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11.
Influence of nitrate on uptake of ammonium by nitrogen-depleted soybean: is the effect located in roots or shoots? 总被引:4,自引:1,他引:3
Saravitz Carole H.; Chaillou Sylvain; Musset Joanne; Raper C. David Jr.; Morot-Gaudry Jean-Francis 《Journal of experimental botany》1994,45(11):1575-1584
In non-nodulated soybean [Glycine max (L.) Merrill cv. Ransom]plants that were subjected to 15 d of nitrogen deprivation inflowing hydroponic culture, concentrations of nitrogen declinedto 1.0 and 1.4mmol Ng1 dry weight in shoots and roots,respectively, and the concentration of soluble amino acids (determinedas primary amines) declined to 40µmol g1 dry weightin both shoots and roots. In one experiment, nitrogen was resuppliedfor 10 d to one set of nitrogen-depleted plants as 1.0 mol m3NH4+ to the whole root system, to a second set as 0.5 mol m3NH4+ plus 0.5 mol m3 NO3 to the whole root system,and to a third set as 1.0 mol m3 NH4+ to one-half ofa split-root system and 1.0 mol m3 NO3 to theother half. In a second experiment, 1.0 mol m3 of nitrogenwas resupplied for 4 d to whole root systems in NH4+ : NO3ratios of 1:0, 9:1, and 1:1. Nutrient solutions were maintainedat pH 6.0. When NH4+ was resupplied in combination with NO3 to thewhole root system in Experiment I, cumulative uptake of NH4+for the 10 d of resupply was about twice as great as when NH4+was resupplied alone. Also, about twice as much NH4+ as NO3was taken up when both ions were resupplied to the whole rootsystem. When NH4+ and NO3 were resupplied to separatehalves of a split-root system, however, cumulative uptake ofNH4+ was about half that of NO3. The uptake of NH4+,which is inhibited in nitrogen-depleted plants, thus is facilitatedby the presence of exogenous NO3, and the stimulatingeffect of NO3 on uptake of NH4+ appears to be confinedto processes within root tissues. In Experiment II, resupplyof nitrogen as both NH4+ and NO3 in a ratio of either1:1 or 9:1 enhanced the uptake of NH4+. The enhancement of NH4+uptake was 1.8-fold greater when the NH4+: NO3-resupplyratio was 1:1 than when it was 9:1; however, only 1.3 timesas much NO3 was taken up by plants resupplied with the1 :1 exogenous ratio. The effect of NO3 on enhancementof uptake of NH4+ apparently involves more than net uptake ofNO3 itself and perhaps entails an effect of NO3uptake on maintenance of K+ availability within the plant. Theconcentration of K+ in plants declined slightly during nitrogendeprivation and continued to decline following resupply of nitrogen.The greatest decline in K+ concentration occurred when nitrogenwas resupplied as NH4+ alone. It is proposed that decreasedavailability of K+ within the NH4+-resup-plied plants inhibitedNH4+ uptake through restricted transfer of amino acids fromthe root symplasm into the xylem. Key words: Ammonium, Glycine max, nitrate, nitrogen-nutrition, nitrogen stress, split-root cultures 相似文献
12.
13.
Peter H. Quail Winslow R. Briggs Joanne Chory Roger P. Hangarter Nicholas P. Harberd Richard E. Kendrick Maarten Koornneef Brian Parks Robert A. Sharrock Eberhard Schäfer William F. Thompson Garry C. Whitelam 《Plant Molecular Biology Reporter》1994,12(2):S50-S56
These recommendations for genes encoding phytochromes were developed independently by Quail et al., but are broadly consistent
with the Commission's guidelines. Their original article, kindly provided in advance of publication, appeared as a Letter
to the Editor inPlant Cell (6:468–471, 1994) and is published with permission of the American Society of Plant Physiologists. 相似文献
14.
Successful control of greenhouse whitefly may be achieved by complementary activity of the parasitoidEncarsia formosa and the fungusAschersonia aleyrodis. One way to obtain an additive mortality effect of both entomopathogen and parasitoid would be achieved by the selection
of healthy hosts by the parasitoid and rejection of fungus-infected hosts. Third and fourth instar larvae ofTrialeurodes vaporariorum which had been treated with a spore suspension ofA. aleyrodis 0, 4, 7, 10 or 14 days beforehand, were presented to female parasitoids. The parasitoids adopted the oviposition posture
on untreated hosts as well as on treated hosts, irrespective of the different stages of infection in the hosts. However, significantly
more hosts were parasitized byE. formosa in the control treatment than in the fungal treatment. The parasitoids offered treated hosts, showed rejection behaviour
after probing on hosts showing detectable signs of infection (containing hyphal bodies or mycelium in the haemolymph). For
instance, when hosts were offered seven days after spore treatment, the parasitoids showed an oviposition posture on a total
of 83 (95.4%) out of 87 infected larvae, but laid only 4 eggs (4.6%). In contrast, on 48 (94.1%) out of 51 noninfected (or
showing no detectable signs of infection) hosts an oviposition posture was adopted and 40 eggs (78.4%) were found after dissection.
When infected hosts were encountered the oviposition posture lasted less than 1′40″ while rejection of non-infected hosts
occurred after more than 1′40″. Other experiments were carried out offering treated hosts for 24 h to the parasitoids. The
hosts were dissected afterwards. Again, significantly more eggs were laid in the non-infected hosts. When hosts were parasitized
shortly after fungal spore treatment they were colonized by the fungus and the parasitoids did not develop. Transmission of
the entomopathogen after probing infected hosts was observed to a limited extent. In conclusion,A. aleyrodis andE. formosa can be used together in a glasshouse situation. The parasitoid will be most effective when introduced more than seven days
after application ofA. aleyrodis, because from that time onwards it is able to detect and reject fungus-infected hosts. 相似文献
15.
Allyson Tucker Dilks Joanne Gilchrist Yik Lam Nathan Nicholes Brad Stanley 《Biotechnology progress》2023,39(4):e3351
No-salt flowthrough hydrophobic interaction chromatography (HIC) has been shown to effectively remove process and product-related impurities from bioprocess streams. In this publication, a panel of six antibodies has been used to demonstrate operating principles for the application of no-salt flowthrough HIC in antibody purification processes. The results indicate that no-salt flowthrough HIC provides robust aggregate clearance across operating conditions including flow rate, and variations in resin ligand density. Additionally, HMW reduction has an optimal pH range relative to the isoelectric point of each molecule and high molecular weight (HMW) reduction can be improved by altering the total protein load and/or HMW concentration to drive binding of high molecular weight species to the resin. 相似文献
16.
Joanne H.E. Ross Denis J. Murphy 《The Plant journal : for cell and molecular biology》1996,9(5):625-637
A large, heterogeneous, highly expressed gene family encoding oleosin-like proteins is described in the Brassicaceae. íeven related cDNA sequences were isolated from Brassica napus anther mRNA using RACE-PCR and compared with other recently described anther-specific oleosin-like genes from B. napus. The expression patterns of four representative members of this diverse gene family were analyzed by Northern blotting and in situ hybridization. In all cases, the genes were expressed specifically in the tapetum of 3–5 mm B. napus buds, which contained microspores at the late-vacuolate and bicellular stages of development. The predicted protein products are ordered into subclasses, each of which has a characteristic C-terminal domain, containing different amino acid motifs or repeated residues. Tryphine (pollen coat) fractions from mature B. napus pollen were found to be particularly enriched in polypeptides of apparent molecular weights 32–38 kDa, plus numerous less abundant polypeptides of less than 15 kDa. The N-terminal 15–20 residues of three of these polypeptides (12, 32 and 38 kDa) were found by microsequencing to be identical to parts of the predicted amino acid sequences of three of the tapetal-expressed oleosin-like genes. This indicates the possibility of post-translational modification of these proteins resulting in a cleavage of the primary translation products in order to generate the mature tryphine polypeptides. These data imply that a large and diverse group of oleosin-like proteins is synthesized in the tapeturn of B. napus anthers and that following tapetal degradation, these proteins, possibly in modified form, then relocate to the developing microspores where they eventually constitute some of the major components of the extracellular tryphine of mature pollen grains. These proteins share a conserved 70 amino acid residue hydrophobic domain and are related structurally to the seed-specific intracellular oleosins, although their biological function may be different. 相似文献
17.
Anne L. Holleran Donald A. Briscoe Gary Fiskum Joanne K. Kelleher 《Molecular and cellular biochemistry》1995,152(2):95-101
A study was undertaken to assess the role of a physiological concentration of glutamine in AS-30D cell metabolism. Flux of14C-glutamine to14CO2 and of14C-acetate to glutamate was detected indicating reversible flux between glutamate and TCA cycle -ketoglutarate. These fluxes were transaminase dependent. A flux analysis was compared using data from three tracers that label -ketoglutarate carbon 5, [2-14C]glucose, [1-14C]acetate and [5-14C]glutamine. The analysis indicated that the probability of flux of TCA cycle -ketoglutarate to glutamate was, at minimum, only slightly less than the probability of flux of -ketoglutarate through -ketoglutarate dehydrogenase. The apparent Km for oxidative flux of [14C]glutamine to14CO2, 0.07 mM, indicated that this flux was at a maximal rate at physiological, 0.75 mM, glutamine. Although oxidative flux through -ketoglutarate dehydrogenase was the major fate of glutamine, flux of glutamine to lipid via reductive carboxylation of -ketoglutarate was demonstrated by measuring incorporation of [5-14C]glutamine into14C-lipid. In media containing glucose (6 mM), and glutamine (0.75 mM) 47 per cent of the lipid synthesized from substrates in the media was derived from glutamine via reductive carboxylation and 49 per cent from glucose. These findings of nearly equal fluxes suggest that lipogenesis via reductive carboxylation may be an important role of glutamine in hepatoma cells. 相似文献
18.
19.
A continuous line derived from a human skin squamous cell carcinoma has been grown in media of high, normal and low Ca2+ concentrations. The growth rate was unaffected by the Ca2+ levels even though morphological changes were observed. Desmosomes were absent at low Ca2+ and areas of cell piling were observed at high Ca2+. Cell protein staining patterns on polyacrylamide gels were identical for cells grown at the three Ca2+ levels. The variations were minor for the glycoproteins reacted with 125I-conA. Lactoper-oxidase iodination revealed changes in cell surface proteins, most markedly in the emergence of new proteins at high Ca2+. 相似文献
20.
Brian L. Partridge Walter Heiligenberg Joanne Matsubara 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1981,145(2):153-168
Summary The Jamming Avoidance Response (JAR), during which weakly electric fish modulate their electric organ discharge rate in response to a foreign electric signal of nearly the same frequency is strongest for frequency differences (f
s) between 3–8 Hz. We have searched for neural correlates of this behavioral specificity. Single unit recordings in the anterior lateral line ganglion (ALLG), the posterior lateral line lobe (PLLL) and the torus semicircularis (TS) ofEigenmannia virescens were made during electrical stimulation simulating jamming by a nearby conspecific.Contrary to previously published reports (Scheich 1974, 1977) we conclude that f specificity does not lie in a single class of receptors or higher-order units in the PLLL tuned to the most effective f
s. No tuning is seen at the receptor level of the PLLL. Specificity seems to be a population effect first visible at the level of the torus semicircularis, with individual units responding most strongly to different f
s, but with most units tuned to approximately + and-4 Hz. By having cells tuned to a variety of f
s but occurring in proportions corresponding to the observed behavior (and the degree to which f
s impair electrolocation), animals would be better equipped to carry out other tasks such as detection of relative motion of objects in space and would also be better able to read complex stimuli corresponding to the more usual case of simultaneous jamming from several conspecifics (Partridge and Heiligenberg 1980).Units in the PLLL show slight differences in the timing of their firing to jamming signals presented at a frequency slightly above (+f) the fish's pacemaker frequency compared to those presented at a frequency slightly below (–f) (Scheich 1977). Firing pattern within the beat cycle produced by interaction of the fish's EOD, or an electrical mimic, S1, and the foreign signal, S2, is largely unaffected by the field orientation of the jamming signal. In the torus, by contrast, two classes of units are encountered which completely reverse the pattern of their firing within the beat cycle if the sign of the f is reversed. And, unlike the PLLL cells, those in TS respond differentially to different stimulus field geometries. Units of class 1 appear to compare T-unit input from different sites on the body surface (Heiligenberg and Bastian 1980) whereas those of class 2 additionally appear to receive input from E- and I-units in the PLLL.
Abbreviations: see MethodsThis study was supported by grants from the National Science Foundation and the National Institutes of Health. 相似文献