treatment and day 1 of the re-watering treatment. After 2 days of drought treatment, PC also showed higher PEPC activity, calcium content, phospholipase D (PLD) activity, C4-pepc and NAC6 transcript levels, and protein kinase activity as compared with PC without treatment. These changes did not occur in WT. Correlation analysis also proved NO associated with these indicators in PC. Based on these results, there was a particular molecular mechanism of drought tolerance in PC. The mechanism is related to the signaling processes via NO and Ca(2+) involving the protein kinase and the transcription factor, resulted in up-regulation of PEPC activity and its gene expression, such as C4pepc. Some genes encode antioxidant system, cu/zn-sod as well, which promote antioxidant system to clear MDA and superoxide anion radical, thereby conferring drought tolerance.

  9. Bacterial-type Phosphoenolpyruvate Carboxylase (PEPC) Functions as a Catalytic and Regulatory Subunit of the Novel Class-2 PEPC Complex of Vascular Plants*

    PubMed Central

    O'Leary, Brendan; Rao, Srinath K.; Kim, Julia; Plaxton, William C.

    2009-01-01

    Phosphoenolpyruvate carboxylase (PEPC) is a tightly regulated anaplerotic enzyme situated at a major branch point of the plant C metabolism. Two distinct oligomeric classes of PEPC occur in the triglyceride-rich endosperm of developing castor oil seeds (COS). Class-1 PEPC is a typical homotetramer composed of identical 107-kDa plant-type PEPC (PTPC) subunits (encoded by RcPpc3), whereas the novel Class-2 PEPC 910-kDa hetero-octameric complex arises from a tight interaction between Class-1 PEPC and distantly related 118-kDa bacterial-type PEPC (BTPC) polypeptides (encoded by RcPpc4). Here, COS BTPC was expressed from full-length RcPpc4 cDNA in Escherichia coli as an active PEPC that exhibited unusual properties relative to PTPCs, including a tendency to form large aggregates, enhanced thermal stability, a high Km(PEP), and insensitivity to metabolite effectors. A chimeric 900-kDa Class-2 PEPC hetero-octamer having a 1:1 stoichiometry of BTPC:PTPC subunits was isolated from a mixture of clarified extracts containing recombinant RcPPC4 and an Arabidopsis thaliana Class-1 PEPC (the PTPC, AtPPC3). The purified Class-2 PEPC exhibited biphasic PEP saturation kinetics with high and low affinity sites attributed to its AtPPC3 and RcPPC4 subunits, respectively. The RcPPC4 subunits: (i) catalyzed the majority of the Class-2 PEPC Vmax, particularly in the presence of the inhibitor l-malate, and (ii) also functioned as Class-2 PEPC regulatory subunits by modulating PEP binding and catalytic potential of its AtPPC3 subunits. BTPCs appear to associate with PTPCs to form stable Class-2 PEPC complexes in vivo that are hypothesized to maintain high flux from PEP under physiological conditions that would otherwise inhibit Class-1 PEPCs. PMID:19605358

  10. Bacterial-type phosphoenolpyruvate carboxylase (PEPC) functions as a catalytic and regulatory subunit of the novel class-2 PEPC complex of vascular plants.

    PubMed

    O'Leary, Brendan; Rao, Srinath K; Kim, Julia; Plaxton, William C

    2009-09-11

    Phosphoenolpyruvate carboxylase (PEPC) is a tightly regulated anaplerotic enzyme situated at a major branch point of the plant C metabolism. Two distinct oligomeric classes of PEPC occur in the triglyceride-rich endosperm of developing castor oil seeds (COS). Class-1 PEPC is a typical homotetramer composed of identical 107-kDa plant-type PEPC (PTPC) subunits (encoded by RcPpc3), whereas the novel Class-2 PEPC 910-kDa hetero-octameric complex arises from a tight interaction between Class-1 PEPC and distantly related 118-kDa bacterial-type PEPC (BTPC) polypeptides (encoded by RcPpc4). Here, COS BTPC was expressed from full-length RcPpc4 cDNA in Escherichia coli as an active PEPC that exhibited unusual properties relative to PTPCs, including a tendency to form large aggregates, enhanced thermal stability, a high K(m)((PEP)), and insensitivity to metabolite effectors. A chimeric 900-kDa Class-2 PEPC hetero-octamer having a 1:1 stoichiometry of BTPC:PTPC subunits was isolated from a mixture of clarified extracts containing recombinant RcPPC4 and an Arabidopsis thaliana Class-1 PEPC (the PTPC, AtPPC3). The purified Class-2 PEPC exhibited biphasic PEP saturation kinetics with high and low affinity sites attributed to its AtPPC3 and RcPPC4 subunits, respectively. The RcPPC4 subunits: (i) catalyzed the majority of the Class-2 PEPC V(max), particularly in the presence of the inhibitor l-malate, and (ii) also functioned as Class-2 PEPC regulatory subunits by modulating PEP binding and catalytic potential of its AtPPC3 subunits. BTPCs appear to associate with PTPCs to form stable Class-2 PEPC complexes in vivo that are hypothesized to maintain high flux from PEP under physiological conditions that would otherwise inhibit Class-1 PEPCs.

  11. Seasonal freeze resistance of rainbow smelt (Osmerus mordax) is generated by differential expression of glycerol-3-phosphate dehydrogenase, phosphoenolpyruvate carboxykinase, and antifreeze protein genes.

    PubMed

    Liebscher, Ryan S; Richards, Robert C; Lewis, Johanne M; Short, Connie E; Muise, Denise M; Driedzic, William R; Ewart, K Vanya

    2006-01-01

    In winter, rainbow smelt (Osmerus mordax) accumulate glycerol and produce an antifreeze protein (AFP), which both contribute to freeze resistance. The role of differential gene expression in the seasonal pattern of these adaptations was investigated. First, cDNAs encoding smelt and Atlantic salmon (Salmo salar) phosphoenolpyruvate carboxykinase (PEPCK) and smelt glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were cloned so that all sequences required for expression analysis would be available. Using quantitative PCR, expression of beta actin in rainbow smelt liver was compared with that of GAPDH in order to determine its validity as a reference gene. Then, levels of glycerol-3-phosphate dehydrogenase (GPDH), PEPCK, and AFP relative to beta actin were measured in smelt liver over a fall-winter-spring interval. Levels of GPDH mRNA increased in the fall just before plasma glycerol accumulation, implying a driving role in glycerol synthesis. GPDH mRNA levels then declined during winter, well in advance of serum glycerol, suggesting the possibility of GPDH enzyme or glycerol conservation in smelt during the winter months. PEPCK mRNA levels rose in parallel with serum glycerol in the fall, consistent with an increasing requirement for amino acids as metabolic precursors, remained elevated for much of the winter, and then declined in advance of the decline in plasma glycerol. AFP mRNA was elevated at the onset of fall sampling in October and remained elevated until April, implying separate regulation from GPDH and PEPCK. Thus, winter freezing point depression in smelt appears to result from a seasonal cycle of GPDH gene expression, with an ensuing increase in the expression of PEPCK, and a similar but independent cycle of AFP gene expression.

  12. Light-dependent activation of phosphoenolpyruvate carboxylase by reversible phosphorylation in cluster roots of white lupin plants: diurnal control in response to photosynthate supply

    PubMed Central

    Feil, Regina; Lunn, John E.; Plaxton, William C.

    2016-01-01

    Background and Aims Phosphoenolpyruvate carboxylase (PEPC) is a tightly regulated enzyme that controls carbohydrate partitioning to organic acid anions (malate, citrate) excreted in copious amounts by cluster roots of inorganic phosphate (Pi)-deprived white lupin plants. Excreted malate and citrate solubilize otherwise inaccessible sources of mineralized soil Pi for plant uptake. The aim of this study was to test the hypotheses that (1) PEPC is post-translationally activated by reversible phosphorylation in cluster roots of illuminated white lupin plants, and (2) light-dependent phosphorylation of cluster root PEPC is associated with elevated intracellular levels of sucrose and its signalling metabolite, trehalose-6-phosphate. Methods White lupin plants were cultivated hydroponically at low Pi levels (≤1 µm) and subjected to various light/dark pretreatments. Cluster root PEPC activity and in vivo phosphorylation status were analysed to assess the enzyme’s diurnal, post-translational control in response to light and dark. Levels of various metabolites, including sucrose and trehalose-6-phosphate, were also quantified in cluster root extracts using enzymatic and spectrometric methods. Key Results During the daytime the cluster root PEPC was activated by phosphorylation at its conserved N-terminal seryl residue. Darkness triggered a progressive reduction in PEPC phosphorylation to undetectable levels, and this was correlated with 75–80 % decreases in concentrations of sucrose and trehalose-6- phosphate. Conclusions Reversible, light-dependent regulatory PEPC phosphorylation occurs in cluster roots of Pi-deprived white lupin plants. This likely facilitates the well-documented light- and sucrose-dependent exudation of Pi-solubilizing organic acid anions by the cluster roots. PEPC’s in vivo phosphorylation status appears to be modulated by sucrose translocated from CO2-fixing leaves into the non-photosynthetic cluster roots. PMID:27063365

  13. Reciprocal Control of Anaplerotic Phosphoenolpyruvate Carboxylase by in Vivo Monoubiquitination and Phosphorylation in Developing Proteoid Roots of Phosphate-Deficient Harsh Hakea1[W][OA

    PubMed Central

    Shane, Michael W.; Fedosejevs, Eric T.; Plaxton, William C.

    2013-01-01

    Accumulating evidence indicates important functions for phosphoenolpyruvate (PEP) carboxylase (PEPC) in inorganic phosphate (Pi)-starved plants. This includes controlling the production of organic acid anions (malate, citrate) that are excreted in copious amounts by proteoid roots of nonmycorrhizal species such as harsh hakea (Hakea prostrata). This, in turn, enhances the bioavailability of mineral-bound Pi by solubilizing Al3+, Fe3+, and Ca2+ phosphates in the rhizosphere. Harsh hakea thrives in the nutrient-impoverished, ancient soils of southwestern Australia. Proteoid roots from Pi-starved harsh hakea were analyzed over 20 d of development to correlate changes in malate and citrate exudation with PEPC activity, posttranslational modifications (inhibitory monoubiquitination versus activatory phosphorylation), and kinetic/allosteric properties. Immature proteoid roots contained an equivalent ratio of monoubiquitinated 110-kD and phosphorylated 107-kD PEPC polypeptides (p110 and p107, respectively). PEPC purification, immunoblotting, and mass spectrometry indicated that p110 and p107 are subunits of a 430-kD heterotetramer and that they both originate from the same plant-type PEPC gene. Incubation with a deubiquitinating enzyme converted the p110:p107 PEPC heterotetramer of immature proteoid roots into a p107 homotetramer while significantly increasing the enzyme’s activity under suboptimal but physiologically relevant assay conditions. Proteoid root maturation was paralleled by PEPC activation (e.g. reduced Km [PEP] coupled with elevated I50 [malate and Asp] values) via in vivo deubiquitination of p110 to p107, and subsequent phosphorylation of the deubiquitinated subunits. This novel mechanism of posttranslational control is hypothesized to contribute to the massive synthesis and excretion of organic acid anions that dominates the carbon metabolism of the mature proteoid roots. PMID:23407057

  14. Overexpression of the Cytosolic Form of Phosphoenolpyruvate Carboxykinase (GTP) in Skeletal Muscle Repatterns Energy Metabolism in the Mouse*s⃞♦

    PubMed Central

    Hakimi, Parvin; Yang, Jianqi; Casadesus, Gemma; Massillon, Duna; Tolentino-Silva, Fatima; Nye, Colleen K.; Cabrera, Marco E.; Hagen, David R.; Utter, Christopher B.; Baghdy, Yacoub; Johnson, David H.; Wilson, David L.; Kirwan, John P.; Kalhan, Satish C.; Hanson, Richard W.

    2015-01-01

    Transgenic mice, containing a chimeric gene in which the cDNA for phosphoenolpyruvate carboxykinase (GTP) (PEPCK-C) (EC 4.1.1.32) was linked to the α-skeletal actin gene promoter, express PEPCK-C in skeletal muscle (1–3 units/g). Breeding two founder lines together produced mice with an activity of PEPCK-C of 9 units/g of muscle (PEPCK-Cmus mice). These mice were seven times more active in their cages than controls. On a mouse treadmill, PEPCK-Cmus mice ran up to 6 km at a speed of 20 m/min, whereas controls stopped at 0.2 km. PEPCK-Cmus mice had an enhanced exercise capacity, with a VO2max of 156 ± 8.0 ml/kg/min, a maximal respiratory exchange ratio of 0.91 ± 0.03, and a blood lactate concentration of 3.7 ± 1.0 mm after running for 32 min at a 25° grade; the values for control animals were 112 ± 21 ml/kg/min, 0.99 ± 0.08, and 8.1 ± 5.0 mm respectively. The PEPCK-Cmus mice ate 60% more than controls but had half the body weight and 10% the body fat as determined by magnetic resonance imaging. In addition, the number of mitochondria and the content of triglyceride in the skeletal muscle of PEPCK-Cmus mice were greatly increased as compared with controls. PEPCK-Cmus mice had an extended life span relative to control animals; mice up to an age of 2.5 years ran twice as fast as 6 −12-month-old control animals. We conclude that overexpression of PEPCK-C repatterns energy metabolism and leads to greater longevity. PMID:17716967

  15. Streptococcus pneumoniae Cell-Wall-Localized Phosphoenolpyruvate Protein Phosphotransferase Can Function as an Adhesin: Identification of Its Host Target Molecules and Evaluation of Its Potential as a Vaccine

    PubMed Central

    Mizrachi Nebenzahl, Yaffa; Blau, Karin; Kushnir, Tatyana; Shagan, Marilou; Portnoi, Maxim; Cohen, Aviad; Azriel, Shalhevet; Malka, Itai; Adawi, Asad; Kafka, Daniel; Dotan, Shahar; Guterman, Gali; Troib, Shany; Fishilevich, Tali; Gershoni, Jonathan M; Braiman, Alex; Mitchell, Andrea M; Mitchell, Timothy J; Porat, Nurith; Goliand, Inna; Chalifa Caspi, Vered; Swiatlo, Edwin; Tal, Michael; Ellis, Ronald; Elia, Natalie; Dagan, Ron

    2016-01-01

    In Streptococcus pneumonia, phosphoenolpyruvate protein phosphotransferase (PtsA) is an intracellular protein of the monosaccharide phosphotransferase systems. Biochemical and immunostaining methods were applied to show that PtsA also localizes to the bacterial cell-wall. Thus, it was suspected that PtsA has functions other than its main cytoplasmic enzymatic role. Indeed, recombinant PtsA and anti-rPtsA antiserum were shown to inhibit adhesion of S. pneumoniae to cultured human lung adenocarcinoma A549 cells. Screening of a combinatorial peptide library expressed in a filamentous phage with rPtsA identified epitopes that were capable of inhibiting S. pneumoniae adhesion to A549 cells. The insert peptides in the phages were sequenced, and homologous sequences were found in human BMPER, multimerin1, protocadherin19, integrinβ4, epsin1 and collagen type VIIα1 proteins, all of which can be found in A549 cells except the latter. Six peptides, synthesized according to the homologous sequences in the human proteins, specifically bound rPtsA in the micromolar range and significantly inhibited pneumococcal adhesion in vitro to lung- and tracheal-derived cell lines. In addition, the tested peptides inhibited lung colonization after intranasal inoculation of mice with S. pneumoniae. Immunization with rPtsA protected the mice against a sublethal intranasal and a lethal intravenous pneumococcal challenge. In addition, mouse anti rPtsA antiserum reduced bacterial virulence in the intravenous inoculation mouse model. These findings showed that the surface-localized PtsA functions as an adhesin, PtsA binding peptides derived from its putative target molecules can be considered for future development of therapeutics, and rPtsA should be regarded as a candidate for vaccine development. PMID:26990554

  16. Regulation of Phosphoenolpyruvate Carboxylase Phosphorylation by Metabolites and Abscisic Acid during the Development and Germination of Barley Seeds1[C][W

    PubMed Central

    Feria, Ana-Belén; Alvarez, Rosario; Cochereau, Ludivine; Vidal, Jean; García-Mauriño, Sofía; Echevarría, Cristina

    2008-01-01

    During barley (Hordeum vulgare) seed development, phosphoenolpyruvate carboxylase (PEPC) activity increased and PEPC-specific antibodies revealed housekeeping (103-kD) and inducible (108-kD) subunits. Bacterial-type PEPC fragments were immunologically detected in denatured protein extracts from dry and imbibed conditions; however, on nondenaturing gels, the activity of the recently reported octameric PEPC (in castor [Ricinus communis] oil seeds) was not detected. The phosphorylation state of the PEPC, as judged by l-malate 50% inhibition of initial activity values, phosphoprotein chromatography, and immunodetection of the phosphorylated N terminus, was found to be high between 8 and 18 d postanthesis (DPA) and during imbibition. In contrast, the enzyme appeared to be in a low phosphorylation state from 20 DPA up to dry seed. The time course of 32/36-kD, Ca2+-independent PEPC kinase activity exhibited a substantial increase after 30 DPA that did not coincide with the PEPC phosphorylation profile. This kinase was found to be inhibited by l-malate and not by putative protein inhibitors, and the PEPC phosphorylation status correlated with high glucose-6-phosphate to malate ratios, thereby suggesting an in vivo metabolic control of the kinase. PEPC phosphorylation was also regulated by photosynthate supply at 11 DPA. In addition, when fed exogenously to imbibing seeds, abscisic acid significantly increased PEPC kinase activity. This was further enhanced by the cytosolic protein synthesis inhibitor cycloheximide but blocked by protease inhibitors, thereby suggesting that the phytohormone acts on the stability of the kinase. We propose that a similar abscisic acid-dependent effect may contribute to produce the increase in PEPC kinase activity during desiccation stages. PMID:18753284

  17. Mitochondrial phosphoenolpyruvate carboxykinase (PEPCK-M) and serine biosynthetic pathway genes are co-ordinately increased during anabolic agent-induced skeletal muscle growth

    PubMed Central

    Brown, D. M.; Williams, H.; Ryan, K. J. P.; Wilson, T. L.; Daniel, Z. C. T. R.; Mareko, M. H. D.; Emes, R. D.; Harris, D. W.; Jones, S.; Wattis, J. A. D.; Dryden, I. L.; Hodgman, T. C.; Brameld, J. M.; Parr, T.

    2016-01-01

    We aimed to identify novel molecular mechanisms for muscle growth during administration of anabolic agents. Growing pigs (Duroc/(Landrace/Large-White)) were administered Ractopamine (a beta-adrenergic agonist; BA; 20 ppm in feed) or Reporcin (recombinant growth hormone; GH; 10 mg/48 hours injected) and compared to a control cohort (feed only; no injections) over a 27-day time course (1, 3, 7, 13 or 27-days). Longissimus Dorsi muscle gene expression was analyzed using Agilent porcine transcriptome microarrays and clusters of genes displaying similar expression profiles were identified using a modified maSigPro clustering algorithm. Anabolic agents increased carcass (p = 0.002) and muscle weights (Vastus Lateralis: p < 0.001; Semitendinosus: p = 0.075). Skeletal muscle mRNA expression of serine/one-carbon/glycine biosynthesis pathway genes (Phgdh, Psat1 and Psph) and the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase-M (Pck2/PEPCK-M), increased during treatment with BA, and to a lesser extent GH (p < 0.001, treatment x time interaction). Treatment with BA, but not GH, caused a 2-fold increase in phosphoglycerate dehydrogenase (PHGDH) protein expression at days 3 (p < 0.05) and 7 (p < 0.01), and a 2-fold increase in PEPCK-M protein expression at day 7 (p < 0.01). BA treated pigs exhibit a profound increase in expression of PHGDH and PEPCK-M in skeletal muscle, implicating a role for biosynthetic metabolic pathways in muscle growth. PMID:27350173

  18. Modulation of Escherichia coli Adenylyl Cyclase Activity by Catalytic-Site Mutants of Protein IIAGlc of the Phosphoenolpyruvate:Sugar Phosphotransferase System

    PubMed Central

    Reddy, Prasad; Kamireddi, Madhavi

    1998-01-01

    It is demonstrated here that in Escherichia coli, the phosphorylated form of the glucose-specific phosphocarrier protein IIAGlc of the phosphoenolpyruvate:sugar phosphotransferase system is an activator of adenylyl cyclase and that unphosphorylated IIAGlc has no effect on the basal activity of adenylyl cyclase. To elucidate the specific role of IIAGlc phosphorylation in the regulation of adenylyl cyclase activity, both the phosphorylatable histidine (H90) and the interactive histidine (H75) of IIAGlc were mutated by site-directed mutagenesis to glutamine and glutamate. Wild-type IIAGlc and the H75Q mutant, in which the histidine in position 75 has been replaced by glutamine, were phosphorylated by the phosphohistidine-containing phosphocarrier protein (HPr∼P) and were equally potent activators of adenylyl cyclase. Neither the H90Q nor the H90E mutant of IIAGlc was phosphorylated by HPr∼P, and both failed to activate adenylyl cyclase. Furthermore, replacement of H75 by glutamate inhibited the appearance of a steady-state level of phosphorylation of H90 of this mutant protein by HPr∼P, yet the H75E mutant of IIAGlc was a partial activator of adenylyl cyclase. The H75E H90A double mutant, which cannot be phosphorylated, did not activate adenylyl cyclase. This suggests that the H75E mutant was transiently phosphorylated by HPr∼P but the steady-state level of the phosphorylated form of the mutant protein was decreased due to the repulsive forces of the negatively charged glutamate at position 75 in the catalytic pocket. These results are discussed in the context of the proximity of H75 and H90 in the IIAGlc structure and the disposition of the negative charge in the modeled glutamate mutants. PMID:9457881

  19. The phosphoenolpyruvate phosphotransferase system in group A Streptococcus acts to reduce streptolysin S activity and lesion severity during soft tissue infection.

    PubMed

    Gera, Kanika; Le, Tuquynh; Jamin, Rebecca; Eichenbaum, Zehava; McIver, Kevin S

    2014-03-01

    Obtaining essential nutrients, such as carbohydrates, is an important process for bacterial pathogens to successfully colonize host tissues. The phosphoenolpyruvate phosphotransferase system (PTS) is the primary mechanism by which bacteria transport sugars and sense the carbon state of the cell. The group A streptococcus (GAS) is a fastidious microorganism that has adapted to a variety of niches in the human body to elicit a wide array of diseases. A ΔptsI mutant (enzyme I [EI] deficient) generated in three different strains of M1T1 GAS was unable to grow on multiple carbon sources (PTS and non-PTS). Complementation with ptsI expressed under its native promoter in single copy was able to rescue the growth defect of the mutant. In a mouse model of GAS soft tissue infection, all ΔptsI mutants exhibited a significantly larger and more severe ulcerative lesion than mice infected with the wild type. Increased transcript levels of sagA and streptolysin S (SLS) activity during exponential-phase growth was observed. We hypothesized that early onset of SLS activity would correlate with the severity of the lesions induced by the ΔptsI mutant. In fact, infection of mice with a ΔptsI sagB double mutant resulted in a lesion comparable to that of either the wild type or a sagB mutant alone. Therefore, a functional PTS is not required for subcutaneous skin infection in mice; however, it does play a role in coordinating virulence factor expression and disease progression.

  20. Boosting Anaplerotic Reactions by Pyruvate Kinase Gene Deletion and Phosphoenolpyruvate Carboxylase Desensitization for Glutamic Acid and Lysine Production in Corynebacterium glutamicum.

    PubMed

    Yokota, Atsushi; Sawada, Kazunori; Wada, Masaru

    In the 1980s, Shiio and coworkers demonstrated using random mutagenesis that the following three phenotypes were effective for boosting lysine production by Corynebacterium glutamicum: (1) low-activity-level citrate synthase (CS(L)), (2) phosphoenolpyruvate carboxylase (PEPC) resistant to feedback inhibition by aspartic acid (PEPC(R)), and (3) pyruvate kinase (PYK) deficiency. Here, we reevaluated these phenotypes and their interrelationship in lysine production using recombinant DNA techniques.The pyk deletion and PEPC(R) (D299N in ppc) independently showed marginal effects on lysine production, but both phenotypes synergistically increased lysine yield, demonstrating the importance of PEPC as an anaplerotic enzyme in lysine production. Similar effects were also found for glutamic acid production. CS(L) (S252C in gltA) further increased lysine yield. Thus, using molecular techniques, the combination of these three phenotypes was reconfirmed to be effective for lysine production. However, a simple CS(L) mutant showed instabilities in growth and lysine yield.Surprisingly, the pyk deletion was found to increase biomass production in wild-type C. glutamicum ATCC13032 under biotin-sufficient conditions. The mutant showed a 37% increase in growth (based on OD660) compared with the ATCC13032 strain in a complex medium containing 100 g/L glucose. Metabolome analysis revealed the intracellular accumulation of excess precursor metabolites. Thus, their conversion into biomass was considered to relieve the metabolic distortion in the pyk-deleted mutant. Detailed physiological studies of various pyk-deleted mutants also suggested that malate:quinone oxidoreductase (MQO) is important to control both the intracellular oxaloacetic acid (OAA) level and respiration rate. These findings may facilitate the rational use of C. glutamicum in fermentation industries.

  1. Pyramiding expression of maize genes encoding phosphoenolpyruvate carboxylase (PEPC) and pyruvate orthophosphate dikinase (PPDK) synergistically improve the photosynthetic characteristics of transgenic wheat.

    PubMed

    Zhang, HuiFang; Xu, WeiGang; Wang, HuiWei; Hu, Lin; Li, Yan; Qi, XueLi; Zhang, Lei; Li, ChunXin; Hua, Xia

    2014-09-01

    Using particle bombardment transformation, we introduced maize pepc cDNA encoding phosphoenolpyruvate carboxylase (PEPC) and ppdk cDNA encoding pyruvate orthophosphate dikinase (PPDK) into the C3 crop wheat to generate transgenic wheat lines carrying cDNA of pepc (PC lines), ppdk (PK lines) or both (PKC lines). The integration, transcription, and expression of the foreign genes were confirmed by Southern blot, Real-time quantitative reverse transcription PCR (Q-RT-PCR), and Western blot analysis. Q-RT-PCR results indicated that the average relative expression levels of pepc and ppdk in the PKC lines reached 10 and 4.6, respectively, compared to their expressions in untransformed plants (set to 1). The enzyme activities of PEPC and PPDK in the PKC lines were 4.3- and 2.1-fold higher, respectively, than in the untransformed control. The maximum daily net photosynthetic rates of the PKC, PC, and PK lines were enhanced by 26.4, 13.3, and 4.5%, respectively, whereas the diurnal accumulations of photosynthesis were 21.3, 13.9, and 6.9%, respectively, higher than in the control. The Fv/Fm of the transgenic plants decreased less than in the control under high temperature and high light conditions (2 weeks after anthesis), suggesting that the transgenic wheat transports more absorbed light energy into a photochemical reaction. The exogenous maize C4-specific pepc gene was more effective than ppdk at improving the photosynthetic performance and yield characteristics of transgenic wheat, while the two genes showed a synergistic effect when they were transformed into the same genetic background, because the PKC lines exhibited improved photosynthetic and physiological traits.

  2. Illumination is necessary and sufficient to induce histone acetylation independent of transcriptional activity at the C4-specific phosphoenolpyruvate carboxylase promoter in maize.

    PubMed

    Offermann, Sascha; Danker, Tanja; Dreymüller, Daniela; Kalamajka, Rainer; Töpsch, Sonja; Weyand, Katrin; Peterhänsel, Christoph

    2006-07-01

    Expression of the C4-specific phosphoenolpyruvate carboxylase (C4-PEPC) gene in maize (Zea mays) is regulated in a tissue-specific manner, but affected by light and nutrient availability. We manipulated these stimuli in a combinatorial manner and analyzed concomitant changes in histone acetylation of the nucleosomes associated with the C4-PEPC gene in relation to transcriptional activity and steady-state mRNA levels. Whereas the transition from the lowest activity to an intermediate activity was observed in the absence of histone acetylation, the light-induced boost to full activity was associated with strong enhancement of the acetylation of both histones H3 and H4 limited to the gene region. Once activated by light, prolonged darkness was necessary to reduce both transcription and, in parallel, histone acetylation. Unexpectedly, histone acetylation was also induced in bundle sheath cells, although the transcriptional activity did not respond to illumination in this tissue. Furthermore, we were able to down-regulate the promoter by nitrogen depletion in the light without any decrease in the hyperacetylation of histone H4. When plants kept in prolonged darkness were nitrogen depleted and then exposed to light, transcription was not induced, but the promoter chromatin became hyperacetylated. We suggest a model where inhibition of a histone deacetylase in the light triggers H4 hyperacetylation at the C4-PEPC gene promoter regardless of the transcriptional activity of the gene. Our data indicate that an understanding of the interplay between histone modification and transcription requires analysis of signal integration on promoters in vivo.

  3. Implications of various phosphoenolpyruvate-carbohydrate phosphotransferase system mutations on glycerol utilization and poly(3-hydroxybutyrate) accumulation in Ralstonia eutropha H16

    PubMed Central

    2011-01-01

    The enhanced global biodiesel production is also yielding increased quantities of glycerol as main coproduct. An effective application of glycerol, for example, as low-cost substrate for microbial growth in industrial fermentation processes to specific products will reduce the production costs for biodiesel. Our study focuses on the utilization of glycerol as a cheap carbon source during cultivation of the thermoplastic producing bacterium Ralstonia eutropha H16, and on the investigation of carbohydrate transport proteins involved herein. Seven open reading frames were identified in the genome of strain H16 to encode for putative proteins of the phosphoenolpyruvate-carbohydrate phosphotransferase system (PEP-PTS). Although the core components of PEP-PTS, enzyme I (ptsI) and histidine phosphocarrier protein (ptsH), are available in strain H16, a complete PTS-mediated carbohydrate transport is lacking. Growth experiments employing several PEP-PTS mutants indicate that the putative ptsMHI operon, comprising ptsM (a fructose-specific EIIA component of PTS), ptsH, and ptsI, is responsible for limited cell growth and reduced PHB accumulation (53%, w/w, less PHB than the wild type) of this strain in media containing glycerol as a sole carbon source. Otherwise, the deletion of gene H16_A0384 (ptsN, nitrogen regulatory EIIA component of PTS) seemed to largely compensate the effect of the deleted ptsMHI operon (49%, w/w, PHB). The involvement of the PTS homologous proteins on the utilization of the non-PTS sugar alcohol glycerol and its effect on cell growth as well as PHB and carbon metabolism of R. eutropha will be discussed. PMID:21906371

  4. Effects of Homologous Phosphoenolpyruvate-Carbohydrate Phosphotransferase System Proteins on Carbohydrate Uptake and Poly(3-Hydroxybutyrate) Accumulation in Ralstonia eutropha H16▿†

    PubMed Central

    Kaddor, Chlud; Steinbüchel, Alexander

    2011-01-01

    Seven gene loci encoding putative proteins of the phosphoenolpyruvate-carbohydrate phosphotransferase system (PEP-PTS) were identified in the genome of Ralstonia eutropha H16 by in silico analysis. Except the N-acetylglucosamine-specific PEP-PTS, an additional complete PEP-PTS is lacking in strain H16. Based on these findings, we generated single and multiple deletion mutants defective mainly in the PEP-PTS genes to investigate their influence on carbon source utilization, growth behavior, and poly(3-hydroxybutyrate) (PHB) accumulation. As supposed, the H16 ΔfrcACB and H16 ΔnagFEC mutants exhibited no growth when cultivated on fructose and N-acetylglucosamine, respectively. Furthermore, a transposon mutant with a ptsM-ptsH insertion site did not grow on both carbon sources. The observed phenotype was not complemented, suggesting that it results from an interaction of genes or a polar effect caused by the Tn5::mob insertion. ptsM, ptsH, and ptsI single, double, and triple mutants stored much less PHB than the wild type (about 10 to 39% [wt/wt] of cell dry weight) and caused reduced PHB production in mutants lacking the H16_A2203, H16_A0384, frcACB, or nagFEC genes. In contrast, mutant H16 ΔH16_A0384 accumulated 11.5% (wt/wt) more PHB than the wild type when grown on gluconate and suppressed partially the negative effect of the ptsMHI deletion on PHB synthesis. Based on our experimental data, we discussed whether the PEP-PTS homologous proteins in R. eutropha H16 are exclusively involved in the complex sugar transport system or whether they are also involved in cellular regulatory functions of carbon and PHB metabolism. PMID:21478317

  5. Bacterial- and plant-type phosphoenolpyruvate carboxylase isozymes from developing castor oil seeds interact in vivo and associate with the surface of mitochondria.

    PubMed

    Park, Joonho; Khuu, Nicholas; Howard, Alexander S M; Mullen, Robert T; Plaxton, William C

    2012-07-01

    Phosphoenolpyruvate carboxylase (PEPC) from developing castor oil seeds (COS) exists as two distinct oligomeric isoforms. The typical class-1 PEPC homotetramer consists of 107-kDa plant-type PEPC (PTPC) subunits, whereas the allosterically desensitized 910-kDa class-2 PEPC hetero-octamer arises from the association of class-1 PEPC with 118-kDa bacterial-type PEPC (BTPC) subunits. The in vivo interaction and subcellular location of COS BTPC and PTPC were assessed by imaging fluorescent protein (FP)-tagged PEPCs in tobacco suspension-cultured cells. The BTPC-FP mainly localized to cytoplasmic punctate/globular structures, identified as mitochondria by co-immunostaining of endogenous cytochrome oxidase. Inhibition of respiration with KCN resulted in proportional decreases and increases in mitochondrial versus cytosolic BTPC-FP, respectively. The FP-PTPC and NLS-FP-PTPC (containing an appended nuclear localization signal, NLS) localized to the cytosol and nucleus, respectively, but both co-localized with mitochondrial-associated BTPC when co-expressed with BTPC-FP. Transmission electron microscopy of immunogold-labeled developing COS revealed that BTPC and PTPC are localized at the mitochondrial (outer) envelope, as well as the cytosol. Moreover, thermolysin-sensitive BTPC and PTPC polypeptides were detected on immunoblots of purified COS mitochondria. Overall, our results demonstrate that: (i) COS BTPC and PTPC interact in vivo as a class-2 PEPC complex that associates with the surface of mitochondria, (ii) BTPC's unique and divergent intrinsically disordered region mediates its interaction with PTPC, whereas (iii) the PTPC-containing class-1 PEPC is entirely cytosolic. We hypothesize that mitochondrial-associated class-2 PEPC facilitates rapid refixation of respiratory CO(2) while sustaining a large anaplerotic flux to replenish tricarboxylic acid cycle C-skeletons withdrawn for biosynthesis.

  6. Phosphorylation of bacterial-type phosphoenolpyruvate carboxylase at Ser425 provides a further tier of enzyme control in developing castor oil seeds.

    PubMed

    O'Leary, Brendan; Rao, Srinath K; Plaxton, William C

    2011-01-01

    PEPC [PEP (phosphoenolpyruvate) carboxylase] is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate metabolism. Two distinct oligomeric PEPC classes were discovered in developing COS (castor oil seeds). Class-1 PEPC is a typical homotetramer of 107 kDa PTPC (plant-type PEPC) subunits, whereas the novel 910-kDa Class-2 PEPC hetero-octamer arises from a tight interaction between Class-1 PEPC and 118 kDa BTPC (bacterial-type PEPC) subunits. Mass spectrometric analysis of immunopurified COS BTPC indicated that it is subject to in vivo proline-directed phosphorylation at Ser425. We show that immunoblots probed with phosphorylation site-specific antibodies demonstrated that Ser425 phosphorylation is promoted during COS development, becoming maximal at stage IX (maturation phase) or in response to depodding. Kinetic analyses of a recombinant, chimaeric Class-2 PEPC containing phosphomimetic BTPC mutant subunits (S425D) indicated that Ser425 phosphorylation results in significant BTPC inhibition by: (i) increasing its Km(PEP) 3-fold, (ii) reducing its I50 (L-malate and L-aspartate) values by 4.5- and 2.5-fold respectively, while (iii) decreasing its activity within the physiological pH range. The developmental pattern and kinetic influence of Ser425 BTPC phosphorylation is very distinct from the in vivo phosphorylation/activation of COS Class-1 PEPC's PTPC subunits at Ser11. Collectively, the results establish that BTPC's phospho-Ser425 content depends upon COS developmental and physiological status and that Ser425 phosphorylation attenuates the catalytic activity of BTPC subunits within a Class-2 PEPC complex. To the best of our knowledge, this study provides the first evidence for protein phosphorylation as a mechanism for the in vivo control of vascular plant BTPC activity.

  7. Leaf hydraulic conductance is coordinated with leaf morpho-anatomical traits and nitrogen status in the genus Oryza.

    PubMed

    Xiong, Dongliang; Yu, Tingting; Zhang, Tong; Li, Yong; Peng, Shaobing; Huang, Jianliang

    2015-02-01

    Leaf hydraulic conductance (K leaf) is a major determinant of photosynthetic rate in plants. Previous work has assessed the relationships between leaf morpho-anatomical traits and K leaf with woody species, but there has been very little focus on cereal crops. The genus Oryza, which includes rice (Oryza sativa) and wild species (such as O. rufipogon cv. Griff), is ideal material for identifying leaf features associated with K leaf and gas exchange. Leaf morpho-anatomical traits, K leaf, leaf N content per leaf area, and CO2 diffusion efficiency were investigated in 11 Oryza cultivars. K leaf was positively correlated with leaf thickness and related traits, and therefore positively correlated with leaf mass per area and leaf N content per leaf area, and negatively with inter-veinal distance. K leaf was also positively correlated with leaf area and its related traits, and therefore negatively correlated with the proportion of minor vein length per area. In addition, coordination between K leaf and CO2 diffusion conductance in leaves was observed. We conclude that leaf morpho-anatomical traits and N content per leaf area strongly influence K leaf. Our results suggest that more detailed anatomical and structural studies are needed to elucidate the impacts of leaf feature traits on K leaf and gas exchange in grasses.

  8. Leaf Senescence by Magnesium Deficiency

    PubMed Central

    Tanoi, Keitaro; Kobayashi, Natsuko I.

    2015-01-01

    Magnesium ions (Mg2+) are the second most abundant cations in living plant cells, and they are involved in various functions, including photosynthesis, enzyme catalysis, and nucleic acid synthesis. Low availability of Mg2+ in an agricultural field leads to a decrease in yield, which follows the appearance of Mg-deficient symptoms such as chlorosis, necrotic spots on the leaves, and droop. During the last decade, a variety of physiological and molecular responses to Mg2+ deficiency that potentially link to leaf senescence have been recognized, allowing us to reconsider the mechanisms of Mg2+ deficiency. This review focuses on the current knowledge about the physiological responses to Mg2+ deficiency including a decline in transpiration, accumulation of sugars and starch in source leaves, change in redox states, increased oxidative stress, metabolite alterations, and a decline in photosynthetic activity. In addition, we refer to the molecular responses that are thought to be related to leaf senescence. With these current data, we give an overview of leaf senescence induced by Mg deficiency. PMID:27135350

  9. Yeasts colonizing the leaf surfaces.

    PubMed

    Sláviková, Elena; Vadkertiová, Renata; Vránová, Dana

    2007-08-01

    The yeasts were isolated from the leaf surfaces of ten species of trees. The study site was a forest park (Zelezná Studnicka) of the Small Carpathians mountain range. One hundred and thirty seven yeast strains belonging to 13 genera were isolated from 320 samples of leaves and needles. Seventeen yeast species were isolated, but only seven occurred regularly: Aureobasidium pullulans, Cryptococcus laurentii, Pichia anomala, Metschnikowia pulcherrima, Saccharomyces sp., Lachancea thermotolerans, and Rhodotorula glutinis. The remaining species were isolated from the leaves and needles of three or less tree species. A. pullulans, Cr. laurentii, and P. anomala were the most frequently found species and they occurred on leaves and needles of all ten tree species. Saccharomyces sp. occurred in leaf samples collected from eight kinds of trees. M. pulcherrima and L. thermotolerans were found in samples collected from six species of trees. Both these species occurred almost always on the leaves of deciduous trees. Rh. glutinis was the most frequently isolated carotenoids producing species. We have found out that the ascomycetous and basidiomycetous species were present in the leaf samples in approximately equal frequency, contrary to the soil samples taken from this forest park, where the ascomycetous species were found rarely.

  10. Cotton leaf curl virus disease.

    PubMed

    Briddon, R W; Markham, P G

    2000-11-01

    Cotton is one of the most important crops of Pakistan, accounting for over 60% of foreign exchange earnings. The present epidemic of cotton leaf curl disease (CLCuD) originated in the Punjab region near the city of Multan and was first reported in 1985, although it was noted in this region as early as 1967. By the early 1990s, CLCuD had become the major limitation to cotton production in Pakistan and it has now spread into India and, more recently, south and west into other provinces of Pakistan. The very characteristic symptoms include leaf curling, darkened veins, vein swelling and enations that frequently develop into cup-shaped, leaf-like structures on the undersides of leaves. Identification of the vector of CLCuD as the whitefly Bemisia tabaci (Genn.) quickly led to the suggestion that the causative agent of the disease is a geminivirus. Researchers soon confirmed the presence of such a virus that is currently ascribed to the genus Begomovirus of the family Geminiviridae, However, in 1999, the aetiology of the disease was shown to be more complex than was originally assumed. Despite the identification of both a begomovirus and a so-called nanovirus-like component, the precise causal agent of CLCuD remains uncertain.

  11. The Influence of Leaf Angle and Leaf Surface Characteristics on the Process of Rainfall Interception

    NASA Astrophysics Data System (ADS)

    Holder, C.; Ginebra, R.; Webb, R.

    2015-12-01

    Individual choice in plant selection for household landscaping influences differences in runoff from urban watersheds because the variation in plant canopy architecture results in rainfall interception differences. Understanding the variables that influence rainfall interception and understanding the mechanism of rainfall interception are important concepts for sustainable watershed management. The broad objective of this study was to explore the influence of leaf hydrophobicity, water droplet retention, and leaf angle on the mechanism and process of rainfall interception and raindrop impaction on leaf surfaces of common tree species from the semi-arid regions of the western United States. Leaf hydrophobicity is determined by the cohesive forces of the water molecules among themselves and the adhesive forces that result from the molecular interactions between the water droplet and the leaf surface. Water droplet retention is a measure of how easily a water droplet drains off a leaf surface. The specific hypotheses examined were 1) larger raindrops falling on leaf surfaces will deflect the leaf to an angle greater than the water droplet retention angle; 2) an increased leaf angle, whether from natural position or deflection due to droplet impact and retention, reduces interception from raindrop impaction on hydrophobic and hydrophilic leaf surfaces; and 3) increased droplet size and frequency decrease rainfall interception more significantly in the hydrophilic case. These hypotheses were addressed in a laboratory experiment by 1) measuring leaf hydrophobicity and water droplet retention using a goniometer with a tilting base; 2) measuring leaf traits such as leaf area, leaf surface roughness, trichome density, and specific storage capacity; 3) examining raindrop splash on leaf surfaces with varying leaf hydrophobicity, water droplet retention, and leaf angle with a raindrop generator and high-speed video camera; and 4) modeling the impact of raindrop splash on leaf

  12. Leaf drop affects herbivory in oaks.

    PubMed

    Pearse, Ian S; Karban, Richard

    2013-11-01

    Leaf phenology is important to herbivores, but the timing and extent of leaf drop has not played an important role in our understanding of herbivore interactions with deciduous plants. Using phylogenetic general least squares regression, we compared the phenology of leaves of 55 oak species in a common garden with the abundance of leaf miners on those trees. Mine abundance was highest on trees with an intermediate leaf retention index, i.e. trees that lost most, but not all, of their leaves for 2-3 months. The leaves of more evergreen species were more heavily sclerotized, and sclerotized leaves accumulated fewer mines in the summer. Leaves of more deciduous species also accumulated fewer mines in the summer, and this was consistent with the idea that trees reduce overwintering herbivores by shedding leaves. Trees with a later leaf set and slower leaf maturation accumulated fewer herbivores. We propose that both leaf drop and early leaf phenology strongly affect herbivore abundance and select for differences in plant defense. Leaf drop may allow trees to dispose of their herbivores so that the herbivores must recolonize in spring, but trees with the longest leaf retention also have the greatest direct defenses against herbivores.

  13. Classification and quantification of leaf curvature

    PubMed Central

    Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

    2010-01-01

    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields. PMID:20400533

  14. Classification and quantification of leaf curvature.

    PubMed

    Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

    2010-06-01

    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields.

  15. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from...

  16. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from...

  17. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed from...

  18. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed...

  19. 7 CFR 30.2 - Leaf tobacco.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... stemming, sweating or fermenting, and conditioning are not regarded as manufacturing processes. Leaf tobacco does not include any manufactured or semimanufactured tobacco, stems which have been removed...

  20. Salinity Effects on Leaf Anatomy

    PubMed Central

    Longstreth, David J.; Nobel, Park S.

    1979-01-01

    Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (Ames/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for CO2 absorption did not lead to higher CO2 uptake rates, since the CO2 resistance expressed on the basis of mesophyll cell wall area (rcell) increased even more with salinity. The differences among species in the sensitivity of photosynthesis to salinity in part reflect the different Ames/A and rcell responses. PMID:16660795

  1. Transcriptional networks in leaf senescence.

    PubMed

    Schippers, Jos H M

    2015-10-01

    Plant senescence is a natural phenomenon known for the appearance of beautiful autumn colors and the ripening of cereals in the field. Senescence is a controlled process that plants utilize to remobilize nutrients from source leaves to developing tissues. While during the past decades, molecular components underlying the onset of senescence have been intensively studied, knowledge remains scarce on the age-dependent mechanisms that control the onset of senescence. Recent advances have uncovered transcriptional networks regulating the competence to senesce. Here, gene regulatory networks acting as internal timing mechanisms for the onset of senescence are highlighted, illustrating that early and late leaf developmental phases are highly connected.

  2. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is American Upland cotton which is lower in leaf grade than...

  3. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is American Upland cotton which is lower in leaf grade than...

  4. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is American Upland cotton which is lower in leaf grade than...

  5. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is American Upland cotton which is lower in leaf grade than...

  6. 7 CFR 28.471 - Below Leaf Grade Cotton.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Below Leaf Grade Cotton. 28.471 Section 28.471... REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Below Leaf Grade Cotton § 28.471 Below Leaf Grade Cotton. Below leaf grade cotton is American Upland cotton which is lower in leaf grade than...

  7. Drought effects on leaf abscission and leaf production in Populus clones

    Treesearch

    Stephen G. Pallardy; Julie L. Rhoads

    1997-01-01

    Leaf abscission and foliation responses to water stress were studied in potted plants of five Populus clones grown in a greenhouse. As predawn leaf water potential (Ψ1) fell to -3 MPa, drought-induced leaf abscission increased progressively to 30% for data pooled across clones. As predawn Ψ1...

  8. Increased phosphoenolpyruvate carboxykinase gene expression and steatosis during hepatitis C virus subgenome replication: role of nonstructural component 5A and CCAAT/enhancer-binding protein β.

    PubMed

    Qadri, Ishtiaq; Choudhury, Mahua; Rahman, Shaikh Mizanoor; Knotts, Trina A; Janssen, Rachel C; Schaack, Jerome; Iwahashi, Mieko; Puljak, Livia; Simon, Francis R; Kilic, Gordan; Fitz, J Gregory; Friedman, Jacob E

    2012-10-26

    Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression

  9. Phosphoenolpyruvate-sugar phosphotransferase transport system of Streptococcus mutans: purification of HPr and enzyme I and determination of their intracellular concentrations by rocket immunoelectrophoresis.

    PubMed Central

    Thibault, L; Vadeboncoeur, C

    1985-01-01

    Enzyme I and HPr, the general proteins of the phosphoenolpyruvate-sugar phosphotransferase system, play a pivotal role in the control of sugar utilization in gram-negative and gram-positive bacteria. To determine whether growth conditions could modify the rate of biosynthesis of these proteins in Streptococcus mutans, we first purified to homogeneity enzyme I and HPr from S. mutans ATCC 27352. Using specific antibodies obtained against these proteins, we determined by rocket electrophoresis the intracellular levels of enzyme I and HPr in cells of S. mutans 27352 grown under various batch culture conditions and in a number of glucose-grown cells of other strains of S. mutans. HPr was purified by the procedure reported by Gauthier et al. (L. Gauthier, D. Mayrand, and C. Vadeboncoeur, J. Bacteriol. 160:755-763, 1984) and displayed a single band with a molecular weight of 6,650 when analyzed by sodium dodecyl sulfate-urea gel electrophoresis. Enzyme I was purified by DEAE-cellulose chromatography, affinity chromatography on an anti-Streptococcus salivarius column, and preparative electrophoresis. The protein migrated as a single band in native and denaturating gel electrophoresis. The subunit molecular weight of enzyme I determined by electrophoresis under denaturating conditions was 68,000. In gel filtration chromatography at 4 degrees C, the enzyme migrated as a 135,000- to 160,000-molecular-weight species, suggesting that enzyme I is a dimer. In double immunodiffusion experiments, antibodies against HPr reacted with several oral streptococci, Streptococcus lactis, Streptococcus faecium, and Lactobacillus casei, but not with Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Antibodies against enzyme I of S. mutans 27352 cross-reacted with enzyme I from all the other oral streptococci tested. No cross-reaction was observed with other gram-positive and gram-negative bacteria. The levels of enzyme I and HPr determined by rocket electrophoresis in S. mutans

  10. The contribution of stored malate and citrate to the substrate requirements of metabolism of ripening peach (Prunus persica L. Batsch) flesh is negligible. Implications for the occurrence of phosphoenolpyruvate carboxykinase and gluconeogenesis.

    PubMed

    Famiani, Franco; Farinelli, Daniela; Moscatello, Stefano; Battistelli, Alberto; Leegood, Richard C; Walker, Robert P

    2016-04-01

    The first aim of this study was to determine the contribution of stored malate and citrate to the substrate requirements of metabolism in the ripening flesh of the peach (Prunus persica L. Batsch) cultivar Adriatica. In the flesh, stored malate accumulated before ripening could contribute little or nothing to the net substrate requirements of metabolism. This was because there was synthesis and not dissimilation of malate throughout ripening. Stored citrate could potentially contribute a very small amount (about 5.8%) of the substrate required by metabolism when the whole ripening period was considered, and a maximum of about 7.5% over the latter part of ripening. The second aim of this study was to investigate why phosphoenolpyruvate carboxykinase (PEPCK) an enzyme utilised in gluconeogenesis from malate and citrate is present in peach flesh. The occurrence and localisation of enzymes utilised in the metabolism of malate, citrate and amino acids were determined in peach flesh throughout its development. Phosphoenolpyruvate carboxylase (essential for the synthesis of malate and citrate) was present in the same cells and at the same time as PEPCK and NADP-malic enzyme (both utilised in the dissimilation of malate and citrate). A hypothesis is presented to explain the presence of these enzymes and to account for the likely occurrence of gluconeogenesis. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  11. “Breath figures” on leaf surfaces—formation and effects of microscopic leaf wetness

    PubMed Central

    Burkhardt, Juergen; Hunsche, Mauricio

    2013-01-01

    “Microscopic leaf wetness” means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 μm, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past. PMID:24167510

  12. "Breath figures" on leaf surfaces-formation and effects of microscopic leaf wetness.

    PubMed

    Burkhardt, Juergen; Hunsche, Mauricio

    2013-01-01

    "Microscopic leaf wetness" means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 μm, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past.

  13. Seasonal variability of multiple leaf traits captured by leaf spectroscopy at two temperate deciduous forests

    DOE PAGES

    Yang, Xi; Tang, Jianwu; Mustard, John F.; ...

    2016-04-02

    Understanding the temporal patterns of leaf traits is critical in determining the seasonality and magnitude of terrestrial carbon, water, and energy fluxes. However, we lack robust and efficient ways to monitor the temporal dynamics of leaf traits. Here we assessed the potential of leaf spectroscopy to predict and monitor leaf traits across their entire life cycle at different forest sites and light environments (sunlit vs. shaded) using a weekly sampled dataset across the entire growing season at two temperate deciduous forests. In addition, the dataset includes field measured leaf-level directional-hemispherical reflectance/transmittance together with seven important leaf traits [total chlorophyll (chlorophyllmore » a and b), carotenoids, mass-based nitrogen concentration (Nmass), mass-based carbon concentration (Cmass), and leaf mass per area (LMA)]. All leaf traits varied significantly throughout the growing season, and displayed trait-specific temporal patterns. We used a Partial Least Square Regression (PLSR) modeling approach to estimate leaf traits from spectra, and found that PLSR was able to capture the variability across time, sites, and light environments of all leaf traits investigated (R2 = 0.6–0.8 for temporal variability; R2 = 0.3–0.7 for cross-site variability; R2 = 0.4–0.8 for variability from light environments). We also tested alternative field sampling designs and found that for most leaf traits, biweekly leaf sampling throughout the growing season enabled accurate characterization of the seasonal patterns. Compared with the estimation of foliar pigments, the performance of Nmass, Cmass and LMA PLSR models improved more significantly with sampling frequency. Our results demonstrate that leaf spectra-trait relationships vary with time, and thus tracking the seasonality of leaf traits requires statistical models calibrated with data sampled throughout the growing season. In conclusion, our results have broad implications for future

  14. 7 CFR 29.2530 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  15. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.) ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  16. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.) ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  17. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.) ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  18. 7 CFR 29.2530 - Leaf structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  19. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.) ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  20. 7 CFR 29.2278 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... structure. The cell development of a leaf as indicated by its porosity. (See chart, § 29.2351.) ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.2278 Section 29.2278 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  1. 7 CFR 29.2530 - Leaf structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  2. 7 CFR 29.2530 - Leaf structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  3. 7 CFR 29.2530 - Leaf structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2530 Leaf structure. The cell development of... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf structure. 29.2530 Section 29.2530 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing...

  4. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco. ...

  5. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco. [42 FR 21092, Apr. 25...

  6. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco. ...

  7. Leaf Histology--Two Modern Methods.

    ERIC Educational Resources Information Center

    Freeman, H. E.

    1984-01-01

    Two methods for examining leaf structure are presented; both methods involve use of "superglue." The first method uses the glue to form a thin, permanent, direct replica of a leaf surface on a microscope slide. The second method uses the glue to examine the three-dimensional structure of spongy mesophyll. (JN)

  8. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists...

  9. 7 CFR 29.2277 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.2277 Section 29.2277 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... scrap. A byproduct of unstemmed tobacco. Leaf scrap results from handling unstemmed tobacco and consists...

  10. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco. [42 FR 21092, Apr. 25...

  11. 7 CFR 29.1029 - Leaf scrap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf scrap. 29.1029 Section 29.1029 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1029 Leaf scrap. A byproduct of stemmed and unstemmed tobacco. [42 FR 21092, Apr. 25...

  12. Leaf Histology--Two Modern Methods.

    ERIC Educational Resources Information Center

    Freeman, H. E.

    1984-01-01

    Two methods for examining leaf structure are presented; both methods involve use of "superglue." The first method uses the glue to form a thin, permanent, direct replica of a leaf surface on a microscope slide. The second method uses the glue to examine the three-dimensional structure of spongy mesophyll. (JN)

  13. [Study on pharmacognosy of Ginkgo leaf].

    PubMed

    Geng, Guo-Ping; Ma, Zhi-Gang; Mao, Chong-Wu

    2007-05-01

    The primary study of Ginkgo leaf such as crude drug macroscopic and powder characteristics were carried out, and the flavonoids content in the leaf of Ginkgo in different areas of Gansu province was determined by HPLC, in order to provide scientific references for the exploitation of Ginkgo in Gansu province.

  14. The unique structural and biochemical development of single cell C4 photosynthesis along longitudinal leaf gradients in Bienertia sinuspersici and Suaeda aralocaspica (Chenopodiaceae).

    PubMed

    Koteyeva, Nuria K; Voznesenskaya, Elena V; Berry, James O; Cousins, Asaph B; Edwards, Gerald E

    2016-04-01

    Temporal and spatial patterns of photosynthetic enzyme expression and structural maturation of chlorenchyma cells along longitudinal developmental gradients were characterized in young leaves of two single cell C4 species, Bienertia sinuspersici and Suaeda aralocaspica Both species partition photosynthetic functions between distinct intracellular domains. In the C4-C domain, C4 acids are formed in the C4 cycle during capture of atmospheric CO2 by phosphoenolpyruvate carboxylase. In the C4-D domain, CO2 released in the C4 cycle via mitochondrial NAD-malic enzyme is refixed by Rubisco. Despite striking differences in origin and intracellular positioning of domains, these species show strong convergence in C4 developmental patterns. Both progress through a gradual developmental transition towards full C4 photosynthesis, with an associated increase in levels of photosynthetic enzymes. Analysis of longitudinal sections showed undeveloped domains at the leaf base, with Rubisco rbcL mRNA and protein contained within all chloroplasts. The two domains were first distinguishable in chlorenchyma cells at the leaf mid-regions, but still contained structurally similar chloroplasts with equivalent amounts of rbcL mRNA and protein; while mitochondria had become confined to just one domain (proto-C4-D). The C4 state was fully formed towards the leaf tips, Rubisco transcripts and protein were compartmentalized specifically to structurally distinct chloroplasts in the C4-D domains indicating selective regulation of Rubisco expression may occur by control of transcription or stability of rbcL mRNA. Determination of CO2 compensation points showed young leaves were not functionally C4, consistent with cytological observations of the developmental progression from C3 default to intermediate to C4 photosynthesis.

  15. The unique structural and biochemical development of single cell C4 photosynthesis along longitudinal leaf gradients in Bienertia sinuspersici and Suaeda aralocaspica (Chenopodiaceae)

    PubMed Central

    Koteyeva, Nuria K.; Voznesenskaya, Elena V.; Berry, James O.; Cousins, Asaph B.; Edwards, Gerald E.

    2016-01-01

    Temporal and spatial patterns of photosynthetic enzyme expression and structural maturation of chlorenchyma cells along longitudinal developmental gradients were characterized in young leaves of two single cell C4 species, Bienertia sinuspersici and Suaeda aralocaspica. Both species partition photosynthetic functions between distinct intracellular domains. In the C4-C domain, C4 acids are formed in the C4 cycle during capture of atmospheric CO2 by phosphoenolpyruvate carboxylase. In the C4-D domain, CO2 released in the C4 cycle via mitochondrial NAD-malic enzyme is refixed by Rubisco. Despite striking differences in origin and intracellular positioning of domains, these species show strong convergence in C4 developmental patterns. Both progress through a gradual developmental transition towards full C4 photosynthesis, with an associated increase in levels of photosynthetic enzymes. Analysis of longitudinal sections showed undeveloped domains at the leaf base, with Rubisco rbcL mRNA and protein contained within all chloroplasts. The two domains were first distinguishable in chlorenchyma cells at the leaf mid-regions, but still contained structurally similar chloroplasts with equivalent amounts of rbcL mRNA and protein; while mitochondria had become confined to just one domain (proto-C4-D). The C4 state was fully formed towards the leaf tips, Rubisco transcripts and protein were compartmentalized specifically to structurally distinct chloroplasts in the C4-D domains indicating selective regulation of Rubisco expression may occur by control of transcription or stability of rbcL mRNA. Determination of CO2 compensation points showed young leaves were not functionally C4, consistent with cytological observations of the developmental progression from C3 default to intermediate to C4 photosynthesis. PMID:26957565

  16. Easy Leaf Area: Automated digital image analysis for rapid and accurate measurement of leaf area1

    PubMed Central

    Easlon, Hsien Ming; Bloom, Arnold J.

    2014-01-01

    • Premise of the study: Measurement of leaf areas from digital photographs has traditionally required significant user input unless backgrounds are carefully masked. Easy Leaf Area was developed to batch process hundreds of Arabidopsis rosette images in minutes, removing background artifacts and saving results to a spreadsheet-ready CSV file. • Methods and Results: Easy Leaf Area uses the color ratios of each pixel to distinguish leaves and calibration areas from their background and compares leaf pixel counts to a red calibration area to eliminate the need for camera distance calculations or manual ruler scale measurement that other software methods typically require. Leaf areas estimated by this software from images taken with a camera phone were more accurate than ImageJ estimates from flatbed scanner images. • Conclusions: Easy Leaf Area provides an easy-to-use method for rapid measurement of leaf area and nondestructive estimation of canopy area from digital images. PMID:25202639

  17. Inferring climate from angiosperm leaf venation networks.

    PubMed

    Blonder, Benjamin; Enquist, Brian J

    2014-10-01

    Leaf venation networks provide an integrative linkage between plant form, function and climate niche, because leaf water transport underlies variation in plant performance. Here, we develop theory based on leaf physiology that uses community-mean vein density to predict growing season temperature and atmospheric CO2 concentration. The key assumption is that leaf water supply is matched to water demand in the local environment. We test model predictions using leaves from 17 temperate and tropical sites that span broad climatic gradients. We find quantitative agreement between predicted and observed climate values. We also highlight additional leaf traits that may improve predictions. Our study provides a novel approach for understanding the functional linkages between functional traits and climate that may improve the reconstruction of paleoclimate from fossil assemblages.

  18. Possible Roles of Strigolactones during Leaf Senescence.

    PubMed

    Yamada, Yusuke; Umehara, Mikihisa

    2015-09-11

    Leaf senescence is a complicated developmental process that involves degenerative changes and nutrient recycling. The progress of leaf senescence is controlled by various environmental cues and plant hormones, including ethylene, jasmonic acid, salicylic acid, abscisic acid, cytokinins, and strigolactones. The production of strigolactones is induced in response to nitrogen and phosphorous deficiency. Strigolactones also accelerate leaf senescence and regulate shoot branching and root architecture. Leaf senescence is actively promoted in a nutrient-poor soil environment, and nutrients are transported from old leaves to young tissues and seeds. Strigolactones might act as important signals in response to nutrient levels in the rhizosphere. In this review, we discuss the possible roles of strigolactones during leaf senescence.

  19. [Photoprotective mechanisms of leaf anthocyanins: research progress].

    PubMed

    Wang, Liang-Zai; Hu, Yan-Bo; Zhang, Hui-Hui; Xu, Nan; Zhang, Xiu-Li; Sun, Guang-Yu

    2012-03-01

    Anthocyanin is widely distributed in plant organs such as root, stem, leaf, flower and fruit, being a kind of secondary metabolites generated in plant morphogenesis or for stress response. Leaf anthocyanin has special chemical structure and spectral properties, playing important roles in plant photoprotection, and becomes a hotspot in plant photosynthetic physiological ecology. This paper summarized the recent research progress in the effects of leaf anthocyanin on plant photosynthesis, including the distribution of leaf anthocyanin, its spectral properties, and its relationships with photosynthetic pigments, with the focus on the potential mechanisms of anthocyanins photoprotection, including light absorption, antioxidation, and osmotic regulation. The further research directions on the effects of leaf anthocyanin on photoprotection were proposed.

  20. Auxin patterns Solanum lycopersicum leaf morphogenesis.

    PubMed

    Koenig, Daniel; Bayer, Emmanuelle; Kang, Julie; Kuhlemeier, Cris; Sinha, Neelima

    2009-09-01

    One of the most striking aspects of plant diversity is variation in leaf shape. Much of this diversity is achieved by the modulation of leaf blade dissection to form lobes or leaflets. Here, we show that the phytohormone auxin is a crucial signal regulating the partitioned outgrowth necessary to develop a dissected leaf. In developing leaves, the asymmetric distribution of auxin, driven by active transport, delineates the initiation of lobes and leaflets and specifies differential laminar outgrowth. Furthermore, homologous members of the AUX/indole-3-acetic acid (IAA) gene family mediate the action of auxin in determining leaf shape by repressing outgrowth in areas of low auxin concentration during both simple and compound leaf development. These results provide molecular evidence that leaflets initiate in a process reminiscent of organogenesis at the shoot apical meristem, but that compound and simple leaves regulate marginal growth through an evolutionarily conserved mechanism, thus shedding light on the homology of compound and simple leaves.

  1. Leaf movement in Calathea lutea (Marantaceae).

    PubMed

    Herbert, Thomas J; Larsen, Parry B

    1985-09-01

    Calathea lutea is a broad-leaved, secondary successional plant which shows complex leaf movements involving both elevation and folding of the leaf surface about the pulvinus. In the plants studied, mean leaf elevation increased from approximately 34 degrees in the early morning to 70 degrees at noon while the angle of leaf folding increased from 13 degrees to 50 degrees over the same time period. During the period from early morning to noon, these movements resulted in a significant decrease in the cosine of the angle of incidence, a measure of the direct solar radiation intercepted. The observed changes in elevational angle significantly reduce the cosine of angle of incidence while folding does not significantly reduce the fraction of direct solar radiation intercepted during the period of direct exposure of the leaf surface to the solar beam. Since elevational changes seem to account for the reduction in exposure to direct solar radiation, the role of folding remains unclear.

  2. Relating Stomatal Conductance to Leaf Functional Traits.

    PubMed

    Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

    2015-10-12

    Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants' regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES.

  3. Relating Stomatal Conductance to Leaf Functional Traits

    PubMed Central

    Kröber, Wenzel; Plath, Isa; Heklau, Heike; Bruelheide, Helge

    2015-01-01

    Leaf functional traits are important because they reflect physiological functions, such as transpiration and carbon assimilation. In particular, morphological leaf traits have the potential to summarize plants strategies in terms of water use efficiency, growth pattern and nutrient use. The leaf economics spectrum (LES) is a recognized framework in functional plant ecology and reflects a gradient of increasing specific leaf area (SLA), leaf nitrogen, phosphorus and cation content, and decreasing leaf dry matter content (LDMC) and carbon nitrogen ratio (CN). The LES describes different strategies ranging from that of short-lived leaves with high photosynthetic capacity per leaf mass to long-lived leaves with low mass-based carbon assimilation rates. However, traits that are not included in the LES might provide additional information on the species' physiology, such as those related to stomatal control. Protocols are presented for a wide range of leaf functional traits, including traits of the LES, but also traits that are independent of the LES. In particular, a new method is introduced that relates the plants’ regulatory behavior in stomatal conductance to vapor pressure deficit. The resulting parameters of stomatal regulation can then be compared to the LES and other plant functional traits. The results show that functional leaf traits of the LES were also valid predictors for the parameters of stomatal regulation. For example, leaf carbon concentration was positively related to the vapor pressure deficit (vpd) at the point of inflection and the maximum of the conductance-vpd curve. However, traits that are not included in the LES added information in explaining parameters of stomatal control: the vpd at the point of inflection of the conductance-vpd curve was lower for species with higher stomatal density and higher stomatal index. Overall, stomata and vein traits were more powerful predictors for explaining stomatal regulation than traits used in the LES

  4. Two WUSCHEL-related homeobox genes, narrow leaf2 and narrow leaf3, control leaf width in rice.

    PubMed

    Ishiwata, Aiko; Ozawa, Misa; Nagasaki, Hiroshi; Kato, Makio; Noda, Yusaku; Yamaguchi, Takahiro; Nosaka, Misuzu; Shimizu-Sato, Sae; Nagasaki, Akie; Maekawa, Masahiko; Hirano, Hiro-Yuki; Sato, Yutaka

    2013-05-01

    Leaf shape is one of the key determinants of plant architecture. Leaf shape also affects the amount of sunlight captured and influences photosynthetic efficiency; thus, it is an important agronomic trait in crop plants. Understanding the molecular mechanisms governing leaf shape is a central issue of plant developmental biology and agrobiotechnology. Here, we characterized the narrow-leaf phenotype of FL90, a linkage tester line of rice (Oryza sativa). Light and scanning electron microscopic analyses of FL90 leaves revealed defects in the development of marginal regions and a reduction in the number of longitudinal veins. The narrow-leaf phenotype of FL90 shows a two-factor recessive inheritance and is caused by the loss of function of two WUSCHEL-related homeobox genes, NAL2 and NAL3 (NAL2/3), which are duplicate genes orthologous to maize NS1 and NS2 and to Arabidopsis PRS. The overexpression of NAL2/3 in transgenic rice plants results in wider leaves containing increased numbers of veins, suggesting that NAL2/3 expression regulates leaf width. Thus, NAL2/3 can be used to modulate leaf shape and improve agronomic yield in crop plants.

  5. Nutrient Influences on Leaf Photosynthesis

    PubMed Central

    Longstreth, David J.; Nobel, Park S.

    1980-01-01

    The net rate of CO2 uptake for leaves of Gossypium hirsutum L. was reduced when the plants were grown at low concentrations of NO3-, PO42-, or K+. The water vapor conductance was relatively constant for all nutrient levels, indicating little effect on stomatal response. Although leaves under nutrient stress tended to be lower in chlorophyll and thinner, the ratio of mesophyll surface area to leaf area did not change appreciably. Thus, the reduction in CO2 uptake rate at low nutrient levels was due to a decrease in the CO2 conductance expressed per unit mesophyll cell wall area (gcellCO2). The use of gcellCO2 and nutrient levels expressed per unit of mesophyll cell wall provides a new means of assessing nutrient effects on CO2 uptake of leaves. PMID:16661231

  6. A model for leaf initiation

    PubMed Central

    Abraham-Shrauner, Barbara; Pickard, Barbara G

    2011-01-01

    A biophysical model is proposed for how leaf primordia are positioned on the shoot apical
    meristem in both spiral and whorl phyllotaxes. Primordia are initiated by signals that propagate
    in the epidermis in both azimuthal directions away from the cotyledons or the most recently
    specified primordia. The signals are linear waves as inferred from the spatial periodicity of the
    divergence angle and a temporal periodicity. The periods of the waves, which represent actively
    transported auxin, are much smaller than the plastochron interval. Where oppositely directed
    waves meet at one or more angular positions on the periphery of the generative circle, auxin
    concentration builds and as in most models this stimulates local movement of auxin to
    underlying cells, where it promotes polarized cell division and expansion. For higher order
    spirals the wave model requires asymmetric function of auxin transport; that is, opposite wave
    speeds differ. An algorithm for determination of the angular positions of leaves in common leaf
    phyllotaxic configurations is proposed. The number of turns in a pattern repeat, number of leaves
    per level and per pattern repeat, and divergence angle are related to speed of auxin transport and
    radius of the generative circle. The rule for composition of Fibonacci or Lucas numbers
    associated with some phyllotaxes is discussed. A subcellular model suggests how the shoot
    meristem might specify either symmetric or asymmetric transport of auxin away from the
    forming primordia that produce it. Biological tests that could make or break the mathematical
    and molecular hypotheses are proposed. PMID:22212121

  7. Are leaf physiological traits related to leaf water isotopic enrichment in restinga woody species?

    PubMed

    Rosado, Bruno H P; De Mattos, Eduardo A; Sternberg, Leonel Da S L

    2013-09-01

    During plant-transpiration, water molecules having the lighter stable isotopes of oxygen and hydrogen evaporate and diffuse at a faster rate through the stomata than molecules having the heavier isotopes, which cause isotopic enrichment of leaf water. Although previous models have assumed that leaf water is well-mixed and isotopically uniform, non-uniform stomatal closure, promoting different enrichments between cells, and different pools of water within leaves, due to morpho-physiological traits, might lead to inaccuracies in isotopic models predicting leaf water enrichment. We evaluate the role of leaf morpho-physiological traits on leaf water isotopic enrichment in woody species occurring in a coastal vegetation of Brazil known as restinga. Hydrogen and oxygen stable isotope values of soil, plant stem and leaf water and leaf traits were measured in six species from restinga vegetation during a drought and a wet period. Leaf water isotopic enrichment relative to stem water was more homogeneous among species during the drought in contrast to the wet period suggesting convergent responses to deal to temporal heterogeneity in water availability. Average leaf water isotopic enrichment relative to stem water during the drought period was highly correlated with relative apoplastic water content. We discuss this observation in the context of current models of leaf water isotopic enrichment as a function of the Péclet effect. We suggest that future studies should include relative apoplastic water content in isotopic models.

  8. Maize YABBY Genes drooping leaf1 and drooping leaf2 Regulate Plant Architecture[OPEN

    PubMed Central

    Briggs, Sarah; Bradbury, Peter J.

    2017-01-01

    Leaf architecture directly influences canopy structure, consequentially affecting yield. We discovered a maize (Zea mays) mutant with aberrant leaf architecture, which we named drooping leaf1 (drl1). Pleiotropic mutations in drl1 affect leaf length and width, leaf angle, and internode length and diameter. These phenotypes are enhanced by natural variation at the drl2 enhancer locus, including reduced expression of the drl2-Mo17 allele in the Mo17 inbred. A second drl2 allele, produced by transposon mutagenesis, interacted synergistically with drl1 mutants and reduced drl2 transcript levels. The drl genes are required for proper leaf patterning, development and cell proliferation of leaf support tissues, and for restricting auricle expansion at the midrib. The paralogous loci encode maize CRABS CLAW co-orthologs in the YABBY family of transcriptional regulators. The drl genes are coexpressed in incipient and emergent leaf primordia at the shoot apex, but not in the vegetative meristem or stem. Genome-wide association studies using maize NAM-RIL (nested association mapping-recombinant inbred line) populations indicated that the drl loci reside within quantitative trait locus regions for leaf angle, leaf width, and internode length and identified rare single nucleotide polymorphisms with large phenotypic effects for the latter two traits. This study demonstrates that drl genes control the development of key agronomic traits in maize. PMID:28698237

  9. The DeoR-type transcriptional regulator SugR acts as a repressor for genes encoding the phosphoenolpyruvate:sugar phosphotransferase system (PTS) in Corynebacterium glutamicum

    PubMed Central

    Gaigalat, Lars; Schlüter, Jan-Philip; Hartmann, Michelle; Mormann, Sascha; Tauch, Andreas; Pühler, Alfred; Kalinowski, Jörn

    2007-01-01

    Background The major uptake system responsible for the transport of fructose, glucose, and sucrose in Corynebacterium glutamicum ATCC 13032 is the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The genes encoding PTS components, namely ptsI, ptsH, and ptsF belong to the fructose-PTS gene cluster, whereas ptsG and ptsS are located in two separate regions of the C. glutamicum genome. Due to the localization within and adjacent to the fructose-PTS gene cluster, two genes coding for DeoR-type transcriptional regulators, cg2118 and sugR, are putative candidates involved in the transcriptional regulation of the fructose-PTS cluster genes. Results Four transcripts of the extended fructose-PTS gene cluster that comprise the genes sugR-cg2116, ptsI, cg2118-fruK-ptsF, and ptsH, respectively, were characterized. In addition, it was shown that transcription of the fructose-PTS gene cluster is enhanced during growth on glucose or fructose when compared to acetate. Subsequently, the two genes sugR and cg2118 encoding for DeoR-type regulators were mutated and PTS gene transcription was found to be strongly enhanced in the presence of acetate only in the sugR deletion mutant. The SugR regulon was further characterized by microarray hybridizations using the sugR mutant and its parental strain, revealing that also the PTS genes ptsG and ptsS belong to this regulon. Binding of purified SugR repressor protein to a 21 bp sequence identified the SugR binding site as an AC-rich motif. The two experimentally identified SugR binding sites in the fructose-PTS gene cluster are located within or downstream of the mapped promoters, typical for transcriptional repressors. Effector studies using electrophoretic mobility shift assays (EMSA) revealed the fructose PTS-specific metabolite fructose-1-phosphate (F-1-P) as a highly efficient, negative effector of the SugR repressor, acting in the micromolar range. Beside F-1-P, other sugar-phosphates like fructose-1,6-bisphosphate (F-1,6-P

  10. Consequences of phosphoenolpyruvate:sugar phosphotranferase system and pyruvate kinase isozymes inactivation in central carbon metabolism flux distribution in Escherichia coli

    PubMed Central

    2012-01-01

    Background In Escherichia coli phosphoenolpyruvate (PEP) is a key central metabolism intermediate that participates in glucose transport, as precursor in several biosynthetic pathways and it is involved in allosteric regulation of glycolytic enzymes. In this work we generated W3110 derivative strains that lack the main PEP consumers PEP:sugar phosphotransferase system (PTS-) and pyruvate kinase isozymes PykA and PykF (PTS-pykA- and PTS-pykF-). To characterize the effects of these modifications on cell physiology, carbon flux distribution and aromatics production capacity were determined. Results When compared to reference strain W3110, strain VH33 (PTS-) displayed lower specific rates for growth, glucose consumption and acetate production as well as a higher biomass yield from glucose. These phenotypic effects were even more pronounced by the additional inactivation of PykA or PykF. Carbon flux analysis revealed that PTS inactivation causes a redirection of metabolic flux towards biomass formation. A cycle involving PEP carboxylase (Ppc) and PEP carboxykinase (Pck) was detected in all strains. In strains W3110, VH33 (PTS-) and VH35 (PTS-, pykF-), the net flux in this cycle was inversely correlated with the specific rate of glucose consumption and inactivation of Pck in these strains caused a reduction in growth rate. In the PTS- background, inactivation of PykA caused a reduction in Ppc and Pck cycling as well as a reduction in flux to TCA, whereas inactivation of PykF caused an increase in anaplerotic flux from PEP to OAA and an increased flux to TCA. The wild-type and mutant strains were modified to overproduce L-phenylalanine. In resting cells experiments, compared to reference strain, a 10, 4 and 7-fold higher aromatics yields from glucose were observed as consequence of PTS, PTS PykA and PTS PykF inactivation. Conclusions Metabolic flux analysis performed on strains lacking the main activities generating pyruvate from PEP revealed the high degree of

  11. Spatial division of phosphoenolpyruvate carboxylase and nitrate reductase activity and its regulation by cytokinins in CAM-induced leaves of Guzmania monostachia (Bromeliaceae).

    PubMed

    Pereira, Paula Natália; Purgatto, Eduardo; Mercier, Helenice

    2013-08-15

    Crassulacean acid metabolism (CAM) is a physiological adaptation of plants that live in stress environment conditions. A good model of CAM modulation is the epiphytic bromeliad, Guzmania monostachia, which switches between two photosynthetic pathways (C3-CAM) in response to different environmental conditions, such as light stress and water availability. Along the leaf length a gradient of acidity can be observed when G. monostachia plants are kept under water deficiency. Previous studies showed that the apical portions of the leaves present higher expression of CAM, while the basal regions exhibit lower expression of this photosynthetic pathway. The present study has demonstrated that it is possible to induce the CAM pathway in detached leaves of G. monostachia kept under water deficit for 7 d. Also, it was evaluated whether CAM expression can be modulated in detached leaves of Guzmania and whether some spatial separation between NO3(-) reduction and CO2 fixation occurs in basal and apical portions of the leaf. In addition, we analyzed the involvement of endogenous cytokinins (free and ribosylated forms) as possible signal modulating both NO3(-) reduction and CO2 fixation along the leaf blade of this bromeliad. Besides demonstrating a clear spatial and functional separation of carbon and nitrogen metabolism along G. monostachia leaves, the results obtained also indicated a probable negative correlation between endogenous free cytokinins - zeatin (Z) and isopentenyladenine (iP) - concentration and PEPC activity in the apical portions of G. monostachia leaves kept under water deficit. On the other hand, a possible positive correlation between endogenous Z and iP levels and NR activity in basal portions of drought-exposed and control leaves was verified. Together with the observations presented above, results obtained with exogenous cytokinins treatments, strongly suggest that free cytokinins might act as a stimulatory signal involved in NR activity regulation and as

  12. Long term leaf phenology and leaf exchange strategies of a cerrado savanna community

    NASA Astrophysics Data System (ADS)

    de Camargo, Maria Gabriela G.; Costa Alberton, Bruna; de Carvalho, Gustavo H.; Magalhães, Paula A. N. R.; Morellato, Leonor Patrícia C.

    2017-04-01

    Leaf development and senescence cycles are linked to a range of ecosystem processes, affecting seasonal patterns of atmosphere-ecosystem carbon and energy exchanges, resource availability and nutrient cycling. The degree of deciduousness of tropical trees and communities depend on ecosystems characteristics such as amount of biomass, species diversity and the strength and length of the dry season. Besides defining the growing season, deciduousness can also be an indicator of species response to climate changes in the tropics, mainly because severity of dry season can intensify leaf loss. Based on seven-years of phenological observations (2005 to 2011) we describe the long-term patterns of leafing phenology of a Brazilian cerrado savanna, aiming to (i) identify leaf exchange strategies of species, quantifying the degree of deciduousness, and verify whether these strategies vary among years depending on the length and strength of the dry seasons; (ii) define the growing seasons along the years and the main drivers of leaf flushing in the cerrado. We analyzed leafing patterns of 107 species and classified 69 species as deciduous (11 species), semi-deciduous (29) and evergreen (29). Leaf exchange was markedly seasonal, as expected for seasonal tropical savannas. Leaf fall predominated in the dry season, peaking in July, and leaf flushing in the transition between dry to wet seasons, peaking in September. Leafing patterns were similar among years with the growing season starting at the end of dry season, in September, for most species. However, leaf exchange strategies varied among years for most species (65%), except for evergreen strategy, mainly constant over years. Leafing patterns of cerrado species were strongly constrained by rainfall. The length of the dry season and rainfall intensity were likely affecting the individuals' leaf exchange strategies and suggesting a differential resilience of species to changes of rainfall regime, predicted on future global

  13. Leaf habit and woodiness regulate different leaf economy traits at a given nutrient supply.

    PubMed

    Ordoñez, Jenny C; van Bodegom, Peter M; Witte, Jan-Philip M; Bartholomeus, Ruud P; van Dobben, Han F; Aerts, Rien

    2010-11-01

    The large variation in the relationships between environmental factors and plant traits observed in natural communities exemplifies the alternative solutions that plants have developed in response to the same environmental limitations. Qualitative attributes, such as growth form, woodiness, and leaf habit can be used to approximate these alternative solutions. Here, we quantified the extent to which these attributes affect leaf trait values at a given resource supply level, using measured plant traits from 105 different species (254 observations) distributed across 50 sites in mesic to wet plant communities in The Netherlands. For each site, soil total N, soil total P, and water supply estimates were obtained by field measurements and modeling. Effects of growth forms, woodiness, and leaf habit on relations between leaf traits (SLA, specific leaf area; LNC, leaf nitrogen concentration; and LPC, leaf phosphorus concentration) vs. nutrient and water supply were quantified using maximum-likelihood methods and Bonferroni post hoc tests. The qualitative attributes explained 8-23% of the variance within sites in leaf traits vs. soil fertility relationships, and therefore they can potentially be used to make better predictions of global patterns of leaf traits in relation to nutrient supply. However, at a given soil fertility, the strength of the effect of each qualitative attribute was not the same for all leaf traits. These differences may imply a differential regulation of the leaf economy traits at a given nutrient supply, in which SLA and LPC seem to be regulated in accordance to changes in plant size and architecture while LNC seems to be primarily regulated at the leaf level by factors related to leaf longevity.

  14. An Apparent Anomaly in Peanut Leaf Conductance

    PubMed Central

    Pallas, James E.

    1980-01-01

    Conductance to gaseous transfer is normally considered to be greater from the abaxial than from the adaxial side of a leaf. Measurements of the conductance to water vapor of peanut leaves (Arachis hypogaea L.) under well watered and stress conditions in a controlled environment, however, indicated a 2-fold higher conductance from the adaxial side of the leaf than from the abaxial. Studies of conductance as light level was varied showed an increase in conductance from either surface with increasing light level, but conductance was always greater from the adaxial surface at any given light level. In contrast, measurements of soybean (Glycine max [L.] Merr.) and snapbean (Phaseolus vulgaris L.) leaf conductance showed an approximate 2-fold greater conductance from the abaxial surface than from the adaxial. Approximately the same number of stomata were present on both peanut leaf surfaces and stomatal size was similar. Electron microscopic examination of peanut leaves did not reveal any major structural differences between stomata on the two surfaces that would account for the differences in conductance. Light microscope studies of leaf sections revealed an extensive network of bundle sheaths with achloraplastic bundle sheath extensions; the lower epidermis was lined with a single layer of large achloraplastic parenchyma cells. Measurements of net photosynthesis made on upper and lower leaf surfaces collectively and individually indicated that two-thirds of the peanut leaf's total net photosynthesis can be attributed to diffusion of CO2 through the adaxial leaf surface. Possibly the high photosynthetic efficiency of peanut cultivars as compared with certain other C3 species is associated with the greater conductance of CO2 through their upper leaf surfaces. Images PMID:16661294

  15. Leaf dynamics and profitability in wild strawberries.

    PubMed

    Jurik, Thomas W; Chabot, Brian F

    1986-05-01

    Leaf dynamics and carbon gain were evaluated for two species of wild strawberry, Fragaria virginiana and F. vesca. Five populations on sites representing a gradient of successional regrowth near Ithaca, N.Y., U.S.A., were studied for two or three years each. A computer-based model of plant growth and CO2 exchange combined field studies of leaf biomass dynamics with previously-determined gas exchange rates to estimate carbon balances of leaves and whole plants in different environments.Leaves were produced throughout the growing season, although there was usually a decline in rate of leaf-production in mid-summer. Leaves produced in late spring had the largest area and longest lifespan (except for overwintering leaves produced in the fall). Specific Leaf Weight (SLW) varied little with time of leaf production, but differed greatly among populations; SLW increased with amount of light received in each habitat. The population in the most open habitat had the least seasonal variation in all leaf characters. F. vesca produced lighter, longer-lived leaves than F. virginiana.Simulations showed that age had the largest effect on leaf carbon gain in high-light environments; water stress and temperature had lesser effects. Leaf carbon gain in lowlight environments was relatively unaffected by age and environmental factors other than light. Leaves in high-light environments had the greatest lifetime profit and the greatest ratio of profit to cost. Increasing lifespan by 1/3 increased profit by 80% in low-light leaves and 50% in high-light leaves. Increasing the number of days during which the leaf had the potential to exhibit high photosynthetic rate in response to high light led to little change in profit of low-light leaves while increasing profit of high-light leaves by 49%.

  16. Global Climatic Controls On Leaf Size

    NASA Astrophysics Data System (ADS)

    Wright, I. J.; Prentice, I. C.; Dong, N.; Maire, V.

    2015-12-01

    Since the 1890s it's been known that the wet tropics harbour plants with exceptionally large leaves. Yet the observed latitudinal gradient of leaf size has never been fully explained: it is still unclear which aspects of climate are most important for understanding geographic trends in leaf size, a trait that varies many thousand-fold among species. The key is the leaf-to-air temperature difference, which depends on the balance of energy inputs (irradiance) and outputs (transpirational cooling, losses to the night sky). Smaller leaves track air temperatures more closely than larger leaves. Widely cited optimality-based theories predict an advantage for smaller leaves in dry environments, where transpiration is restricted, but are silent on the latitudinal gradient. We aimed to characterize and explain the worldwide pattern of leaf size. Across 7900 species from 651 sites, here we show that: large-leaved species predominate in wet, hot, sunny environments; smaller-leaved species typify hot, sunny environments only when arid; small leaves are required to avoid freezing in high latitudes and at high elevation, and to avoid overheating in dry environments. This simple pattern was unclear in earlier, more limited analyses. We present a simple but robust, fresh approach to energy-balance modelling for both day-time and night-time leaf-to-air temperature differences, and thus risk of overheating and of frost damage. Our analysis shows night-chilling is important as well as day-heating, and simplifies leaf temperature modelling. It provides both a framework for modelling leaf size constraints, and a solution to one of the oldest conundrums in ecology. Although the path forward is not yet fully clear, because of its role in controlling leaf temperatures we suggest that climate-related leaf size constraints could usefully feature in the next generation of land ecosystem models.

  17. Leaf-closing substance in Leucaena leucocephala.

    PubMed

    Sohtome, Yoshihiro; Tokunaga, Takashi; Ueda, Katsuhiro; Yamamura, Shosuke; Ueda, Minoru

    2002-01-01

    Potassium (2R,3R)-2,3,4-trihydroxy-2-methylbutanoate (1) was identified as a leaf-closing substance in the nyctinastic plant, Leucaena leucocephala. Compound 1 showed strong leaf-closing activity toward L. leucocephala and was not effective against other nyctinastic plants. The potassium ion was indispensable for the bioactivity of 1. Compound 1 gradually lost its bioactivity because of the exchange of the counter cation during isolation. A leaf-opening substance was also observed in the same plant.

  18. Why so strong for the lotus leaf?

    NASA Astrophysics Data System (ADS)

    Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

    2008-11-01

    The authors discussed the potential reasons why the lotus leaf is so strong by means of scanning electron microscopy (SEM). The results showed that the good mechanical properties of lotus leaf should be attributed to its architecture, such as paralleled microtubes structure, umbrellalike structure, and hierarchically layered hexagon structure. The important observation from this work is that the surface of the rear face of the lotus leaf seems to be constituted by the layers of hexagons whose hierarchical pilling up of size decreases as we go deeper from surface. This is a typical fractal-like phenomenon.

  19. A climatology of leaf surface wetness

    NASA Astrophysics Data System (ADS)

    Klemm, O.; Milford, C.; Sutton, M. A.; Spindler, G.; van Putten, E.

    The wetness of plant leaf surfaces is an important parameter in the deposition process of atmospheric trace gases. Particularly gases with high water solubility tend to deposit faster to a wet surface, compared to a dry one. Further, drying up of a wet leaf surface may lead to revolatilization of previously deposited gases. Despite the high importance of leaf surface wetness in biosphere/atmosphere exchange, there is no quantitative description of this parameter on the ecosystem scale, quantifying its initiation, duration, dissipation, correlation with parameters such as air humidity, turbulence, vegetation type, plant physiology, and others. This contribution is a first step towards a climatology of leaf surface wetness, based on a large data basis from various ecosystems. Leaf surface wetness was monitored at two grassland and two forest research sites in NW and central Europe throughout the vegetation period of 1998. It was sensed through measurement of the electrical conductivity between two electrodes that were clipped to the living plant leaf surfaces. This yields a relative signal that responds promptly to the presence of leaf wetness. A routine is presented that combines the data from several sensors to the dimensionless leaf wetness, LW, with values between zero and one. Periods of high leaf wetness (LW>0.9) were in most cases triggered by precipitation events. After termination of rain, LW decreased quickly at the forest sites and dropped to values below 0.1 within less than 24 hours in most cases. At the grassland sites, the formation of dew led to a more complex pattern, with the occurrence of diurnal cycles of LW. Although periods of low relative air humidity (e.g., rH<50%) are normally associated with periods of low leaf wetness, the extent of correlation between these two parameters at rH>60% varies between the different sites. The grassland sites show very similar distributions of the LW data with rH, indicating a positive correlation between LW and

  20. The times they are a-changin': seasonal variations of leaf spectra in relation with leaf biochemical and biophysical properties

    NASA Astrophysics Data System (ADS)

    Yang, X.; Tang, J.; Mustard, J. F.

    2013-12-01

    Leaf traits such as chlorophyll concentration, leaf mass per area (LMA), and mesophyll cell area exposed to the internal area space per leaf area (Ames/A) are key biochemical or biophysical properties to understand the vegetation functioning. Measurements of leaf spectra provided a non-destructive way to estimate those parameters. Many studies have linked leaf spectra with some of leaf traits successfully, but the understanding of spectra-traits relationship is still limited in the following aspects: (1) how does the ability of spectra to estimate leaf traits change (or not) throughout the growing season? (2) How to quantify leaf internal structure with leaf spectra? (3) What are the leaf traits that contribute to the structure parameter in leaf reflectance model such as PROSPECT? To answer the questions above, we conducted weekly measurements of leaf spectra, leaf biochemical properties (chlorophyll, carotenoids, water, and total carbon and nitrogen) and biophysical properties (LMA and internal structures) during the growing seasons of year 2011 and 2012. We found that leaf traits express themselves in the leaf spectra at different wavelengths; the relationships between spectra and leaf traits vary throughout the season. Leaf internal structure parameters are mostly related to the near-infrared reflectance. The structure parameter (N) in PROSPECT is related to the Ames/A, LMA, and water content. Our results have broad implications for using hyperspectral imagers/sensors to monitor vegetations that have clear seasonal patterns.

  1. Evaluation of Methane from Sisal Leaf Residue and Palash Leaf Litter

    NASA Astrophysics Data System (ADS)

    Arisutha, S.; Baredar, P.; Deshpande, D. M.; Suresh, S.

    2014-12-01

    The aim of this study is to evaluate methane production from sisal leaf residue and palash leaf litter mixed with different bulky materials such as vegetable market waste, hostel kitchen waste and digested biogas slurry in a laboratory scale anaerobic reactor. The mixture was prepared with 1:1 proportion. Maximum methane content of 320 ml/day was observed in the case of sisal leaf residue mixed with vegetable market waste as the feed. Methane content was minimum (47 ml/day), when palash leaf litter was used as feed. This was due to the increased content of lignin and polyphenol in the feedstock which were of complex structure and did not get degraded directly by microorganisms. Sisal leaf residue mixtures also showed highest content of volatile fatty acids (VFAs) as compared to palash leaf litter mixtures. It was observed that VFA concentration in the digester first increased, reached maximum (when pH was minimum) and then decreased.

  2. Leaf anatomy mediates coordination of leaf hydraulic conductance and mesophyll conductance to CO2 in Oryza.

    PubMed

    Xiong, Dongliang; Flexas, Jaume; Yu, Tingting; Peng, Shaobing; Huang, Jianliang

    2017-01-01

    Leaf hydraulic conductance (Kleaf ) and mesophyll conductance (gm ) both represent major constraints to photosynthetic rate (A), and previous studies have suggested that Kleaf and gm is correlated in leaves. However, there is scarce empirical information about their correlation. In this study, Kleaf , leaf hydraulic conductance inside xylem (Kx ), leaf hydraulic conductance outside xylem (Kox ), A, stomatal conductance (gs ), gm , and anatomical and structural leaf traits in 11 Oryza genotypes were investigated to elucidate the correlation of H2 O and CO2 diffusion inside leaves. All of the leaf functional and anatomical traits varied significantly among genotypes. Kleaf was not correlated with the maximum theoretical stomatal conductance calculated from stomatal dimensions (gsmax ), and neither gs nor gsmax were correlated with Kx . Moreover, Kox was linearly correlated with gm and both were closely related to mesophyll structural traits. These results suggest that Kleaf and gm are related to leaf anatomical and structural features, which may explain the mechanism for correlation between gm and Kleaf .

  3. Effect of harvest timing and leaf hairiness on fiber quality

    USDA-ARS?s Scientific Manuscript database

    Recent concerns over leaf grades have generated questions of how both time of day cotton is harvested, as well as leaf hairiness levels of certain varieties, influence fiber quality. To address this, two smooth leaf varieties and two varieties with higher levels of leaf pubescence were harvested at...

  4. 7 CFR 30.31 - Classification of leaf tobacco.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Classification of leaf tobacco. 30.31 Section 30.31... REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this classification leaf tobacco...

  5. 7 CFR 30.31 - Classification of leaf tobacco.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Classification of leaf tobacco. 30.31 Section 30.31... REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this classification leaf tobacco...

  6. 7 CFR 30.31 - Classification of leaf tobacco.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Classification of leaf tobacco. 30.31 Section 30.31... REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this classification leaf tobacco...

  7. 7 CFR 30.31 - Classification of leaf tobacco.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Classification of leaf tobacco. 30.31 Section 30.31... REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this classification leaf tobacco...

  8. 7 CFR 30.31 - Classification of leaf tobacco.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Classification of leaf tobacco. 30.31 Section 30.31... REGULATIONS TOBACCO STOCKS AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.31 Classification of leaf tobacco. For the purpose of this classification leaf tobacco...

  9. What Is a Leaf? An Online Tutorial and Tests

    ERIC Educational Resources Information Center

    Burrows, Geoffrey

    2008-01-01

    A leaf is a fundamental unit in botany and understanding what constitutes a leaf is fundamental to many plant science activities. My observations and subsequent testing indicated that many students could not confidently and consistently recognise a leaf from a leaflet, or recognise basic leaf arrangements and the various types of compound or…

  10. 7 CFR 29.1163 - Smoking Leaf (H Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Smoking Leaf (H Group). 29.1163 Section 29.1163... REGULATIONS TOBACCO INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group consists of... Quality Orange Smoking Leaf Mellow, open leaf structure, medium body, lean in oil, strong color...

  11. 7 CFR 29.1163 - Smoking Leaf (H Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Smoking Leaf (H Group). 29.1163 Section 29.1163... REGULATIONS TOBACCO INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group consists of... Quality Orange Smoking Leaf Mellow, open leaf structure, medium body, lean in oil, strong color...

  12. 7 CFR 29.1163 - Smoking Leaf (H Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Smoking Leaf (H Group). 29.1163 Section 29.1163... REGULATIONS TOBACCO INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group consists of... Quality Orange Smoking Leaf Mellow, open leaf structure, medium body, lean in oil, strong color...

  13. 7 CFR 29.1163 - Smoking Leaf (H Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Smoking Leaf (H Group). 29.1163 Section 29.1163... REGULATIONS TOBACCO INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group consists of... Quality Orange Smoking Leaf Mellow, open leaf structure, medium body, lean in oil, strong color...

  14. 7 CFR 29.1163 - Smoking Leaf (H Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Smoking Leaf (H Group). 29.1163 Section 29.1163... REGULATIONS TOBACCO INSPECTION Standards Grades § 29.1163 Smoking Leaf (H Group). This group consists of... Quality Orange Smoking Leaf Mellow, open leaf structure, medium body, lean in oil, strong color...

  15. 7 CFR 29.3647 - Heavy Leaf (B Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., close leaf structure, rough, lean in oil, dull finish, pale color intensity, inelastic, narrow, 70..., medium body, close leaf structure, rough, lean in oil, dull finish, pale color intensity, inelastic... Leaf. Mature, heavy, close leaf structure, rough, lean in oil, dull finish, pale color intensity...

  16. 7 CFR 29.3648 - Thin Leaf (C Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... tolerance. C1F Choice Quality Medium-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, rich in oil... tolerance. C2F Fine Quality Medium-brown Thin Leaf. Ripe, thin, open leaf structure, smooth, rich in oil... that are thin to medium in body and show little or no ground injury. Grades Grade names, minimum...

  17. Effect of herbivore damage on broad leaf motion in wind

    NASA Astrophysics Data System (ADS)

    Burnett, Nicholas; Kothari, Adit

    2015-11-01

    Terrestrial plants regularly experience wind that imposes aerodynamic forces on the plants' leaves. Passive leaf motion (e.g. fluttering) and reconfiguration (e.g. rolling into a cone shape) in wind can affect the drag on the leaf. In the study of passive leaf motion in wind, little attention has been given to the effect of herbivory. Herbivores may alter leaf motion in wind by making holes in the leaf. Also, a small herbivore (e.g. snail) on a leaf can act as a point mass, thereby affecting the leaf's motion in wind. Conversely, accelerations imposed on an herbivore sitting on a leaf by the moving leaf may serve as a defense by dislodging the herbivore. In the present study, we investigated how point masses (>1 g) and holes in leaves of the tuliptree affected passive leaf motion in turbulent winds of 1 and 5 m s-1. Leaf motion was unaffected by holes in the leaf surface (about 10% of leaf area), but an herbivore's mass significantly damped the accelerations of fluttering leaves. These results suggest that an herbivore's mass, but not the damage it inflicts, can affect leaf motion in the wind. Furthermore, the damping of leaf fluttering from an herbivore's mass may prevent passive leaf motions from being an effective herbivore defense.

  18. What Is a Leaf? An Online Tutorial and Tests

    ERIC Educational Resources Information Center

    Burrows, Geoffrey

    2008-01-01

    A leaf is a fundamental unit in botany and understanding what constitutes a leaf is fundamental to many plant science activities. My observations and subsequent testing indicated that many students could not confidently and consistently recognise a leaf from a leaflet, or recognise basic leaf arrangements and the various types of compound or…

  19. Genetic control of leaf curl in maize.

    PubMed

    Entringer, G C; Guedes, F L; Oliveira, A A; Nascimento, J P; Souza, J C

    2014-03-17

    Among the many implications of climatic change on agriculture, drought is expected to continue to have a major impact on agribusinesses. Leaf curling is an anatomical characteristic that might be potentially used to enhance plant tolerance to water deficit. Hence, we aimed to study the genetic control of leaf curl in maize. From 2 contrasting inbred lines for the trait, generations F1, F2, and the backcrosses were obtained. All of these generations were evaluated in a randomized block design with 2 replicates. Leaf curl samples were collected from 3 leaves above the first ear at the tasseling stage, and quantified by dividing the width of the leaf blade with natural curling against its extended width. The mean and variance components were estimated by the weighted least square method. It was found that the trait studied has predominance of the additive effects, with genetic control being attributed to few genes that favor selection and exhibit minimal influence from the environment.

  20. Monitoring Air Quality with Leaf Yeasts.

    ERIC Educational Resources Information Center

    Richardson, D. H. S.; And Others

    1985-01-01

    Proposes that leaf yeast serve as quick, inexpensive, and effective techniques for monitoring air quality. Outlines procedures and provides suggestions for data analysis. Includes results from sample school groups who employed this technique. (ML)

  1. Interaction between photons and leaf canopies

    NASA Technical Reports Server (NTRS)

    Knyazikhin, Yuri V.; Marshak, Alexander L.; Myneni, Ranga B.

    1991-01-01

    The physics of neutral particle interaction for photons traveling in media consisting of finite-dimensional scattering centers that cross-shade mutually is investigated. A leaf canopy is a typical example of such media. The leaf canopy is idealized as a binary medium consisting of randomly distributed gaps (voids) and regions with phytoelements (turbid phytomedium). In this approach, the leaf canopy is represented by a combination of all possible open oriented spheres. The mathematical approach for characterizing the structure of the host medium is considered. The extinction coefficient at any phase-space location in a leaf canopy is the product of the extinction coefficient in the turbid phytomedium and the probability of absence gaps at that location. Using a similar approach, an expression for the differential scattering coefficient is derived.

  2. A hotspot model for leaf canopies

    NASA Technical Reports Server (NTRS)

    Jupp, David L. B.; Strahler, Alan H.

    1991-01-01

    The hotspot effect, which provides important information about canopy structure, is modeled using general principles of environmental physics as driven by parameters of interest in remote sensing, such as leaf size, leaf shape, leaf area index, and leaf angle distribution. Specific examples are derived for canopies of horizontal leaves. The hotspot effect is implemented within the framework of the model developed by Suits (1972) for a canopy of leaves to illustrate what might occur in an agricultural crop. Because the hotspot effect arises from very basic geometrical principles and is scale-free, it occurs similarly in woodlands, forests, crops, rough soil surfaces, and clouds. The scaling principles advanced are also significant factors in the production of image spatial and angular variance and covariance which can be used to assess land cover structure through remote sensing.

  3. Reflectance model of a plant leaf

    NASA Technical Reports Server (NTRS)

    Kumar, R.; Silva, L.

    1973-01-01

    A light ray, incident at 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's Equations and Snell's Law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A Spectroreflectometer. Similarly a light ray, incident at about 60 deg to the normal, is drawn through the palisade cells of a soybean leaf to illustrate the pathway of light, incident at an oblique angle, through the palisade cells.

  4. Photosynthesis and Respiration in Leaf Slices.

    ERIC Educational Resources Information Center

    Brown, Simon

    1998-01-01

    Demonstrates how leaf slices provide an inexpensive material for illustrating several fundamental points about the biochemistry of photosynthesis and respiration. Presents experiments that illustrate the effects of photon flux density and herbicides and carbon dioxide concentration. (DDR)

  5. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco...

  6. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco...

  7. 7 CFR 29.3528 - Leaf surface.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3528 Leaf surface. The roughness or smoothness of the web or lamina of a tobacco...

  8. The red edge of plant leaf reflectance

    NASA Technical Reports Server (NTRS)

    Horler, D. N. H.; Dockray, M.; Barber, J.

    1983-01-01

    A detailed study of the red edge spectral feature of green vegetation based on laboratory reflectance spectrophotometry is presented. A parameter lambda is defined as the wavelength is defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration. Species, development stage, leaf layering, and leaf water content of vegetation also influences lambda. The maximum slope parameter is found to be independent of simulated ground area coverage. The results are interpreted in terms of Beer's Law and Kubelka-Munk theory. The chlorophyll concentration dependence of lambda seems to be explained in terms of a pure absorption effect, and it is suggested that the existence of two lambda components arises from leaf scattering properties. The results indicate that red edge measurements will be valuable for assessment of vegetative chlorophyll status and leaf area index independently of ground cover variations, and will be particularly suitable for early stress detection.

  9. Spectroscopic Measurement of Leaf Water Status

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Boardman, Joseph W.

    1995-01-01

    A leaf drying experiment was carried out in the laboratory in which simultaneous spectral reflectance in the 350-2450 nm region, and leaf weights, were measured at 10 second intervals over a 40 minute period. As the leaf water weight dropped from approximately 60 to 38%. a nearly-linear rise in reflectance at all wavelengths beyond 1000 nm was observed. A principal components analysis of the time series of spectra in the 2000-2500 nm wavelength region showed that over 99% of the variance in the spectra, that were individually scaled to have a sum equal to that of the mean spectrum and subsequently mean corrected, was in the first component. This result shows that it is feasible to determine leaf water content remotely with an imaging spectrometer independent of the surface irradiance effects caused by topography.

  10. The red edge of plant leaf reflectance

    NASA Technical Reports Server (NTRS)

    Horler, D. N. H.; Dockray, M.; Barber, J.

    1983-01-01

    A detailed study of the red edge spectral feature of green vegetation based on laboratory reflectance spectrophotometry is presented. A parameter lambda is defined as the wavelength is defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration. Species, development stage, leaf layering, and leaf water content of vegetation also influences lambda. The maximum slope parameter is found to be independent of simulated ground area coverage. The results are interpreted in terms of Beer's Law and Kubelka-Munk theory. The chlorophyll concentration dependence of lambda seems to be explained in terms of a pure absorption effect, and it is suggested that the existence of two lambda components arises from leaf scattering properties. The results indicate that red edge measurements will be valuable for assessment of vegetative chlorophyll status and leaf area index independently of ground cover variations, and will be particularly suitable for early stress detection.

  11. Monitoring Air Quality with Leaf Yeasts.

    ERIC Educational Resources Information Center

    Richardson, D. H. S.; And Others

    1985-01-01

    Proposes that leaf yeast serve as quick, inexpensive, and effective techniques for monitoring air quality. Outlines procedures and provides suggestions for data analysis. Includes results from sample school groups who employed this technique. (ML)

  12. Photosynthesis and Respiration in Leaf Slices.

    ERIC Educational Resources Information Center

    Brown, Simon

    1998-01-01

    Demonstrates how leaf slices provide an inexpensive material for illustrating several fundamental points about the biochemistry of photosynthesis and respiration. Presents experiments that illustrate the effects of photon flux density and herbicides and carbon dioxide concentration. (DDR)

  13. Semi-Rolled Leaf2 modulates rice leaf rolling by regulating abaxial side cell differentiation.

    PubMed

    Liu, Xiaofei; Li, Ming; Liu, Kai; Tang, Ding; Sun, Mingfa; Li, Yafei; Shen, Yi; Du, Guijie; Cheng, Zhukuan

    2016-04-01

    Moderate leaf rolling maintains the erectness of leaves and minimizes the shadowing between leaves which is helpful to establish ideal plant architecture. Here, we describe asrl2(semi-rolled leaf2) rice mutant, which has incurved leaves due to the presence of defective sclerenchymatous cells on the abaxial side of the leaf and displays narrow leaves and reduced plant height. Map-based cloning revealed that SRL2 encodes a novel plant-specific protein of unknown biochemical function.SRL2 was mainly expressed in the vascular bundles of leaf blades, leaf sheaths, and roots, especially in their sclerenchymatous cells. The transcriptional activities of several leaf development-related YABBY genes were significantly altered in the srl2 mutant. Double mutant analysis suggested that SRL2 and SHALLOT-LIKE1(SLL1)/ROLLED LEAF9(RL9) function in distinct pathways that regulate abaxial-side leaf development. Hence, SRL2 plays an important role in regulating leaf development, particularly during sclerenchymatous cell differentiation.

  14. Semi-Rolled Leaf2 modulates rice leaf rolling by regulating abaxial side cell differentiation

    PubMed Central

    Liu, Xiaofei; Li, Ming; Liu, Kai; Tang, Ding; Sun, Mingfa; Li, Yafei; Shen, Yi; Du, Guijie; Cheng, Zhukuan

    2016-01-01

    Moderate leaf rolling maintains the erectness of leaves and minimizes the shadowing between leaves which is helpful to establish ideal plant architecture. Here, we describe a srl2 (semi-rolled leaf2) rice mutant, which has incurved leaves due to the presence of defective sclerenchymatous cells on the abaxial side of the leaf and displays narrow leaves and reduced plant height. Map-based cloning revealed that SRL2 encodes a novel plant-specific protein of unknown biochemical function. SRL2 was mainly expressed in the vascular bundles of leaf blades, leaf sheaths, and roots, especially in their sclerenchymatous cells. The transcriptional activities of several leaf development-related YABBY genes were significantly altered in the srl2 mutant. Double mutant analysis suggested that SRL2 and SHALLOT-LIKE1 (SLL1)/ROLLED LEAF9 (RL9) function in distinct pathways that regulate abaxial-side leaf development. Hence, SRL2 plays an important role in regulating leaf development, particularly during sclerenchymatous cell differentiation. PMID:26873975

  15. Nutrient influences on leaf photosynthesis

    SciTech Connect

    Longstreth, D.J.; Nobel, P.S.

    1980-01-01

    The net rate of CO/sub 2/ uptake for leaves of Gossypium hirsutum L. was reduced when the plants were grown at low concentrations of NO/sub 3//sup -/, PO/sub 4//sup 2 -/, or K/sup +/. The water vapor conductance was relatively constant for all nutrient levels, indicating little effect on stomatal response. Although leaves under nutrient stress tended to be lower in chlorophyll and thinner, the ratio of mesophyll surface area to leaf area did not change appreciably. Thus, the reduction in CO/sub 2/ uptake rate at low nutrient levels was due to a decrease in the CO/sub 2/ conductance expressed per unit mesophyll cell wall area (g/sub CO/sup cell//sub 2/). The use of g/sub CO//sup cell//sub 2/ and nutrient levels expressed per unit of mesophyll cell wall provides a new means of assessing nutrient effects on CO/sub 2/ uptake of leaves. 14 figures, 1 table.

  16. Characterization of potato leaf starch.

    PubMed

    Santacruz, Stalin; Koch, Kristine; Andersson, Roger; Aman, Per

    2004-04-07

    The starch accumulation-degradation process as well as the structure of leaf starch are not completely understood. To study this, starch was isolated from potato leaves collected in the early morning and late afternoon in July and August, representing different starch accumulation rates. The starch content of potato leaves varied between 2.9 and 12.9% (dry matter basis) over the night and day in the middle of July and between 0.6 and 1.5% in August. Scanning electron microscopy analyses of the four isolated starch samples showed that the granules had either an oval or a round shape and did not exceed 5 microm in size. Starch was extracted by successive washing steps with dimethyl sulfoxide and precipitated with ethanol. An elution profile on Sepharose CL-6B of debranched starch showed the presence of a material with a chain length distribution between that generally found for amylose and amylopectin. Amylopectin unit chains of low molecular size were present in a higher amount in the afternoon than in the morning samples. What remains at the end of the night is depleted in specific chain lengths, mainly between DP 15 and 24 and above DP 35, relative to the end of the day.

  17. Remote sensing of leaf water status

    NASA Technical Reports Server (NTRS)

    Ripple, William J.; Schrumpf, Barry J.

    1987-01-01

    Relative water content (RWC) measurements were made concurrently with spectral reflectance measurements from individual snapbean leaves. The relationships between spectra and RWC were described using second order polynomial equations. The middle infrared bands most sensitive to changes in leaf RWC also had the highest water absorption coefficients, as published by Curcio Petty (1951). The relationship between reflectance at 2100nm and total water potential for a single leaf was found to be linear.

  18. Antibacterial activity on Citrullus colocynthis Leaf extract

    PubMed Central

    gowri, S. Shyamala; Priyavardhini, S.; Vasantha, K.; Umadevi, M.

    2009-01-01

    Studies on the antibacterial activities of the leaf extract of Citrullus colocynthis (Cucurbitaceae), a medicinal plant used for the treatment of various ailments was carried out using agar disc diffusion technique. The results revealed that the crude acetone extract exhibited antibacterial activities against Pseudomonas aeruginosa with zones of inhibition measuring 14.0mm. The chloroform leaf extract exhibited no antibacterial activity against Staphylococcus aureus. The minimum inhibitory concentration for the chloroform extract was 4.0mm for Escherichia coli. PMID:22557336

  19. An esterase gene from Lactobacillus casei cotranscribed with genes encoding a phosphoenolpyruvate:sugar phosphotransferase system and regulated by a LevR-like activator and sigma54 factor.

    PubMed

    Yebra, María J; Viana, Rosa; Monedero, Vicente; Deutscher, Josef; Pérez-Martínez, Gaspar

    2004-01-01

    A new esterase-encoding gene was found in the draft genome sequence of Lactobacillus casei BL23 (CECT5275). It is located in an operon together with genes encoding the EIIA, EIIB, EIIC, and EIID proteins of a mannose class phosphoenolpyruvate:sugar phosphotransferase system. After overproduction in Escherichia coli and purification, the esterase could hydrolyze acetyl sugars, hence the operon was named esu for esterase-sugar uptake genes. Upstream of the genes encoding the EII components (esuABCD) and the esterase (esuE), two genes transcribed in the opposite sense were found which encode a Bacillus subtilis LevR-like transcriptional activator (esuR) and a sigma54-like transcriptional factor (rpoN). As compared with the wild-type strain, elevated fructose phosphorylation was detected in L. casei mutants constitutively expressing the esu operon. However, none of the many sugars tested could induce the esu operon. The fact that EsuE exhibits esterase activity on acetyl sugars suggests that this operon could be involved in the uptake and metabolism of esterified sugars. Expression of the esu operon is similar to that of the B. subtilis lev operon: it contains a -12,-24 consensus promoter typical of sigma54-regulated genes, and EsuR and RpoN are essential for its transcription which is negatively regulated by EIIB(Esu). The esuABCDE transcription unit represents the first sigma54-regulated operon in lactobacilli. Furthermore, replacement of His852 in the phosphoenolpyruvate:sugar phosphotransferase system regulation domain II of EsuR with Ala indicated that the transcription activator function of EsuR is inhibited by EIIB(Esu)-mediated phosphorylation at His852.

  20. Phosphorylation of bacterial-type phosphoenolpyruvate carboxylase by a Ca2+-dependent protein kinase suggests a link between Ca2+ signalling and anaplerotic pathway control in developing castor oil seeds.

    PubMed

    Hill, Allyson T; Ying, Sheng; Plaxton, William C

    2014-02-15

    The aim of the present study was to characterize the native protein kinase [BTPC (bacterial-type phosphoenolpyruvate carboxylase)-K (BTPC Ser451 kinase)] that in vivo phosphorylates Ser451 of the BTPC subunits of an unusual Class-2 PEP (phosphoenolpyruvate) carboxylase hetero-octameric complex of developing COS (castor oil seeds). COS BTPC-K was highly purified by PEG fractionation and hydrophobic size-exclusion anion-exchange and affinity chromatographies. BTPC-K phosphorylated BTPC strictly at Ser451 (Km=1.0 μM; pH optimum=7.3), a conserved target residue occurring within an intrinsically disordered region, as well as the protein histone III-S (Km=1.7 μM), but not a COS plant-type PEP carboxylase or sucrose synthase or α-casein. Its activity was Ca2+- (K0.5=2.7 μM) and ATP- (Km=6.6 μM) dependent, and markedly inhibited by trifluoperazine, 3-phosphoglycerate and PEP, but insensitive to calmodulin or 14-3-3 proteins. BTPC-K exhibited a native molecular mass of ~63 kDa and was soluble rather than membrane-bound. Inactivation and reactivation occurred upon BTPC-K's incubation with GSSG and then DTT respectively. Ser451 phosphorylation by BTPC-K inhibited BTPC activity by ~50% when assayed under suboptimal conditions (pH 7.3, 1 mM PEP and 10 mM L-malate). Our collective results indicate a possible link between cytosolic Ca2+ signalling and anaplerotic flux control in developing COS.