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81.
Induced single fertilization in maize 总被引:1,自引:1,他引:0
Akio Kato 《Sexual plant reproduction》1997,10(2):96-100
Bicellular pollen with one vegetative nucleus and one diploid arrested generative cell (”monospermic” pollen) was induced
by trifluralin treatment of diploid maize plants at 7–9 days before flowering. The arrested generative cell (seemingly a diploid
sperm cell) fused with the central cell of diploid plants and produced shriveled endosperm resembling that of a 2n×4n cross
in maize. Dual pollination experiments with a purple embryo marker revealed single fertilization events in which the union
of one sperm cell with the egg occurs but there is no union of a second sperm cell with the central cell. Singly fertilized
ovules survived at least 4 days. Furthermore, many viable triploid plants were obtained. This technique therefore appears
to have the potential for manipulating ploidy level in crops and may become useful in investigating fertilization mechanisms
of angiosperms.
Received: 1 October 1996 / Revision accepted: 8 January 1997 相似文献
82.
用固相pH梯度(pH 5.05~5.60)等电聚焦技术对随机抽取的188名北京地区健康汉族人的血清转铁蛋白(Tf)进行分型调查,并统计基因频率,检出了在中国还未见报道的TfC3基因.其表型分别是:TfC1, TfC2, TfC1C2, TfC1C3, TfC1Dchi, TfC2Dchi.TfC1=0.7420, TfC2=0.2420, TfC3=0.0027, TfDchi=0.0133, 符合Hardy-Weinberg定律, 并与其他已见报道的汉族 Tf基因频率大致相符. 相似文献
83.
Bernardo Celda Clelia Biamonti Maria Jose Arnau Roberto Tejero Gaetano T. Montelione 《Journal of biomolecular NMR》1995,5(2):161-172
Summary A large portion of the 13C resonance assignments for murine epidermal growth factor (mEGF) at pH 3.1 and 28°C has been determined at natural isotope abundance. Sequence-specific 13C assignments are reported for 100% of the assignable C, 96% of the C, 86% of the aromatic and 70% of the remaining peripheral aliphatic resonances of mEGF. A good correlation was observed between experimental and back-calculated C chemical shifts for regions of regular -sheet structure. These assignments also provide the basis for interpreting 1H–13C heteronuclear NOE (HNOE) values in mEGF at natural isotope abundance. Some of the backbone polypeptide segments with high internal mobility, indicated by these 1H–13C HNOE measurements, correlate with locations of residues involved in the putative mEGF-receptor binding site. Using four families of mEGF structures obtained over the last few years, we demonstrate that standard deviations between experimental and back-calculated C values can be used to monitor the refinement of this protein's structure, particularly for -sheet regions. Improved agreement between calculated and observed values of C is correlated with other measures of structure quality, including lowered values of residual constraint violations and more negative values of conformational energy. These results support the view that experimental conformation-dependent chemical shifts, C, can provide a reliable source of information for monitoring the process of protein structure refinement and are potentially useful restraints for driving the refinement.Abbreviations HSQC
heteronuclear single-quantum coherence spectroscopy
- PFG
pulsed-field gradient
- TOCSY
1H-1H total correlation spectroscopy
- EGF
epidermal growth factor
- mEGF
murine EGF
- hEGF
human EGF
- hTGF
human type- transforming growth factor
- DIPSI
spm-locking pulse sequence
- NOE
nuclear Overhauser effect
- HNOE
heteronuclear Overhauser effect 相似文献
84.
Summary New H2O-selective homonuclear and heteronuclear 2D NMR experiments have been designed for the observation of protein hydration (PHOGSY, Protein Hydration Observed by Gradient Spectroscop Y). These experiments utilize selective excitation of the H2O resonance and pulsed field gradients for coherence selection and efficient H2O suppression. The method allows for a rapid and sensitive detection of H2O molecules in labelled and unlabelled proteins. In addition it opens a way to measure the residence time of water bound to proteins. Its application to uniformly 15N-labelled FKBP-12 (FK-506 binding protein) is demonstrated. 相似文献
85.
罗汉果双受精过程的细胞学观察 总被引:3,自引:1,他引:2
罗汉果(Siraitiagrosvenori(Swingle)C.Jemey)双受精过程属有丝分裂前配子融合类型,授粉后24~48h,花粉管进入胚囊,穿过一个助细胞,放出两个精子。雌雄核融合和雄核与次生核融合同时发生在授粉后62~72,雄核与次生核融合速度快于配子融合,72h后即可见到初生胚乳核分裂。合子中的雌雄核仁在授粉后第5~6d融合,授粉后8~9d合成分裂形成二细胞胚。在双受精过程中,多次观察到有多条花粉管进入胚囊和多精入极核现象。原胚期有附加花粉管从珠孔进入。 相似文献
86.
This study was conducted to determine the optimal concentration of sperm to use for the insemination of females to detect differences among strains of mice in the percentage of eggs fertilized. Female ICR mice were inseminated with sperm of concentrations ranging from 0.25 to 8 × 106/50 μl from males of either DBA/2N, CF1, or C57BL/6N strains. Differences among strains were detected only when approximately 50% of the eggs were fertilized but not when each of the strains fertilized either a high or low percentage of eggs. The optimal concentration of sperm therefore was the concentration that gave approximately 50% fertilized eggs. 相似文献
87.
88.
Daniel P. Rossignol Aimee J. Roschelle William J. Lennarz 《Journal of cellular biochemistry》1981,15(4):347-358
We have attempted to identify a surface component of echinoderm eggs that is involved in the species-specific binding of sperm. Cell surface membranes from eggs of the sea urchins Strongylocentrotus purpuratus or Arbacia punctulata were radioiodinated, detergent-treated, and subjected to density-gradient centrifugation. In the presence of bindin, the complementary binding protein isolated from sperm, one component of the membranes sedimented to a different density. This membrane component bound-species specifically to sperm that had undergone the acrosome reaction. This binding led to an inhibition of the ability of treated sperm to fertilize eggs. Exhaustive proteolytic digestion of this receptor fraction yields a high molecular weight glycopeptide that can also bind to bindin. It therefore appears that this egg surface membrane fraction contains a functionally intact, species-specific receptor for sperm. 相似文献
89.
Sea urchin sperm–egg adhesion is mediated by bindin, a sperm surface protein that has lectin-like activity. Bindin agglutinates eggs, and this interaction has been shown to be inhibited by glycopeptides released from the egg surface by protease treatment. In this study, we report the purification and properties of such an egg surface glycoconjugate that may be involved in sperm adhesion. The glycoconjugate was partially purified by gel filtration and affinity chromatography on bindin particles. Upon gel filtration on Sepharose CL 4-B, the glycoconjugate elutes near the void volume, suggesting that it has a molecular weight in excess of one million. In addition, we have found that the egg surface glycoconjugate agglutinates bindin particles, indicating that it is multivalent. Carbohydrate analysis indicates that the glycoconjugate is composed primarily of fucosc, xylose, galactose, and glucose. This purified egg surface component is the most potent inhibitor of bindin-mediated egg agglutination yet described. 相似文献
90.
Hovey Lambert 《Molecular reproduction and development》1981,4(6):525-533
The temperature dependence of capacitation in bat sperm (Myotis lucifugus lucifugus) was studied by monitoring fertilizations rates of zona-free hamster ova at different temperatures. Spermatozoa were cultured in BWW medium at temperatures 4°C, 24°C, 32°C, 42°C, and 55°C from 0–24 hr. Activation of sperm could be determined visually due to the change in movement seen through light microscopy. Activation was later confirmed by higher rates of fertilization. Preincubation of the bat sperm was found to have a direct effect on the success of penetration of the zona-free hamster ova. Holding bat spermatozoa at low temperature for long intervals allowed them to remain motile but unable to fertilize. Sperm are not irreversibly damaged, however, and activation, when the temperature is increased to 32°C, is faster than when sperm are intitially put at 32°C, resulting in good fertilization rates. 相似文献