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FRANCESCA TRIELLI DAVIDE CERVIA GRAZIANO DI GIUSEPPE CHIARA RISTORI THOMAS KRUPPEL BRUNO BURLANDO GRAZIANO GUELLA ALDO VIARENGO PAOLA BAGNOLI MARIA UMBERTA DELMONTE CORRADO FERNANDO DINI 《The Journal of eukaryotic microbiology》2008,55(5):365-373
ABSTRACT. Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca2+ and Na+, suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment. 相似文献
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UV-B photon reception by the Arabidopsis thaliana homodimeric UV RESISTANCE LOCUS8 (UVR8) photoreceptor leads to its monomerization and a crucial interaction with CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Relay of the subsequent signal regulates UV-B-induced photomorphogenesis and stress acclimation. Here, we report that two separate domains of UVR8 interact with COP1: the β-propeller domain of UVR8 mediates UV-B-dependent interaction with the WD40 repeats-based predicted β-propeller domain of COP1, whereas COP1 activity is regulated by interaction through the UVR8 C-terminal C27 domain. We show not only that the C27 domain is required for UVR8 activity but also that chemically induced expression of the C27 domain is sufficient to mimic UV-B signaling. We further show, in contrast with COP1, that the WD40 repeat proteins REPRESSOR OF UV-B PHOTOMORPHOGENESIS1 (RUP1) and RUP2 interact only with the UVR8 C27 domain. This coincides with their facilitation of UVR8 reversion to the ground state by redimerization and their potential to interact with UVR8 in a UV-B-independent manner. Collectively, our results provide insight into a key mechanism of photoreceptor-mediated signaling and its negative feedback regulation. 相似文献
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Characterization of the Nrt2.6 Gene in Arabidopsis thaliana: A Link with Plant Response to Biotic and Abiotic Stress 总被引:1,自引:0,他引:1
The high affinity nitrate transport system in Arabidopsis thaliana involves one gene and potentially seven genes from the NRT1 and NRT2 family, respectively. Among them, NRT2.1, NRT2.2, NRT2.4 and NRT2.7 proteins have been shown to transport nitrate and are localized on the plasmalemma or the tonoplast membranes. NRT2.1, NRT2.2 and NRT2.4 play a role in nitrate uptake from soil solution by root cells while NRT2.7 is responsible for nitrate loading in the seed vacuole. We have undertaken the functional characterization of a third member of the family, the NRT2.6 gene. NRT2.6 was weakly expressed in most plant organs and its expression was higher in vegetative organs than in reproductive organs. Contrary to other NRT2 members, NRT2.6 expression was not induced by limiting but rather by high nitrogen levels, and no nitrate-related phenotype was found in the nrt2.6-1 mutant. Consistently, the over-expression of the gene failed to complement the nitrate uptake defect of an nrt2.1-nrt2.2 double mutant. The NRT2.6 expression is induced after inoculation of Arabidopsis thaliana by the phytopathogenic bacterium Erwinia amylovora. Interestingly, plants with a decreased NRT2.6 expression showed a lower tolerance to pathogen attack. A correlation was found between NRT2.6 expression and ROS species accumulation in response to infection by E. amylovora and treatment with the redox-active herbicide methyl viologen, suggesting a probable link between NRT2.6 activity and the production of ROS in response to biotic and abiotic stress. 相似文献
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Physiological Changes in Cultured Sorghum Cells in Response to Induced Water Stress : II. Soluble Carbohydrates and Organic Acids 下载免费PDF全文
Eight cultivars Sorghum bicolor (L.) Moench were grown as callus cultures under induced, prolonged water stress (8 weeks), with polyethylene glycol in the medium. Concentrations of soluble carbohydrates and organic acids in callus were measured at the end of the growth period to determine differences in response to prolonged water stress. Sucrose, glucose, fructose, and malate were the predominant solutes detected in all callus at all water potentials. All cultivars had high levels of solutes in the absence of water stress and low levels in the presence of prolonged water stress. However, at low water potentials, low levels of solutes were observed in drought-tolerant cultivar callus and high solute levels were observed in drought-susceptible cultivar callus. Estimated sucrose concentrations were significantly higher in water-stressed, susceptible cultivar callus. Large solute concentrations in susceptible cultivar callus were attributed to osmotic adjustment and/or reduced growth during water stress. 相似文献
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Begoña Blasco Juan J. Rios Luis M. Cervilla Eva Sánchez-Rodríguez María M. Rubio-Wilhelmi Miguel A. Rosales Juan M. Ruiz Luis Romero 《Journal of Plant Growth Regulation》2010,29(4):477-486
Iodine is vital to human health, and iodine biofortification programs help improve human intake through plant consumption.
There is no research on whether iodine biofortification influences basic plant physiological processes. Because nitrogen (N)
uptake, utilization, and accumulation are determining factors in crop yield, the aim of this work was to establish the effect
of the application of different doses (20, 40, and 80 μM) and forms of iodine (iodate [IO3
−] vs. Iodide [I−]) on N metabolism and photorespiration. For this study we analyzed shoot biomass and the activities of nitrate reductase
(NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AAT), glutamate
dehydrogenase (GDH), glycolate oxidase (GO), glutamate:glyoxylate aminotransferase (GGAT), serine:glyoxylate aminotransferase
(SGAT), hydroxypyruvate reductase (HR) and catalase (CAT), nitrate (NO3
−), ammonium (NH4
+), organic and total N, amino acids, proteins, serine (ser), malate, and α-ketoglutaric acid in edible lettuce leaves. Application
of I− at doses of at least 40 μM reduced the foliar concentration of NO3
− with no decrease in biomass production, which may improve the nutritional quality of lettuce plants. In contrast, the application
of 80 μM of I− is phytotoxic for lettuce plants, reducing the biomass, foliar concentration of organic N and NO3
−, and NR and GDH activities. HR activity is significantly inhibited with all doses of I−; the least inhibition was at 80 μM. This may involve a decrease in the incorporation of carbonated skeletons from photorespiration
into the Calvin cycle, which may be partially associated with the biomass decrease. Finally, the application of IO3
− increases biomass production, stimulates NO3
− reduction and NH4
+ incorporation (GS/GOGAT), and optimizes the photorespiratory process. Hence, this appears to be the most appropriate form
of iodine from an agronomic standpoint. 相似文献
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Humans can anticipate and prepare for uncertainties to achieve a goal. However, it is difficult to maintain this effort over a prolonged period of time. Inappropriate behavior is impulsively (or mindlessly) activated by an external trigger, which can result in serious consequences such as traffic crashes. Thus, we examined the neural mechanisms underlying such impulsive responding using functional magnetic resonance imaging (fMRI). Twenty-two participants performed a block-designed sustained attention to response task (SART), where each task block was composed of consecutive Go trials followed by a NoGo trial at the end. This task configuration enabled us to measure compromised preparation for NoGo trials during Go responses using reduced Go reaction times. Accordingly, parametric modulation analysis was conducted on fMRI data using block-based mean Go reaction times as an online marker of impulsive responding in the SART. We found that activity in the right dorsolateral prefrontal cortex (DLPFC) and the bilateral intraparietal sulcus (IPS) was positively modulated with mean Go reaction times. In addition, activity in the medial prefrontal cortex (MPFC) and the posterior cingulate cortex (PCC) was negatively modulated with mean Go reaction times, albeit statistically weakly. Taken together, spontaneously reduced activity in the right DLPFC and the IPS and spontaneously elevated activity in the MPFC and the PCC were associated with impulsive responding in the SART. These results suggest that such a spontaneous transition of brain activity pattern results in impulsive responding in monotonous situations, which in turn, might cause human errors in actual work environments. 相似文献
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Objective: To characterize dyslipidemia before and after weight loss in the severely obese. Research Methods and Procedures: Five hundred fifteen subjects who had Lap‐Band surgery were followed with yearly conventional lipid profiles for up to 4 years. Preoperative data were collected from the most recent 381 subjects, and predictors of dyslipidemia were sought. One hundred seventy‐one subjects completed a 1‐year review, providing data to assess predictors of change in lipids. Results: Favorable changes in fasting triglycerides (TG), high‐density lipoprotein‐cholesterol (HDL‐C), and total cholesterol (TC):HDL‐C ratio occurred within 1 year. All improvements were maintained up to 4 years. Male gender, central obesity, elevated fasting glucose, and insulin resistance were associated with less favorable lipid levels. Fasting plasma glucose best predicted TG (r = 0.46, p < 0.001), whereas insulin sensitivity using the homeostatic model assessment (HOMA %S) correlated best with the HDL‐C (r =0.34, p < 0.001). Higher preoperative fasting glucose best predicted the decrease in TG; improved HOMA %S with weight loss correlated best with HDL‐C. The extent of weight loss had limited influence on lipid changes. However, low preoperative HOMA %S was associated with lower weight loss. Greater weight loss was associated with more favorable lipid measures after controlling for preoperative HOMA %S. Discussion: Dyslipidemia of obesity is related to weight distribution, insulin sensitivity, and impaired glucose tolerance. Improvement with weight loss is related to the decrease in fasting glucose, improvement in insulin sensitivity, and the extent of weight lost. Improvement in dyslipidemia is sustained with long‐term weight loss. 相似文献
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在获得拟南芥NAC同源基因(NAC019、NAC055和NAC072)双突变体和三突变体纯系的基础上,进一步分析它们对ABA响应的生理差异及其ABA诱导相关下游基因的表达变化,深入探讨它们与ABA响应的关系。结果表明,在种子绿胚建成的过程中,NAC055和NAC072基因与ABA响应相关;在根生长方面,三者在ABA响应中作用不明显。经ABA处理后,突变体nac072和nac055nac072与野生型比较,RAB18、RD29A和RD29B基因表达上调显著,推测在ABA响应的基因表达调控过程中,NAC072和NAC055起负调控协同作用,而NAC019则发挥拮抗作用。 相似文献
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Effects of external pH (pHo) on the cytoplasmic pH (pHc) ofChara corallina have been measured with the weak acid 5, 5-dimethyloxazolidine-2,4-dione (DMO) following standardized pretreatment of cells insolutions at pHo 4.5, 6.3 and 8.3. Irrespective of pHc duringpretreatment, pHo responded to pHo during the experimental periodsof 150180 min or (in one experiment) 90110 min.There were increases or decreases of about 0.5 in pHo when cellswere transferred from pHo 4.5 to 8.3 or vice versa. In the darkpHc was 0.20.3 units lower than the corresponding valuein the light. The results are discussed in relation to the factorsinvolved in the regulation of pHc in C. corallina, which maybegin to break down below about pHo4.5, as indicated by relativelylarge decreases in pHc at low pHo. Key words: Chara corallina, Cytoplasmic pH, External pH, DMO 相似文献
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Cucumis sativus L.) seedlings were irradiated or not irradiated with UV-B for several days in environment-controlled growth chambers. The
first leaves irradiated with UV-B were retarded in growth but simultaneously acquired a remarkably high tolerance to oxidative
stress, as induced by paraquat treatment, compared with the non-irradiated leaves. This enhanced tolerance was observed within
1d after the start of UV-B irradiation and was maintained during the 12 d period of UV-B treatment. The effects of UV-B on
several antioxidative enzymes were examined, and activities of superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase,
but not of glutathione reductase, were found to be enhanced. However, activation of these enzymes occurred only from 6 d after
the start of irradiation. In contrast, accumulation of phenolic compounds was observed within 1d after the start of UV-B irradiation.
HPLC analysis of phenolic compounds showed the distinct enhancement of a substance, which may have antioxidative properties
in cucumber seedlings irradiated with UV-B. On the basis of these results, we conclude that not only antioxidative enzymes
but also other factors in cucumber seedlings irradiated with UV-B, such as phenolic compounds, may participate in the enhanced
tolerance to oxidative stress.
Received 10 June 2000/ Accepted in revised form 1 July 2000 相似文献
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