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1.
Nitrogen fixation in several grain legume species with contrasting sensitivities to copper nutrition
Henryka Seliga 《Acta Physiologiae Plantarum》1998,20(3):263-267
The nitrogen fixation response to copper nutrition in faba bean, yellow lupin and soybean was studied. Copper nutrition significantly
increased the pod yields of all tested grain legumes but faba bean gave the greatest Cu-use efficiency for pod and grain production.
The accumulation of dry matter in vegetative parts, nodules, N and leghemoglobin concentration in nodules and nitrogen accumulation
in the whole plants were increased by copper supply in faba bean and yellow lupin in contrast with soybean. Cu nutrition significantly
increased the Cu concentrations in nodules of all cultivated plants. The differential sensitivity of N2 fixation in tested grain legume species to copper nutrition could be connected with the level of phenols in nodules and depended
on both the host plants and strains of rhizobia, which differ in their ability to produce catechol-like siderophores. Copper
requirements by symbiotic N2 fixation could also depend on the nature of phenols in nodules (presence of o-dihydroxyphenols or number of hydroxyls in
molecule). 相似文献
2.
Summary Root nodule homogenates of actinorhizal plants may representFrankia in a symbiotic stage but released from environmental influence of the host plant. Anaerobic homogenization with a blender in buffer supplied with sucrose, polyvinylpyrrolidone and reducing substances gave three times higher yields of nitrogenase activity (C2H2-reduction) than crushing the nodules in liquid nitrogen. The activity in the homogenates was very reproducible and was, on average, nearly twice as high as the activity in excised nodules and c. 10% of the activity in intact plants. The difference in activity between excised nodules and intact plants was, roughly by halves, due to removal of the root system from the pot and to excision of the nodules. The nitrogenase activity in the homogenates was slightly higher when nodule excision was done in Ar or under water as well as after treatment of the homogenate with toluene or Triton X-100 or osmotic shock. These gains in activity were considered too small to outweigh the increased complications of preparing homogenates for routine use. Due to the reproducible recovery of nitrogenase in the homogenates the technique seems useful for physiological studies on nitrogen fixation inAlnus incana. 相似文献
3.
Henryka Seliga 《Acta Physiologiae Plantarum》1999,21(4):427-431
Copper nutrition inhibited lipid peroxidation in root nodules of yellow lupin plants at the early growth stages by about 50
%. The antioxidative activity of copper in the process of lipid peroxidation could be associated with Cu taking part in oxidative
reaction of nodule catechol-like siderophores and its effect on iron accumulation and reactivity. The obtained results, for
the first time, suggest that the ability of copper to inhibit lipid peroxidation in nodules could be considered as a major
function for Cu requirements by symbiotic N2 fixation in grain legume nodules. 相似文献
4.
The physiology of spore-negative and spore-positive root nodules was investigated inMyrica gale L. grown in water culture in a growth chamber. Spore(–) nodules were induced withFrankia cultures and spore(+) nodules with crushed nodules. Gas exchange was measured in a flow-through system.The time course of acetylene reduction following addition of acetylene was essentially the same in both spore(–) and spore(+) nodules with a stable maximum between 2 and 4 minutes followed by a steep decline to a minimum (37% of the maximum) between 9 and 30 minutes depending on the plant. The minimum was followed by a partial recovery. Nodule CO2 evolution showed a similar pattern but the minimum rate (83% of the maximum) was not nearly as low.Plants nodulated with one spore(–) and one spore(+) strain were compared at 6, 8 and 10 weeks after inoculation. At 6 weeks the spore(–) plants had 52% greater specific nitrogenase activity and 46% more biomass than the spore(+) plants. At 8 and 10 weeks, however, the differences between plants with spore(–) and spore(+) nodules became smaller.Plants nodulated with 4 spore(–) and 5 spore(+) strains were compared at 8 weeks after inoculation. Collectively the spore(–) plants exhibited a 32% greater specific nitrogenase activity, a 15% lower energy cost of nitrogenase activity (CO2/C2H4), and invested 31% less biomass in nodules than the spore(+) plants. The spore(–) plants also produced 16% more biomass indicating that spore(–) strains are generally more desirable than spore(+) strains. However, two spore(+) strains were as effective as the spore(–) strains. 相似文献
5.
T. A. Lie 《Plant and Soil》1981,61(1-2):125-134
Summary
Pisum sativum ecotype fulvum forms ineffective nodules with Rhizobium strains, isolated from effective nodules of the cultivated pea in Europe. Rhizobium strains isolated from nodules of fulvum peas in Israel are fully effective on this host plant, but in association with the cultivated pea they induce nodules of poor N2-fixing activity. The distribution of these fulvum-specific Rhizobium strains is restricted to regions where the fulvum pea occurs naturally. Rhizobium strains from other geographical regions induce mainly ineffective, or partially effective nodules on fulvum plants.A wide genetic variation, with regard to symbiotic response to a standard set of Rhizobium strains, was demonstrated in the fulvum plants collected in Israel. Based on variation in N2-fixation three groups of plants can be distinguished. These plants offer the possibility for the study of host-genetic control on symbiotic nitrogen fixation. 相似文献
6.
G. Caetano-Anollés P. M. Gresshoff 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(5-6):624-632
Summary
Rhizobium nodulation genes can produce active extracellular signals for legume nodulation. The R. meliloti host-range nodH gene has been postulated to mediate the transfer of a sulfate to a modified lipo-oligosaccharide, which in its sulfated form is a specific nodulation factor for alfalfa (Medicago sativa L.). We found that alfalfa was capable of effective nodulation with signal-defective and non-nodulating nodH mutants (Nnr) defining a novel gene-for-gene interaction that conditions nodulation. Bacteria-free nodules that formed spontaneously at about a 3–5% rate in unselected seed populations of alfalfa cv Vernal in the total absence of Rhizobium (Nar) exhibited all the histological, regulatory and ontogenetic characteristics of alfalfa nodules. Inoculation of such populations with nodH mutants, but not with nodA or nodC mutants, produced a four- to five-fold increase in the percentage of nodulated plants. Some 10–25% of these nodulated plants formed normal pink nitrogen-fixing nodules instead of white empty nodules. About 70% of the S1 progeny of such Nnr+ plants retained the parental phenotype; these plants were also able to form nodules in the absence of Rhizobium. If selected Nar+ plants were self-pollinated almost the entire progeny exhibited the parental Nar+ phenotype. Segregation analysis of S1 and S2 progeny from selected Nar+ plants suggests that the Nar character is monogenic dominant and that the nodulation phenotype is controlled by a gene dose effect. The inoculation of different S1 Nar+ progeny with nodH mutant bacteria gave only empty non-fixing nodules. Our results indicate that certain alfalfa genotypes can be selected for suppression of the non-nodulation phenotype of nodH mutants. The fact that the Nnr plant phenotype behaved as a dominant genetic trait and that it directly correlated with the ability of the selected plants to form nodules in the absence of Rhizobium suggests that the interaction of plant and bacterial alleles occurs early during signal transduction through the alteration of a signal reception component of the plant so that it responds to putative signal precursors.Abbreviations
Nara
Nodulation in the absence of Rhizobium
-
Nara
nodulation with non-nodulating Rhizobium 相似文献
7.
Luis Bolaños Marta Martín Abdelaziz El-Hamdaoui Rafael Rivilla Ildefonso Bonilla 《Plant and Soil》2006,280(1-2):135-142
In order to shed new light on the mechanisms of salt-mediated symbiotic N2-fixation inhibition, the effect of salt stress (75 mM) on N2-fixation in pea root nodules induced by R. leguminosarum was studied at the gene expression, protein production and enzymatic activity levels. Acetylene reduction assays for nitrogenase
activity showed no activity in salt-stressed plants. To know whether salt inhibits N2-fixing activity at a molecular or at a physiological level, expression of the nifH gene, encoding the nitrogenase reductase component of the nitrogenase enzyme was analyzed by RT-PCR analysis of total RNA
extracted from nodulated roots. The nifH messenger RNA was present both in plants grown in the presence and absence of salt, although a reduction was observed in
salt-stressed plants. Similar results were obtained for the immunodetection of the nitrogenase reductase protein in Western-blot
assays, indicating that nitrogen fixation failed mainly at physiological level. Given that nutrient imbalance is a typical
effect of salt stress in plants and that Fe is a prosthetic component of nitrogenase reductase and other proteins required
by symbiotic N2-fixation, as leghemoglobin, plants were analyzed for Fe contents by atomic absorption and the results confirmed that Fe levels
were severely reduced in nodules developed in salt-stressed plants. In a previous papers (El-Hamdaoui et al., 2003b), we have
shown that supplementing inoculated legumes with boron (B) and calcium (Ca) prevents nitrogen fixation decline under saline
conditions stress. Analysis of salt-stressed nodules fed with extra B and Ca indicated that Fe content and nitrogenase activity
was similar to that of non-stressed plants. These results indicate a linkage between Fe deprivation and salt-mediated failure
of nitrogen fixation, which is prevented by B and Ca leading to increase of salt tolerance. 相似文献
8.
The nitrate reductase activity (NR) of selected uptake hydrogenase-positive (hup
+) and uptake hydrogenase-negative (hup
-) strains of Bradyrhizobium japonicum were examined both in free-living cells and in symbioses with Glycine max L. (Marr.) cv. Williams. Bacteria were cultured in a defined medium containing either 10 mM glutamate or nitrate as the sole nitrogen source. Nodules and bacteriods were isolated from plants that were only N2-dependent or grown in the presence of 2 mM KNO3. Rates of activity in nodules were determined by an in vivo assay, and those of cultured cells and bacteriods were assayed after permeabilization of the cells with alkyltrimethyl ammonium bromide. All seven strains examined expressed NR activity as free-living cells and as symbiotic forms, regardless of the hup genotype of the strain used for inoculation. Although the presence of nitrate increased nitrate reduction by cultures cells and nodules, no differences in NR activity were observed between bacteroids isolated from nodules of plants fed with nitrate or grown on N2-fixation exclusively. Cultured cells, nodules and bacteriods of strains with hup
- genotype (USDA 138, L-236, 3. 15B3 and PJ17) had higher rates of NR activity than those with hup
+ genotype (USDA 110, USDA 122 DES and CB1003). These results suggest that NR activity is reduced in the presence of a genetic determinant associated with the hup region of B. japonicum.Abbreviations EDTA
ethylene-diamine tetraacetic acid
- Hup
hydrogen uptake
- MOPS
3-(N-morpholino)-propane sulfonic acid
- NR
nitrate reductase
- PVP
polyvinyl-polypyrrolidone
- Tris
Tris(hydroxymethyl)-aminomethane 相似文献
9.
Summary The purpose of this study was to establish an efficient in vitro nodulation device for producing actinorhizal root nodules on Allocasuarina verticillata and Casuarina glauca. Seeds from the two species were germinated aseptically and seedlings with at least two photosynthetic branchlets and a 3–5
cm long root system were transferred into Petri dishes containing a biphasic (solid/liquid) medium. To assess the nodulation
capacity, four different culture media were tested. As soon as the root system developed and spread adequately on the surface
of the medium, plants were deprived of nitrogen for at least 1 wk and inoculated with the Frankia strain. The time course nodulation for A. verticillata showed that the basal Hoagland medium supplemented with CaCO3 and KNO3 was most efficient, with 83% of plantlets forming nodules, while the medium supplemented with CaCO3 reached 100% nodulation for C. glauca. This procedure can provide a valuable tool for the study of early events of actinorhizal nodulation and spatio-temporal
expression of symbiotic genes in transgenic Casuarinaceae. 相似文献
10.
Fougnies L Renciot S Muller F Plenchette C Prin Y de Faria SM Bouvet JM Sylla SN Dreyfus B Bâ AM 《Mycorrhiza》2007,17(3):159-166
Pterocarpus officinalis (Jacq.) seedlings inoculated with the arbuscular mycorrhizal fungus, Glomus intraradices, and the strain of Bradyrhizobium sp. (UAG 11A) were grown under stem-flooded or nonflooded conditions for 13 weeks after 4 weeks of nonflooded pretreatment
under greenhouse conditions. Flooding of P. officinalis seedlings induced several morphological and physiological adaptive mechanisms, including formation of hypertrophied lenticels
and aerenchyma tissue and production of adventitious roots on submerged portions of the stem. Flooding also resulted in an
increase in collar diameter and leaf, stem, root, and total dry weights, regardless of inoculation. Under flooding, arbuscular
mycorrhizas were well developed on root systems and adventitious roots compared with inoculated root systems under nonflooding
condition. Arbuscular mycorrhizas made noteworthy contributions to the flood tolerance of P. officinalis seedlings by improving plant growth and P acquisition in leaves. We report in this study the novel occurrence of nodules
connected vascularly to the stem and nodule and arbuscular mycorrhizas on adventitious roots of P. officinalis seedlings. Root nodules appeared more efficient fixing N2 than stem nodules were. Beneficial effect of nodulation in terms of total dry weight and N acquisition in leaves was particularly
noted in seedlings growing under flooding conditions. There was no additive effect of arbuscular mycorrhizas and nodulation
on plant growth and nutrition in either flooding treatment. The results suggest that the development of adventitious roots,
aerenchyma tissue, and hypertrophied lenticels may play a major role in flooded tolerance of P. officinalis symbiosis by increasing oxygen diffusion to the submerged part of the stem and root zone, and therefore contribute to plant
growth and nutrition. 相似文献
11.
根瘤是微生物侵染植物根部并与之形成的共生结构,这些微生物都可被称为植物内生菌。豆科植物根瘤中的内生菌常常又被称为根瘤菌,而侵染非豆科植物形成根瘤的主要是放线菌弗兰克氏菌,这些非豆科植物又被称为放线菌结瘤植物。西藏沙棘是一种典型的放线菌结瘤植物,由于其分布生境的特殊性,对其根瘤内生菌的研究具有重要的生态意义。对于西藏沙棘根瘤内生菌的研究,培养方法因难以模拟自然条件而不易获得纯培养,高通量测序技术对其多样性的研究提供了便利。因此,本研究以生长在甘肃省天祝县金强河河滩地的西藏沙棘根瘤为材料,采用16S rRNA基因扩增子高通量测序方法,结合OTU分析,对西藏沙棘根瘤内生菌的多样性进行探讨。实验结果表明,西藏沙棘根瘤内生菌具有丰富的多样性,根瘤内的优势属为共生固氮的弗兰克氏菌属(Frankia),其相对丰度为47.63%,共检测到7个弗兰克氏菌属的OTUs;根瘤内除弗兰克氏菌外,还存在大量的非弗兰克氏菌,共检测到1523个OTUs,隶属于22个门、33个纲、69个目、113个科和202个属,相对丰度排名前9的属中有25个非弗兰克氏菌属的OTUs。该研究也表明,西藏沙棘根瘤内生菌具有丰富的多样性,西藏沙棘根瘤中不仅存在着可共生固氮的弗兰克氏菌,并且还分布着非弗兰克氏菌;在同一根瘤样品中,弗兰克氏菌属还具有不同的物种。本研究不仅拓展了西藏沙棘根瘤内生菌多样性的研究方法,还为同一寄主植物中弗兰克氏菌多样性的研究提供了分析思路。 相似文献
12.
Cloned plants of Alnus incana (L.) Moench were inoculated and grown without combined nitrogen for seven weeks. The effects of ammonium on the function and structure of the root nodules were studied by adding 20 mM NH4Cl (20 mM KCl=control) for four days. Nitrogenase activity decreased to ca. 50% after one day and to less than 10% after two days in ammonium treated plants, but was unaffected in control plants. The results were similar at photon flux densities of 200 and 50 mol m-2 s-1. At the higher light level the effect was concentration dependent between 2 and 20 mM NH4Cl. The recovery was slow, and more than 11 d were needed for plants treated with 20 mM ammonium to reach initial activity. The distribution of 14C to the root nodules after assimilation of 14CO2 by the plants was not changed by the ammonium treatment. Microscopical studies of root nodules showed high frequencies of endophyte vesicles being visually damaged in nodules from ammonium-treated plants, but not in nodules from control plants. When nitrogenase activity was restored, visually damaged vesicles were again few, whereas young developing vesicles were numerous. The slow recovery, the 14C-translocation pattern, and the structural changes of the endophyte indicate a more complex mechanism of ammonium influence than simply a short-term reduction in supply of carbon compounds to the nodules. 相似文献
13.
Combined light and transmission electron microscopy were used to examine the effect of nitrate on the development of root nodules in lucerne (alfalfa, Medicago sativa L.) following induction by the nitrogen-fixing symbiont, Rhizobium meliloti. The timing of NO
3
-
addition was varied in order to study its effect on all of the recognized morphogenetic steps of nodule formation. Roots of plants inoculated in the presence of 18 mM NO
3
-
had straight root hairs which were devoid of adherent rhizobia and infection threads, and developed no nodules. However, nodules were formed on roots if 18 mM NO
3
-
was added 5 d after inoculation. At this time, the initiation of nodule primordia had already commenced in the root cortex. The histology and ultrastructure of young nodules which had developed for 5 d in the absence of NO
3
-
and another 5 d in the presence of 18 mM NO
3
-
resembled nodules developing under N-free conditions, except that in the infection threads within the infection zone of the nodule 1) some bacteria tended to loose their normal shape and gain more electron density, indicating premature degradation, and 2) the matrix of the infection threads was abnormally enlarged. In the presence of high NO
3
-
levels in the medium, lysis and degeneration of the bacteria released from the infection threads were observed in the infection and bacteroid zones of developing nodules, indicative of premature senescence. On the other hand, the nodule meristems continued to proliferate even after 12 d of exposure of 18 mM NO
3
-
. This was the only morphogenetic step of root nodulation which was insensitive to levels of combined nitrogen that completely prevented infection if present at the time of inoculation. These data indicate that all of the recognized steps of root nodule morphogenesis in which the bacteria play a key role are sensitive to the inhibitory effect of combined nitrogen. 相似文献
14.
T. Yoneyama T. Murakami N. Boonkerd P. Wadisirisuk S. Siripin K. Kouno 《Plant and Soil》1990,128(2):287-292
The leaves and nodules from the shrub and tree legumes, particularly, Aeschynomene spp., Sesbania spp., Mimosa spp. and Leucaena spp., and Casuarina spp. and the leaves from neighbouring non-fixing plants were analyzed for their natural abundances of 15N ( 15N).The 15N in the leaves of non-fixing plants was +5.9% on average, whereas those from shrub legumes and Casuarina spp. were lower and close to the values of atmospheric N2, suggesting the large contribution of N2 fixation as the N source in these plants. The 15N values of the leaves from tree legumes except for Leucaena spp. were between the shrub legumes and non-fixing plants, which suggests that the fractional contribution of fixed N2 in tree legumes may be smaller than that in the shrub legumes. Casuarina spp. was highly dependent on N2 fixation. The 15N values of the nodules from most of the shrub legumes investigated were higher than those of the leaves. 相似文献
15.
Dwarf french beans, Phaseolus vulgaris L., were grown with or without inoculation with rhizobia (strain 3644), and with or without a combined nitrogen source (nitrate or ammonium ions). The distribution of radioactivity into products of dark 14CO2 assimilation was studied in roots or nodules from these plants. A detailed study was also made of the distribution and rates of excretion of nitrogen in xylem bleeding sap in 28 day old plants grown on the various sources of nitrogen. Whereas detached nodules accumulated radioactive glycine, serine and glutamate when incubated with 14CO2, bleeding sap from plants root fed 14CO2 contained low levels of radioactivity in these compounds but higher levels in allantoin. Chemical analysis showed allantoin to be the major compound transported in the xylem of nodulated plants, whether or not they were fed on combined nitrogen. In contrast uninoculated plants accumulated mainly amino acids in the bleeding sap, the amount and chemical composition of which depended on the combined nitrogen source.Abbreviations PEP
phosphoenol pyruvate
- OAA
oxaloacetate 相似文献
16.
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.
This work was supported by a grant from the Australian Research Council (to C.A.A.) and an Australian Development Assistance
Bureau postgraduate fellowship (to F.D.D.). 相似文献
17.
Tjepkema J.D. Schwintzer C.R. Burris R.H. Johnson G.V. Silvester W.B. 《Plant and Soil》2000,219(1-2):285-289
Substantial enrichment of some plant parts in 15N relative to the rest of the plant is unusual, but is found in the nitrogen-fixing nodules of many legumes. A range of actinorhizal plants was surveyed to determine whether the nodules of any of them are also substantially enriched in 15N. The nonlegume Parasponia, nodulated by a rhizobium, was also included. Four of the actinorhizal genera and Parasponia were grown in N-free culture, and three actinorhizal genera were collected from the field. Nodules of Parasponia, Casuarina and Alnus were15N enriched relative to other plant parts, but only Parasponia approached the degree of enrichment found in some legume nodules. The nodules of Datisca, Myrica, Elaeagnus, Shepherdia, and Coriaria were depleted in 15N. Thus many actinorhizal nodules are depleted in 15N compared to other plant parts and enrichment is modest when it does occur. Whole plant 15N content (15N) in four actinorhizal plants and Parasponia showed a relatively narrow range of –1.41 to –1.90. Hence regardless of the degree of nodule enrichment or depletion, whole plant 15N content appears to vary little in plants grown in N-free culture. 相似文献
18.
When excised root nodules ofCoriaria arborea are assayed for nitrogenase activity at various pO2 they show a broad optimum between 20 and 40 kPa O2, with some evidence for adaptation. Continuous flow assays of nodulated root systems of intact plants indicate that Coriaria shows an acetylene induced decline in nitrogenase activity. When root systems were subject to step changes in pO2 nitrogenase activity responded with a steep decline followed by a slower rise in activity both at lower and higher than ambient pO2. Thus Coriaria nodules are able to adapt rapidly to oxygen levels well above and well below ambient. Measurement of nodule diffusion resistance showed that the adaptation is accompanied by rapid increase in resistance at above ambient pO2 and decrease in resistance at below ambient pO2. Plants grown with root systems at pO2 from 5–40 kPa O2 did not differ in growth or nodulation. The anatomy of Coriaria nodules shows they have a dense periderm which encircles the nodule and also closely invests the infected zone. The periderm is both thicker and more heavily suberised in nodules grown at high pO2 than at low pO2. Vacuum infiltration of India ink indicates that oxygen diffusion is entirely through the lenticel and via a small gap adjacent to the stele. 相似文献
19.
Summary The nodulation and the morphology and physiology of the nodules were studied onDatisca cannabina, a perennial herb from northern Pakistan andAlnus nitida, a nodulated tree in the same locality. Both species bear coralloid clusters of actinorhizal nodules. The main free amino acid inD. cannabina nodules was arginine while the predominant free amino acid inA. nitida nodules was citrulline. The infectivity of crushed nodules of both types of plants on their respective host was about 106 infective particles per gram of nodule fresh wt. In cross-inoculation experiments crushed nodule inoculum fromA. nitida failed to induce nodulation onD. cannabina seedlings but the crushed nodule inoculum fromD. cannabina caused low nodulation on seedlings ofA. nitida (103 infective particles. g. nodule fresh wt.).The activity of nitrogenase, hydrogenase and respiration (O2 uptake) were measured in detached nodules, nodule homogenates and the 20 m residue and 20 m filtrate preparations from the nodules of both species. Both species showed similar patterns of activities except that only the nodule homogenate and 20 m residue preparations fromD. cannabina showed pronounced enhancement of the O2 uptake by succinate which was further stimulated by ADP. This has in part been explained by the presence of mitochondria in close connection with the endophyte. 相似文献
20.
Grønlund M Gustafsen C Roussis A Jensen D Nielsen LP Marcker KA Jensen EO 《Plant molecular biology》2003,52(2):303-316
To elucidate the function of the ndx homeobox genes during the Rhizobium-legume symbiosis, two Lotus japonicus ndxgenes were expressed in the antisense orientation under the control of the nodule-expressed promoter Psenod12 in transgenic Lotus japonicus plants. Many of the transformants obtained segregated into plants that failed to sustain proper development and maintenance of root nodules concomitant with down-regulation of the two ndx genes. The root nodules were actively fixing nitrogen 3 weeks after inoculation, but the plants exhibited a stunted growth phenotype. The nodules on such antisense plants had under-developed vasculature and lenticels when grown on medium lacking nitrogen sources. These nodules furthermore entered senescence earlier than the wild-type nodules. Normal plant growth was resumed upon external addition of nitrogen. This suggests that assimilated nitrogen is not properly supplied to the plants in which the two ndx genes are down-regulated. The results presented here, indicate that the ndx genes play a role in the development of structural nodule features, required for proper gas diffusion into the nodule and/or transport of the assimilated nitrogen to the plant. 相似文献