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51.
Plant hormone response mutants 总被引:4,自引:0,他引:4
I. M. Scott 《Physiologia plantarum》1990,78(1):147-152
A variety of plant hormone response mutants has now been described, and is surveyed in this article. In addition to hormone-insensitive mutant phenotypes with defects in hormone-related features, there exist mutants apparently constitutive for the gibberellin responses, and also a mutant hyper-responsive to gibberellin. Although there is still little biochemical evidence on the nature of these mutants, the emerging picture of their genetic dominance relationships has given rise to tentative suggestions of the involvement of represser functions in hormonal control systems. 相似文献
52.
Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F1, F2, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other. 相似文献
53.
David G. Griffiths Michael D. Partis Perry Churchill Stephen C. Brenner Sidney Fleischer Roger J. Moore R. Brian Beechey 《Journal of bioenergetics and biomembranes》1990,22(5):691-707
A series of amphiphilic polymethylenecarboxymaleimides has been synthesized for use as sulfhydryl reagents applicable to membrane proteins. Physical properties of the compounds which are relevant to their proposed mode of action have been determined. By comparing rates of reaction in aqueous and aprotic solvents, the compounds have been shown to react exclusively with the thiolate ion. The effects of the reagents on three membrane-associated proteins are reported, and in two cases a comparative study has been made of the effects on the proteins in the absence of membranes. A mechanism is proposed whereby the reagents are anchored at the lipid/water interface by the negatively charged carboxyl group, thus siting the reactive maleimide in a plane whose depth is defined by the length of the reagent. Supporting evidence for this model is provided by the inability of the reagents to traverse membranes, and variation of their inhibitory potency with chain length when the proteins are embedded in the membrane, but not when extracted into solution. As examples of general use of the reagents to probe sulfhydryl groups in membrane proteins, the reagents have been used to (a) determine the depths in the membrane at which two populations of sulfhydryl groups occur in the mitochondrial phosphate transporter; (b) locate a single sulfhydryl associated with the active site ofD--hydroxybutyrate dehydrogenase in the inner mitochondrial membrane; (c) examine sulfhydryl groups in theD-3-glyceraldehyde phosphate dehydrogenase associated with the human red blood cell membrane. 相似文献
54.
E.V. Sviderskaya E. Jazrawi S.A. Baldwin C.C. Widnell C.A. Pasternak 《The Journal of membrane biology》1996,149(2):133-140
The stimulation of glucose transport in response to various types of stress has been studied. There is no relationship between
effects of stress-inducing agents on glucose transport and their effects on cellular protein synthesis. Although the effect
of stress on glucose transport appears analogous to its stimulation by insulin, cells that are slightly insulin-sensitive
in terms of glucose transport (BHK cells) show a similar degree of stimulation as highly insulin-sensitive cells (differentiated
3T3-L1 cells). External labeling of the transporter protein with a photoactivatable derivative of mannose, 2-N-4-(1-azi-2,2,2-trifluoroethyl)
benzoyl-1, 3-bis-(D-mannos-4-yloxy)-propylamine, shows that most of the increased glucose transport activity correlates with
an increase in the amount of the transporter on the cell surface. Cells subjected to K+-depletion, which inhibits endocytosis and results in an accumulation of receptors at the cell surface, show the same increase
in glucose transport as cells exposed to stress; stressed cells show no further increase in glucose transport when subjected
to K+ depletion. These results support the view (Widnell, C.C., Baldwin, S.A., Davies, A., Martin, S., Pasternak, C.A. 1990. FASEB J
4:1634–1637) that cellular stress increases glucose transport by promoting the accumulation of glucose transporter molecules
at the cell surface.
Received: 20 June 1995/Revised: 29 September 1995 相似文献
55.
Nicotine Effects on Dopamine Clearance in Rat Nucleus Accumbens 总被引:2,自引:0,他引:2
Abstract: In vivo voltammetry was used to measure the clearance of exogenously applied dopamine (DA) in the nucleus accumbens following acute systemic nicotine administration in urethane-anesthetized rats. The IVEC-5 system was used for continuous in vivo electrochemical measurements. A finite amount of DA was pressure-ejected (25–100 nl, 200 µ M barrel concentration) at 5-min intervals from micropipettes (tip diameter, 10–15 µm) positioned 250 ± 50 µm from the recording electrode. The peak DA concentration after each DA ejection was significantly decreased in rats following nicotine, but not in rats given saline. In addition, when mecamylamine was administered 20 min before nicotine it clearly antagonized nicotine effects. These results suggest that nicotine may actually facilitate DA transporter systems within the nucleus accumbens. 相似文献
56.
Hidefumi Yoshioka Hideyo Ohuchi Yoshiyasu Ishimaru Tetsuya Ishikawa Tsutomu Nohno Kaoru Saigo Sumihare Noji 《Development, growth & differentiation》1996,38(6):617-624
Members of the fibroblast growth factor (FGF) family play important roles in various developmental processes in vertebrates. Since two genes closely related to the vertebrate FGF receptor (FGFR) genes DFR1 and DFR2/breathless have already been reported in Drosophila , the existence of a Drosophila FGF has been predicted. In the present study, we examined whether DFR1 is functionally interchangeable with a vertebrate FGFR in the Xenopus system. First, we found that the expression of DFR1 promoted Ca2+ efflux in response to human basic (b)FGF in Xenopus oocytes, whereas the coexpression of a dominant negative form of DFR1 (ΔDFR1) with a chick FGFR1/cek1 inhibited promotion of Ca2+ efflux induced by the expression of cek1 in the oocyte. Second, the expression of ΔDFR1 was observed to induce a defect in the posterior structure of the Xenopus embryo at stage 30, as observed with a dominant negative form of cek1 (Δcek1). Third, we found that the expression of ΔDFR1 inhibited the expression of FGF-regulated genes such as Xbra, Xnot , and Xshh in Xenopus embryos at stage 11, while the coexpression of DFR1 with ΔDFR1 could rescue the inhibited expression of FGF-regulated genes. These results indicate that DFR1 acts as an FGFR in Xenopus embryos and that an FGF is likely to exist in Drosophila . 相似文献
57.
Junko Komura Ikumi Tamai Mizuho Senmaru Tetsuya Terasaki Yoshimichi Sai Akira Tsuji 《Journal of neurochemistry》1996,67(1):330-335
Abstract: The characteristics of β-alanine transport at the blood-brain barrier were studied by using primary cultured bovine brain capillary endothelial cells. Kinetic analysis of the β-[3 H]alanine transport indicated that the transporter for β-alanine functions with Kt of 25.3 ± 2.5 µ M and J max of 6.90 ± 0.48 nmol/30 min/mg of protein in the brain capillary endothelial cells. β-[3 H]Alanine uptake is mediated by an active transporter, because metabolic inhibitors (2,4-dinitrophenol and NaN3 ) and low temperature reduced the uptake significantly. Furthermore, the uptake of β-[3 H]alanine required Na+ and Cl− in the external medium. Stoichiometric analysis of the transport demonstrated that two sodium ions and one chloride ion are associated with one β-alanine molecule. The Na+ and Cl− -dependent uptake of β-[3 H]alanine was stimulated by a valinomycin-induced inside-negative K+ -diffusion potential. β-Amino acids (β-alanine, taurine, and hypotaurine) inhibited strongly the uptake of β-[3 H]alanine, whereas α- and γ-amino acids had little or no inhibitory effect. In ATP-depleted cells, the uptake of β-[3 H]alanine was stimulated by preloading of β-alanine or taurine but not l -leucine. These results show that β-alanine is taken up by brain capillary endothelial cells, via the secondary active transport mechanism that is common to β-amino acids. 相似文献
58.
Influx and efflux of inorganic carbon in Synechococcus UTEX625 总被引:1,自引:0,他引:1
The CO2 and HCO3? fluxes in air-grown cells of Synechococcus UTEX 625 al pH 8-0 were measured during dark to light and light to dark transitions using a mass spectrometer and sampling of the reaction medium. The kinetic parameters for initial uptake of CO2 and HCO3? were determined during the initial period of illumination. The development of the internal Ci pool was followed up to steady-state photosynthesis, which occurred when the size of the internal inorganic carbon pool remained apparently constant for a limited period. The experimental procedure confirmed that only CO2 transport occurred with 100mmolm?3 Na+ and that both CO2 and HCO?3 transport occurred with 25molm?3 Na+. The K1/2 values of initial CO2 and HCO3 uptake were 0.7 and 17.2 mmolm?3respectively and agreed closely with the K1/2 values of net CO2 and HCO3? transport during steady-state photosynthesis, which were 0.66 and 17.1 mmolm?3 respectively. Maximum rates of CO2and HCO3? transport were 423 and 219mmolh?1 g?1 Chl. Maximum CO2 efflux observed upon darkening was 118mmolh?1 g?1 Chl. A permeability coefficient of the cell for CO2 of 3 × 10?8 m s?1 was determined from the dark CO2 efflux assuming an internal pH of 7.2 in the dark. Following the initial CO2 uptake in the light, the extracellular [CO2] steadily declined when only CO2 transport was allowed, but an increase in the extracellular [CO2] when HCO3? transport was allowed to proceed suggested that an enhanced CO2 efflux occurred as a result of the larger size of the intracellular Ci pool. 相似文献
59.
Stimulation of root hair elongation in Arabidopsis thaliana by low phosphorus availability 总被引:29,自引:4,他引:25
Low phosphorus availability stimulates root hair elongation in many plants, which may have adaptive significance in soil phosphorus acquisition. We investigated the effect of low phosphorus on the elongation of Arabidopsis thaliana root hairs. Arabidopsis thaliana plants were grown in plant culture containing high (1000 mmol m?3) or low (1 mmol m?3) phosphorus concentrations, and root hair elongation was analysed by image analysis. After 15d of growth, low-phosphorus plants developed root hairs averaging 0.9 mm in length while high-phosphorus plants of the same age developed root hairs averaging 0.3 mm in length. Increased root hair length in low-phosphorus plants was a result of both increased growth duration and increased growth rate. Root hair length decreased logarithmically in response to increasing phosphorus concentration. Local changes in phosphorus availability influenced root hair growth regardless of the phosphorus status of the plant. Low phosphorus stimulated root hair elongation in the hairless axr2 mutant, exogenously applied IAA stimulated root hair elongation in wild-type high-phosphorus plants and the auxin antagonist CM PA inhibited root hair elongation in low-phosphorus plants. These results indicate that auxin may be involved in the low-phosphorus response in root hairs. 相似文献
60.
2,4-dichlorophenoxyacetic (2,4-D) applied to excised leaves of Cassia fasciculata modified the dark-induced (scotonasty) and light-induced (photonasty) leaflet movements, showing that this compound acts on rapid turgor variation and the concomitant ion migrations, in particular K+. 2,4-D inhibited the scotonastic closure in a dose-dependent manner from 10–8
M to 10–5
M and promoted the photonastic opening in the same range of concentrations. The compound acted rapidly since a treatment as short as 5 min gave an obvious effect on the motile reaction; however, a lag period of 45–60 min was needed to observe its effect. Although 2,4-D is a weak acid, its greatest physiological efficiency was obtained with pH values close to neutrality. The physiological results are discussed in relation to the chemical properties and the characteristics of transport of the molecule.Abbreviations ABA
abscisic acid
- 6-BAP
6-benzylaminopurine
- 2,4-D
2,4 dichlorophenoxyacetic acid
- GA3
gibberellic acid
- HEPES
N-[2-hydroxyethyl] piperazine-N-[2-ethanesulphonic acid]
- IAA
indole-3-acetic acid
- NAA
1-naphthaleneacetic acid
- MES
2-(N-morpholino)-ethanesulphonic acid 相似文献