RESUMEN
Water and its dissociated species at the solidâliquid interface play critical roles in catalytic science; e.g., functions of oxygen species from water dissociation are gradually being recognized. Herein, the relationship between oxide identity (PtOHads, PtOads, and PtO2) and electrocatalytic activity of platinum for ethanol electrooxidation was obtained in perchlorate acidic solution over a wide potential range with an upper potential of 1.5 V (reversible hydrogen electrode, RHE). PtOHads and α-PtO2, rather than PtOads, act as catalytic centers promoting ethanol electrooxidation. This relationship was corroborated on Pt(111), Pt(110), and Pt(100) electrodes, respectively. A reaction mechanism of ethanol electrooxidation was developed with DFT calculations, in which platinum oxides-mediated dehydrogenation and hydrated reaction intermediate, geminal diol, can perfectly explain experimental results, including pH dependence of product selectivity and more active α-PtO2 than PtOHads. This work can be generalized to the oxidation of other substances on other metal/alloy electrodes in energy conversion and electrochemical syntheses.
RESUMEN
Multiprotein bridging factor 1 (MBF1) is a transcription coactivator that has a general defense response to pathogens. However, the regulatory mechanisms of MBF1 resistance bacterial wilt remain largely unknown. Here, the role of StMBF1c in potato resistance to Ralstonia solanacearum infection was characterized. qRT-PCR assays indicated that StMBF1c could was elicited by SA, MJ and ABA and the time-course expression pattern of the StMBF1c gene induced by R. solanacearum was found to be twice significant upregulated expression during the early and middle stages of bacterial wilt. Combined with the co-expression analysis of disease-resistant marker genes, gain-of-function and loss-of-function assays demonstrated that StMBF1c was associated with defence priming. Overexpression or silencing the MBF1c could enhance plants resistance or sensitivity to R. solanacearum through inducing or reducing NPR and PR genes related to SA signal pathway. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) experiment results confirmed the interaction of StMBF1c with StTPS5 which played a key role in ABA signal pathway in potato. It is speculated that by combining StTPS5 and resistance marker genes, StMBF1c is activated twice to participate in potato bacterial wilt resistance, in which EPI, PTI involved.
Asunto(s)
Resistencia a la Enfermedad/genética , Interacciones Huésped-Patógeno/genética , Ralstonia solanacearum , Solanum tuberosum/genética , Solanum tuberosum/microbiología , Regulación hacia Arriba/genética , Regulación hacia Arriba/fisiología , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Marcadores Genéticos , Enfermedades de las Plantas/microbiologíaRESUMEN
Bacterial wilt (BW) is a serious disease that affects potato (Solanum tuberosum L.) production. Although resistance to this disease has been reported, the underlying mechanism is unknown. In this study, we identified a NAC family transcription factor (StNACb4) from potato and characterised its structure, function, expression, its localisation at the tissue and its role in BW resistance. To this end, the transgenic Nicotiana benthamiana Domin lines were generated in which the expression of NACb4 was constitutively upregulated or suppressed using RNAi. Different tobacco mutants were stained after inoculating with Ralstonia solanacearum to observe the cell death and callose deposition. The results indicated that StNACb4 could be upregulated under the induction of R. solanacearum, and salicylic acid, abscisic acid and methyl jasmonate could also induce the expression of StNACb4. Tissue localisation analysis indicated that its expression was tissue specific, and it was mainly in the phloem of the vascular system of stems and leaves. NbNACb4 gene silencing can enhance the sensitivity of tobacco to R. solanacearum; on the contrary, StNACb4 gene overexpression can enhance the tolerance of tobacco to R. solanacearum. Meanwhile, StNACb4 gene overexpression can induce cell death and callose deposition in tobacco. The upregulated expression of StNACb4 can also activate the StPR10 gene expression. Our results provide important new insights into the regulatory mechanisms of bacterial wilt resistance in potato.
Asunto(s)
Ralstonia solanacearum , Solanum tuberosum , Enfermedades de las Plantas/genética , Solanum tuberosum/genética , Nicotiana , Factores de Transcripción/genéticaRESUMEN
Solanum tuberosum Zinc transporter 11 (StZnT11) is very important for maintaining zinc homeostasis in cells. The study on the expression of StZnT11 under abiotic stress and biotic stress laid a foundation for verifying the role of potato StZnT11 in the process of biotic stress of Ralstonia solanacearum species complex. According to the designated EST sequence, the homology of the original sequence was analyzed by using the Blast tool in NCBI, and a homologous object sequence with the highest similarity, coverage and e expectation value was selected. StZnT11 gene is obtained by Silico Cloning. The sequence and coding amino acid composition, physicochemical properties, molecular evolution, phosphorylation site and advanced structure of Solanum tuberosum StZnT11 gene were analyzed by bioinformatics method. The results showed that the cDNA gene is 1 300 bp in length, encoding a protein containing 348 amino acid residues, including 23 phosphorylation sites, one signal peptide and nine transmembrane regions, and is a hydrophobic protein located the plasma membrane. Through amino acid sequence alignment, StZnT11 protein has a high homology with zinc transporter from tobacco, tomato, pepper and other plants. The results of real-time fluorescence quantitative polymerase chain reaction showed that, StZnT11 is up-regulated by different concentrations of exogenous plant hormone abscisic acid (ABA). Tissue localization showed that StZnT11 was mainly expressed in specific tissues (phloem and leaf vascular bundles of stem vascular system). These results provide a theoretical basis for further experimental cloning and functional verification of the gene.
Asunto(s)
Solanum tuberosum , Secuencia de Aminoácidos , Proteínas Portadoras , Clonación Molecular , Biología Computacional , Regulación de la Expresión Génica de las Plantas , Proteínas de PlantasRESUMEN
Five peptidomimetic prodrugs of didanosine (DDI) were synthesized and designed to improve bioavailability of DDI following oral administration via targeting intestinal oligopeptide transporter (PepT1) and enhancing chemical stability. The permeability of prodrugs was screened in Caco-2 cells grown on permeable supports. 5'-O-L-valyl ester prodrug of DDI (compound 4a) demonstrated the highest membrane permeability and was selected as the optimal target prodrug for further studies. The uptake of glycylsarcosine (Gly-Sar, a typical substrate of PepT1) by Caco-2 cells could be inhibited by compound 4a in a concentration-dependent manner. The Caco-2 cells were treated with 0.2 nM leptin for enhanced PepT1 expression. The uptake of compound 4a was markedly increased in the leptin-treated Caco-2 cells compared with the control Caco-2 cells, both of which were obviously inhibited by 20 mM Gly-Sar. The K(m) and V(max) values of kinetic study of compound 4a transported by PepT1 in Caco-2 cells were 0.91 mM and 11.94 nmol/mg of protein/10 min, respectively. The chemical stability studies were performed in simulated gastric fluid (SGF), phosphate buffers under various pH conditions, rat tissue homogenates and plasma at 37 °C. The concentrations of DDI could not be detected in the two minutes in SGF. But compound 4a could significantly increase DDI acidic stability, and its t(½) was extended to as long as 36 min in SGF. Compound 4a was stable in pH 6.0 phosphate buffer but could be quickly transformed into DDI in plasma and tissue homogenates. The oral absolute bioavailability of DDI was 47.2% and 7.9% after compound 4a and DDI were orally administered to rats at a dose of 15 mg/kg, respectively. The coadministration with antiacid agent could also suggest that compound 4a was more stable under harsh acidic conditions compared with DDI. Compound 4a bioavailability in rats was reduced to 33.9% when orally co-administered with Gly-Sar (100 mg/kg). The In Vivo bioactivation mechanism of compound 4a was investigated by comparing the levels of DDI and compound 4a in the jugular and portal veins in rats. The plasma concentration of intact compound 4a was very low in portal veins and could hardly be detected in the jugular vein. In conclusion, compound 4a could significantly improve the oral bioavailability of DDI in rats through PepT1-mediated absorption and enhanced acidic stability, followed by rapid and mostly intracellular bioactivation, the majority in the intestinal cells but the minority in the liver. Additionally, the prodrug strategy targeted to intestinal PepT1 could offer a promising strategy to improve oral bioavailability of poorly absorbed didanosine.
Asunto(s)
Permeabilidad de la Membrana Celular/efectos de los fármacos , Didanosina/análogos & derivados , Didanosina/química , Absorción Intestinal/efectos de los fármacos , Intestinos/efectos de los fármacos , Peptidomiméticos , Profármacos/farmacología , Profármacos/farmacocinética , Valina/análogos & derivados , Ácidos/química , Administración Oral , Animales , Disponibilidad Biológica , Células CACO-2 , Didanosina/síntesis química , Didanosina/farmacocinética , Didanosina/farmacología , Humanos , Hígado/efectos de los fármacos , Masculino , Profármacos/síntesis química , Ratas , Ratas Sprague-Dawley , Distribución Tisular , Migración Transendotelial y Transepitelial , Valina/síntesis química , Valina/farmacocinética , Valina/farmacologíaRESUMEN
A rapid, sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method with hydrophilic interaction chromatography has been developed and validated for the simultaneous determination of didanosine and valdidanosine (L-valine amino acid ester prodrug of didanosine) in rat plasma. Solid-phase extraction (SPE) column was employed to extract the analytes from rat plasma, with high extraction recovery (>85%) for both didanosine and valdidanosine. The analytes were then separated by hydrophilic interaction chromatography (HILIC column) and detected by a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source. The method was linear over the concentration ranges of 2-20,000 ng/mL for didanosine and 4-300 ng/mL for valdidanosine. The lower limit of quantitation (LLOQ) of didanosine and valdidanosine was 2 and 4 ng/mL, respectively. The intra-day and inter-day relative standard deviation (RSD) were less than 15% and the relative errors (RE) were all within 15%. Finally, the validated UPLC-MS/MS method was successfully applied to the pharmacokinetic study after either didanosine or valdidanosine orally administrated to the Sprague-Dawley rats.