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11.
Lin Hsueh-Shih van der Toorn Caroline Raemakers Krit J.J.M. Visser Richard G.F. De Jeu Marjo J. Jacobsen Evert 《Molecular breeding : new strategies in plant improvement》2000,6(4):369-377
Transgenic plants were obtained after particle bombardment of embryogenic callus derived from stem segments of two tetraploid Alstroemeria genotypes with plasmids containing different selection/reporter genes. Firstly, a plasmid containing a firefly luciferase reporter gene driven by the maize ubiquitin promoter (Ubi1), was bombarded into both friable embryogenic callus and proembryos. Transient and stable expression of luciferase was visually detected by a luminometer. This selection method is non-destructive and can be applied over the whole developmental process from callus to embryo and plantlet. Molecular proof of transformation was obtained both by PCR analysis and Southern hybridization. Secondly, a plasmid containing the bar gene together with an uidA gene coding for -glucuronidase both driven by the Ubi1 promoter was bombarded into proembryos. The transgenic callus was effectively selected from the callus clumps four months after bombardment on a medium containing 5 mg/l phosphinotricin (PPT). Selection by PPT was efficient and labour-saving. Stable expression of GUS was confirmed by the histochemical staining assay and molecular proof was obtained by PCR analysis. 相似文献
12.
In cassava, somatic embryogenesis starts with the culture of leaf explants on solid Murashige and Skoog-based medium supplemented
with auxins. Mature somatic embryos are formed within 6 wk. The cotyledons of the primary somatic embryos are used as explants
for a new cycle of somatic embryogenesis. The cotyledons undergo secondary somatic embryogenesis on both liquid and solid
Murashige and Skoog-based medium supplemented with auxins. Depending on the auxin, new somatic embryos are formed after 14–30
d after which they can be used for a new cycle of somatic embryogenesis. In liquid medium, more than 20 secondary somatic
embryos are formed per initial cultured embryo. In both primary and secondary somatic embryogenesis, the somatic embryos originate
directly from the explants. Transfer of clumps of somatic embryos to a Greshoff and Doy-based medium supplemented with auxins
results in indirect somatic embryogenesis. The direct form of somatic embryogenesis has a high potential for use in plant
propagation, whereas the indirect has a high potential for use in genetic modification of cassava.
Mature somatic embryos germinate into plants after desiccation and culture on a Murashige and Skoog-based medium supplemented
with benzylaminopurine (BA). Depending on the used BA concentration, plants can either be transferred either directly to the
greenhouse or after using standard multiplication protocols. 相似文献
13.
A highly efficient, repetitive system of organogenesis was developed in soybean. Seeds of soybean cv. White hilum pretreated with TDZ formed multiple bud tissue(s) (MBT) at the cotyledonary nodes. MBT initiation occurred only if the axillary buds were not removed from the cotyledonary node. The best MBT formation was achieved by pretreating the seeds for 1 week on medium supplemented with 0.1 mg/l TDZ, followed by culture of the cotyledonary node on medium supplemented with 0.5 mg/l BA for 4 weeks. Culture of the MBT on medium supplemented with 0.1 mg/l TDZ resulted in the proliferation of MBT. MBT was maintained in this way for 12 months. Three hundred thirty six shoots were obtained when 1 g of MBT was subcultured on medium supplemented with 0.5 mg/l BA. Plants were rooted on medium without growth regulators. The regenerated plants grew normally in the greenhouse. Unfortunately, they did not set seeds because of the long-day conditions during growth. This system was successfully applied in three other genotypes. 相似文献
14.
Ellis C. O'Neill Clare E. M. Stevenson Krit Tantanarat Dimitrios Latousakis Matthew I. Donaldson Martin Rejzek Sergey A. Nepogodiev Tipaporn Limpaseni Robert A. Field David M. Lawson 《The Journal of biological chemistry》2015,290(50):29834-29853
The degradation of transitory starch in the chloroplast to provide fuel for the plant during the night requires a suite of enzymes that generate a series of short chain linear glucans. However, glucans of less than four glucose units are no longer substrates for these enzymes, whereas export from the plastid is only possible in the form of either maltose or glucose. In order to make use of maltotriose, which would otherwise accumulate, disproportionating enzyme 1 (DPE1; a 4-α-glucanotransferase) converts two molecules of maltotriose to a molecule of maltopentaose, which can now be acted on by the degradative enzymes, and one molecule of glucose that can be exported. We have determined the structure of the Arabidopsis plastidial DPE1 (AtDPE1), and, through ligand soaking experiments, we have trapped the enzyme in a variety of conformational states. AtDPE1 forms a homodimer with a deep, long, and open-ended active site canyon contained within each subunit. The canyon is divided into donor and acceptor sites with the catalytic residues at their junction; a number of loops around the active site adopt different conformations dependent on the occupancy of these sites. The “gate” is the most dynamic loop and appears to play a role in substrate capture, in particular in the binding of the acceptor molecule. Subtle changes in the configuration of the active site residues may prevent undesirable reactions or abortive hydrolysis of the covalently bound enzyme-substrate intermediate. Together, these observations allow us to delineate the complete AtDPE1 disproportionation cycle in structural terms. 相似文献
15.
Rhesus monkey rhadinovirus (RRV) is a gamma-2 herpesvirus closely related to human herpesvirus 8 (HHV8). RRV encodes viral FLICE inhibitory protein (vFLIP), which has death effector domains. Little is known about RRV vFLIP. This study intended to examine its function in apoptosis. Here we found that RRV vFLIP inhibits apoptosis induced by tumor necrosis factor-α (TNF-α) and cycloheximide. In HeLa cells with vFLIP expression, the cleavage of poly [ADP-ribose] polymerase 1 (PARP-1) and activities of caspase 3, 7, and 9 were much lower than those in controls. Cell viability of HeLa cells with vFLIP expression was significantly higher than control cells after apoptosis induction. However, RRV vFLIP appears unable to induce NF-κB signaling when tested in NF-κB reporter assay. RRV vFLIP was able to enhance cell survival under starved conditions or apoptosis induction. At early time points after apoptosis induction, autophagosome formation was enhanced and LC3-II level was elevated in cells with vFLIP and, when autophagy was blocked with chemical inhibitors, these cells underwent apoptosis. Moreover, RRV latent infection of BJAB B-lymphoblastoid cells protects the cells against apoptosis by enhancing autophagy to maintain cell survival. Knockdown of vFLIP expression in the RRV-infected BJAB cells with siRNA abolished the protection against apoptosis. These results indicate that vFLIP protects cells against apoptosis by enhancing autophagosome formation to extend cell survival. The finding of vFLIP's inhibition of apoptosis via the autophagy pathway provides insights of vFLIP in RRV pathogenesis. 相似文献
16.
Krit?Raemakers Marianne?Schreuder Luc?Suurs Heleen?Furrer-Verhorst Jean-Paul?Vincken Nick?de?Vetten Evert?Jacobsen Richard?G.?F.?VisserEmail author 《Molecular breeding : new strategies in plant improvement》2005,16(2):163-172
Cassava is a poor man's crop which is mainly grown as a subsistence crop in many developing countries. Its commercial use
was first as animal feed (also known as tapioca), but has shifted since the late sixties to a source of native starch. The
availability of native starches, which on the one hand do not require substantial chemical derivatisation and on the other
hand have improved properties, would make cassava also for small farmers a potentially attractive cash crop. Since breeding
is difficult in this polyploid, vegetatively propagated, crop a transgenic approach would be ideal to improve certain characteristics.
We have created a cassava genotype producing amylose-free starch by genetic modification. The absence of amylose increased
the clarity and stability of gels made with the transgenic starch, without requiring treatment with environment-unfriendly
chemicals such as epoxides (propylene oxide, ethylene oxide) and acetic anhydride, which are normally used to improve stability.
The amylose-free starch showed no changes in particle size distribution, chain length distribution or phosphorous content
when compared to amylose-containing starch, but the granule melting temperature was increased by almost 2°C. Furthermore,
the amylose-free cassava starch shows enhanced clarity and stability properties. These improved functionalities are desired
in technical applications in paper and textile manufacturing, but also in the food industry for the production of sauces,
dairy products and noodles. 相似文献
17.
The crystalline states of cimetidine and piroxicam, when coprecipitated from solvents containing 1:1 mole ratio, were transformed
to amorphous states as observed using powder X-ray diffraction (PXRD). Amorphous forms of drugs generally exhibit higher water
solubility than crystalline forms. It is therefore interesting to investigate the interactions that cause the transformation
of both the crystalline drugs. Intermolecular interactions between the drugs were determined using Fourier-transform infrared
spectroscopy (FTIR) and solid-state 13C CP/MAS NMR. Molecular dynamic (MD) simulation was performed for the first time for this type of study to indicate the specific
groups involved in the interactions based on radial distribution function (RDF) analyses. RDF is a useful tool to describe
the average density of atoms at a distance from a specified atom. FTIR spectra revealed a shift of the C≡N stretching band
of cimetidine. The 13C CP/MAS NMR spectra indicated downfield shifts of C11, C15 and C7 of piroxicam. RDF analyses indicated that intermolecular interactions occurred between the amide oxygen atom as well as the
pyridyl nitrogen of piroxicam and H-N3 of cimetidine. The hydrogen atom (O–H) at C7 interacts with the N1 of cimetidine. Since the MD simulation results are consistent with, and complementary to the experimental analyses, such
simulations could provide a novel strategy for investigating specific interacting groups of drugs in coprecipitates, or in
amorphous mixtures. 相似文献
18.
Krit Thirapanmethee Kanokporn Pothisamutyothin Surakit Nathisuwan Mullika T. Chomnawang Chanpen Wiwat 《Microbiology and immunology》2014,58(12):655-665
Extended‐spectrum β‐lactamases (ESBLs) produced by Enterobacteriaceae are one of the resistance mechanisms to most β‐lactam antibiotics. ESBLs are currently a major problem in both hospitals and community settings worldwide. Rapid and reliable means of detecting ESBL‐producing bacteria is necessary for identification, prevention and treatment. Loop‐mediated isothermal amplification (LAMP) is a technique that rapidly amplifies DNA with high specificity and sensitivity under isothermal conditions. This study was aimed to develop a convenient, accurate and inexpensive method for detecting ESBL‐producing bacteria by a LAMP technique. ESBLs‐producing Escherichia coli and Klebsiella pneumoniae were isolated from a tertiary hospital in Bangkok, Thailand and reconfirmed by double‐disk synergy test. A set of four specific oligonucleotide primers of LAMP for detection of blaCTX‐M9 gene was designed based on blaCTX‐M9 from E. coli (GenBank Accession No. AJ416345). The LAMP reaction was amplified under isothermal temperature at 63°C for 60 min. Ladder‐like patterns of band sizes from 226 bp of the blaCTX‐M9 DNA target was observed. The LAMP product was further analyzed by restriction digestion with MboI and TaqI endonucleases. The fragments generated were approximately 168, 177 and 250 bp in size for MboI digestion and 165, 193, 229, 281 and 314 bp for TaqI digestion, which is in agreement with the predicted sizes. The sensitivity of the LAMP technique to blaCTX‐M9 was greater than that of the PCR method by at least 10,000‐fold. These results showed that the LAMP primers specifically amplified only the blaCTX‐M9 gene. Moreover, the presence of LAMP amplicon was simply determined by adding SYBR Green I in the reaction. In conclusion, this technique for detection of ESBLs is convenient, reliable and easy to perform routinely in hospitals or laboratory units in developing countries. 相似文献
19.
Maskiet Boonyareth Jureepan Saranak Darawan Pinthong Yupin Sanvarinda Kenneth W. Foster 《Biologia》2009,64(6):1058-1065
Chlamydomonas reinhardtii swims toward or away from light (phototaxis) in a graded way depending on various conditions. Activation of rhodopsin provides
signals to control the steering of this unicellular organism relative to a light source and to up-regulate rhodopsin biosynthesis.
Intracellular cAMP and cGMP concentrations were measured in positive (1117, swims toward light) and negative (806, swims away
from light) phototactic strains with and without light stimulation or 3-isobutyl-1-methylxanthine (IBMX). In the dark, the
levels of cAMP and cGMP were significantly higher in the strain with positive phototaxis than in the strain with negative
phototaxis. To test whether either cyclic nucleotide influenced the direction, their pre-stimulus levels were pharmacologically
manipulated. Higher pre-stimulus levels of cAMP biased the cells to swim toward green light and lower levels biased the cells
to swim away. In addition, green-light activation of rhodopsin or addition of IBMX causes a sustained increase in cAMP in
both strains. As a consequence of this increase in cAMP, carotenogenesis is induced, as shown by recovery of phototaxis in
a carotenoid mutant. Thus, two functions for cAMP were identified: high pre-stimulus level biases swimming toward a light
source and sustained elevation following rhodopsin activation increases rhodopsin biosynthesis. 相似文献
20.
Vimon Tantishaiyakul Sarunyoo Songkro Krit Suknuntha Pattakarn Permkum Pattawee Pipatwarakul 《AAPS PharmSciTech》2009,10(3):789-795
We have recently demonstrated that coprecipitation of cimetidine (C) and piroxicam (P) at a mole ratio of 1:1 results in the
transformation of the crystalline forms of both drugs to an amorphous state. In this study, coprecipitates and physical mixtures
of cimetidine and piroxicam were further investigated at C/P mole ratios of 1:10, 1:5, 1:4, 1:2, 10:1, 20:1, 30:1, 40:1, and
52.5:1, the latter being the composition of a clinically used dosage. The physicochemical properties of these samples were
examined using X-ray diffraction and Fourier transform infrared spectroscopy. Additionally, dissolution of piroxicam in the
samples at C/P mole ratios of 10:1, 20:1, 30:1, 40:1, and 52.5:1 was investigated at pH 1.2 and pH 4. In coprecipitates with
C/P mole ratios of 10:1, 20:1, 30:1, and 40:1, crystalline forms of both drugs were transformed to amorphous states. A mixture
of an amorphous state and cimetidine crystalline form A was observed for the coprecipitate with a C/P mole ratio of 52.5:1.
For the coprecipitates with C/P mole ratios of 1:2, 1:4, 1:5, and 1:10, cimetidine form A was transformed to form C, whereas
piroxicam form II was modified to form I. It is interesting that small molecules, instead of polymers or solvents, can cause
such crystal structure transformations. The dissolution of piroxicam at pH 4 is lower than that at pH 1.2. Additionally, the
coprecipitates and physical mixtures with C/P mole ratios of 10:1, 20:1, 30:1, 40:1, and 52.5:1 demonstrate substantially
higher dissolution of piroxicam compared to that of drug alone. 相似文献