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  • 1
    Electronic Resource
    Electronic Resource
    Gaseous diffusive properties of soybean nodules cultured with non-ambient pO2 (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Measurements of the short-term response of nodulated roots of soybean (Glycine max L. Merr, cv. Harosoy: Bradyrhizobium japonicum USDA 16) to rapid changes in surrounding pO2 indicate that their ability to reversibly adjust gaseous diffusive resistance is retained whether plants are cultured in rhizospheres of very low (2.8%) or very high (61.2%) pO2. Thus the capacity for reversible short-term diffusion adjustment is additional to structural changes in the fixed diffusional barriers of nodules which allow their continued fixation of N2 in unfavourably high or low external pO2. Anatomical evidence, involving quantitative measurement of intercellular spaces in the cortical tissues using electron microscopy of thin sections, indicates that the major fixed diffusional barrier is a boundary layer of cells in the inner cortex which may be as small as one cell thick in nodules from 2.8% O2 to 5 or 6 cells thick, and almost completely devoid of intercellular spaces, in those from 61.2% O2. The data are interpreted to indicate that the variable diffusion harrier is distinct from the boundary layer and is most likely to be a property of cells and/or intercellular spaces inside the boundary layer of the nodule cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb08795.x
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  • 2
    Electronic Resource
    Electronic Resource
    A metabolic connection between nitrogenase activity and the synthesis of ureides in nodulated soybean (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 84 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Application of allopurinol (AP; 1H-pyrazolo-[3,5-d]pyrimidine-4-o1) to intact nodulated roots of ureide-forming legumes causes rapid inhibition of NAD:xanthine dehydrogenase (XDH: EC 1.2.1.37), cessation of ureide synthesis and, subsequently, severe nitrogen deficiency (Atkins et al. 1988. Plant Physiology 88: 1229–1234). Nitrogen deficiency is a result of inhibited nitrogenase (EC 1.7.99.2) activity. Using an open gas exchange system to measure H2 and CO2 evolution, short term effects of AP application were examined in a Hup− soybean symbiosis [Glycine max (L.) Merr. cv. Harosoy: USDA 16]. The onset of inhibition of nitrogenase was detected after ca 2 h exposure of the roots to AP. At the same time xanthine began to accumulate and ureide levels declined in nodules as a result of inhibition of XDH. The decline in H2 evolution following AP application was not due to altered electron allocation between N2 and H+ by nitrogenease but was coincident with increased gaseous diffusive resistance of nodules and a decline in intracellular oxygen concentration. A possible scheme for the intermediary metabolism of soybean nodules which might account for a direct connection between nitrogenase activity and ureide synthesis is proposed. The suggested mechanism envisages coupling production of reducing power by cytosolic enzymes of purine oxidation to synthesis of dicarboxylic acid substrates (malate and succinate) required for bacteroid respiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb04688.x
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  • 3
    Electronic Resource
    Electronic Resource
    Translocation of nitrogen and expression of nodule-specific uricase (nodulin-35) in Robinia pseudoacacia (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Uricase (urate oxidase, EC 1.7.3.3) activity and nodule-specific uricase II (nodulin-35) were detected in the nodules from a number of legume: Rhizobium symbioses (Vigna unguiculata (L.) Walp., Phaseolus vulgaris L., and Kennedia coccinea Vent.) in the Phaseoleae, as well as in those of Robinia pseudoacacia L. which belongs to the tribe Robineae. Neither uricase activity nor nodulin-35 was detected in nodules from Lupinus angustifolius L., an amide-forming symbiosis of the tribe Genisteae. Nodules of R. pseudoacacia also showed high levels of allantoinase (EC 3.5.2.5) activity but activity of enzymes earlier in the pathway of ureide synthesis (xanthine dehydrogenase, EC 1.2.1.37; inosine monophosphate dehydrogenase, EC 1.2.1.14; and xanthosine nucleosidase, EC 3.2.2.1) could not be detected. Analysis of transport fluids (xylem, phloem and nodule exudates) from R. pseudoacacia found that asparagine, and, to a lesser extent, glutamine were the major translocated nitrogenous solutes. Ureides accounted for, at most, 2.6% of the N in transport fluids (tracheal xylem sap) and in nodule exudate, 0.1%. In common with nodules of the ureide-forming symbioses, those of R. pseudoacacia contained a high proportion of uninfected interstitial cells (53.7 ± 2.3%) in the central N2-fixing tissue whereas in L. angustifolius only 2.5 ± 0.4% of cells in this tissue were uninfected. These data have been interpreted to indicate that expression of nodule-specific uricase is related to the differentiation of uninfected interstitial cells in nodules and not to the synthesis of ureides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb00124.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of oxygen pressure on synthesis and export of nitrogenous solutes by nodules of cowpea (1990)
    Springer
    Planta 182 (1990), S. 565-571 
    Details
    ISSN: 1432-2048
    Keywords: Bradyrhizobium ; Oxygen pressure and root nodule function ; Root nodules ; Symbiosis (legume —Rhizobium) ; Ureide synthesis ; Uricase ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nodules of cowpea plants (Vigna unguiculata (L.) Walp. cv. Vita 3 :Bradyrhizobium CB756) cultured for periods of 23 d with their root systems maintained in atmospheres containing a range of partial pressures of O2 (pO2; 1–80%, v/v, in N2) formed and exported ureides (allantoin and allantoic acid) as the major products of fixation at all pO2 tested. In sub-ambient pO2 (1 and 2.5%) nodules contained specific activities of uricase (urate: O2 oxidoreductase; EC 1.7.3.3) and allantoinase (allantoin hydrolyase; EC 3.5.2.5) as much as sevenfold higher than in those from air. On a cell basis, uninfected cells in nodules from 1% O2 contained around five times the level of uricase. Except for NAD: glutamate synthase (EC 1.4.1.14), which was reduced in sub-ambient O2, the activities of other enzymes of ureide synthesis were relatively unaffected by pO2. Short-term effects of pO2 on assimilation of fixed nitrogen were measured in nodules of air-grown plants exposed to subambient pO2 (1, 2.5 or 5%, v/v in N2) and15N2. Despite a fall in total15N2 fixation, ureide synthesis and export was maintained at a high level except in 1% O2 where formation was halved. The data indicate that in addition to the structural and diffusional adaptations of cowpea nodules which allow the balance between O2 supply and demand to be maintained over a wide range of pO2, nodules also show evidence of biochemical adaptations which maintain and enhance normal pathways for the assimilation of fixed nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341033
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  • 5
    Electronic Resource
    Electronic Resource
    Morphological and structural adaptation of nodules of cowpea to functioning under sub- and supra-ambient oxygen pressure (1990)
    Springer
    Planta 182 (1990), S. 572-582 
    Details
    ISSN: 1432-2048
    Keywords: Bradyrhizobium ; Oxygen pressure and root nodule structure ; Root nodules (structural adaptation) Symbiosis (legume-Rhizobium) ; Vigna Symbol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nodules of cowpea (Vigna unguiculata (L.) Walp. cv. Vita 3:Bradyrhizobium CB 756) from 28-d-old plants cultured for 23 d with their root systems maintained in O2 levels from 1 to 80% (v/v, in N2) in the external gas phase showed a range of structural changes which have been interpreted in relation to an over- or under-supply of O2. A response to the partial pressure of O2 in the gas phase (pO2) was noted with respect to nodule size, lenticel development, the relative distributions of cortical and infected central tissue, the differentiation of cortex, especially the inner cortex, the frequency and size of infected and uninfected interstitial cells, the volume of extracellular spaces both in cortex and infected tissue, and in the frequency of bacteroids. As a consequence of these changes the surface area of inner cortex relative to the nitrogenase-containing units of fixing tissue (infected cells or bacteroids) was increased by as much as 20-fold. Effectiveness of bacteroid functioning increased from 0.10 ± 0.02 · 10-9 μmol acetylene reduced per bacteroid in air-grown nodules to 0.9 ± 0.16 · 10-9 (same units) per bacteroid in those cultured in 1% O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341034
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  • 6
    Electronic Resource
    Electronic Resource
    Air synthetase in cowpea nodules: a single gene product targeted to two organelles? (1998)
    Springer
    Plant molecular biology 36 (1998), S. 811-820 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; nodules ; phosphoribosyl aminoimidazole synthetase ; purine biosynthesis ; N assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA (VUpur5) encoding phosphoribosyl aminoimidazole (AIR) synthetase, the fifth enzyme of the de novo purine biosynthesis pathway has been isolated from a cowpea nodule cDNA library. It encodes a 388 amino acid protein with a predicted molecular mass of 40.4 kDa. The deduced amino acid sequence has significant homology with AIR synthetase from other organisms. AIR synthetase is present in both mitochondria and plastids of cowpea nodules [7]. A signal sequence encoded by the VUpur5 cDNA has properties associated with plastid transit sequences but there is no consensus cleavage site as would be expected for a plastid targeted protein. Although the signal sequence does not have the structural features of a mitochondrial targeted protein, it has a mitochondrial cleavage site motif (RX/XS) close to the predicted N-terminus of the mature protein. Southern analysis suggests that AIR synthetase is encoded by a single gene raising questions as to how the product of this gene is targeted to the two organelles. VUpur5 is expressed at much higher levels in nodules compared to other cowpea tissues and the gene is active before nitrogen fixation begins. These results suggest that products of nitrogen fixation do not play a role in the initial induction of gene expression. VUpur5 was expressed in Escherichia coli and the recombinant protein used to raise antibodies. These antibodies recognize two forms of AIR synthetase which differ in molecular size. Both forms are present in mitochondria, although the larger protein is more abundant. Only the smaller protein was detected in plastids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005969830314
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  • 7
    Electronic Resource
    Electronic Resource
    Transformation of a grain legume (Lupinus angustifolius L.) via Agrobacterium tumefaciens-mediated gene transfer to shoot apices (1997)
    Springer
    Molecular breeding 3 (1997), S. 341-349 
    Details
    ISSN: 1572-9788
    Keywords: Agrobacterium tumefaciens ; bar gene ; grain legume ; Lupinus angustifolius ; phosphinothricin ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Transgenic plants of Lupinus angustifolius L. (cvs. Unicrop and Merrit) were routinely generated using Agrobacterium-mediated gene transfer to shoot apices. The bar gene for resistance to phosphinothricin (PPT, the active ingredient of the herbicide Basta) was used as the selectable marker. After co-cultivation, the shoot apex explants were transferred onto a PPT-free regeneration medium and their tops were thoroughly wetted with PPT solution (2 mg/ml). The multiple axillary shoots developing from the shoot apices were excised onto a medium containing 20 mg/l PPT. The surviving shoots were transferred every second week onto fresh medium containing 20 mg/l PPT. At each transfer, the number of surviving shoots decreased, until it stabilized. Indeed, some of these chimeric shoots surviving the PPT selection, eventually produced new green healthier axillary shoots which could be transferred to soil. This whole process took from 5 to 9 months after co-cultivation. Average transformation frequencies of 2.8% for cv. Unicrop and of 0.4% for the commercial cultivar Merrit were achieved. Molecular analysis of T0, T1, and T2 generations demonstrated stable integration of the foreign gene into the plant genome and expression of the integrated gene. Transformed plants of the T1 and T2 generations were resistant in glasshouse trials where the herbicide Basta (0.1 mg/ml) was sprayed onto whole plants. These results demonstrate that Agrobacterium-mediated gene transfer to preorganised meristematic tissue combined with axillary regeneration can form the basis of a routine transformation system for legume crop species which are difficult to regenerate from other explants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009642620907
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