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Plant Physiol. (1999) 120: 867-878 Sucrose Synthase in Legume Nodules Is Essential for Nitrogen Fixation1
Department of Environmental Biology, Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceridigion SY23 3EB, United Kingdom
The role of sucrose synthase (SS) in the fixation of N was examined in the rug4 mutant of pea (Pisum sativum L.) plants in which SS activity was severely reduced. When dependent on nodules for their N supply, the mutant plants were not viable and appeared to be incapable of effective N fixation, although nodule formation was essentially normal. In fact, N and C resources invested in nodules were much greater in mutant plants than in the wild-type (WT) plants. Low SS activity in nodules (present at only 10% of WT levels) resulted in lower amounts of total soluble protein and leghemoglobin and lower activities of several enzymes compared with WT nodules. Alkaline invertase activity was not increased to compensate for reduced SS activity. Leghemoglobin was present at less than 20% of WT values, so O2 flux may have been compromised. The two components of nitrogenase were present at normal levels in mutant nodules. However, only a trace of nitrogenase activity was detected in intact plants and none was found in isolated bacteroids. The results are discussed in relation to the role of SS in the provision of C substrates for N fixation and in the development of functional nodules.
Legume nodules are primarily dependent on the import and
metabolism of Suc to provide the energy and C skeletons for biological N fixation, the assimilation of ammonia, and the export of nitrogenous fixation products. Suc is synthesized in the leaves and exported in the
phloem to sinks such as the nodules. Once unloaded in the nodule
cortex, Suc must diffuse into the infected region of the nodule to be
metabolized. The products of Suc catabolism (usually malic acid;
Udvardi and Day, 1997 Suc is first metabolized by one of two enzymes, SS (EC 2.4.1.13) or AI
(EC 3.2.1.26; in mature nodules there is no acid invertase activity).
These reactions produce UDP-Glc and free hexoses, which, after
phosphorylation by hexokinases, enter the glycolytic or oxidative
pentose phosphate pathways and are metabolized to PEP. PEP is converted
to oxaloacetic acid and then to L-malate by PEPC (EC
4.1.1.31) and MDH (EC 1.1.1.37), respectively.
The initial hydrolysis of Suc is a key step in N fixation. The gene
encoding SS was discovered to be one of a class of genes termed
"nodulins," which are highly or uniquely expressed in nodules (Thummler and Verma, 1987 Less is known about AI, the other nodule enzyme capable of Suc
hydrolysis. AI does not appear to be regulated allosterically, and the
first AI gene has only recently been cloned from plants (Gallagher and
Pollock, 1998 These questions can now be addressed with the availability of
rug4 mutants of pea (Pisum sativum L.) in which
SS activity is greatly reduced (Craig et al., 1999 Preliminary analysis has shown that SS activity is also greatly reduced
in nodules produced by these mutants (Craig et al., 1999 Preliminary work on rug4 mutant nodules by Craig et al.
(1999) Plant Growth
Nodule Harvest and Growth Analysis Cabinet-grown plants were harvested at 3, 4, 5, and 6 weeks for growth analysis and assay of nodule biochemical parameters. Vermiculite was carefully washed from the roots of three replicate plants of each line, and nodules were quickly placed onto ice, weighed into 100- to 200-mg samples in screwcap vials, and frozen in liquid N. The remaining plants were divided into shoots and roots, and, with one nodule subsample, dried at 70°C for 48 h before weighing (total nodule dry weight was determined from the known total fresh weight and the measured fresh weight:dry weight ratio of the subsample). These plant fractions were milled, subsamples were weighed, and the total N content was determined (see below).Measurements of Nodule Gas-Exchange Parameters ANA and root respiration of intact, undisturbed plants were measured simultaneously and continuously using a flow-through gas system (Minchin et al., 1983 ) housed in a controlled-environment cabinet (Fisons Ltd., Altringham, UK), providing conditions identical to those described earlier. Nodulated root systems were sealed into the
growth pots and allowed to stabilize for 18 to 21 h in a flow of
air. At the start of the measurement period H2
and CO2 production were determined for nodulated
roots in air. After 5 min the root systems were exposed to a gas stream
containing 79% (v/v) Ar and 21% (v/v) O2.
H2 production was measured using an electrochemical H2 sensor (City Technology Ltd.,
Portsmouth, UK), as recently described by Witty and Minchin (1998).
Respiratory CO2 production was measured by IR gas
analysis. Maximum rates of ANA were determined from the maximum
predecline rate of H2 production (i.e. before any
Ar-induced decline; Minchin et al., 1983).
Measurement of Nitrogenase Activity in Isolated Bacteroids Bacteroids were isolated anaerobically from nodules of 4-week-old plants in an anaerobic chamber (Mark 3 system supplied by Don Whitley Scientific Limited, West Yorkshire, UK) and flushed with N using a method modified from Suganuma et al. (1998). Buffers were saturated
with Ar before use. Freshly harvested nodules were placed in 50 mM K-phosphate isolation buffer (pH 7.0) containing 200 mM sorbitol and 10 mM DTT, vacuum evacuated,
and saturated with Ar. The nodules were homogenized with a mortar and
pestle in the same buffer. The homogenate was filtered through
Miracloth prewetted with the isolation buffer. The filtrate was
centrifuged at 3000g for 5 min, and the pellet was washed
once with 50 mM Mops-KOH buffer (pH 7.0)
containing 200 mM sorbitol, 4 mM MgCl2, and 10 mM DTT. All operations were carried out at 4°C.
The resulting pellet was re-suspended in an assay buffer (see below)
and used to determine ARA (see below) and bacteroid soluble protein
content (Lowry et al., 1951).
Extraction of Host Plant and Bacteroid Proteins Nodules were homogenized in a mortar and pestle with 50 mM Mops-KOH (pH 7.0), 4 mM MgCl2, 20 mM KCl, 200 mM sorbitol, and 10 mM DTT at 0°C to 2°C (5 mL/g fresh weight). The homogenate was centrifuged at 20,000g for 30 min at 2°C. Samples (50 µL) of the supernatant fraction were retained for immediate PEPC assay, and 1-mL aliquots were desalted by low-speed centrifugation (180g for 1 min) through 5-mL columns of Bio-Gel P6DG (Bio-Rad) equilibrated with 50 mM Mops-KOH (pH 7) and 4 mM MgCl2. The desalted extract was used to assay for soluble protein (Lowry et al., 1951), Lb (Appleby and Bergersen,
1980), and several enzymes. PEPC, SS, AI, GS (EC 6.3.1.2), and
AAT (EC 2.6.1.1) assays were as described in Gonzalez et al. (1995).
MDH, PFK (EC 2.7.1.11), and PPi-dependent, Fru-6-P phosphotransferase
(EC 2.7.1.90) were assayed as described in Gordon (1991). NADH-GOGAT
(EC 1.4.1.13) was assayed using the method of Groat and Vance (1981).
PDC (EC 4.1.1.1) and ADH (EC 1.1.1.1) were assayed according to the
method of John and Greenway (1976).
Extraction of Bacteroid Proteins Nodules were extracted and the homogenate centrifuged as described above. The 20,000g pellet containing intact bacteroids was washed three times by resuspension in extraction buffer and recentrifugation at 20,000g for 30 min at 2°C. The washed pellet was re-suspended a fourth time in the same buffer lacking sorbitol and the bacteroids were broken by sonication (two 30-s pulses at 0°C). The supernatant obtained after a further centrifugation step (as before) was retained for soluble protein determination (see above). SDS-PAGE and immunoblotting of nitrogenase proteins are described below.SDS-PAGE and Immunoblotting Soluble host plant protein and bacteroid protein extracts were denatured and prepared for electrophoresis and blotting as described in Gordon and Kessler (1990) and Cresswell et al. (1992). Nitrocellulose
membranes onto which host plant proteins were blotted were probed with
antibodies specific for SS (Gordon et al., 1992), Lb (Gordon and
Kessler, 1990) and GS (provided by J.V. Cullimore, Warwick University,
UK). Bacteroid proteins were detected using antibodies specific for
nitrogenase components 1 and 2 (provided by P.W. Ludden, University of
Wisconsin, Madison). Color development using a secondary antibody
conjugated to horseradish peroxidase was as described in Gordon and
Kessler (1990).
Nodule Extraction for Carbohydrates and Total Amino Acids and Amides Nodules (approximately 0.2 g fresh weight) were extracted four times in a total of approximately 50 mL of boiling 80% (v/v) ethanol. The ethanol-soluble extracts were dried under vacuum, and the soluble compounds were redissolved in 4 mL of distilled water and centrifuged at 20,000g for 10 min. The supernatant fluid was frozen in liquid N and stored at 80°C for later analysis. The
ethanol-insoluble residue was extracted for starch as in MacRae (1971),
and Glc was analyzed as described below.
Soluble Carbohydrate Analysis Glc, Fru, and Suc were determined using a plate reader (model EL340, Bio-Tek Instruments, Winooski, VT) at 340 nm in enzymic reactions coupled to the production of NADH. Samples (up to 50 µL) in the wells of a 96-well plate were assayed for Glc after incubation with 200 µL of buffer (50 mM imidazole, pH 7.0, 1 mM MgCl2, 0.75 mM NAD, and 0.85 mM ATP) containing 0.04 unit of Glc-6-P dehydrogenase from Leuconostoc mesenteroides and 0.1 unit of hexokinase. Fru and Suc were estimated in the same way after further additions of phospho-Glc isomerase (0.4 unit/well) and acid invertase (20 units/well), respectively.Nitrogenous Compounds Total free amino acids were assayed according to the method of Vogels and Van der Drift (1970). The total N content of dried, milled
plant tissue samples was determined using a mass spectrometer (model
20/20, Europa Scientific, Cheshire, UK) coupled to a solid/liquid preparation module.
Plant Growth Plants of the rug4 mutant of pea, grown with an adequate supply of nitrate, were visually indistinguishable from WT plants, apart from the wrinkled appearance of the seed, which was the means by which they were originally selected.
N Accumulation
N Content N accumulated in WT plants from an initial value of 11 mg per seed to approximately 160 mg per plant at 6 weeks (Fig. 2). In contrast, mutant seeds contained somewhat lower amounts of N (8 mg per seed) and accumulation during growth was severely impaired. In rug4-a, in particular, the N content of the whole plant at 6 weeks appeared to be no higher than that present in the original seed.
Nodule ANA ANA of mutant plants was barely detectable and was only about 3% of WT rates at 5 weeks (Table I). The effect of raising external O2 concentration was to increase ANA somewhat in the mutant plants. However, the fact that ANA was still extremely low compared with WT, even under elevated O2, indicates that mutant nodules lacked sufficient metabolic capacity to function at higher rates. Exposing nodulated roots of intact WT plants to elevated O2 levels tended to decrease ANA.
Nitrogenase Activity of Isolated Bacteroids Although little ANA was detected in the mutants with whole plant assays, nitrogenase proteins were present in the bacteroids (see below), and it remained a possibility that nitrogenase was active, but was limited by C sub-strates and/or O2. However, anaerobically isolated bacte-roids of mutant nodules from 23-d-old plants displayed no measurable nitrogenase activity when assayed in the presence of optimal O2 concentrations (determined with bacteroids isolated from WT nodules) and with succinate as the C substrate. In contrast, nitrogenase activity of isolated bacteroids from control WT plants of the same age was substantial (253 ± 13 nmol acetylene h 1 mg1 bacteroid
protein; n = 19).
Biochemistry The precise effect of the mutation was assessed by analyzing protein, Lb, and SS levels (Fig. 3), maximum catalytic activities of a selection of nodule enzymes (Fig. 4), and by immunoblotting using specific antibodies (Fig. 5).
Nodule Enzymes In assays of host plant enzymes we confirmed that the nodules of mutant plants contained much reduced activities of SS (in the Suc cleavage and Suc synthesis directions) compared with activities in WT nodules (Figs. 3 and 4). The 90% reduction in activity (expressed g1 fresh weight) measured here
compares with about 95% reduction in activity when these plants were
grown in less favorable conditions (Craig et al., 1999). Associated
with this reduced SS activity, total host plant soluble protein content
of nodules declined from approximately 70% of WT levels at 3 weeks to
approximately 40% of WT levels at 6 weeks (Fig. 3). Lb was present at
less than 20% of WT levels and, in addition to reduced SS activity,
may have contributed to the inability of mutant nodules to fix
N2.
Western Blotting Immunoblotting provided a more direct measure of the amounts of specific polypeptides associated with Lb and some enzymes (Fig. 5). The low GS and Lb levels indicated by direct assay were reflected in the lower amounts of protein recognized by specific antibodies. However, the SS polypeptide content of the two mutants was not consistently related to measured enzyme activity. The amount of SS subunit in rug4-b nodules appeared to be about the same as that in WT nodules, although activity was much lower (Figs. 4 and 5). In rug4-a nodules, in contrast, the lower SS polypeptide content indicated by immunoblotting more closely matched the low enzyme activity. Therefore, the reason for the low SS activity in vitro does not appear to be the same for these two mutants.Metabolite Levels The data in Figure 6 are expressed on a starch-free dry-weight basis to eliminate the large but variable contribution that starch made to nodule dry weight. Starch-free dry weight corresponds to nodule structural dry weight. During growth between 3 and 6 weeks, there were no significant differences in the Suc content of WT and mutant nodules, which declined from about 150 to 50 mg g1 nodule dry weight (Fig. 6). Glc levels
were consistently higher in the mutant nodules, whereas Fru, present at
about 10% of Glc levels, showed no trends. Starch levels were very
high in WT nodules, whereas the amount in mutant nodules, although
substantial, was always lower. Starch levels declined in both mutant
and WT nodules over the time course. Total amino acids levels in
nodules also showed a declining trend, but WT levels were always higher
than in mutant nodules.
The two allelic rug4 mutants used in this study were
selected and genetically characterized on the basis of their wrinkled seed phenotype (Wang and Hedley, 1993
2 Present address: A.N. Bach Institute of Biochemistry, Leninsky Pr 33, Moscow 117071, Russia. * Corresponding author; e-mail tony.gordon{at}bbsrc.ac.uk; fax 44-9-70-828-357. Received December 28, 1998;
accepted April 6, 1999.
Abbreviations: AAT, Asp aminotransferase. ADH, alcohol dehydrogenase. AI, alkaline invertase. ANA, apparent nitrogenase activity. GOGAT, Gln-oxoglutarate aminotransferase. GS, Gln synthetase. Lb, leghemoglobin. MDH, malate dehydrogenase. PDC, pyruvate decarboxylase. PEPC, PEP carboxylase. PFK, phosphofructokinase. SS, Suc synthase. WT, wild type.
We are grateful to Trevor Wang and Cliff Hedley for providing seeds of the mutant and WT pea used in this work and for constructive comments on this manuscript. We also thank Josephine Craig, Alison Smith, Paul Barratt, Trevor Wang, and Cliff Hedley (John Innes Centre) for useful discussions about their studies with these mutants before publication.
Appleby CA, Bergersen FJ (1980) Preparation and experimental use of leghemoglobin. In FJ Bergersen, ed, Methods for Evaluating Biological Nitrogen Fixation. Wiley, New York, pp 315-336 Craig J, Barratt P, Tatge H, Dejardin A, Handley L, Gardner CD, Barber L, Wang T, Hedley C, Martin C, and others (1999) Mutations at the rug4 locus alter the carbon and nitrogen metabolism of pea plants through an effect on sucrose synthase. Plant J 17: 353-362 Cresswell A, Gordon AJ, Mytton LR (1992) The physiology and biochemistry of cultivar strain interactions in the white clover-Rhizobium symbiosis. Plant Soil 139: 47-57 Déjardin A, Rochat C, Maugenest S, Boutin J-P (1997) Purification, characterization and physiological role of sucrose synthase in the pea seed coat (Pisum sativum L). Planta 201: 128-137 [CrossRef][Web of Science][Medline] de Lima ML, Oresnik IJ, Fernando SM, Hunt S, Smith R, Turpin DH, Layzell DB (1994) The relationship between nodule adenylates and the regulation of nitrogenase activity by O2 in soybean. Physiol Plant 91: 687-695 [CrossRef] Fernández-Pascual M, De Lorenzo C, De Felipe MR, Rajalakshmi S, Gordon AJ, Thomas BJ, Minchin FR (1996) Possible reason for relative salt stress tolerance in nodules of white lupin cv. Multolupa. J Exp Bot 47: 1709-1716
Gallagher JA,
Pollock CJ
(1998)
Isolation and characterization of a cDNA clone from Lolium temulentum L. encoding for a sucrose hydrolytic enzyme which shows alkaline/neutral invertase activity.
J Exp Bot
49:
789-795
González EM,
Gordon AJ,
James CL,
Arrese-Igor C
(1995)
The role of sucrose synthase in the response of soybean nodules to drought.
J Exp Bot
46:
1515-1523
Gordon AJ
(1991)
Enzyme distribution between the cortex and the infected region of soybean nodules.
J Exp Bot
42:
961-967
Gordon AJ (1992) Carbon metabolism in the legume nodule. In CJ Pollock, JF Farrar, AJ Gordon, eds, Carbon Partitioning Within and Between Organisms. Bios Scientific Publishers, Oxford, UK, pp 133-162 Gordon AJ (1995) Sucrose metabolism to support N2 fixation in legume root nodules. In IA Tikhonovich, NA Provorov, VI Romanov, WE Newton, eds, Nitrogen Fixation: Fundamentals and Applications. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp 533-538 Gordon AJ, James CL (1997) Enzymes of carbohydrate and amino acid metabolism in developing and mature nodules of white clover. J Exp Bot 48: 895-903
Gordon AJ,
Kessler W
(1990)
Defoliation-induced stress in nodules of white clover. 2. Immunological and enzymic measurements of key proteins.
J Exp Bot
41:
1255-1262
Gordon AJ, Minchin FR, Skøt L, James CL (1997) Stress-induced declines in soybean N2 fixation are related to nodule sucrose synthase activity. Plant Physiol 114: 937-946 [Abstract] Gordon AJ, Thomas BJ, Reynolds PHS (1992) Localization of sucrose synthase in soybean root nodules. New Phytol 122: 35-44
Groat RG,
Vance CP
(1981)
Root nodule enzymes of ammonia assimilation in alfalfa (Medicago sativa L.).
Plant Physiol
67:
1198-1203
Huber C, Huber JL, Liao PC, Gage DA, McMichael RW, Chourey PS, Hannah LC, Koch K (1996) Phosphorylation of serine-15 of maize leaf sucrose synthase. Occurrence in vivo and possible regulatory significance. Plant Physiol 112: 793-802 [Abstract] John CD, Greenway H (1976) Alcoholic fermentation and activity of some enzymes in rice roots under anaerobiosis. Aust J Plant Physiol 3: 325-336 Kuzma MM, Topunov AF, Layzell DB (1995) Effects of temperature on infected cell O2 concentration and adenylate levels in attached soybean nodules. Plant Physiol 107: 1209-1216 [Abstract]
Kuzma MM,
Winter H,
Storer P,
Oresnik I,
Atkins CA,
Layzell DB
(1999)
The site of oxygen limitation in soybean nodules.
Plant Physiol
119:
399-407
Lowry OH,
Rosebrough NJ,
Farr AL,
Randall RJ
(1951)
Protein measurement with the Folin phenol reagent.
J Biol Chem
193:
265-275
MacRae JC (1971) Quantitative measurement of starch in very small amounts of leaf tissue. Planta 96: 101-108 [CrossRef]
Minchin FR,
Witty JF,
Sheehy JE,
Muller M
(1983)
A major error in the acetylene reduction assay: decreases in nodular nitrogenase activity under assay conditions.
J Exp Bot
34:
641-649
Nakai T,
Konishi T,
Zhang X-Q,
Chollet R,
Tonouchi N,
Tsuchida T,
Yoshinaga F,
Mori H,
Sakai F,
Hayashi T
(1998)
An increase in apparent affinity for sucrose of mung bean sucrose synthase is caused by in vitro phosphorylation or directed mutagenesis of Ser11.
Plant Cell Physiol
39:
1337-1341
Romanov VI,
Gordon AJ,
Minchin FR,
Witty JR,
Skøt L,
James CL,
Borisov AY,
Tikhonovich IA
(1995)
Anatomy, physiology and biochemistry of root nodules of Sprint-2 Fix
Romanov VI,
Gordon AJ,
Minchin FR,
Witty JR,
Skøt L,
James CL,
Tikhonovich IA
(1998)
Physiological and biochemical characteristics of FN1, a "fixation impaired" mutant of pea (Pisum sativum L.).
J Exp Bot
49:
1789-1796
Ryle GJA,
Powell CE,
Gordon AJ
(1978)
Effect of source of nitrogen on the growth of Fiskeby soybean: the carbon economy of whole plants.
Ann Bot
42:
637-648
Singletary GW, Banisdar R, Keeling PL (1997) Influence of gene dosage on carbohydrate synthesis and enzymic activities in endosperm of starch-deficient mutants of maize. Plant Physiol 113: 293-304 [Abstract]
Soupene E,
Foussard M,
Boistard P,
Truchet G,
Batut J
(1995)
Oxygen as a key developmental regulator of rhizobium-meliloti N2 fixation gene-expression within the alfalfa root-nodule.
Proc Natl Acad Sci USA
92:
3759-3763
Suganuma N,
La Rue
(1993)
Comparison of enzymes involved in carbon and nitrogen metabolism in normal nodules and ineffective nodules induced by a mutant E135 (sym13).
Plant Cell Physiol
34:
761-765
Suganuma N,
Sonoda N,
Nakane C,
Hayashi K,
Hayashi T,
Tamaoki M,
Kouchi H
(1998)
Bacteroids isolated from ineffective nodules of Pisum sativum mutant E135 (sym13) lack nitrogenase activity but contain the two protein components of nitrogenase.
Plant Cell Physiol
39:
1093-1098
Thummler F,
Verma DPS
(1987)
Nodulin-100 of soybean is the subunit of sucrose synthase regulated by the availability of free heme in nodules.
J Biol Chem
262:
14730-14736
Udvardi MK, Day DA (1997) Metabolite transport across symbiotic membranes of legume nodules. Annu Rev Plant Physiol Plant Mol Biol 48: 493-523 [CrossRef][Web of Science] Vance CP, Heichel GH (1991) Carbon in N2 fixation: limitation and exquisite adaptation. Annu Rev Plant Physiol Plant Mol Biol 42: 373-392 [CrossRef][Web of Science] Vogels GD, Van der Drift C (1970) Differential analysis of glyoxylate derivatives. Anal Biochem 33: 143-157 [CrossRef][Web of Science][Medline] Wang TL, Hadavizideh A, Harwood A, Welham TJ, Harwood WA, Faulks R, Hedley CL (1990) An analysis of seed development in Pisum sativum. XIII. The chemical induction of storage product mutants. Plant Breed 105: 311-320 Wang TL, Hedley CL (1993) Seed mutants in Pisum. Pisum Genet 25: 64-70
Witty JF,
Minchin FR
(1998)
Methods for the continuous measurement of O2 consumption and H2 production by nodulated legume root systems.
J Exp Bot
49:
1041-1047
Zhang X-Q, Chollet R (1997) Seryl-phosphorylation of soybean nodule sucrose synthase (nodulin-100) by a Ca2+-dependent protein kinase. FEBS Lett 420: 126-130 Zrenner R, Salanoubat M, Willmitzer L, Sonnewald U (1995) Evidence of the crucial role of Suc synthase for sink strength using transgenic potato plants (Solanum tuberosum L.). Plant J 7: 97-107 [CrossRef][Web of Science][Medline]
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G. G. Desbrosses, J. Kopka, and M. K. Udvardi Lotus japonicus Metabolic Profiling. Development of Gas Chromatography-Mass Spectrometry Resources for the Study of Plant-Microbe Interactions Plant Physiology, April 1, 2005; 137(4): 1302 - 1318. [Abstract] [Full Text] [PDF]
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E. Etxeberria and P. Gonzalez Evidence for a tonoplast-associated form of sucrose synthase and its potential involvement in sucrose mobilization from the vacuole J. Exp. Bot., May 1, 2003; 54(386): 1407 - 1414. [Abstract] [Full Text] [PDF]
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S. Silvente, A. Camas, and M. Lara Heterogeneity of sucrose synthase genes in bean (Phaseolus vulgaris L.): evidence for a nodule-enhanced sucrose synthase gene J. Exp. Bot., February 1, 2003; 54(383): 749 - 755. [Abstract] [Full Text] [PDF]
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E. Goulas, F. Le Dily, J.-C. Simon, and A. Ourry Morphological pattern of development affects the contribution of nitrogen reserves to regrowth of defoliated white clover (Trifolium repens L.) J. Exp. Bot., September 1, 2002; 53(376): 1941 - 1948. [Abstract] [Full Text] [PDF]
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A.J. Gordon, L. Skot, C.L. James, and F.R. Minchin Short-term metabolic responses of soybean root nodules to nitrate J. Exp. Bot., March 1, 2002; 53(368): 423 - 428. [Abstract] [Full Text] [PDF]
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Abstract
Introduction
N15
analyses indicated that mutant plants derived little of their N from
N2 fixation. The objective of the work described
here was to carry out much more detailed physiological, biochemical,
and growth analyses on mutant and WT plants to test the hypothesis that
deficient SS activity in nodules renders them incapable of effective N
fixation.
, WT; 
, rug4-a; 
,
rug4-b. Values are means ± SE
(n = 3).
