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11.
Cytokinin-binding proteins 总被引:3,自引:0,他引:3
This article is focused on the modalities of reception of cytokinins which remain largely unknown. It summarizes the main steps of the different protocols used to study cytokinin-binding proteins (CBPs). We place emphasis on the significance and specificity of the detection according to the properties of the probes used: radioactive or photoreactive cytokinins, fluorescent anticytokinins, anti-idiotype antibodies. The purification procedures are also examined. The cellular localisation and the putative physiological roles of the numerous and different CBPs found are considered. The interest of genetic and molecular studies is discussed. 相似文献
12.
A respiration-deficient (RD) mutant was isolated from the petite-negative, salt-tolerant yeast Zygosaccharomyces rouxii. One strain among sixteen glycerol-non-utilizing mutants exhibited vigorous liberation of CO2 but no uptake of O2. Furthermore, this strain lacked cytochrome aa3 and had a reduced level of cytochrome b. The few mitochondria found in cells of this strain contained few or no cristae. Salt tolerance and intracellular accumulation of glycerol by the RD strain were almost equal to that of the wild-type strain in media containing NaCl up to 2.5 M. In media with more than 3 M NaCl, the growth of the RD mutant was retarded and the intracellular accumulation of glycerol was depressed in spite of ample production. 相似文献
13.
The metabolic consequences of two defects in pyruvate metabolism of the hyphal fungus Aspergillus nidulans have been investigated by natural abundance 13C-NMR spectroscopy. A pyruvate dehydrogenase complex (pdh) mutant, grown on acetate, accumulates alanine upon starvation which is derived from mannitol reserves. The
-alanine level increases further upon incubation with the non-permissive substrate
-glucose.
-Glutamate is absent from these spectra as it is required both for the transamination of pyruvate and as a reaction on an impaired energy metabolism in such a pdh-deficient strain. A pyruvate carboxylase (pyc) mutant, grown upon acetate, only starts to accumulate alanine after a long incubation period with
-glucose, due to the long-lasting presence of phosphoenolpyruvate carboxykinase and malic enzyme, which are both induced by growth on acetate. When this strain is grown on
-fructose and
-glutamate, alanine also accumulates within 3 h upon transfer to
-glucose. 相似文献
14.
P. A. Scolnik P. Hinton I. M. Greenblatt G. Giuliano M. R. Delanoy D. L. Spector D. Pollock 《Planta》1987,171(1):11-18
The tomato (Lycopersicon esculentum (L.) Mill.) ghost plant is a mutant of the San Marzano cultivar affected in carotenoid biosynthesis. ghost plants exhibit a variable pattern of pigment biosynthesis during development. Cotyledons are green but true leaves are white. Green sectors, which appear to be clonal in origin, are frequently observed in the white tissue. Because of the lack of photosynthesis ghost plants have a very low viability in soil. We have developed a strategy for propagating ghost plants that employs organ culture to generate variegated green-white plants which, supported by the photosynthetic green areas, develop in soil to almost wild-type size. These plants were used to analyze the pigment content of the different tissues observed during development and plastid ultrastructure. Cotyledons and green leaves contain both colored carotenoids and chlorophyll but only the colorless carotenoid phytoene accumulates in white leaves. the plastids in the white tissue of ghost leaves lack internal membrane structures but normal chloroplasts can be observed in the green areas. The chromoplasts of white fruits are also impaired in their ability to form thylakoid membranes. 相似文献
15.
Alain Levine Gilles Henckes Françoise Vannier Simone J. Séror 《Molecular & general genetics : MGG》1987,208(1-2):37-44
Summary When the dnaB37 initiation mutant of Bacillus subtilis is returned to a permissive temperature following a period at 45° C, a synchronous round of DNA replication immediately ensues. Using this system we have been able to analyse the first fragments to be replicated while avoiding the use of thymine starvation or inhibitors of DNA replication. Such treatments are necessary to achieve even modest synchrony in germinating spores. Our results showed that the first fragment to be replicated was a 4kb BamHI-SalI restriction fragment, BS6. In contrast, when the analysis was performed out in the presence of novobiocin, an inhibitor of DNA gyrase, replication from BS6 was inhibited and the first fragment to be replicated was BS5, a 5.6 kb fragment located 1.7 kb to the right of BS 6. Replication from both putative origins was suppressed by rifamycin and was dependent upon dnaB. The results are discussed in relation to previous attempts to identify the first replicating fragment in germinating spores. We also discuss the possibility that B. subtilis contains two origins and suggest that either can act as the primary origin under certain conditions, or alternatively that both origins may act in concert in normal bidirectional replication, each site being required for the leading strand in each direction. 相似文献
16.
Mutations in the E1a gene of type 5 adenovirus result in oncogenic transformation of Fischer rat embryo cells 总被引:1,自引:0,他引:1
G J Duigou L E Babiss W S Liaw S G Zimmer H S Ginsberg P B Fisher 《Journal of cellular biochemistry》1987,33(2):117-126
Transformation of a specific clone of Fischer rat embryo (CREF) cells with wild-type 5 adenovirus (Ad5) or the E1a plus E1b transforming gene regions of Ad5 results in epithelioid transformants that grow efficiently in agar but that do not induce tumors when inoculated into nude mice or syngeneic Fischer rats. In contrast, CREF cells transformed by a host-range Ad5 mutant, H5hrl, which contains a single base-pair deletion of nucleotide 1055 in E1a resulting in a 28-kd protein (calculated) in place of the wild-type 51-kd acidic protein, display a cold-sensitive transformation phenotype and an incomplete fibroblastic morphology but surprisingly do induce tumors in nude mice and syngeneic rats. Tumors develop in both types of animals following injection of CREF cells transformed by other cold-sensitive Ad5 E1a mutants (H5dl101 and H5in106), which contain alterations in their 13S mRNA and consequently truncated 289AA proteins. CREF cells transformed with only the E1a gene (0-4.5 m.u.) from H5hrl or H5dl101 also produce tumors in these animals. To directly determine the role of the 13S E1a encoded 289AA protein and the 12S E1a encoded 243AA protein in initiating an oncogenic phenotype in adenovirus-transformed CREF cells, we generated transformed cell lines following infection with the Ad2 mutant pm975, which synthesizes the 289AA E1a protein but not the 243AA protein, and the Ad5 mutant H5dl520 and the Ad2 mutant H2dl1500, which do not produce the 289AA E1a protein but synthesize the normal 243AA E1a protein. All three types of mutant adenovirus-transformed CREF cells induced tumors in nude mice and syngeneic rats. Tumor formation by these mutant adenovirus-transformed CREF cells was not associated with changes in the arrangement of integrated adenovirus DNA or in the expression of adenovirus early genes. These results indicate, therefore, that oncogenic transformation of CREF cells can occur in the presence of a wild-type 13S E1a protein or a wild-type 12S E1a protein when either protein is present alone, but does not occur when both wild-type E1a proteins are present. 相似文献
17.
Immunological cross-reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase generated both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, beta and beta', and the two small and intact subunits, alpha and sigma. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state. Using this method, degradation in vivo was found for some, but not all, of the amber fragments of beta subunit in merodiploid cells carrying both wild-type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli, degradation of the full-sized subunits was found in two cases, i.e., several temperature-sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary-phase cells of a wild-type E. coli. The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure. 相似文献
18.
The fluorescence of the lipophilic prbe N-phenyl-1-naphthylamine (NPN) bound to intact cells of Escherichia coli is quenched by the addition of glucose, succinate,
-lactate, pyruvate, formate and glycerol. Partial recovery of fluorescence occurs on anaerobiosis. Use of mutants with defects in the ATP synthase or the respiratory chain show that quenching of fluorescence may be energized either by ATP hydrolysis or by substrate oxidation through the respiratory chain. Permeabilization of the outer membrane by treatment of intact cells with EDTA, or use of a mutant with an outer membrane permeable to lipophilic substances, results in a more rapid binding of NPN and in a decrease in quenching observed on substrate addition. NPN binds rapidly to everted membrane vesicles, but does not respond to membrane energization. It is proposed that inner membrane energization in intact cells alters the binding or environment of NPN in the outer membrane. The fluorescence recovery which occurs on anaerobiosis has two components. One component represents a reversal of the changes which occur on membrane energization. The other component of the fluorescence change is insensitive to the uncoupler CCCP and resembles the behaviour of NPN with everted membrane vesicles. It is suggested that a portion of the fluorescence events seen with NPN involves a response of the probe to changes in the inner membrane. 相似文献
19.
Hiroshi Taniguchi Takuya Tokida Hiroshi Fujita Hiraku Itikawa 《Molecular & general genetics : MGG》1989,217(2-3):317-323
Summary IndnaK7(Ts) mutant cells, scission of DNA strands occurred after temperature shift up. When cells at 30°C were labeled with [3H]-thymidine and then shifted to 46° or 49°C for 20 min, the profiles of sedimentation of thier cellular DNA in an alkaline
sucrose gradient revealed a decrease in the size of DNA to a quarter of that at 30°C in the mutant, but not in wild-type cells.
The level of manganese-containing superoxide dismutase (MnSOD) in the mutant was about twice that in wild-type cells, even
at the permissive temperature, implying increased production of superoxide radical anion, which may cleave DNA strands directly
or indirectly in the mutant. Moderate increase in the MnSOD level on temperature shift up was observed in both strains. These
results indicated that some components of the DnaK protein participate in protection of cellular membrane functions from thermal
damage resulting from elevated production of the superoxide anion radical. 相似文献
20.
Joseph C. Polacco Adam K. Judd Jody K. Dybing Silvia R. Cianzio 《Molecular & general genetics : MGG》1989,217(2-3):257-262
Summary We reported earlier the recovery of two classes of soybean urease mutants in soybean (Glycine max L. Merr. cv. Williams). Class I mutants lack the embryo-specific urease while class II mutants lack the activities of both
urease isozymes, the embryo-specific and the ubiquitous urease, the latter found in all tissues examined. We report here the
recovery of a true-breeding mutant, aj3, which represents the third phenotypic class: normal levels of embryo-specific urease
and little or no ubiquitous urease. Unlike class II mutant plants which lack urease in all tissue, aj3 lacks urease activity
only in leaves (ca. 2% normal activity); its roots have near normal urease activity. Callus derived from leaves of aj3 has
14% to 40% the urease activity of Williams 82 callus. This partial reduction in urease activity in aj3 callus is sufficient
to reduce growth with urea as sole nitrogen source and to confer resistance to 50 mM urea added to callus maintenance medium.
Leaves of aj3 produce more than 40 times the urease antigen expected from their urease activity. The aj3 trait is due to a
single recessive lesion which is not allelic with lesions at theEu2, Eu3 (class II) orEu1 (class I) loci. We designate the aj3 genotype aseu4/eu4. 相似文献