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31.
32.
Acquisition of phosphorus and copper by VA-mycorrhizal hyphae and root-to-shoot transport in white clover 总被引:17,自引:0,他引:17
White clover (Trifolium repens L.) plants were grown in a calcareous soil in pots with three compartments, a central one for root growth and two outer ones
for growth of vesicular-arbuscular (VA) mycorrhizal (Glomus mosseae [Nicol. & Gerd.] Gerdemann & Trappe) hyphae (hyphal compartments). Phosphorus (P) was applied at three levels (0, 20 and
50 mg kg−1 soil) in the outer compartments in mycorrhizal treatments. Root and shoot dry weight were increased in mycorrhizal plants
with hyphal access to outer compartments. Growth of the mycorrhizal hyphae in the outer compartments was not significantly
affected by variation in P level in these compartments. However, both concentration and amount of P in roots and shoots sharply
increased with increasing P supply in the outer (hyphal) compartments. With increasing P levels the calculated delivery of
P by the hyphae from the outer compartments increased from 34% to 90% of total P uptake.
Hyphal access to the outer compartments also significantly increased both concentration and quantity of Cu in the plants.
The calculated delivery of Cu by the hyphae from the outer compartments ranged from 53% to 62% of total Cu uptake, irrespective
of the P levels and the amounts of P taken up and transported by the hyphae. However, the distribution of Cu over roots and
shoots was largely dependent on P levels. With increase in P level in the outer compartments the calculated hyphal contribution
to the total amount of Cu in the shoots increased from 12% to 58%, but decreased in the roots from 75% to 46%.
In conclusion, uptake and transport by VA-mycorrhizal hyphae may contribute substantially not only to P nutrition, but also
to Cu nutrition of the host. 相似文献
33.
Xiao-yan Ding Wallace L. McKeehan Jianming Xu Horst Grunz 《Development genes and evolution》1992,201(6):334-339
Summary Mesoderm formation is a result of cell-cell interactions between the vegetal and animal hemisphere and is thought to be mediated by inducing peptide growth factors including members of the FGF and TGF superfamilies. Our immunochemical study analyses the distribution of FGF receptors coded by the human flg gene during embryogenesis of Xenopus laevis. Immunostaining was detected in the dorsal and ventral ectoderm and also in the marginal zone of early cleavage, blastula and gastrula stages. Signals were very strong in the mid and late blastula (stage 8 and 9) and declined slightly in the early gastrula (stage 10). A dramatic decrease was observed up to the late gastrula (stage 11+). In stage 13 embryos, immunostaining was only found in cells around the blastopore. Isolated ectoderm cultured in vitro showed a similar temporal expression and decrease of the signal as the normal embryos. These results indicate that receptor expression is independent of the interaction of the animal cells with the vegetal part of the embryo. Of interest is the fact that the signal cannot only be found at or near the cell surface but also within the cell. This suggests the presence of an intracellular isoform of the receptor resulting from the endogenous expression of splice variants and the internalization of transmembrane receptor. Taken together our results suggest that the loss of competence (for bFGF around stage 10) is not directly correlated with the presence of receptors. The possible roles of heparan sulphate glucosaminoglycans (low affinity receptors) and control mechanisms in the intracellular signalling pathway downstream of the receptor level should be taken into consideration. 相似文献
34.
Transformation of cereals via Agrobacterium and the pollen pathway: a critical assessment 总被引:1,自引:0,他引:1
Peter Langridge Reinhold Brettschneider Paul Lazzeri † Horst Lörz 《The Plant journal : for cell and molecular biology》1992,2(4):631-638
It has been proposed that transgenic plants of cereals can be generated by inoculating florets with Agrobacterium at or near anthesis. This procedure is shown to lead to the production of embryos of wheat and barley with enhanced resistance to antibiotic selection. It has also been possible to recover plants of wheat, barley and maize that gave positive hybridization signals with probes produced from within the T-DNA of the Agrobacterium vector. However, no evidence was found for transmission of the bands detected by hybridization in the progeny of the putative transgenic plants nor could enzyme activity associated with the resistance genes be found in plant extracts. Furthermore, undigested genomic DNA from the plants that were positive when probed with the T-DNA, showed hybridization to bands smaller than the genomic DNA. It is suggested that the apparent transformation is an artifact of the procedure and does not reflect transformation of the plant nuclear genome. 相似文献
35.
Rolf Altenburger Sibylle Abarzua Rainer Callies L. Horst Grimme Adalbert Mayer Dieter Leibfritz 《Archives of microbiology》1991,156(6):471-476
Cultures of the cyanobacterium Microcystis firma show rhythmic uptake and release of ammonia under conditions of carbon limitation. The massive removal of ammonia from the medium during the first light phase has little impact on the intracellular pH: a pH shift of less than 0.2 U towards the alkaline can be measured by in vivo 31P NMR. Furthermore, the energy status of the cells remains regulated. In vivo 15N NMR of M. firma, cultivated either with labelled nitrate or ammonia as the sole nitrogen source, reveals only gradual differences in the pool of free amino acids. Additionally both cultivation types show -aminobutyric acid, acid amides and yet unassigned secondary metabolites as nitrogen storing compounds. Investigating the incorporation of nitrogen under carbon limitation, however, only the amide nitrogen of glutamine is found permanently labelled in situ. While transamination reactions are blocked, nitrate reduction to ammonia can still proceed. Cation exchange processes in the cell wall are considered regarding the ammonia disappearance in the first phase, and the control of ammonia uptake is discussed with respect to the avoidance of intracellular toxification.Abbreviations GABA
-aminobutyric acid
- GOGAT
glutamate synthase
- GS
glutamine synthetase
- MDP
methylene diphosphonate
- MOPSO
3-(N-morpholino)-2-hydroxy-propanesulfonic acid
- NDPS
nucieoside diphosphosugars
- NOE
nuclear Overhauser effect
- NMR
nuclear magnetic resonance
For convenience, the term ammonia is used throughout to denote ammonia or ammonium ion when there is no good evidence as to which chemical species is involved 相似文献
36.
37.
Marta Zygulska Antonin Eigel Christa Aulehla-Scholz Jacek J. Pietrzyk Jürgen Horst 《Human genetics》1991,86(3):292-294
Summary Out of a population of 138598 infants born in southern Poland between 1987 and 1989, and screened for phenylketonuria (PKU), 28 cases were ascertained giving an incidence of 1 in 5000. DNA from 22 of these probands and their parents was isolated and eight polymorphic restriction sites were analyzed within the phenylalanine hydroxylase gene region. Twenty-one different haplotypes (HT) were revealed, five of them representing new categories. The most common haplotypes among those carrying normal alleles were: HT1 (27.3%) and HT4 (11.4%). Within the group of haplotypes with mutant alleles the most frequent was HT2 (56.8%), whereas the frequency of this haplotype in other European populations, such as French, Danish and German, ranged from 12% to 24%. HT3, being the most common in Danish (38%), and relatively frequent in the other western European (13–14%) populations, appeared to be very rare in our sample (2.3%). The mutation of codon 408 (exon 12, CT, ArgTrp), which has been described to be tightly linked to HT2, was tested on amplified DNA by dot-blot hybridization. This mutation was found in 25 out of 44 proband chromosomes. In one case it was linked to HT5, in the remaining 24 to HT2. Our results confirm molecular heterogeneity of PKU haplotypes, as well as their significant interpopulation variation. 相似文献
38.
Cytogenetic and molecular characterization of a newly established neuroblastoma cell line LS 总被引:2,自引:0,他引:2
Günter Rudolph Karin Schilbach-Stückle Rupert Handgretinger Peter Kaiser Horst Hameister 《Human genetics》1991,86(6):562-566
Summary A new human neuroblastoma cell line (LS) that originated from an abdominal tumor of a 16-month-old girl is presented; it was classified, according to Evans, as being stage III. Morphological (dense-core particles) and biochemical characteristics (dopamine--hydroxylase, acetylcholinesterase, neuron-specific-enolase) confirmed the diagnosis. In addition to a slightly variable modal chromosome number of 48 or 49 (because of marker-chromosomes and autosomal trisomies), cytogenetic analysis revealed two constantly appearing chromosomes with homogeneously stained regions (HSR's). The karyo-type remained constant over 50 passages in vitro [49,XX, –12,+der5, + 17,+mar1,+mar2]. Double minutes were a rare phenomenon and appeared only in a few metaphases. In situ hybridization showed that some of the HSR's consisted of amplified N-myc copies. The distribution of the N-myc copies according to in situ hybridization signals along the HSR's was compared with the data of Southern and Northern blotting analyses. 相似文献
39.
S N Walters T A Reinhardt M A Dominick R L Horst E T Littledike 《Archives of biochemistry and biophysics》1986,246(1):366-373
In order to investigate the subcellular distribution of unoccupied 1,25-dihydroxyvitamin D3 receptors, highly purified cytoplasts and nucleoplasts were prepared from two kidney cell lines (PK1 and MDBK). This was accomplished utilizing the technique of enucleation by cytochalasin B and density gradient centrifugation. Unoccupied 1,25-dihydroxyvitamin D3 receptors were found in both the nuclear and cytosolic compartments, with approximately 70% of the receptors localized in the cytoplasm. When cells were pretreated with 1,25-[3H]dihydroxyvitamin D, prior to enucleation, it was found that 90% of the receptor-hormone complex was associated with nucleoplasts, thus demonstrating that cytochalasin B treatment does not alter the high-affinity association of the receptor-hormone complex with the nucleus. The ratio of unoccupied receptor/protein was found to be the same in whole cells, cytoplasts, and nucleoplasts for both cell types. The ratio of unoccupied receptor/DNA was highest in cytoplasts and lowest in nucleoplasts. Taken together, these data indicate that the unoccupied 1,25-dihydroxyvitamin D receptor is generally associated with cell proteins and not specifically associated with cell DNA. We therefore propose, at least for these cells, that the unoccupied 1,25-dihydroxyvitamin D receptor exists in equilibrium between the nuclear and cytosolic compartments of the whole cell, and receptor-hormone binding shifts this equilibrium to favor nuclear localization. 相似文献
40.
Scenedesmus cells reach full hydrogen activity after 2.5 h ofanaerobic adaptation. Exposure to oxygen inactivates the hydrogenaseimmediately. Readaptation occurs with the same kinetics as primaryadaptation. The fast activation and reactivation as well asthe insensibility to cycloheximide suggest that hydrogenase,inactive or activated, is present in the chloroplast all thetime. The activation and even more the readaptation are sensitiveto chloramphenicol. Thus, we propose that hydrogenase itselfor an activating protein in the chloroplast have a rather fastturnover.
1 Present address: Pharathiar University, Dept. of Botany, Coimbatore,India. 相似文献