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161.
Evolution of reproductive systems in the genus Silene 总被引:2,自引:0,他引:2
Desfeux C Maurice S Henry JP Lejeune B Gouyon PH 《Proceedings. Biological sciences / The Royal Society》1996,263(1369):409-414
The genus Silene contains both hermaphrodite, gynodioecious and dioecious species, dioecy being represented in three sections of the genus. To locate the events of change of reproductive systems, we compared ITS sequences of 22 species of Silene chosen throughout the whole genus, and four putative outgroup species. Gynodioecy, which is the most common reproductive system within the genus Silene and in closely related genera such as Saponaria and Dianthus, is proposed to be ancestral in the genus. Dioecy has evolved at least twice: once in the section containing S. latifolia, and once in the clade containing S. otites and S. acaulis ssp. bryoides. Evolution towards hermaphroditism, associated with evolution of selfing has also occurred at least twice, in S. gallica and S. comica. 相似文献
162.
Rospars Jean-Pierre Lánský Petr Tuckwell Henry C. Vermeulen Arthur 《Journal of computational neuroscience》1996,3(1):51-72
The coding of odor intensity by an olfactory receptor neuron model was studied under steady-state stimulation. Our model neuron is an elongated cylinder consisting of the following three components: a sensory dendritic region bearing odorant receptors, a passive region consisting of proximal dendrite and cell body, and an axon. First, analytical solutions are given for the three main physiological responses: (1) odorant-dependent conductance change at the sensory dendrite based on the Michaelis-Menten model, (2) generation and spreading of the receptor potential based on a new solution of the cable equation, and (3) firing frequency based on a Lapicque model. Second, the magnitudes of these responses are analyzed as a function of odorant concentration. Their dependence on chemical, electrical, and geometrical parameters is examined. The only evident gain in magnitude results from the activation-to-conductance conversion. An optimal encoder neuron is presented that suggests that increasing the length of the sensory dendrite beyond about 0.3 space constant does not increase the magnitude of the receptor potential. Third, the sensivities of the responses are examined as functions of (1) the concentration at half-maximum response, (2) the lower and upper concentrations actually discriminated, and (3) the width of the dynamic range. The overall gain in sensitivity results entirely from the conductance-to-voltage conversion. The maximum conductance at the sensory dendrite appears to be the main tuning constant of the neuron because it determines the shift toward low concentrations and the increase in dynamic range. The dynamic range of the model cannot exceed 5.7 log units, for a sensitivity increase at low odor concentration is compensated by a sensitivity decrease at high odor concentration. 相似文献
163.
P. W. J. Taylor J. R. Geijskes H.-L. Ko T. A. Fraser R. J. Henry R. G. Birch 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(7-8):1169-1173
Random amplified polymorphic DNA (RAPD) analysis using 10-mer oligonucleotide primers efficiently differentiated sugarcane cultivars and proved suitable for detecting gross genetic change such as that which can occur in sugarcane subjected to prolonged tissue culture, for example in protoplast-derived callus. However, RAPD analysis was not sufficiently sensitive to detect smaller genetic changes that occur during sugarcane genetic transformation. The length of DNA scored for polymorphism per primer averaged 13.2 kb, or 0.0001% of the typical sugarcane genome size of 1.2 × 107 kb (2C). RAPD analysis of sugarcane plants regenerated from embryogenic callus revealed very few polymorphisms, indicating that gross genetic change is infrequent during this tissue culture procedure, although epigenetic effects result in transient morphological changes in regenerated plants. More sensitive variations on the RAPD technique may increase the practicality of DNA-based screening of regenerated plant lines to reveal somaclonal variants. 相似文献
164.
The use of bulk segregant analysis to identify a RAPD marker linked to leaf rust resistance in barley 总被引:4,自引:0,他引:4
D. M. E. Poulsen R. J. Henry R. P. Johnston J. A. G. Irwin R. G. Rees 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(2):270-273
An F2 population from a cross between barley accession Q21861 and the Australian barley variety Galleon was used to develop RAPD markers for resistance to barley leaf rust (Puccinia hordei). Resistant and susceptible DNA bulks were constructed following the classification of F2 plants by leaf rust infection type. Bulked segregant analysis was then used to identify a 2.7-kb marker, designated OU022700 and located approximately 12cM from RphQ, a leaf rust resistance gene in Q21861. The marker was generated by PCR with the oligonucleotide primer OPU-02 (Operon). Infection types of F3 progeny were used to confirm assignment of F2 genotypes. OU022700 was shown, retrospectively, to be useful in the identification of individual F2 plants that had been originally misclassified as having susceptible infection types. Both the RAPD marker and RphQ will be potentially useful in the development of new barley cultivars. 相似文献
165.
166.
Studies were carried out in the laboratory on the influences of time of day, temperature, relative humidity and starvation
on flight initiation byProstephanus truncatus (Horn) (Coleoptera: Bostrichidae). Flight occurred throughout the 12 h photophase and at the beginning of the scotophase
but peaked at 2–0 h before darkness. Temperature exerted a significant effect on flight. The frequency of flight take-off
increased with temperature over the range 20–30°C but declined sharply at 35°C. Flight activity increased with starvation
up to a maximum at 2 days after which it began to decline. 相似文献
167.
Stephen M. Henry Per-?ke Jovall Sohbat Ghardashkhani Mikael L. Gustavsson Bo E. Samuelsson 《Glycoconjugate journal》1995,12(3):309-317
Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Lec), H type 1 (Led), Lea and Leb epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc1-2Gal1-3GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Leb blood group glycolipids (Fuc1-2Gal1-3(Fuc1-4)GlcNAc1-3Gal1-4Glc1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals.
Abbreviations: HPLC, high performance liquid chromatography; TLC, (high performance) thin layer chromatography; EI-MS, electron impact ionisation mass spectrometry; LSIMS, liquid secondary ion mass spectrometry; NMR, nuclear magnetic resonance spectroscopy. The sugar types are abbreviated to Hex for hexose, HexNAc forN-acetylhexosamine and dHex for deoxyhexose (fucose). The ceramide types are abbreviated to d for dihydroxy and t for trihydroxy base, n for non-hydroxy and h for hydroxy fatty acids; LCB, long chain base. 相似文献
168.
The effect of different genotypes of the ectomycorrhizal fungus Hebeloma cylindrosporum on in vitro rooting of micropropagated cuttings of Prunus avium and P. cerasus was studied in an attempt to determine whether ectomycorrhizal fungi could enhance in vitro adventitious root formation in
plants which form arbuscular endomycorrhizas. The rooting percentage of P. avium cuttings was approximately 16% in the absence of hormonal treatment; it increased up to 30% in the presence of 5.7 μM IAA
which was the most favourable auxin concentration. The rooting percentage of cuttings cultivated in the absence of IAA was
enhanced by all the studied strains of H. cylindrosporum. It ranged from 50 to 60% with the IAA-overproducing mutant D 111 or the wild-type dikaryon D1, to 100% in the presence of
the mutants 331 or D 117. The cuttings of P. cerasus showed a higher rooting ability than those of P. avium since approximately 40% of them were able to root in the absence of hormonal treatment. Except for the mutant D117, their
rooting percentage was not significantly improved by H. cylindrosporum. Fungal inoculation also affected the survival of cuttings at acclimatization: 50% of the uninoculated P. avium cuttings survived whereas the survival percentage of inoculated cuttings ranged from 30 to 100% depending on the fungal genotype.
With P. cerasus, the percentage of survival of uninoculated cuttings ranged from 85 to 100% and fungi either did not significantly improve
it or lowered it. At acclimatization fungal hyphae could be observed in close contact with adventitious roots, but they did
not establish mycorrhizal association. The shoot height of P. avium plantlets obtained from inoculated cuttings was not significantly different from that of plantlets originating from uninoculated
ones. By contrast, fungal inoculation generally depressed the growth of acclimatized P. cerasus plantlets. The possibility of using ectomycorrhizal fungi as a tool to enhance rooting of micropropagated cuttings of plants
which do not form ectomycorrhizas is discussed.
Received: 25 November 1996 / Accepted: 2 June 1997 相似文献
169.
Targeting Determinants and Proposed Evolutionary Basis for the Sec and the Delta pH Protein Transport Systems in Chloroplast Thylakoid Membranes 总被引:3,自引:0,他引:3 下载免费PDF全文
Ralph Henry Matthew Carrigan Michael McCaffery Xianyue Ma Kenneth Cline 《The Journal of cell biology》1997,136(4):823-832
Transport of proteins to the thylakoid lumen is accomplished by two precursor-specific pathways, the Sec and the unique Delta pH transport systems. Pathway selection is specified by transient lumen-targeting domains (LTDs) on precursor proteins. Here, chimeric and mutant LTDs were used to identify elements responsible for targeting specificity. The results showed that: (a) minimal signal peptide motifs consisting of charged N, hydrophobic H, and cleavage C domains were both necessary and sufficient for pathway-specific targeting; (b) exclusive targeting to the Delta pH pathway requires a twin arginine in the N domain and an H domain that is incompatible with the Sec pathway; (c) exclusive targeting to the Sec pathway is achieved by an N domain that lacks the twin arginine, although the twin arginine was completely compatible with the Sec system. A dual-targeting signal peptide, constructed by combining Delta pH and Sec domains, was used to simultaneously compare the transport capability of both pathways when confronted with different passenger proteins. Whereas Sec passengers were efficiently transported by both pathways, Delta pH passengers were arrested in translocation on the Sec pathway. This finding suggests that the Delta pH mechanism evolved to accommodate transport of proteins incompatible with the thylakoid Sec machinery. 相似文献
170.
The yeast Peptide Sensitive Channel (PSC), a cationic channel of the mitochondrial outer membrane closes with slow kinetics
at potentials of either polarity. The properties of this inactivation closely resemble those of the Voltage-Dependent Anion
Channel (VDAC) slow kinetics closures. Addition of trypsin to one compartment suppresses the inactivation observed when this
compartment is made positive, but does not affect the inactivation observed at potentials of reverse polarity. Both sides
of the channel are sensitive. The reduced form of the Mast Cell Degranulating peptide (rMCD) increases the rate of inactivation,
but only when the polarity of the compartment to which it is added is positive. The effect is not reversed by washing the
peptide out, but is suppressed by trypsin. The peptide can bind to both sides of the membrane. The effect of rMCD on PSC closely
resembles that of the ``modulator' on VDAC. The similarities between PSC and VDAC suggest that the former might be a cationic
porin of the mitochondrial outer membrane possessing a structure closely related to that of VDAC.
Received: 2 February 1996/Revised: 18 October 1996 相似文献