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Desiccation, a major environmental stress, affects water potential and turgor in the plants leading to physiological imbalance. Though bryophytes have the ability to endure desiccation, the adverse environmental conditions may cause them to dry irreversibly. In the present study, desiccation tolerance mechanism of Brachythecium procumbens (Mitt.) A. Jaeger was analysed in terms of its antioxidative response and photosynthetic pigments. Plants of B. procumbens were subjected to desiccation stress for varying durations (24–96 h) along with control (0 h) at room temperature. Monitoring was done using antioxidant enzyme activities, photosynthetic pigments, chlorophyll stability index, as well as, relative water content. The antioxidative enzymes—superoxide dismutase and peroxidase—showed higher activity in desiccated plants as compared to control and increased significantly with duration of desiccation. However, the activity of catalase decreased during desiccation. The amount of chlorophyll increased up to 48 h of desiccation treatment as compared to control, whereas in rehydrated samples, relatively lower value was obtained. Majority of bryophytes may withstand a certain level of desiccation for at least a few days, but some are much more tolerant than that. The bryophyte system studied showed basic difference in enzyme activities and chlorophyll under different periods of desiccation. Hence, drought-tolerant genera need to be identified and propagated so that some pioneer colonizers of the ecosystem are naturally conserved. 相似文献
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Cre-mediated recombination, a method widely used in mice for tissue-specific inactivation of endogenous genes or activation of transgenes, is critically dependent on the availability of mouse lines in which Cre recombinase functions in the tissue of interest or its progenitors. Here we describe a transgenic mouse line, Osr1-cre, in which Cre is active from embryonic day (E)11.5 in a few specific tissues. These include the endoderm of the posterior foregut, midgut, hindgut, and developing urogenital system, the heart left atrium, extra-ocular muscle progenitors, and mesenchyme in particular regions of the limb. Furthermore, starting at E12.5, Cre functions in limb interdigital mesenchyme. Within the urogenital system, recombination appears to be virtually complete in the epithelium of the bladder and urethra just posterior to it by E14.5. In males, some of these urethral cells form the prostate. The spatiotemporal pattern of Cre activity in Osr1-cre makes it a unique resource among the lines available for Cre-mediated recombination experiments. 相似文献
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Three iridoid glycosides 6-O-(3'-O-benzoyl)-alpha-l-rhamnopyranosylcatalpol (1a), 6-O-(3'-O-trans-cinnamoyl)-alpha-l-rhamnopyranosylcatalpol (2a) and 6-O-(3'-O-cis-cinnamoyl)-alpha-l-rhamnopyranosylcatalpol (3a) were isolated from aerial parts of Gmelina arborea and structures were elucidated by spectral analysis. Additionally a known iridoid 6-O-(3', 4'-O-dibenzoyl)-alpha-l-rhamnopyranosylcatalpol (4) was also isolated and identified. 相似文献
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Manoj K. Rai Pooja Asthana Shashi Kant Singh V.S. Jaiswal U. Jaiswal 《Biotechnology advances》2009,27(6):641-679
Encapsulation technology is an exciting and rapidly growing area of biotechnological research. This has drawn tremendous attention in recent years because of its wide use in conservation and delivery of tissue cultured plants of commercial and economic importance. Production of synthetic seeds by encapsulating somatic embryos, shoot buds or any other meristmatic tissue helps in minimizing the cost of micropropagated plantlets for commercialization and final delivery. In most of fruit crops, seed propagation has not been successful because of heterozygosity of seeds, minute seed size, presence of reduced endosperm, low germination rate, and also some are having seedless varieties. Many species have desiccation-sensitive intermediate or recalcitrant seeds and can be stored for only a few weeks or months. Under these circumstances, increasing interest has been shown recently to use encapsulation technology for propagation and conservation. Many fruit plants are studied worldwide for breeding, genetic engineering, propagation, and pharmaceutical purposes. In this context, synthetic seeds would be more applicable in exchange of elite and axenic plant material between laboratories and extension centers due to small bead size and ease in handling. Due to these advantages, interest in using encapsulation technology has continuously been increasing in several fruit plant species. The purpose of this review is to focus upon current information on development of synthetic seeds in several fruit crops. 相似文献
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The aerobic nitrogen fixing xylanolytic bacterium Paenibacillus pabuli strain ATSKP produces loosely attached capsular polysaccharide KP-EPS. On 0.5% birchwood xylan 70 ± 5.02 mg of KP-EPS was
produced per gram dry weight of cells by the fourth day of growth in the absence of combined nitrogen source at 30°C. It was
separated and purified using centrifugation, cold acetone precipitation and dialysis and is a sulfate containing heteropolymer
as revealed by FT-IR spectrometry and elemental analysis. CHN analysis revealed the presence of 37.50% carbon, 5.90% hydrogen
and 8.28% nitrogen in KP-EPS. Absence of phosphorus was confirmed by 31P NMR. ICP-OES analysis showed the presence of various metals in small concentrations. Specific binding with aniline blue
suggested the presence of (1,3)-β-d-glucan. Thermal gravimetric analysis and differential scanning calorimetric analysis confirmed its thermal stability as high
as 200°C. The EPS was not pseudo plastic and the viscosity was less than xanthan. The intrinsic viscosity did not reduce drastically
when dissolved in 0.1 M NaCl. 相似文献
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Traditional concealed information paradigms rely on the idea that stimuli that are meaningful to a person (critical items)
will draw attentional resources disproportionately, relative to stimuli that are not (irrelevant items), generating detectable
differences on a suitable dependent variable (behavioral, psychophysiological, or neural). Here, we introduce a behavioral
paradigm that could be used to reveal concealed information by exploiting the link between concealed information and attentional
processes more directly. This novel paradigm is based on the attentional blink phenomenon in which detection of a stimulus
reduces detection accuracy rates of subsequent target stimuli within a 200–500 ms time window. We hypothesized that a well-known
face used as a critical item could capture attentional resources automatically, making it harder to detect the occurrence
of a subsequently presented target face. The results confirmed this hypothesis, and showed that concealed knowledge of a famous
face could be detected in 9 out of 12 individuals by looking for a relative dip in target detection accuracy after the presentation
of a critical item. 相似文献
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Jason J. Paxman Natalie A. Borg James Horne Philip E. Thompson Yanni Chin Pooja Sharma Jamie S. Simpson Jerome Wielens Susannah Piek Charlene M. Kahler Harry Sakellaris Mary Pearce Stephen P. Bottomley Jamie Rossjohn Martin J. Scanlon 《The Journal of biological chemistry》2009,284(26):17835-17845
Oxidative protein folding in Gram-negative bacteria results in the formation of disulfide bonds between pairs of cysteine residues. This is a multistep process in which the dithiol-disulfide oxidoreductase enzyme, DsbA, plays a central role. The structure of DsbA comprises an all helical domain of unknown function and a thioredoxin domain, where active site cysteines shuttle between an oxidized, substrate-bound, reduced form and a DsbB-bound form, where DsbB is a membrane protein that reoxidizes DsbA. Most DsbA enzymes interact with a wide variety of reduced substrates and show little specificity. However, a number of DsbA enzymes have now been identified that have narrow substrate repertoires and appear to interact specifically with a smaller number of substrates. The transient nature of the DsbA-substrate complex has hampered our understanding of the factors that govern the interaction of DsbA enzymes with their substrates. Here we report the crystal structure of a complex between Escherichia coli DsbA and a peptide with a sequence derived from a substrate. The binding site identified in the DsbA-peptide complex was distinct from that observed for DsbB in the DsbA-DsbB complex. The structure revealed details of the DsbA-peptide interaction and suggested a mechanism by which DsbA can simultaneously show broad specificity for substrates yet exhibit specificity for DsbB. This mode of binding was supported by solution nuclear magnetic resonance data as well as functional data, which demonstrated that the substrate specificity of DsbA could be modified via changes at the binding interface identified in the structure of the complex. 相似文献
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