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111.
Yves Parmentier Andrée Durr Jacqueline Marbach Cathy Hirsinger Marie-Claire Criqui Jacqueline Fleck Elisabeth Jamet 《Plant molecular biology》1995,29(2):279-292
A cDNA clone (6PExt 1.2) encoding a novel extensin was isolated from a cDNA library made from 6 h old mesophyll protoplasts of Nicotiana sylvestris. The screening was performed with a heterologous probe from carrot. The encoded polypeptide showed features characteristic of hydroxyproline-rich glycoproteins such as Ser-(Pro)4 repeats and a high content in Tyr and Lys residues. The presence of four Tyr-X-Tyr-Lys motifs suggests the possibility for intramolecular isodityrosine cross-links whereas three Val-Tyr-Lys motifs may participate in intermolecular cross-links. The analysis of genomic DNA gel blots using both the N. sylvestris and the carrot clones as probes showed that the 6PExt 1.2 gene belongs to a complex multigene family encoding extensin and extensin-related polypeptides in N. sylvestris as well as in related Nicotianeae including a laboratory hybrid. This was confirmed by the analysis of RNA gel blots: a set of mRNAs ranging in size from 0.3 kb to 3.5 kb was found by the carrot extensin probe. The 6PExt 1.2 probe found a 1.2 kb mRNA in protoplasts and in wounded tissues as well as a 0.9 kb mRNA which seemed to be stem-specific. The gene encoding 6PExt 1.2 was induced by wounding in protoplasts, in leaf strips and after Agrobacterium tumefaciens infection of stems. 相似文献
112.
Tovée MJ 《Trends in ecology & evolution》1995,10(11):455-460
Until very recently, the role of ultra-violet (UV) colour perception in vertebrate and invertebrate vision has largely been ignored. However, in the past few years, a host of detailed information has become available on the widespread distribution of UV receptors in different species - from insects to mammals - and the important functions they seem to play in navigation, foraging, intraspecies communication and the control of circadian rhythms. 相似文献
113.
The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold. 总被引:4,自引:0,他引:4
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A Carfi S Pares E Duée M Galleni C Duez J M Frère O Dideberg 《The EMBO journal》1995,14(20):4914-4921
The 3-D structure of Bacillus cereus (569/H/9) beta-lactamase (EC 3.5.2.6), which catalyses the hydrolysis of nearly all beta-lactams, has been solved at 2.5 A resolution by the multiple isomorphous replacement method, with density modification and phase combination, from crystals of the native protein and of a specially designed mutant (T97C). The current model includes 212 of the 227 amino acid residues, the zinc ion and 10 water molecules. The protein is folded into a beta beta sandwich with helices on each external face. To our knowledge, this fold has never been observed. An approximate internal molecular symmetry is found, with a 2-fold axis passing roughly through the zinc ion and suggesting a possible gene duplication. The active site is located at one edge of the beta beta sandwich and near the N-terminal end of a helix. The zinc ion is coordinated by three histidine residues (86, 88 and 149) and a water molecule. A sequence comparison of the relevant metallo-beta-lactamases, based on this protein structure, highlights a few well-conserved amino acid residues. The structure shows that most of these residues are in the active site. Among these, aspartic acid 90 and histidine 210 participate in a proposed catalytic mechanism for beta-lactam hydrolysis. 相似文献
114.
The first highly efficient protocol is described for the electrotransfection of Propionibacterium freudenreichii with DNA phage. The transfection efficiency is 7 times 105 transfectants per μg of DNA under optimal conditions. Optimized parameters included the field strength (12.5 kV, 200 Ohms, 25 μF), phage DNA concentration (1 μg ml-1 ) and cell density (1.5 times 1010 cells ml-1 ). Growth in the presence of glycine and harvesting of cells during the early exponential growth phase increased the transfection efficiency. This electrotransfection protocol is of importance for the genetic improvement of dairy propionibacteria. 相似文献
115.
The photosynthetic performance of a helical tubular photobioreactor ("Biocoil"), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25-m(2)basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m(2)) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air-lift system ncorporating 4%CO(2) was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g . d biomass/L . day, or 5.44 g . d biomass/m(2)(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO(2) was efficiently removed from the gaseous stream; monitoring the CO(2) the outlet and inlet gas streams showed a 70% removal of CO(2) from the inlet gas over an 8-h period with almost maximum growth rate. (c) 1995 John Wiley & Sons, Inc. 相似文献
116.
Expression of Bcl-2 protein in the epiphyseal plate cartilage and trabecular bone of growing rats 总被引:2,自引:0,他引:2
Ying Wang Renée Toury Michelle Hauchecorne N. Balmain 《Histochemistry and cell biology》1997,108(1):45-55
The protooncogene protein, Bcl-2, protects cells from apoptosis and ensures their survival in vitro by inhibiting the action
of the apoptosis-inducer, Bax. Its expression in proliferative and long-lived cells in vivo also indicates that it protects
against cell death. The chondrocytes of the epiphyseal plate cartilage undergo a series of maturation steps and deposit mineral
in the cartilage matrix before dying. The possibility that Bcl-2 helps protect chondrocytes until mineral deposition is completed
was investigated by determining the distribution of Bcl-2 immunoreactivity in the epiphyseal plate cartilage of growing rats
and its subcellular localization, using a specific antibody. The involvement of Bax in the triggering of chondrocyte death
was checked by immunocytochemistry. Bcl-2 expression in the osteoblasts and the final result of their evolution, the osteocytes,
was also examined in trabecular bone. Bcl-2 immunoreactivity was non-uniformly distributed throughout the epiphyseal cartilage.
It was maximal in proliferative chondrocytes, decreased in mature chondrocytes, and low in hypertrophic chondrocytes, whereas
there was Bax immunoreactivity in all chondrocytes examined. Immunolabeling was intense in osteoblasts but considerably lower
in fully differentiated osteocytes. Bcl-2 immunoreactivity was mainly in the cytoplasm of chondrocytes, osteoblasts, and early
osteocytes; the nuclei appeared clear. The subcellular distribution of Bcl-2 immunolabeling in chondrocytes, revealed by gold
particles in the electron microscope, showed that gold particles were frequently concentrated in the mitochondria in all the
cartilage zones and lay mainly within the organelles, not at their periphery. The endoplasmic reticulum contained moderate
immunoreactivity and there were few gold particles in the cytoplasm and nuclei. The number of gold particles decreased in
all the subcellular compartments from proliferative to hypertrophic chondrocytes. In contrast, Bax immunoreactivity changed
little during chondrocyte terminal evolution, and its subcellular distribution mirrored that of Bcl-2. These immunocytochemical
data indicate that Bcl-2 helps maintain chondrocytes and osteoblasts until their terminal maturation.
Accepted: 19 February 1997 相似文献
117.
118.
Artificial crosses between Helianthus annuus and H. petiolaris using 1:9, 1:1, and 9:1 mixtures of intraspecific: interspecific pollen were conducted to determine the role of interspecific pollen competition as a reproductive barrier in Helianthus. Of 1,245 achenes analyzed from the pollen competition experiments, only 49 were hybrids. The number of hybrids observed was significantly less than expectations for all three pollen mixtures, regardless of the identity of maternal parent (P < 0.01). Stigma age and pollen ratio had no significant impact on hybrid frequency. However, hybrids were significantly more frequent with H. annuus than with H. petiolaris as the maternal parent (P < 0.01). Analysis of pollen tube growth rates revealed no differences in the rate of growth of intraspecific vs. interspecific pollen. Likewise, pollinations with either intraspecific or interspecific pollen or with different pollen ratios did not affect the percentage of filled achenes. Thus, the mechanism responsible for selective fertilization by intraspecific pollen in mixed pollen loads remains unclear. Nonetheless, these findings suggest that interspecific pollen competition plays an important role in controlling the formation of hybrids between H. annuus and H. petiolaris and may partially account for patterns or differential cytoplasmic vs. nuclear introgression in Helianthus. 相似文献
119.
Bertrand Dommée Andrée Biascamano Nicole Denelle Jean-Louis Bompar John D. Thompson 《American journal of botany》1995,82(6):734-740
Natural populations of Thymelaea hirsuta have previously been shown to comprise four distinct sexual morphs: males, females, protogynous individuals, i.e., first female then male, and protandrous individuals, i.e., first male then female. The objective of the present study has been to confirm the genetic basis of this sexual tetramorphism by quantifying morph ratios in the open-pollinated progeny of the four sexual phenotypes growing in a natural population. All four phenotypes were recovered in the progeny of each morph. All observed plants displayed a single sexual phenotype, thus confirming the genetic basis of the tetramorphism. The progeny sex ratios indicate that the genetic determination of sex in this species may be influenced by cytoplasmic factors, while the observed levels of functional female fertility suggest a near-dioecious system. The evolutionary significance of this tetramorphism as a transitional stage in the evolution of dioecy is discussed. 相似文献
120.
H. G. de Vries J. M. Collée W. P. Meeuwsen H. Scheffer L. P. Ten Kate 《Human genetics》1995,95(5):575-576
Number and sex of offspring were determined in a group of 7,841 randomly selected blood donors who were screened for the F508 mutation. We did not find any evidence for differences in number or sex ratio of offspring between F508 carriers and non-carriers. 相似文献