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31.
Jan-Wolfhard Kellmann Tatjana Kleinow Kerstin Engelhardt Christina Philipp Dorothee Wegener Jeff Schell Peter H. Schreier 《Plant molecular biology》1996,30(2):351-358
Two different genes encoding class II chitinases from peanut (Arachis hypogaea L. cv. NC4), A.h.Chi2;1 and A.h.Chi2;2, have been cloned. In peanut cell suspension cultures, mRNA levels of A.h.Chi2;2 increased after ethylene or salicylate treatment and in the presence of conidia from Botrytis cinerea. The second gene, A.h.Chi2;1, was only expressed after treatment with the fungal spores. Transgenic tobacco plants containing the complete peanut A.h.Chi2;1 gene exhibited essentially the same expression pattern in leaves as observed in peanut cell cultures. Expression characteristics of transgenic tobacco carrying a promoter-GUS fusion of A.h.Chi2;1 are described. 相似文献
32.
Jeff Prideaux 《Acta biotheoretica》1996,44(3-4):219-233
This paper explores the consequences of the theoretical forward activation enzymatic pathway A
0 A
1 A
2 A
3 where E
1 convents A
0 to A
1, E
2 converts A
1 to A
2 and E
3 converts A
2 to A
3. A
0, which is environmentally determined, also serves to activate (or modulate) the activity of E
3 in such a way as to keep the concentration of A
2 ([A
2]) constant at a particular set-point value. For mathematical simplicity, first order rate kinetics are used where k
1, k
2 and k
3 are the rate constants for E
1, E
2, and E
3 respectively. It is shown that if k
3 is modulated appropriately so as keep [A
2] at the setpoint value with a changing upstream [A
0], then the modulation of k
3 must be anticipatory of the dynamics of the biochemical pathway. In other words, the rate of change of k
3, will be a function of [A
0], k
1, k
2, k
3, and the set-point value of [A
2]. If the modulation of k
3 does not perfectly model (anticipate) the reaction pathway of which it is a part, then the actual [A
2] will deviate from the set-point value. This type of anticipatory feed-forward activation may represent an important aspect of biological organization. 相似文献
33.
Cultured steroidogenic cells derived from the adrenal glands of duck embryos were used to study changes in the distribution of actin associated with the corticotropic responsiveness. Actin-containing components were identified by rhodamine-phalloidin staining. The actin in most of the unstimulated cells occurred as stress fibers that either ran parallel throughout the cell or were present as domains of parallel fibers at angles to one another. When incubated in Krebs-Henseleit buffer containing 1–24 ACTH, the cells released approximately equal amounts of corticosterone and aldosterone. Incubation of the cells in buffer containing cytochalasin D caused the cells to lose their stress fibers, and the actin became distributed at the periphery in what appeared to be fragments of stress fibers and clumps of fibrous material in the central cytoplasm. Although cytochalasin D did not affect the basal output of corticosterone and aldosterone, the 1–24 ACTH-induced rates of both hormones were suppressed significantly. After the cells had been washed in unadulterated buffer, the normal distribution of actin stress fibers was restored and the cells responded normally when incubated in buffer containing 1–24 ACTH. These results suggest that the actin components of the cytoskeleton are important determinants of corticotropin-induced steroidogenic responsiveness. 相似文献
34.
Kowit Chaisurisri Jeff B. Mitton Yousry A. El-Kassaby 《American journal of botany》1994,81(11):1410-1415
Five allozyme polymorphisms were used to analyze the mating system in a Sitka spruce seed orchard in Saanichton, British Columbia. Allelic frequencies differed between the pollen and maternal pools at three of the five loci, with alleles rare in the maternal pool being even rarer in the effective pollen pool. Minor differences in pollen allelic frequencies were observed in the upper vs. lower crown. The multilocus outcrossing rate of the upper crown (tm = 0.909) exceeded that of the lower crown (tm = 0.764). Single-locus estimates of the outcrossing rate were significantly heterogeneous, with the lowest estimate of outcrossing, t = 0.773, observed for PGM-2 locus. Analyses of the mating system for the three maternal PGM-2 genotypes revealed heterogeneous pollen allelic frequencies and heterogeneous outcrossing rates, possibly due to assortative mating at this locus. 相似文献
35.
We review the recent history of the Mute Swan in Great Britain and discuss the factors known to be affecting the population. Following a rise in the national population during the 1950s, numbers decreased sharply during the 1960s, and changed relatively little between 1970/71 and 1984/85. However, there has been considerable regional variation in the fortunes of Mute Swan populations during this period, with dramatic declines in some areas. Although several factors were thought to be contributing to such declines, poisoning from the ingestion of lead fishing weights was shown to be the largest single cause of death amongst swans in a number of areas. Voluntary measures to address this problem were initiated in 1982 and culminated in the banning by law of use of lead weights in 1987.Winter counts were used to investigate the current status and distribution of the Mute Swan in Great Britain and to examine long-term regional trends. The maximum total count reached 12600 birds in January 1990, which compares with an average of 9550 for the previous five winters. However, accounting for birds missed, the population may now number at least 25 000. Peak total numbers have mostly occurred in September, after which numbers remain approximately stable until December and then decline. Patterns of seasonal abundance vary between regions and habitats and these are discussed.The British population has increased dramatically since 1986/87 and reached its highest level for 27 years in 1987/88. There have been recent increases in most regions with record levels being reached mostly in 1987 or 1988, and there has been growth in the numbers on all habitat types, especially on reservoirs, gravel extraction pits and freshwater marshes. The timing of these increases corresponds very closely with the introduction of legislation against the use of lead fishing weights, and the incidence of lead poisoning is known to have been considerably reduced by such measures. 相似文献
36.
Cloning and expression of a soluble sialidase from Chinese hamster ovary cells: sequence alignment similarities to bacterial sialidases 总被引:10,自引:2,他引:8
A cDNA encoding a soluble sialidase from Chinese hamster ovary(CHO) cells has been cloned and expressed. Completely degenerateoligonucleotide primers, which were based on the amino acidsequence of peptides obtained from the purified sialidase (Warneret al., Glycobiology, 3, 455463, 1993), and the polymerasechain reaction, with single-stranded cDNA template, were employedto generate a unique oligonucleotide probe. The unique probeof 93 bp was used for screening a 相似文献
37.
38.
Melvin J. Oliver David L. Ferguson John J. Burke Jeff Velten 《Molecular & general genetics : MGG》1993,239(3):425-434
Tobacco plants were genetically transformed to generate antisense RNA from a gene construct comprised of a full-length cucumber NADH-dependent hydroxypyruvate reductase (HPR) cDNA placed in reverse orientation between the cauliflower mosaic virus 35S promoter and a nopaline synthase termination/polyadenylation signal sequence. In vivo accumulation of antisense HPR RNA within eight independent transgenic tobacco plants resulted in reductions of up to 50% in both native HPR activity and protein accumulation relative to untransformed tobacco plants (mean transgenote HPR activity=67% wild type, mean transgenote HPR protein=63% wild type). However, in contrast to previous reports describing antisense RNA effects in plants, production of the heterologous HPR antisense RNA did not systematically reduce levels of native tobacco HPR mRNA (mean transgenote HPR mRNA level=135% wild type). Simple regression comparison of the steady-state levels of tobacco HPR mRNA to those of HPR antisense RNA showed a weak positive correlation (r value of 0.548, n=9 ; n is wild type control plus eight independent transformants; significant at 85% confidence level), supporting the conclusion that native mRNA levels were not reduced within antisense plants. Although all transgenic antisense plants examined displayed an apparent reduction in both tobacco HPR protein and enzyme activity, there is no clear correlation between HPR activity and the amount of either sense (r=0.267, n=9) or antisense RNA (r=0.175, n=9). This compares to a weak positive correlation between HPR mRNA levels and the amount of HPR activity observed in wild-type SRI tobacco plants (r=0.603, n=5). The results suggest that in vivo production of this heterologous HPR antisense RNA is inhibitory at the level of HPR-specific translation and produces its effect in a manner not dependent upon, nor resulting in, a reduction in steady-state native HPR mRNA levels. In this context, the observed antisense effect appears to differ mechanistically from most antisense systems described to date. 相似文献
39.
40.
Jeff Elhai 《FEMS microbiology letters》1993,114(2):179-184
Abstract The strengths of several promoters were assessed in the cyanobacterium Anabaena PCC 7120 by fusing them to luxAB , encoding bacterial luciferase. Two promoters, P tac and P psbA , with sequences nearly identical to consensus Escherichia coli σ 70 promoters, gave as high or higher expression than the strong Anabaena promoter, P rbc . P npt , the natural promoter driving expression of the kanamycin-resistance determinant from Tn5, was poorly expressed in Anabaena . The Lac repressor partially repressed expression from P tac , permitting regulated expression in Anabaena after induction with isopropyl thiogalactoside to a level 4–5-fold higher than without inducer. 相似文献