Summary The establishment of actinorhizal root nodules involves penetration of host cell walls and intracellular colonization by the nitrogen-fixing endosymbiont,Frankia (Actinomycetales). In the early stages of the infection process inAlnus, unusual cell walls with undulate profiles were observed in root tip meristematic derivatives, and in early (preinfection) derivatives of the nodule lobe meristem, inFrankia-inoculated plants. The irregular cell walls attached obliquely to preexisting walls, but were not discontinuous. Serial sections revealed that the unusual walls divided two daughter cells. Microtubules in bundled arrays were abundant near the undulate walls, and radiated in several planes. In the root tips, the anomalous cell walls were observed within one day of inoculation withFrankia. 相似文献
Intra-population quinoline alkaloid profiles surveying quinine, quinidine, cinchonine and cinchonidine were determined for each of five populations of Cinchona ledgeriana grown as shoot-culture for 125 days. No significant difference in respect of mean alkaloid content between populations was detected. In contrast, there was considerable between-seedling variation in alkaloid content within each population. When nutrients were delivered to shoot-cultures in droplet form by means of an aerosol spray (as compared to the supply of nutrients direct from agar-or liquid-based reservoirs) alkaloid profile was greatly perturbed; most notable in this respect was a four-fold increase in the production of cinchonidine concomitant with a four-fold decrease in the production of cinchonine. These data are discussed with reference to the optimisation of quinoline alkaloid production by juvenile shoot-cultures of Cinchona ledgeriana. 相似文献
A protocol is described for high frequency plant regeneration from isolated leaf protoplasts of several genotypes of the wild tomato species Lycopersicon hirsutum f. hirsutum based on modified tomato protoplast culture methods. Three to four week old seedlings exposed to a low light pretreatment yielded protoplasts capable of sustained divisions on modified Lycopersicon Culture Medium. Plating efficiencies varied from 7.2%–25.9%. Colonies were transferred to modified solid greening medium after 25–35 days. Developing calli that turned bright green and produced dark green bud primordia were transferred to shoot induction medium. Shoot formation efficiencies ranged from 60%–85%. Shoots rooted easily and regenerated plants grown to complete maturity showed only transient somaclonal variation.Abbreviations BA
benzylamino purine
- MES
2-(N-morpholino)-ethane sulfonic acid
- NAA
naphthalene acetic acid 相似文献
An affinity matrix for the purification of norsolorinic acid dehydrogenase, an enzyme involved in aflatoxin biosynthesis, was prepared by coupling norsolorinic acid to an agarose gel. This matrix was found to be ineffective in isolating active enzyme, and was therefore modified by methylation, using diazomethane. The methylated matrix produced a one-step purification of the enzyme from a crude homogenate, resulting in a 138-fold purification. The active isolate was found to contain one major and two minor bands upon nondenaturing electrophoresis, and all the norsolorinic acid dehydrogenase activity was associated with the major band. It was concluded that the matrix exhibited true affinity for the enzyme, and that affinity chromatography was a valuable approach to isolating other secondary metabolic enzymes involved in the biosynthesis of the aflatoxins. 相似文献
Genes for 51.4- and 41.9-kDa insecticidal proteins of Bacillus sphaericus were separately cloned and expressed in Escherichia coli. Both proteins were required for toxicity. Approximately equal numbers of cells containing the 51.4- and 41.9-kDa proteins produced the greatest toxicity; excess 41.9-kDa protein did not affect toxicity, whereas excess 51.4-kDa protein reduced activity. Larvae were killed when 41.9-kDa protein was fed up to 24 h after the 51.4-kDa protein, but not when the order of feeding was reversed. Radiolabelled toxins bound in approximately equal amounts to the gastric caecum and posterior midgut of Culex quinquefasciatus larvae. Radiolabelled 51.4-kDa protein was rapidly degraded by ca. 12-13 kDa in the larval gut, while 41.9-kDa protein was degraded by 1-2 kDa. Nonreduced toxin extracted from B. sphaericus produced a band on SDS-PAGE of ca. 68-74 kDa that contained both 51.4- and 41.9-kDa proteins based on sequence analysis, and a band of ca. 51 kDa that contained primarily 41.9-kDa protein. Escherichia coli containing 51.4-kDa protein enhanced toxicity of the latter eluted SDS-PAGE band. These proteins may associate very strongly, and trace amounts of 51.4-kDa protein in preparations of 41.9-kDa protein from B. sphaericus may be responsible for the previously reported toxicity of the latter. 相似文献
Summary Some of the extract and intracellular enzyme activities in K2nB strain of Saccharomyces cerevisiae that growing in the condition which induce spontaneous cell rupture, were measured. B-1-3-glucanase, invertase, acid phosphatase and active chitin synthetase zymogen showed a reduced activity in ruptured cell while alkaline phosphatase shows no differences in its activity. 相似文献
Addition of coformycin (0.5 microgram/ml) to a culture medium containing adenine causes in Chinese hamster fibroblasts a lethal depletion of IMP. Resistant variants have been recovered, some of which exhibit increased adenylate deaminase activity. (Debatisse et al., J. Cell. Physiol., 106:1-11, 1981). The selective medium was made more specific for the isolation of this class of variants by supplementation with azaserine. The hyperactive variants remained sensitive to coformycin concentrations above that used for their selection and were unstable. Their frequency was not increased by ethyl methane sulfonate mutagenesis. The resistant phenotype and the increased activity of adenylate deaminase behaved as semidominant traits in hybrids. No change was detected in the Km for AMP, the cofactor requirement, or the chromatographic properties of adenylate deaminase in the variants. Through stepwise selection in media supplemented with increasing coformycin concentrations, unstable clones with adenylate deaminase activity up to 150-fold the wild-type level were isolated; from an unstable clone, a stable subclone with reduced resistance and enzyme activity was recovered. Evidence that increased adenylate deaminase activity is the manifestation of overaccumulation of the enzyme protein was supplied by the correlation of enzyme activity with the intensity of a protein band comigrating with purified adenylate deaminase during sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cell extracts. Several unidentified additional bands showed comparable quantitative changes. The striking similarity between the adenylate deaminase-overproducing lines and unstable dihydrofolate reductase-overproducing lines generated by gene amplification strongly suggests that the coformycin-resistant variants also resulted from amplification of an adenylate deaminase gene. 相似文献
The temperature boundary for phase separation of membrane lipids extracted from Nerium oleander leaves was determined by analysis of spin label motion using electron spin resonance spectroscopy and by analysis of polarization of fluorescence from the probe, trans-parinaric acid. A discontinuity of the temperature coefficient for spin label motion, and for trans-parinaric acid fluorescence was detected at 7°C and −3°C with membrane lipids from plants grown at 45°C/32°C (day/night) and 20°C/15°C, respectively. This change was associated with a sharp increase in the polarization of fluorescence from trans-parinaric acid indicating that significant domains of solid lipid form below 7°C or −3°C in these preparations but not above these temperatures. In addition, spin label motion indicated that the lipids of plants grown at low temperatures are more fluid than those of plants grown at higher temperatures.
A change in the molecular ordering of lipids was also detected by analysis of the separation of the hyperfine extrema of electron spin resonance spectra. This occurred at 2°C and 33°C with lipids from the high and low temperature grown plants, respectively. According to previous interpretation of spin label data the change at 29°C (or 33°C) would have indicated the temperature for the initiation of the phase separation process, and the change at 7°C (or −3°C) its completion. Because of the present results, however, this interpretation needs to be modified.
Differences in the physical properties of membrane lipids of plants grown at the hot or cool temperatures correlate with differences in the physiological characteristics of plants and with changes in the fatty acid composition of the corresponding membrane lipids. Environmentally induced modification of membrane lipids could thus account, in part, for the apparently beneficial adjustments of physiological properties of this plant when grown in these regimes.
Rats were injected subcutaneously for 147 consecutive days with large volumes of urine from control subjects and from patients with Huntington's chorea (HC) in an effort to test for presence of a possible neurotoxic substance in HC. No evidence of illness was observed in animals treated with HC urine, and their behavior did not differ from animals treated with control urine. After rats were sacrificed, striatum was examined for the biochemical and neuropathological changes seen in human striatum in HC. No deficiency of γ-aminobutyric acid content, nor reduction in activities of glutamic acid decarboxylase and choline acetyltransferase, was found in striatum of rats chronically treated with HC urine. Also, no significant differences were found between striatum of control and experimental rats by light or electron microscopy. These results neither support for exclude the possibility of a neurotoxic mechanism for the neuronal loss characteristic of HC. 相似文献