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991.
Paul T. LynchJason W. Johnston Susan M. Trigwell Aradhana MehraCarla Benelli Maurizio Lambardi 《Plant science》2011,181(1):47-56
A three-day pretreatment of olive somatic embryos (SE) with 0.75 M sucrose, combined with cryoprotection (0.5 M DMSO, 1 M sucrose, 0.5 M glycerol and 0.009 M proline) and controlled rate cooling, supported regrowth (as 34.6% fresh weight gain) and resumption of embryo development after cryopreservation. Pretreatment with mannitol or sorbitol did not support regrowth. Profiles of sugars, proline, antioxidant enzymes, Reactive oxygen species (ROS), secondary oxidation products and ethylene were constructed for the most successful (0.75 M) pretreatment series. Sucrose was the optimal pretreatment for supporting recovery, it also elevated glutathione reductase (GR) activity compared to controls, whereas superoxide dismutase (SOD), catalase and guaiacol peroxidase activities remained relatively unchanged. Superoxide dismutase activity was higher in SE pretreated with sucrose, compared with those pretreated with polyols; H2O2 was enhanced in SE pretreated with sorbitol and sucrose compared to mannitol. The overall trend for ethylene and OH production revealed their levels were highest in SE pretreated with polyols albeit, for individual treatments this was not always the case. Generally, pretreatments did not significantly change embryo secondary oxidation profiles of ThioBarbituric Acid Reactive Substances (TBARS) and Schiff's bases. In combination these studies suggest oxidative processes may influence regrowth of cryopreserved olive SE and that optimal pretreatments could, in part, increase tolerance by an overall enhancement of endogenous antioxidants (particularly GR), proline and sugars. 相似文献
992.
Iron (Fe) is an essential nutrient for plant growth and development. In plant tissues, approximately 80% of Fe is found in photosynthetic cells. This study was carried out to determine the effect of different iron concentrations on the photosynthetic characteristics of sweet potato plants. The fluorescence transient of chlorophyll a (OJIP), chlorophyll index and gas exchange were measured in plants grown for seven days in Hoagland solution containing an iron concentration of 0.45, 0.90, 4.50 or 9.00 mM Fe (as Fe-EDTA). The initial and maximum fluorescence increased in the plants receiving 9.00 mM Fe. In the analysis of the fluorescence kinetic difference, L- and K-bands appeared in all of the treatments, but the amplitude was higher in plants receiving 4.50 or 9.00 mM Fe. In plants grown in 9.00 mM Fe, the parameters of the JIP-Test indicated a better efficiency in the capture, absorption and use of light energy, and although the chlorophyll index was higher, the net photosynthesis was lower. The overall data showed that sweet potato plants subjected to high iron concentrations may not exhibit the toxicity symptoms, but the light reactions of photosynthesis can be affect, which may result in a declining net assimilation rate. 相似文献
993.
Morkunas I Narożna D Nowak W Samardakiewicz S Remlein-Starosta D 《Journal of plant physiology》2011,168(5):424-433
This study investigated the effects of cross-talk interactions of sucrose and infection caused by a pathogenic fungus Fusarium oxysporum f.sp. lupini on the regulation of the phenylpropanoid pathway, i.e. the level of expression of genes encoding enzymes participating in flavonoid biosynthesis, as well as cell location and accumulation of these compounds in embryo axes of Lupinus luteus L. cv. Polo. Embryo axes, both non-inoculated and inoculated, were cultured for 96 h on Heller medium with 60 mM sucrose (+Sn and +Si) or without it (−Sn and −Si). Real-time RT-PCR to assess expression levels of the flavonoid biosynthetic genes, phenylalanine ammonialyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI) and isoflavone synthase (IFS) were used. Sucrose alone strongly stimulated the expression of these genes. There was a very high expression level of these genes in +Si embryo axes in the early phase of infection. Signal amplification by sucrose and the infection was most intense in the 48-h +Si axes, resulting in the highest level of expression of flavonoid biosynthetic genes. In −Si tissues, the expression level of these genes increased at 48 and 72 h after inoculation relative to 24 h; however, the relative level of expression was much lower than in +Si axes, except at 72 h for PAL and CHS.Moreover, at 48 h of culture, considerably higher activity of CHI (EC 5.5.1.6) was observed in axes with a high level of sucrose than in those with a sucrose deficit. CHI activity in +Si axes at 48 and 96 h post-inoculation was over 1.5 and 2 times higher than that in +Sn axes, as well as higher than in −Si axes.Observations of yellow lupine embryo axes under a confocal microscope showed an increased post-infection accumulation of flavonoids, particularly in cells of embryo axes infected with F. oxysporum and cultured on a medium containing sucrose (+Si). Up to 48 h post-infection in +Si axes, a very intensive emission of green fluorescence was observed, indicating high accumulation of these compounds in whole cells. Moreover, a nuclear location of flavonoids was recorded in cells. Strong staining of flavonoid end products in +Si embryo axes was consistent with the expression of PAL, CHS, CHI and IFS.These results indicate that, in the early phase of infection, the flavonoid biosynthesis pathway is considerably enhanced in yellow lupine embryo axes as a strong signal amplification effect of sucrose and the pathogenic fungus F. oxysporum. 相似文献
994.
Konya C Hatanaka Y Fujiwara Y Uchida K Nagai Y Wada K Kabuta T 《Neurochemistry international》2011,59(2):251-258
Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) is an intracellular protein abundantly expressed in neurons, and a mutation in UCH-L1 has been identified in familial Parkinson’s disease. UCH-L1 has been detected in human cerebrospinal fluid, raising the possibility that UCH-L1 is secreted from neurons. In the present study, we showed that a portion of UCH-L1 is secreted from cultured cells. The secretion of D30K UCH-L1, which lacks ubiquitin binding activity, was decreased compared with that of wild-type UCH-L1, while the secretion of C90S UCH-L1, which lacks hydrolase activity, was not. Treatment with Brefeldin A, an inhibitor of vesicle transport from the endoplasmic reticulum to the Golgi, did not block the secretion of UCH-L1, indicating that UCH-L1 is secreted by an unconventional pathway. The UCH-L1 sequence from Leu-32 to Leu-39 is similar to the unconventional secretory signal sequence of engrailed 2, and substitution of the leucines within this region (L32S/L32A/L34S/L34A/L39S/L39A) reduced the secretion of UCH-L1. We found that the Parkinson’s disease-associated mutation I93M in UCH-L1 decreased the secretion of I93M UCH-L1. In addition, Parkinson’s disease-linked α-synuclein mutants reduced the secretion of endogenous UCH-L1. Our results indicate that the hydrolase activity is not necessary for the unconventional secretion of UCH-L1, and suggest that the ubiquitin binding activity and the sequence between Leu-32 and Leu-39 are involved in the secretion. Moreover, the secretion of UCH-L1 could be involved in the pathology of Parkinson’s disease. 相似文献
995.
The feasibility of using soy skim, a co-product of the aqueous processing of soybeans, in ethanol production from corn was evaluated. Specific growth rates were compared when Saccharomyces cerevisiae was grown in soy skim and peptone-yeast extract media supplemented with glucose. Such soy skim was proved to be a good nitrogen source for yeast growth. Next, fermentation of dry-ground corn to ethanol using soy skim as the media was simulated on 1.5-L scale. Replacing water with soy skim increased the initial ethanol production rates by 4-32% while final ethanol yield was about 39 g/100 g dry corn, similar to the result when water was used. Solid and protein contents in the finished beer increased with the addition of soy skim. Thus, replacing water in corn-ethanol fermentation with soy skim is feasible, and may improve the economics of both aqueous soybean processing and corn ethanol fermentation. 相似文献
996.
Robust critical systems are characterized by power laws which occur over a broad range of conditions. Their robust behaviour has been explained by local interactions. While such systems could be widespread in nature, their properties are not well understood. Here, we study three robust critical ecosystem models and a null model that lacks spatial interactions. In all these models, individuals aggregate in patches whose size distributions follow power laws which melt down under increasing external stress. We propose that this power-law decay associated with the connectivity of the system can be used to evaluate the level of stress exerted on the ecosystem. We identify several indicators along the transition to extinction. These indicators give us a relative measure of the distance to extinction, and have therefore potential application to conservation biology, especially for ecosystems with self-organization and critical transitions. 相似文献
997.
Oxidative stress is a putative factor responsible for reducing function and increasing apoptotic signaling in skeletal muscle with aging. This study examined the contribution and functional significance of the xanthine oxidase enzyme as a potential source of oxidant production in aged skeletal muscle during repetitive in situ electrically stimulated isometric contractions. Xanthine oxidase activity was inhibited in young adult and aged mice via a subcutaneously placed time-release (2.5 mg/day) allopurinol pellet, 7 days before the start of in situ electrically stimulated isometric contractions. Gastrocnemius muscles were electrically activated with 20 maximal contractions for 3 consecutive days. Xanthine oxidase activity was 65% greater in the gastrocnemius muscle of aged mice compared to young mice. Xanthine oxidase activity also increased after in situ electrically stimulated isometric contractions in muscles from both young (33%) and aged (28%) mice, relative to contralateral noncontracted muscles. Allopurinol attenuated the exercise-induced increase in oxidative stress, but it did not affect the elevated basal level of oxidative stress that was associated with aging. In addition, inhibition of xanthine oxidase activity decreased caspase-3 activity, but it had no effect on other markers of mitochondrial-associated apoptosis. Our results show that compared to control conditions, suppression of xanthine oxidase activity by allopurinol reduced xanthine oxidase activity, H2O2 levels, lipid peroxidation, and caspase-3 activity; prevented the in situ electrically stimulated isometric contraction-induced loss of glutathione; prevented the increase in catalase and copper-zinc superoxide dismutase activities; and increased maximal isometric force in the plantar flexor muscles of aged mice after repetitive electrically evoked contractions. 相似文献
998.
Mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene are responsible for hypophosphatasia, an inborn error of bone and teeth metabolism associated with reduced levels of serum alkaline phosphatase activity. A missense mutation (c.346G>A) of TNSALP gene, which converts Ala to Thr at position 116 (according to standardized nomenclature), was reported in dominantly transmitted hypophosphatasia patients (A.S. Lia-Baldini et al. Hum Genet. 109 (2001) 99-108). To investigate molecular phenotype of TNSALP (A116T), we expressed it in the COS-1 cells or Tet-On CHO K1 cells. TNSALP (A116T) displayed not only negligible alkaline phosphatase activity, but also a weak dominant negative effect when co-expressed with the wild-type enzyme. In contrast to TNSALP (W, wild-type), which was present mostly as a non-covalently assembled homodimeric form, TNSALP (A116T) was found to exist as a monomer and heterogeneously associated aggregates covalently linked via disulfide bonds. Interestingly, both the monomer and aggregate forms of TNSALP (A116T) gained access to the cell surface and were anchored to the cell membrane via glycosylphosphatidylinositol (GPI). Co-expression of secretory forms of TNSALP (W) and TNSALP (A116T), which are engineered to replace the C-terminal GPI anchor with a tag sequence (his-tag or flag-tag), resulted in the release of heteromeric complexes consisting of TNSALP (W)-his and TNSALP (A116T)-flag. Taken together, these findings strongly suggest that TNSALP (A116T) fails to fold properly and forms disulfide-bonded aggregates, though it is indeed capable of interacting with the wild-type and reaching the cell surface, therefore explaining its dominant transmission. 相似文献
999.
N.E. Belyaeva F.-J. SchmittV.Z. Paschenko G.Yu. RiznichenkoA.B. Rubin G. Renger 《Bio Systems》2011,103(2):188-195
Our recently presented PS II model (Belyaeva et al., 2008) was improved in order to permit a consistent simulation of Single Flash Induced Transient Fluorescence Yield (SFITFY) traces that were earlier measured by Steffen et al. (2005) on whole leaves of Arabidopsis (A.) thaliana at four different energies of the actinic flash. As the essential modification, the shape of the actinic flash was explicitly taken into account assuming that an exponentially decaying rate simulates the time dependent excitation of PS II by the 10 ns actinic flash. The maximum amplitude of this excitation exceeds that of the measuring light by 9 orders of magnitude. A very good fit of the SFITFY data was achieved in the time domain from 100 ns to 10 s for all actinic flash energies (the maximum energy of 7.5 × 1016 photons/(cm2 flash) is set to 100%, the relative energies of weaker actinic flashes were of ∼8%, 4%, ∼1%). Our model allows the calculation and visualization of the transient PS II redox state populations ranging from the dark adapted state, via excitation energy and electron transfer steps induced by pulse excitation, followed by final relaxation into the stationary state eventually attained under the measuring light. It turned out that the rate constants of electron transfer steps are invariant to intensity of the actinic laser flash. In marked contrast, an increase of the actinic flash energy by more than two orders of magnitude from 5.4 × 1014 photons/(cm2 flash) to 7.5 × 1016 photons/(cm2 flash), leads to an increase of the extent of fluorescence quenching due to carotenoid triplet (3Car) formation by a factor of 14 and of the recombination reaction between reduced primary pheophytin (Phe−) and P680+ by a factor of 3 while the heat dissipation in the antenna complex remains virtually constant.The modified PS II model offers new opportunities to compare electron transfer and dissipative parameters for different species (e.g. for the green algae and the higher plant) under varying illumination conditions. 相似文献
1000.
André MJ 《Bio Systems》2011,103(2):239-251
In closed systems, the O2 compensation point (ΓO) was previously defined as the upper limit of O2 level, at a given CO2 level, above which plants cannot have positive carbon balance and survive. Studies with 18O2 measure the actual O2 uptake by photorespiration due to the dual function of Rubisco, the enzyme that fixes CO2 and takes O2 as an alternative substrate. One-step modelling of CO2 and O2 uptakes allows calculating a plant specificity factor (Sp) as the sum of the biochemical specificity of Rubisco and a biophysical specificity, function of the resistance to CO2 transfer from the atmosphere to Rubisco. The crossing points (Cx, Ox) are defined as CO2 and O2 concentrations for which O2 and CO2 uptakes are equal. It is observed that: (1) under the preindustrial atmosphere, photorespiration of C3 plants uses as much photochemical energy as photosynthesis, i.e. the Cx and Ox are equal or near the CO2 and O2 concentrations of that epoch; (2) contrarily to ΓC, a ΓO does not practically limit the plant growth, i.e. the plant net CO2 balance is positive up to very high O2 levels; (3) however, in a closed biosystem, ΓO exists; it is not the limit of plant growth, but the equilibrium point between photosynthesis and the opposite respiratory processes; (4) a reciprocal relationship exists between ΓO and ΓC, as unique functions of the respective CO2 and O2 concentrations and of Sp, this invalidates some results showing two different functions for ΓO and ΓC, and, consequently, the associated analyses related to greenhouse effects in the past; (5) the pre-industrial atmosphere levels of O2 and CO2 are the ΓO and ΓC of the global bio-system. They are equal to or near the values of Cx and Ox of C3 plants, the majority of land plants in preindustrial period. We assume that the crossing points represent favourable feedback conditions for the biosphere-atmosphere equilibrium and could result from co-evolution of plants-atmosphere-climate. We suggest that the evolution of Rubisco and associated pathways is directed by an optimisation between photosynthesis and photorespiration. 相似文献