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1.
Assembly of DNA into chromatin allows for the formation of a barrier that protects naked DNA from protein and chemical agents
geared to degrade or metabolize DNA. Chromatin assembly occurs whenever a length of DNA becomes exposed to the cellular elements,
whether during DNA synthesis or repair. This report describes tools to study chromatin assembly in the model systemSaccharomyces cerevisiae. Modifications to anin vitro chromatin assembly assay are described that allowed a brute force screen of temperature sensitive (ts) yeast strains in order to identify chromatin assembly defective extracts. This screen yielded mutations in genes encoding
two ubiquitin protein ligases (E3s):RSP5, and a subunit of the Anaphase Promoting Complex (APC),APC5. Additional modifications are described that allow for a rapid analysis and anin vivo characterization of yeast chromatin assembly mutants, as well as any other mutant of interest. Our analysis suggests that
thein vitro andin vivo chromatin assembly assays are responsive to different cellular signals, including cell cycle cues that involve different
molecular networks.
Published: July 3, 2003 相似文献
2.
In this study, Dendrobium Sonia 17 plantlets were used to induce in vitro flowering. Inflorescences were induced and rooting was inhibited in the half-strength Murashige and Skoog medium containing
20 μM N
6-benzyladenine (BA). The medium with high P and low N contents was effective to induce inflorescences while the medium with
low P and high N contents was only effective to promote forming of shoots. In addition, the induced in vitro inflorescences were able to multiply and maintain without exhibiting a distinctive vegetative phase. Different morphologies
of in vitro flowers such as incomplete flower structures, abnormal and unresupinated in vitro flowers were observed. 相似文献
3.
This paper describes multiple shoot regeneration from leaf and nodal segments of a medicinally important herb Centella asiatica L. on Murashige and Skoog’s (MS) medium supplemented with a range of growth regulators. The highest number of multiple shoots
was observed on MS augmented with 3.0 mg dm−3 N6-benzylaminopurine (BAP) and 0.05 mg dm−3 α-naphthaleneacetic acid (NAA). Leaf explant showed maximum percentage of cultures regenerating shoots (81.6 %), with the
highest shoot number (8.3 shoots per explant) and the shoot length (2.1 cm) whereas, nodal explant showed less number of shoots
with callus formation at the base cut end. Successive shoot cultures were established by repeatedly sub-culturing the original
explant on a fresh medium. Rooting of in vitro raised shoots was best induced on half strength MS supplemented with 0.5 mg dm−3 indole-3-butyric acid (IBA) with highest percentage of shoot regenerating roots (76.8 %) with 3–4 roots per shoot. Plantlets
were acclimated in Vermi-compost and eventually established in soil. Contents of chlorophyll, total sugars, reducing sugars and proteins were estimated in
leaf tissue from both in vivo and in vitro raised plants. Chlorophyll content was higher in in vivo plants, whereas other three components were higher in in vitro plants. 相似文献
4.
The activities and isoenzyme pattern of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) have been studied
during germination of Chenopodium murale seeds. CAT and SOD activities were similar in dry seeds and during first 2 d of imbibition. CAT activity increased during
radicle protrusion and early seedling development. The maximum SOD activity was found at final stages of germination and early
seedling development. POD activity was not detected until the 6th day of germination, indicating POD involvement not until early seedling development. Gibberellic acid (GA3, 160 μM) delayed and synchronized C. murale germination. 相似文献
5.
Mature osteoclasts, multinucleated giant cells responsible for bone resorption, are terminally differentiated cells with a
short life span. Recently, we have demonstrated that osteoclast apoptosis is regulated by ERK activity and Bcl-2 family member
Bim. In this paper, we summarize the methods we used to study osteoclast apoptosis in vitro and in vivo. Using adenovirus and retrovirus vectors, we were able to introduce foreign genes into osteoclasts and examine their effects
on osteoclast survival in vitro. In addition, we established the modified methods for in situ hybridization and BrdU labeling of bone sections from mice
to study osteoclast survival in vivo. The detailed methods described here could be useful for studying the biological process in bone. 相似文献
6.
An efficient micropropagation protocol was established for Capsicum chinense Jacq. cv. Umorok, a pungent chilli cultivar. Shoot-tip explants were cultured on Murashige and Skoog (MS) medium containing
cytokinins (22.2–88.8 μM 6-benzylaminopurine, BAP, 23.2–93.0 μM kinetin, Kin, or 22.8–91.2 μM zeatin, Z) alone or in combination
with 5.7 μM indole-3-acetic acid (IAA). Maximum number of shoots were induced on medium containing 91.2 μM Z or 31.1 μM BAP
with 4.7 μM Kin. The separated shoots rooted and elongated on medium containing 2.5 or 4.9 μM indole-3-butyric acid (IBA).
Axillary shoots were induced from in vitro raised plantlets by decapitating them. The axillary shoot-tip explants were used for further multiple shoot buds induction.
A maximum of about 150 plantlets were obtained from a single seedling. Hardened and acclimatized plantlets were successfully
established in the soil. 相似文献
7.
Wang J Ohmuraya M Hirota M Baba H Zhao G Takeya M Araki K Yamamura K 《Histochemistry and cell biology》2008,130(2):387-397
Recent evidence shows that the serine protease inhibitor Kazal type 3 (Spink3) has more diverse functions than expected. To gain insight into its function, we analyzed the spatiotemporal expression profile of Spink3, using in situ hybridization (ISH) and a Spink3 ( +/lacZ ) knock-in mouse, in which lacZ was inserted into the Spink3 locus. Spink3 ( lacZ ) expression was first observed in the foregut, midgut, hindgut and the forebrain/midbrain junction region at 9.5 days post coitus (dpc). In the pancreas, Spink3 mRNA was detected at 11.5 dpc, before formation of the typical shape of the exocrine structure of the pancreas. Acinar cell expression was clearly identified by 13.5 dpc. After differentiation of the intestinal tract, Spink3 ( lacZ ) expression was observed in the large intestine at 11.5 dpc, followed by expression in the small intestine at 13.5 dpc, before appearance of intestinal digestive enzymes. Spink3 mRNA and Spink3 ( lacZ ) activity were also detected in other tissues, including the mesonephric tubules and the urogenital ridge at 11.5 dpc, the genital swelling at 13.5 dpc, the ductus epididymis at 17.5 dpc, and the seminal vesicle at 8 weeks. These data suggest that Spink3 may play important roles in proliferation and/or differentiation of various cell types during development. 相似文献
8.
D. Skálová M. Dziechciarková A. Lebeda E. Křístková B. Navrátilová 《Biologia Plantarum》2008,52(4):775-778
Embryo-rescue was used to facilitate interspecific hybridization of Cucumis anguria L. and C. zeyheri Sond. Embryos were excised from developing fruits at one week intervals for six weeks after hand pollination. Medium containing
coconut water was the most suitable for initial germination, and a medium with ascorbic acid was the best for embryo development
and plant recovery. Viable plants were obtained from embryos and these plants showed morphological characteristics different
from both parents. The analysis of the leucine aminopeptidase (LAP) locus revealed three hybrid types, H1.1, H1.2 and H2. 相似文献
9.
We have isolated a cDNA clone for the antifungal protein,CaAFP, from hot pepper,Capsicum annuum L. Its open reading frame encodes 85 amino acids, including 8 cysteine residues. CaAFP consists of three domains: a signal
peptide, a chitin-binding domain, and a C-terminal peptide domain. The deduced amino acid sequence of the chitin-binding domain
shows 92% and 85% similarity to the same domain from PnAMPs and hevein, respectively. Southern blot analysis indicated that
CaAFP is present as a single copy, while the northern blots revealed that the clone is highly expressed in the leaves and
flower buds, but not in the roots. However, wounding treatments and chemicals generally known to induce PR proteins did not
stimulate its expression.In situ hybridization also showed that CaAFP is expressed in the parenchyma cells of the floral sepals. As seen in our functional
analysis, this clone was expressed inEscherichia coli, and the fusion protein was purified using nickel-affinity column chromatography. This purified AFP fusion protein inhibited
spore germination and appressoria formation in several plant pathogenic fungi, includingFusarium oxisporum andColletotrichum gloeosporioides. Our results suggest CaAFP is an antifungal protein that defends developing seeds against pathogen invasion while also having
a specific biological role during floral development. 相似文献
10.
M. E. Cocom Pech W. de J. May-Itzá L. A. Medina Medina J. J. G. Quezada-Euán 《Insectes Sociaux》2008,55(4):428-433
Euglossa viridissima is an orchid bee that forms both solitary and multiple female nests, making it a suitable species for the study of factors
leading to diverse degrees of sociality in Euglossines. We conducted observations in eight reused nests (where a first generation
of bees had been produced) kept in artificial boxes from the Yucatan Peninsula, Mexico. Five nests were reused (reactivated)
by a single female (SFN), two nests reused by a mother and one daughter (MFN1) and one nest reused by the mother and two daughters
(MFN2). No single nest was reactivated by unrelated females. The number of foraging trips, their duration and the duration
of cell provisioning was not different between SFN and MFN. The overall production of cells per female was not different either
between both types of nest. However, in MFN although all females did lay eggs, there was a reproductive skew in favor of the
mother (95 and 45% of the brood produced in MFN1 and MFN2 respectively). She showed reproductive control of her daughters
through oophagy and displaying threatening behavior when the daughters tried to open a cell where she had laid an egg. Brood
losses to parasites (Anthrax sp. (Bom-byliidae) and Hoplostelis bivittata (Megachilidae)) were only found in SFN which possibly reflects and advantage of MFN in this respect. Our results coupled
with other studies in Euglossa, reveal that a wide range of social behaviors occur in this genus, from solitary and communal to primitive reproductive division
of labor. Multiple factors involving different levels of pressure imposed by food availability and parasites may favor such
a diverse range of nesting behaviors. Interestingly, female associations in E. viridissima seem a result of kin selection that is enforced by coercion from mother females on their daughters. More studies are needed
to shed light upon the social organization of Euglossa and other Euglossines and on their phylogenetic relationships in order to trace the origins of eusociality in Apidae.
Received 12 February 2008; revised 25 June 2008; accepted 17 July 2008. 相似文献
11.
M. Chandrika Thoyajaksha V. Ravishankar Rai K. Ramachandra Kini 《Biologia Plantarum》2008,52(4):735-739
In the present study, a polymerase chain reaction (PCR)-based method namely inter simple sequence repeat (ISSR) was employed
to assess genetic stability in tissue culture-derived Dictyospermum ovalifolium plantlets. To study genomic stability of micropropagated plants, 14 individuals were randomly tagged among a population of
2500 regenerants and were compared with single donor mother plant. A total of 51 clear and reproducible bands ranging from
200 bp to 2.1 kb were scored corresponding to an average of 3.64 bands per primer. Two of the 51 bands were polymorphic (3.92
%) among 14 individuals, thus indicating the occurrence of low level genomic variation in the micropropagated plants. Cluster
analysis indicates that genetic similarity values were 0.978 which allows classification of the plants to distinct groups.
Further an attempt was made to reintroduce the micropropagated plants into their natural habitat. Over one thousand six hundred
fifty plants were successfully established. 相似文献
12.
In 7-d-old seedlings of Brassica juncea chromium (VI) promoted photosystem 2 (PS 2) mediated photoreactions. The increase in PS 2 activity in the thylakoids from
Cr-treated seedlings, in the presence of uncoupler (5 mM NH4Cl), was similar to that recorded with the control thylakoids. Thus Cr enhanced PS 2 activity was not due to uncoupling of
electron transport from photophosphorylation. Photon saturation kinetics revealed that the PS 2 activity of thylakoids from
Cr-treated seedlings was significantly higher at almost all irradiances in comparison to that of controls. PS 2 activity of
thylakoids from Cr-treated plants at 25 % of the saturating irradiance was in par with the PS 2 activity of the thylakoids from control plants at saturating irradiance. Thylakoids from both control and Cr-treated
seedlings exhibited maximum PS 2 activity at pH 7.5. The PS 2 activity of thylakoids from Cr-treated plants remained high
even at pH 8.0 and 8.5, demonstrating Cr enhances tolerance of PS 2 to alkaline pH. 相似文献
13.
X. Wei Y. S. Jiang S. Y. Jiang X. X. Qi Z. C. Xiong W. H. Ye Z. M. Wang 《Photosynthetica》2008,46(2):312-314
Saturation (SI) and compensation (CI) irradiances [μmol(photon) m−2 s−1] were 383.00±18.40 and 12.95±0.42 for wild C. nitidissima (in mid-July) and 691.00±47.39 and 21.91±1.28 for wild C. sinensis, respectively. C. nitidissima is a shade tolerant species, whereas C. sinensis has a wide ecological range of adaptability to irradiance. Both wild and cultivated C. nitidissima demonstrated low maximum net photosynthetic rate, maximum carboxylation rate, maximum electron transfer rate, and SI, which
indicated low photosynthesis ability of leaves that were unable to adapt to strong irradiance environment. Both C. nitidissima and C. sinensis demonstrated strong photosynthetic adaptabilty in new environments. Hence proper shading may raise photosynthetic efficiency
of cultivated C. nitidissima and promote its growth. 相似文献
14.
15.
J. A. Bunce 《Photosynthetica》2008,46(4):517-524
Plants differ in how much the response of net photosynthetic rate (P
N) to temperature (T) changes with the T during leaf development, and also in the biochemical basis of such changes in response. The amount of photosynthetic acclimation
to T and the components of the photosynthetic system involved were compared in Arabidopsis thaliana and Brassica oleracea to determine how well A. thaliana might serve as a model organism to study the process of photosynthetic acclimation to T. Responses of single-leaf gas exchange and chlorophyll fluorescence to CO2 concentration measured over the range of 10–35 °C for both species grown at 15, 21, and 27 °C were used to determine the
T dependencies of maximum rates of carboxylation (VCmax), photosynthetic electron transport (Jmax), triose phosphate utilization rate (TPU), and mesophyll conductance to carbon dioxide (g’m). In A. thaliana, the optimum T of P
N at air concentrations of CO2 was unaffected by this range of growth T, and the T dependencies of VCmax, Jmax, and g’m were also unaffected by growth T. There was no evidence of TPU limitation of P
N in this species over the range of measurement conditions. In contrast, the optimum T of P
N increased with growth T in B. oleracea, and the T dependencies of VCmax, Jmax, and g’m, as well as the T at which TPU limited P
N all varied significantly with growth T. Thus B. oleracea had much a larger capacity to acclimate photosynthetically to moderate T than did A. thaliana. 相似文献
16.
Gametophores of mosses Mnium undulatum and Polytrichum commune were submerged in distilled water or in calcium chloride solution (0.9 mM Ca2+) to induce hypoxia. The net photosynthetic (PN) and dark respiration rate (RD) were measured in the air containing 300–400 μmol(CO2)·mol−1(air) and 0.21 mol(O2)·mol−1(air). PN of M. undulatum gametophores decreased to 58 % of the control after 1-h submersion in water, whereas to 80 % of the control in P. commune gametophores. A smaller decrease in PN was observed when the gametophores were immersed in CaCl2 solution. In hypoxia, RD in the tested mosses species was a little higher than in the control. 相似文献
17.
A rapid and efficient plant regeneration protocol for a wide range of alfalfa genotypes was developed via direct organogenesis. Through a successive excision of the newly developed apical and axillary shoots, a lot of adventitious
buds were directly induced from the cotyledonary nodes when hypocotyl of explants were vertically inserted into modified Murashige
and Skoog (MS) medium supplemented with 0.025 mg dm−3 thidiazuron (TDZ) and 3 mg dm−3 AgNO3. When the lower part of shoots excised from explants were immersed into the liquid medium with 1.0 mg dm−3 α-naphthaleneacetic acid (NAA) for 2 min, and then transferred to hormone free half-strength MS medium, over 83.3 % of the
shoots developed roots, and all plantlets could acclimatize and establish in soil. The protocol has been successfully applied
to eight genotypes, with regeneration frequencies ranging from 63.8 to 82.5 %. 相似文献
18.
Salmonella enterica serovar Typhimurium is capable of swarming over semi-solid surfaces. Although its swarming behavior shares many readily observable
similarities with other swarming bacteria, the phenomenon remains somewhat of an enigma in this bacterium since some attributes
skew away from the better characterized systems. Swarming is quite distinct from the classic swimming motility, as there is
a prerequisite for cells to first undergo a morphological transformation into swarmer cells. In some organisms, swarming is
controlled by quorum sensing, and in others, swarming has been shown to be coupled to increased expression of important virulence
factors. Swarming in serovar Typhimurium is coupled to elevated resistance to a wide variety of structurally and functionally
distinct classes of antimicrobial compounds. As serovar Typhimurium differentiates into swarm cells, thepmrHFIJKLM operon is up-regulated, resulting in a more positively charged LPS core. Furthermore, as swarm cells begin to de-differentiate,
thepmr operon expression is down-regulated, rapidly reaching the levels observed in swim cells. This is one potential mechanism
which confers swarm cells increased resistance to antibiotics such as the cationic antimicrobial peptides. However, additional
mechanisms are likely associated with the cells in the swarm state that confer elevated resistance to such a broad spectrum
of antimicrobial agents.
Published: September 26, 2003 相似文献
19.
Epicotyl segments of kumquat (Fortunella crassifolia Swingle cv. Jindan) were transformed with Agrobacterium tumefaciens GV3101 harboring neomycin phosphotransferase gene (npt II) containing plant expression vectors. Firstly, the explants were cultured in darkness at 25 °C on kanamycin free shoot
regeneration medium (SRM) for 3 d, and then on SRM supplemented with 25 mg dm−3 kanamycin and 300 mg dm−3 cefotaxime for 20 d. Finally, they were subcultured to fresh SRM containing 50 mg dm−3 kanamycin monthly and grown under 16-h photoperiod. Sixty five kanamycin resistant shoots were regenerated from 500 epicotyl
explants after four-month selection. Shoot tips of 20 strong shoots were grafted to 50-day-old kumquat seedlings and survival
rate was 55 %. Among the 11 whole plants, 3 were transgenic as confirmed by Southern blotting. This is the first report on
transgenic kumquat plants, and a transformation efficiency of 3.6 % was achieved. 相似文献