Iturin A is a potential lipopeptide antibiotic produced by Bacillus subtilis. Optimization of iturin A yield by adding various concentrations of asparagine (Asn), glutamic acid (Glu) and proline (Pro) during the fed-batch fermentation process was studied using an artificial neural network-genetic algorithm (ANN-GA) and uniform design (UD). Here, ANN-GA based on the UD data was used for the first time to analyze the fed-batch fermentation process. The ANN-GA and UD methodologies were compared based on their fitting ability, prediction and generalization capacity and sensitivity analysis.
The plant hormone abscisic acid (ABA) is an important regulator in many aspects of plant growth and development, as well as stress resistance. Here, we investigated the effects of exogenous ABA application on the interaction between tomato (Solanum lycopersicon L.) and Alternaria solani (early blight). Foliar spraying of 7.58 ?M ABA was effective in reducing disease severity in tomato plants. Previously, increased activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) were observed in exogenous ABA-treated tomato leaves. Moreover, these enzyme activities were maintained at higher levels in ABA-pretreated and A. solani challenged tomato plants. Tomato defense genes, such as PR1, ?-1, 3-glucanase (GLU), PPO, POD, and superoxide dismutase (SOD), were rapidly and significantly up-regulated by exogenous ABA treatment. Furthermore, a subsequent challenge of ABA-pretreated plants with the pathogen A. solani resulted in higher expression of defense genes, compared to water-treated or A. solani inoculated plants. Therefore, our results suggest that exogenous ABA could enhance disease resistance against A. solani infection in tomato through the activation of defense genes and via the enhancement of defense-related enzymatic activities.
A novel scheme for scanning electrochemical microscopy (SECM) assay of DNA based on hairpin probe and enzymatic amplification biosensor was described. In this method, streptavidin-horseradish peroxidase (HRP) was captured by double-stranded DNA (ds-DNA) modified gold substrate via biotin-streptavidin interaction after hybridization of target DNA to the immobilized hairpin probe functioned with a biotin at its 3 end. In the presence of H2O2, hydroquinone (H2Q) was oxidized to benzoquinone (BQ) at the modified substrate surface through the HRP catalytic reaction, and the generated BQ corresponding to the amount of target DNA was reduced in solution by a SECM tip. The resulting reduction current allowed concentration detection of target DNA and SECM imaging of hybridization between the target DNA and the immobilized hairpin probe. The detection limit of this method was as low as 17 pM for complementary target DNA and it had good selectivity to discriminate between the complementary sequence and one containing base mismatches.
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