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PubMed1981

Soluble Cell Wall Polysaccharides Released from Pea Stems by Centrifugation : I. EFFECT OF AUXIN.

The metabolism of polysaccharides by pea stem segments treated with and without auxin was investigated using a centrifugation technique for removing solution from the free space of the cell wall. Glucose is the predominant sugar in both the ethanol-soluble and ethanol-insoluble fractions of the cell wall solution extracted with water. In the water-soluble, ethanol-insoluble polysaccharides, arabinose, xylose, galactose, and glucose make up 9.5, 23.8, 23.9, and 39.9%, respectively, of the neutral sugars, while rhamnose, fucose, and mannose are present at concentrations between 0.5 and 2.0%.Auxin treatment enhances the levels of xylose and glucose in ethanol-insoluble polysaccharides relative to controls, and this difference can be detected within 30 minutes of auxin treatment. Cellulose-binding experiments show that the enhanced levels of xylose and glucose are in a polymer having the cellulose-binding properties of xyloglucan. (3)H-glucose labeling experiments confirm the auxin-enhanced metabolism of the xyloglucan fraction; however, increased labeling of arabinose is also observed in auxin-treated sections. Auxin treatment also causes a marked increase in the level of uronic acids centrifuged from pea internode sections. Thus, after 3 hours of incubation in indoleacetic acid, the level of uronic acids in the ethanol-insoluble polysaccharides which can be recovered by centrifugation is increased 2- to 3-fold over sections incubated in water. These auxin-enhanced changes in xylose, glucose, and uronic acids are correlated with enhanced rates of section growth.Incubation of excised pea internode sections in acidic buffers also enhances the rate of xyloglucan and polyuronide metabolism. This acid-enhanced metabolism of xyloglucan and polyuronide is inhibited by low temperature, suggesting that it is enzyme-mediated.Extraction of the cell wall solution with CaCl(2) increases the yield of all neutral sugars. Arabinose and mannose are increased 4- and 3-fold, respectively, and xylose and glucose by about 20%, while galactose levels are 40% higher in cell wall solution extracted with CaCl(2) than in that extracted with water. Although calcium increases the amount of neutral sugars extracted, it does not affect the auxin-induced changes in neutral sugars. Extraction of the cell wall solution with ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'tetraacetic acid enhances the yield of uronic acids and also increases the difference due to auxin treatment.

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PubMed1981

Effects of Light and of Fusarium solani on Synthesis and Activity of Phenylalanine Ammonia-Lyase in Peas.

Phenylalanine ammonia-lyase was purified from peas, and a specific antiserum against the enzyme was produced in rabbits. The antiserum was used to study the first 8 hours of the phenylalanine ammonia-lyase activity response in two different organs of the pea from different developmental stages and in response to two different stimuli. Etiolated seedlings were pulse-labeled with l-[(35)S]methionine after either no light exposure or after specific periods of irradiation with blue light. Immature pods were pulse labeled with mixed l-[(3)H]amino acids after specific time periods following inoculation of the pod endocarp surfaces with macroconidia of Fusarium solani. Immunoprecipitates isolated from extracts of each group were analyzed with sodium dodecyl sulfate disc gel electrophoresis and were found to contain a radioactive protein with an electrophoretic mobility identical to that of the phenylalanine ammonia-lyase subunit (M(r) 81,000). The radioactivity contained in the subunit band was interpreted as being due to de novo synthesis of the enzyme. The net rate of phenylalanine ammonia-lyase labeling, found to be initially low in both tissue types, rose dramatically, peaking at approximately a six- to ten-fold greater level at 4 hours after the beginning of the stimulus. Thereafter, the rate of labeling declined slowly. Inoculation with F. solani f. sp. pisi, a true pathogen of peas, caused a fifty per cent greater rate of peak labeling than did inoculation with a nonpathogen, F. solani f. sp. phaseoli. The time profile of the changing rate of labeling correlates with the changing activity level of the enzyme which peaks at 12 hours after the onset of the stimulus. The data presented favor a model which explains the changing activity of phenylalanine ammonia-lyase as being due to a changing rate of synthesis or degradation (or both) of the enzyme rather than due to the activation of a preformed zymogen.

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PubMed1981

Hexokinase II of Pea Seeds.

A second hexokinase (EC 2.7.1.1) was obtained from pea seed (Pisum sativum L. var. Progress No. 9) extracts. The enzyme, termed hexokinase II, had a high affinity (K(m), 48 micromolar) for glucose and a relatively low affinity (K(m), 10 millimolar) for fructose. The K(m) for MgATP was 86 micromolar. Mg(2+) was required for activity, but excess Mg(2+) was inhibitory. MgADP inhibited hexokinase II. The addition of salts of monovalent cations increased hexokinase II activity. Al(3+) was a strong inhibitor of the enzyme at pH 6.6 but not at the optimum pH (8.2). Citrate and 3-phosphoglycerate activated pea seed hexokinase II at pH 6.6, probably by coordinating with aluminum present as a contaminant in commercial ATP. The properties of hexokinase II are compared with those of the other three hexose kinases obtained from pea seed extracts. The possible role of these enzymes in plant carbohydrate metabolism is discussed.

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PubMed1981

The effect of rotenone on respiration in pea cotyledon mitochondria.

Respiration utilizing NAD-linked substrates in mitochondria isolated from cotyledons of etiolated peas (Pisum sativum L. var. Homesteader) by sucrose density gradient centrifugation exhibited resistance to rotenone. The inhibited rate of alpha-ketoglutarate oxidation was equivalent to the recovered rate of malate oxidation. (The recovered rate is the rate following the transient inhibition by rotenone.) The inhibitory effect of rotenone on malate oxidation increased with increasing respiratory control ratios as the mitochondria developed. The cyanide-resistant and rotenone-resistant pathways followed different courses of development as cotyledons aged. The rotenone-resistant pathway transferred reducing equivalents to the cyanide-sensitive pathway. Malic enzyme was found to be inhibited competitively with respect to NAD by rotenone concentrations as low as 1.67 micromolar. In pea cotyledon mitochondria, rotenone was transformed into elliptone. This reduced its inhibitory effect on intact mitochondria. Malate dehydrogenase was not affected by rotenone or elliptone. However, elliptone inhibited malic enzyme to the same extent that rotenone did when NAD was the cofactor. The products of malate oxidation reflected the interaction between malic enzyme and malate dehydrogenase. Rotenone also inhibited the NADH dehydrogenase associated with malate dehydrogenase. Thus, rotenone seemed to exert its inhibitory effect on two enzymes of the electron transport chain of pea cotyledon mitochondria.

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PubMed1982

Sequestration of pea reserve proteins by rough microsomes.

Free polysomes, polysomes released from membranes, and rough microsomal vesicles isolated from developing cotyledons of Pisum sativum L. cv. Burpeeana were used to direct cell-free protein synthesis in a wheat germ system. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the polypeptide products had molecular weights ranging from 12,000 to 74,000. Some of the polypeptides migrated during electrophoresis with the same mobility as polypeptides present in legumin and vicilin preparations. By the use of rabbit antibodies raised against pea reserve proteins it was established that polysomes released from membranes and rough microsomes directed the synthesis of polypeptides that were related to reserve proteins whereas free polysomes did not.Centrifugation studies indicated that the majority of the radioactivity incorporated by rough microsomes was specifically associated with the microsomes. The incorporated radioactivity of sedimented microsomes was not released by treatment with KCl and was resistant to proteolysis unless detergent was present. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the sequestered translation products were related to pea reserve proteins. It is concluded that the reserve proteins of pea cotyledons are synthesized exclusively by membrane-bound polysomes and that they are sequestered within the rough endoplasmic reticulum.

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PubMed1982

Evidence that Envelope and Thylakoid Membranes from Pea Chloroplasts Lack Glycoproteins.

Envelope and thylakoid membranes from pea (Pisum sativum var. Laxton's Progress No. 9) chloroplasts were analyzed for the presence of glycoproteins using two different approaches. First, the sugar composition of delipidated membrane polypeptides was measured directly using gas chromatographic analysis. The virtual absence of sugars suggests that plastid membranes lack glycoproteins. Second, membrane polypeptides separated by sodium dodecyl sulfate gel electrophoresis were tested for reactivity toward three different lectins: Concanavalin A, Ricinus communis agglutinin, and wheat germ agglutinin. In each case, there was no reactivity between any of the lectins and the plastid polypeptides. Microsomal membranes from pea tissues were used as a positive control. Glycoproteins were readily detectable in microsomal membranes using either of the two techniques. From these results it was concluded that pea chloroplast membranes do not contain glycosylated polypeptides.

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PubMed1983

A new growth inhibitor, pisumin, involved in light inhibition of epicotyl growth of dwarf peas.

A new growth inhibitor, tentatively named pisumin, which increased under red light and remained at initial level or decreased when dwarf pea (Pisum sativum L. cv Progress No. 9) seedlings were transferred from red light to dark, has been isolated in the form of a colorless powder from light-exposed epicotyls of dwarf peas, and characterized partially as an aliphatic carboxylic acid (molecular weight 284) by spectrometric analyses.Exogenous pisumin inhibited the growth of epicotyl segments of dwarf peas at concentrations higher than 0.1 millimolar in the dark.

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PubMed1984

Utilization of the amide groups of asparagine and 2-hydroxysuccinamic Acid by young pea leaves.

The fate of nitrogen originating from the amide group of asparagine in young pea leaves (Pisum sativum) has been studied by supplying [(15)N-amide]asparagine and its metabolic product, 2-hydroxysuccinamate (HSA) via the transpiration stream. Amide nitrogen from asparagine accumulated predominantly in the amide group of glutamine and HSA, and to a lesser extent in glutamate and a range of other amino acids. Treatment with 5-diazo,4-oxo-L-norvaline (DONV) a deamidase inhibitor, caused a decrease in transfer of label to glutamine-amide. Virtually no (15)N was detected in HSA of leaves supplied with asparagine and the transaminase inhibitor aminooxyacetate. When [(15)N]HSA was supplied to pea leaves, most of the label was also found in the amide group of glutamine and this transfer was blocked by the addition of methionine sulfoximine, which caused a large increase in NH(3) accumulation. DONV was not specific for asparaginase, and inhibited the deamidation of HSA, causing a decrease in transfer of (15)N into glutamine-amide, NH(3), and other amino acids. It is concluded from these results that use of the amide group of asparagine as a nitrogen source for young pea leaves involves deamidation of both asparagine and its transamination product HSA (possibly also oxosuccinamate). The amide group, released as ammonia, is then reassimilated via the glutamine synthetase/glutamate synthase system.

Journal Article↗
PubMed1984

Pea xyloglucan and cellulose : I. Macromolecular organization.

A macromolecular complex composed of xyloglucan and cellulose was obtained from elongating regions of etiolated pea (Pisum sativum L. var. Alaska) stems. Xyloglucan could be solubilized by extraction of this complex with 24% KOH-0.1% NaBH(4) or by extended treatment with endo-1,4-beta-glucanase. The polysaccharide was homogeneous by ultracentrifugal analysis and gel filtration on Sepharose CL-6B, molecular weight 330,000. The structure of pea xyloglucan was examined by fragmentation analysis of enzymic hydrolysates, methylation analysis, and precipitation tests with fucose- or galactose-binding lectins. The polysaccharide was composed of equal amounts of two subunits, a nonasaccharide (glucose/xylose/galactose/fucose, 4:3:1:1) and a heptasaccharide (glucose/xylose, 4:3), which appeared to be distributed at random, but primarily in alternating sequence. The xyloglucan:cellulose complex was examined by light microscopy using iodine staining, by radioautography after labeling with [(3)H]fucose, by fluorescence microscopy using a fluorescein-lectin (fucose-binding) as probe, and by electron microscopy after shadowing. The techniques all demonstrated that the macromolecule was present in files of cell shapes, referred to here as cell-wall ;ghosts,' in which xyloglucan was localized both on and between the cellulose microfibrils. Since the average chain length of pea xyloglucan was many times the diameter of cellulose microfibrils, it could introduce cross-links by binding to adjacent fibrils and thereby contribute rigidity to the wall.

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PubMed1985

Studies on N-glycosylation by elongating tissues and membranes from pea stems.

Glucosamine and mannose were incorporated into oligosaccharides linked to either polar membrane-lipids or to asparagine residues of endogenous proteins in apical growing tissues of the etiolated pea stem. The glycolipids were subject to turnover in pulse-chase tests and protein-linked oligosaccharides accumulated with time, as expected for a precursor-product relationship. The newly formed glycoproteins were hydrolyzed by endo-beta-N-acetylglucosaminidase H to oligosaccharides in the same size range as those released by dilute acid from the lipid-linked oligosaccharides formed during the pulse. The glycoproteins were also partly degraded to free N-acetylglucosamine by beta-N-acetylhexosaminidase. Affinity of the carbohydrate moiety of the protein for concanavalin A increased between the beginning and the end of the chase, indicating processing following core glycosylation.The addition of UDP-N-acetyl-[(14)C]glucosamine plus external peptide acceptors (derived from carboxymethylated alpha-lactalbumin) to membrane preparations from the pea stem resulted in peptide glycosylation at the expense of lipid-linked oligosaccharide. Glycosylation of endogenous protein acceptors did not take place via lipid intermediates but directly from the sugar nucleotide substrate. Tunicamycin inhibited glycosyltransfer to both glycolipids and added peptides, but not to endogenous protein. It is concluded that limiting factors for N-glycosylation by pea membranes in vitro could include the unavailability of endogenous acceptors or the inability to fully elongate and internalize lipid precursors, but is not due to any limitation in capacity for N-glycosylation.

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PubMed1985

Homology among 3S and 7S Globulins from Cereals and Pea.

The globulins from wheat caryopses were found to consist primarily of protein sedimenting at approximately 3S and 7S. These proteins displayed a molecular weight distribution similar to that of the purified vicilin-like fractions from oat and pea, with variations occurring in the isoelectric points and relative quantities of their major subunits. concanavalin A Sepharose chromatography suggested that the major polypeptides of the wheat (3S + 7S) fraction are glycosylated. Western blot analysis using antioat (3S + 7S) globulin immunoglobulin G revealed the vicilins from pea and the globulin fractions of oat, wheat, barley, rye, corn, and rice to contain immunologically homologous polypeptides. Major groups of polypeptides were shared by all the cereals and pea, including subunits of approximately 75, 50, 40 kilodaltons and 20 to 25 kilodaltons. These results indicate that legume-like 3S and 7S globulins have been conserved and are being expressed in cereals.

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PubMed1986

Distinction between Cytosol and Chloroplast Fructose-Bisphosphate Aldolases from Pea, Wheat, and Corn Leaves.

A reinvestigation of cytosol and chloroplast fructose-1,6-bisphosphate (FBP) aldolases from pea (Pisum sativum L.), wheat (Triticum aestivum L.) and corn leaves (Zea mays L.) revealed that the two isoenzymes can be separated by chromatography on diethylaminoethyl (DEAE)-cellulose although the separation was often less clear-cut than for the two aldolases from spinach leaves. Definite distinction was achieved by immunoprecipitation of the two isoenzymes with antisera raised against the respective isoenzymes from spinach leaves. The proportion of cytosol aldolase as part of total aldolase activity was 8, 9, 14, and 4.5% in spinach (Spinacia oleracea L.), pea, wheat, and corn leaves, respectively. For corn leaves we also obtained values of up to 15%. The K(m) (FBP) values were about 5-fold lower for the cytosol (1.1-2.3 micromolar concentration) than for the chloroplast enzymes (8.0-10.5 micromolar concentration). The respective K(m) (fructose-1-phosphate, F1P) values were about equal for the cytosol (1.0-2.3 millimolar concentration) and for the chloroplast aldolase (0.6-1.7 millimolar concentration). The ratio V (FIP)/V (FBP) was 0.20 to 0.27 for the cytosol and 0.07 to 0.145 for the chloroplast aldolase. Thus, cytosol and chloroplast aldolases from spinach, pea, wheat, and corn leaves differ quite considerably in the elution pattern from DEAE-cellulose, in immunoprecipitability with antisera against the respective isoenzymes from spinach leaves, and in the affinity to FBP.

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PubMed1986

ent-Kaurene Biosynthesis in Cell-Free Extracts of Excised Parts of Tall and Dwarf Pea Seedlings.

Investigations on the sites of ent-kaur-16-ene (ent-kaurene) biosynthesis were conducted with cell-free extracts from several excised parts of 10-, 13-, and 16-d-old tall and dwarf pea (Pisum sativum L.) seedlings. [(14)C]Mevalonic acid was incorporated into ent-kaurene in cell-free extracts from young developing leaves and elongating internodes of tall (;Alaska') and dwarf (;Progress No.9') pea seedlings at all three stages of development. ent-Kaurene biosynthesis also occurred readily in cell-free extracts from shoot tips, petioles, and stipules near the young elongating internodes. The ent-kaurene-synthesizing activity found in young developing tissues declined as tissues matured. Little or no activity was detectable in enzyme extracts from cotyledons and root tips at different stages. In light grown tall pea internodes ent-kaurene-synthesizing activity was low as they began to elongate, reached a maximum when the internodes reached about 2 cm in length and declined as they matured. Activity in extracts of dwarf shoot tips and internodes was generally lower than in equivalent tall plants, but the activity in dwarf leaves and stipules was somewhat higher than in tall plants. With the exception of root tips, there is a strong correlation between growth potential of a tissue and the rate of ent-kaurene biosynthesis in extracts from that tissue.

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PubMed1986

Photoperiod modification of [C]gibberellin a(12) aldehyde metabolism in shoots of pea, line g2.

In G2 peas (Pisum sativum L.) apical senescence occurs only in long days (LD), and indeterminate growth is associated with elevated gibberellin (GA) levels in the shoot in short days (SD). Metabolism of GA(12) aldehyde was investigated by feeding shoots grown in SD or LD with [(14)C]GA(12) aldehyde through the cut end of the stem for 0.5 to 6 hours in the light and analyzing the tissue extract by high performance liquid chromatography. More radioactive products were detected than can be accounted for by the two GA metabolic pathways previously known to be present in peas. Three of the major products appear to be GA conjugates, but an additional pathway(s) of GA metabolism may be present. The levels of putative C(20) GAs, [(14)C]GA(53), [(14)C]GA(44), [(14)C]GA(19), and/or [(14)C] GA(17), were all elevated in SD as compared to LD. Putative [(14)C]GA, was slightly higher in LD than in SD. Putative [(14)C]GA(53) was a major metabolite after 30 minutes of treatment in SD but had declined after longer treatment times to be replaced by elevated levels of putative [(14)C] GA(44) and [(14)C]GA(19/17). Metabolism of GA(20) was slow in both photoperiods. Although GA(20) and GA(19) are the major endogenous GAs as determined by gas chromatography-mass spectrometry, putative [(14)C]GA(20) and [(14)C]GA(19) were never major products of [(14)C]GA(12) aldehyde metabolism. Thus, photoperiod acts in G2 peas to change the rate of GA(53) production from GA(12) aldehyde, with the levels of the subsequent GAs on the 13-OH pathway being determined by the amount of GA(53) being produced.

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PubMed1987

Some properties of pea mitochondrial phospho-pyruvate dehydrogenase-phosphatase.

Reactivation of the pea mitochondrial pyruvate dehydrogenase complex was the result of dephosphorylation catalyzed by phospho-pyruvate dehydrogenase-phosphatase, an intrinsic component of the complex. Phosphatase activity was dependent upon divalent metal ions, with Mg(2+) more effective than Mn(2+) or Co(2+). The Michaelis constants for Mg(2+), Mn(2+), and Co(2+) were 3.8, 1.7, and 1.4 millimolar, respectively. Neither the rate nor the extent of activation of the phosphatase by Mg(2+) or Mn(2+) was effected by up to 100 units per assay of megamodulin. Calcium ions did not activate pea mitochondrial phospho-pyruvate dehydrogenase-phosphatase, and low concentrations of Ca(2+) antagonized activation by other divalent cations. Phosphatase activity was inhibited by fluoride and ortho-phosphate but not by molybdate or vanadate. Krebs cycle intermediates, adenylates, polyamines, amino acids, and phosphoamino acids were without effect upon pea mitochondrial phospho-pyruvate dehydrogenase-phosphatase activity in vitro.

Journal Article↗
PubMed1988

Evidence against the involvement of ionically bound cell wall proteins in pea epicotyl growth.

Ionically bound cell wall proteins were extracted from 7 day old etiolated pea (Pisum sativum L. cv Alaska) epicotyls with 3 molar LiCl. Polyclonal antiserum was raised in rabbits against the cell wall proteins. Growth assays showed that treatment of growing region segments (5-7 millimeters) of peas with either dialyzed serum, serum globulin fraction, affinity purified immunoglobulin, or papain-cleaved antibody fragments had no effect on growth. Immunofluorescence microscopy confirmed antibody binding to cell walls and penetration of the antibodies into the tissues. Western blot analysis, immunoassay results, and affinity chromatography utilizing Sepharose-bound antibodies confirmed recognition of the protein preparation by the antibodies. Experiments employing in vitro extension as a screening measure indicated no effect upon extension by antibodies, by 50 millimolar LiCl perfusion of the apoplast or by 3 molar LiCl extraction. Addition of cell wall protein to protease pretreated segments did not restore extension nor did addition of cell wall protein to untreated segments increase extension. It is concluded that, although evidence suggests that protein is responsible for the process of extension, the class(es) of proteins which are extracted from pea cell walls with 3 molar LiCl are probably not involved in this process.

Autolysis↗
PubMed1988

Sucrose and Malic Acid as the Compounds Exported to the Apical Bud of Pea following CO(2) Labeling of the Fruit : No Evidence for a Senescence Factor.

The G2 line of peas (Pisum sativum L.) displays senescence and death of the apical bud only in long days and in the presence of fruit. As the removal of fruit prevents senescence, one possible mechanism by which fruits induce senescence is that the fruits produce some ;senescence factor' under long day conditions, which is then transported to the apical bud. Allowing developing fruits to photosynthesize in the presence of (14)CO(2) results in the recovery of label in the apical bud. In order to determine the chemical nature of this radiolabeled material, fruits of G2 peas, growing under long days, were exposed to (14)CO(2) at the time when the first senescence symptoms start to appear. The radiolabeled material from apical buds was then extracted, purified, and identified. Using HPLC and GC-MS the major labeled compound found in the apical bud following exposure of pea fruits to (14)CO(2) was identified as sucrose, while malic acid was identified as the major ethyl acetate-soluble compound. These compounds accounted for about 73 and 16%, respectively, of the radioactivity in the apical bud. No other compounds were present in significant amounts. As neither of these chemicals is likely to have any kind of senescence effect, we report no evidence for a senescence factor.

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PubMed1988

Occurrence of alternative respiratory capacity in soybean and pea.

Capacity for the alternative respiratory pathway was assessed in leaf and root tissue of male-sterile and fertile soybean (Glycine max [L.] Merr.) plants and in leaf, embryonic axis, and epicotyl tissue as well as isolated mitochondria of pea (Pisum sativum L.) by measurement of oxygen uptake in the presence and absence of KCN and salicylhydroxamic acid. Male-sterile and fertile soybean tissues showed similar responses to the inhibitors, and both possessed a capacity for alternative respiration. We also found that tissue and isolated mitochondria from ;Progress No. 9' pea possessed alternative respiratory capacity similar to that of ;Alaska' pea.

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