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101.
Xuan Yi Akihiro Yamazaki Eulandria Biddle Quan Zeng Ching‐Hong Yang 《Molecular microbiology》2010,77(3):787-800
Cyclic diguanylate (c‐di‐GMP) is a second messenger implicated in the regulation of various cellular properties in several bacterial species. However, its function in phytopathogenic bacteria is not yet understood. In this study we investigated a panel of GGDEF/EAL domain proteins which have the potential to regulate c‐di‐GMP levels in the phytopathogen Dickeya dadantii 3937. Two proteins, EcpB (contains GGDEF and EAL domains) and EcpC (contains an EAL domain) were shown to regulate multiple cellular behaviours and virulence gene expression. Deletion of ecpB and/or ecpC enhanced biofilm formation but repressed swimming/swarming motility. In addition, the ecpB and ecpC mutants displayed a significant reduction in pectate lyase production, a virulence factor of this bacterium. Gene expression analysis showed that deletion of ecpB and ecpC significantly reduced expression of the type III secretion system (T3SS) and its virulence effector proteins. Expression of the T3SS genes is regulated by HrpL and possibly RpoN, two alternative sigma factors. In vitro biochemical assays showed that EcpC has phosphodiesterase activity to hydrolyse c‐di‐GMP into linear pGpG. Most of the enterobacterial pathogens encode at least one T3SS, a major virulence factor which functions to subvert host defences. The current study broadens our understanding of the interplay between c‐di‐GMP, RpoN and T3SS and the potential role of c‐di‐GMP in T3SS regulation among a wide range of bacterial pathogens. 相似文献
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104.
Subbiyan Maruthasalam Ling Yin Shiu Murugan Loganathan Wei Ching Lien Yi Lun Liu Ching Mei Sun Chih Wen Yu Shu Hsien Hung Yeong Ko Chin Ho Lin 《Plant Growth Regulation》2010,60(2):83-90
Ethylene, a gaseous plant hormone, is responsible for the initiation of reproductive development in pineapple. Reproductive
development can be forced in pineapple (Ananas comosus var. comosus) throughout the year with ethylene. Inhibition of natural flowering initiation with aviglycine [(S)-trans-2-amino-4-(2-aminoethoxy)-3-butenoic acid hydrochloride], an inhibitor of ethylene biosynthesis, provides evidence
that reproductive development in response to cold stress and short daylength is also in response to ethylene production. We
studied the effect of cold treatment of pineapple on ethylene production and flower induction by applying a short-term cold
stress to stem apices. Shoot apices of pineapple treated with ice crystals also produced twice as much ethylene as did those
of control plants and significantly more than was produced by “D” leaf basal tissue. Moreover, pineapple plants treated four
times with ice crystals or ice water were induced to flower under field conditions and the forcing efficiency, as evaluated
by the percentages of inflorescence emergence and fruit harvest, was comparable to forcing with calcium carbide (CaC2) and ethephon. In another field experiment two applications of a 1.0% solution of CaC2 or 0.15% ethephon applied at 48 h intervals was sufficient to force reproductive development of ‘Tainon 17’. Furthermore,
0.5 or 1.0% solutions of CaC2 supplemented with 0.5% activated charcoal (AC) significantly improved the forcing effectiveness of CaC2. This could/would make it possible to reduce the number or concentration, or both, of CaC2 required to effect forcing in pineapple. 相似文献
105.
Chiung-Chih Chang Chun-Chung Lui Jiun-Jie Wang Shu-Hua Huang Cheng-Hsien Lu Ching Chen Chih-Feng Chen Min-Chien Tu Chi-Wei Huang Wen-Neng Chang 《BMC neurology》2010,10(1):59
Background
Cerebrotendinous xanthomatosis (CTX) is a rare genetic disorder. Recent studies show that brain damage in CTX patients extends beyond the abnormalities observed on conventional magnetic resonance imaging (MRI). We studied the MRI and 99 mTc-ethyl cysteinate dimer single photon emission computed tomography (SPECT) findings of CTX patients and made a correlation with the neuropsychological presentations.Methods
Diffusion tensor imaging (DTI) and 3D T1-weighted images of five CTX patients were compared with 15 age-matched controls. Voxel-based morphometry (VBM) was use to delineate gray matter (GM) and white matter (WM) volume loss. Fractional anisotropy (FA), mean diffusivity (MD), and eigenvalues derived from DTI were used to detect WM changes and correlate with neuropsychological results. SPECT functional studies were used to correlate with GM changes.Results
Cognitive results showed that aside from moderate mental retardation, the patient group performed worse in all cognitive domains. Despite the extensive GM atrophy pattern, the cerebellum, peri-Sylvian regions and parietal-occipital regions were correlated with SPECT results. WM atrophy located in the peri-dentate and left cerebral peduncle areas corresponded with changes in diffusion measures, while axial and radial diffusivity suggested both demyelinating and axonal changes. Changes in FA and MD were preceded by VBM in the corpus callosum and corona radiata. Cognitive results correlated with FA changes.Conclusion
In CTX, GM atrophy affected the perfusion patterns. Changes in WM included atrophy, and axonal changes with demyelination. Disconnection of major fiber tracts among different cortical regions may contribute to cognitive impairment.106.
Rice (Oryza sativa L.) seedlings stressed with CdCl2 (0.5 mM or 50 μM) showed typical Cd toxicity (leaf chlorosis, decrease in chlorophyll content, or increase in H2O2 and malondialdehyde contents). Rice seedlings pretreated with heat shock at 45°C (HS) for 2 or 3 h were protected against
subsequent Cd stress. Rice seedlings pretreated with HS had similar Cd concentration in leaves caused by CdCl2 as those non-HS. The content of H2O2 increased in leaves 1 h after HS exposure. However, APX and GR activities were higher in HS-treated leaves than their respective
control, and it occurred after 2 h of HS treatment. Pretreatment of rice seedlings with H2O2 under non-HS conditions resulted in an increase in APX, GR, and CAT activities and protected rice seedlings from subsequent
Cd stress. HS-induced H2O2 production and protection against subsequent Cd stress can be counteracted by imidazole, an inhibitor of NADPH oxidase complex.
Results of the present study suggest that early accumulation of H2O2 during HS signals the increase in APX and GR activities, which in turn prevents rice seedlings from Cd-caused oxidative damage. 相似文献
107.
The protective effect of polyamines against Cd toxicity of rice (Oryza sativa) leaves was investigated. Cd toxicity to rice leaves was determined by the decrease in protein content. CdCl2 treatment results in (1) increased Cd content, (2) induction of Cd toxicity, (3) increase in H2O2 and malondialdehyde (MDA) contents, (4) decrease in ascorbic acid (ASC) and reduced glutathione (GSH) contents, and (5) increase
in the activities of antioxidative enzymes (superoxide dismutase, glutathione reductase, ascorbate peroxidase, catalase, and
peroxidase). Spermidine (Spd) and spermine (Spm), but not putrescine (Put), were effective in reducing CdCl2-induced toxicity. Spd and Spm prevented CdCl2-induced increase in the contents of H2O2 and MDA, decrease in the contents of ASC and GSH, and increase in the activities of antioxidative enzymes. Spd and Spm pretreatments
resulted in a decrease in Cd content when compared with H2O pretreatment, indicating that Spd and Spm may reduce the uptake of Cd. Results of the present study suggest that Spd and
Spm are able to protect Cd-induced oxidative damage and this protection is most likely related to the avoidance of H2O2 generation and the reduction of Cd uptake. 相似文献
108.
109.
Kwok CF Juan CC Ho LT 《American journal of physiology. Endocrinology and metabolism》2007,292(2):E648-E652
Recent studies have shown that CD36 plays important roles as a major scavenger receptor for oxidized low-density lipoproteins and as a crucial transporter for long-chain fatty acids. CD36 deficiency might be associated with insulin resistance and abnormal dynamics of long-chain fatty acids. Endothelin-1 (ET-1), which is synthesized and secreted by vascular endothelial cells, is the most potent endogenous vasoconstrictor known and also stimulates the proliferation of vascular smooth muscle cells (VSMCs) and thus is believed to play an important role in the development of various circulatory disorders, including hypertension and atherosclerosis. The aim of the present study was to investigate the regulatory effect of ET-1 on CD36 expression in cultured VSMCs. VSMCs were treated for different times (0-24 h) with a fixed concentration (100 nM) of ET-1 or with different concentrations (0-100 nM) for a fixed time (24 h); then CD36 expression was determined using Western blots. CD36 expression was significantly decreased by ET in a time- and dose-dependent manner. This inhibitory effect was prevented by the ET(A) receptor antagonist BQ-610 (10 microM) but not the ET(B) receptor antagonist BQ-788 (10 microM). To further explore the underlying mechanisms of ET-1 action, we examined the involvement of the tyrosine kinase-mediated and MAPK-mediated pathways. The inhibitory effect of ET-1 on CD36 protein expression was blocked by inhibition of tyrosine kinase activation by use of genistein (100 microM) and by the ERK inhibitor PD-98059 (75 microM) but not by the p38 MAPK inhibitor SB-203580 (20 microM). In conclusion, we have demonstrated that ET-1, acting via the ET(A) receptor, suppresses CD36 protein expression in VSMCs by activation of the tyrosine kinase and ERK pathways. 相似文献
110.
Ammonium is a central intermediate in the nitrogen metabolism of plants. We have previously shown that methyl jasmonate (MJ) not only increases the content of H(2)O(2), but also causes NH(4)(+) accumulation in rice leaves. More recently, H(2)O(2) is thought to constitute a general signal molecule participating in the recognition of and the response to stress factors. In this study, we examined the role of H(2)O(2) as a link between MJ and subsequent NH(4)(+) accumulation in detached rice leaves. MJ treatment resulted in an accumulation of NH(4)(+) in detached rice leaves, which was preceded by a decrease in the activity of glutamine synthetase (GS) and an increase in the specific activities of protease and phenylalanine ammonia-lyase (PAL). GS, PAL, and protease appear to be the enzymes responsible for the accumulation of NH(4)(+) in MJ-treated detached rice leaves. Dimethylthiourea (DMTU), a chemical trap for H(2)O(2), was observed to be effective in inhibiting MJ-induced NH(4)(+) accumulation in detached rice leaves. Scavengers of free radicals (sodium benzoate, SB, and glutathione, GSH), nitric oxide donor (N-tert-butyl-alpha-phenylnitrone, PBN), the inhibitors of NADPH oxidase (diphenyleneiodonium chloride, DPI, and imidazole, IMD), and inhibitors of phosphatidylinositol 3-kinase (wortmannin, WM, and LY 294002, LY), which have previously been shown to prevent MJ-induced H(2)O(2) production in detached rice leaves, inhibited MJ-induced NH(4)(+) accumulation. Similarly, changes in enzymes responsible for NH(4)(+) accumulation induced by MJ were observed to be inhibited by DMTU, SB, GSH, PBN DPI, IMD, WM, or LY. Seedlings of rice cultivar Taichung Native 1 (TN1) are jasmonic acid (JA)-sensitive and those of cultivar Tainung 67 (TNG67) are JA-insensitive. On treatment with JA, H(2)O(2) accumulated in the leaves of TN1 seedlings but not in the leaves of TNG67. Ethylene action inhibitor, silver thiosulfate, was observed to inhibit MJ- and abscisic acid-induced accumulation of NH(4)(+) and changes in enzymes responsible for NH(4)(+) accumulation in detached rice leaves, suggesting that the action of MJ and ABA is ethylene dependent. 相似文献