Overexpression of StRbohA in Arabidopsis thaliana enhances defence responses against Verticillium dahliae

Plant NADPH oxidases are key regulators of plant–microbe interactions and reactive oxygen species (ROS) are essential to plant defences against pathogens. A significant part in the role played by ROS has been ascribed to plant respiratory burst oxidase homologs (RBOHs). In potato (Solanum tuberosum), where RBOHs were previously shown to be involved in wound-induced oxidative burst, we assessed their expression after inoculation with Verticillium dahliae Kleb. and showed that StRbohA was the only homolog to be differentially induced in potato in response to inoculation. In order to investigate the potential role of this gene in plant protection against wilt diseases, we used Agrobacterium-mediated transformation of Arabidopsis to assess the effects of its overexpression on plant responses to V. dahliae. After inoculation with this pathogen, the transformed Arabidopsis line overexpressing StRbohA showed lower disease severity (percent damaged leaf area and vascular discoloration) as compared to the wild type. It also had higher ROS production and more cell death caused by hydrogen peroxide (H₂O₂), compared to the wild type. Suberization of root cells was also more pronounced in the line overexpressing StRbohA, and supports a possible role for StRBOHA in plant resistance to V. dahliae. Together, these findings indicate that overexpressed StRbohA in Arabidopsis enhances the ROS-mediated defence mechanisms against V. dahliae and can be a potential tool to improve plant resistance to this and other soilborne pathogens that cause wilts in economically important crops.     

Identification and characterization of the enzymes responsible for the metabolism of the non‐steroidal anti‐inflammatory drugs,flunixin meglumine and phenylbutazone,in horses

The in vivo metabolism and pharmacokinetics of flunixin meglumine and phenylbutazone have been extensively characterized; however, there are no published reports describing the in vitro metabolism, specifically the enzymes responsible for the biotransformation of these compounds in horses. Due to their widespread use and, therefore, increased potential for drug–drug interactions and widespread differences in drug disposition, this study aims to build on the limited current knowledge regarding P450‐mediated metabolism in horses. Drugs were incubated with equine liver microsomes and a panel of recombinant equine P450s. Incubation of phenylbutazone in microsomes generated oxyphenbutazone and gamma‐hydroxy phenylbutazone. Microsomal incubations with flunixin meglumine generated 5‐OH flunixin, with a kinetic profile suggestive of substrate inhibition. In recombinant P450 assays, equine CYP3A97 was the only enzyme capable of generating oxyphenbutazone while several members of the equine CYP3A family and CYP1A1 were capable of catalyzing the biotransformation of flunixin to 5‐OH flunixin. Flunixin meglumine metabolism by CYP1A1 and CYP3A93 showed a profile characteristic of biphasic kinetics, suggesting two substrate binding sites. The current study identifies specific enzymes responsible for the metabolism of two NSAIDs in horses and provides the basis for future study of drug–drug interactions and identification of reasons for varying pharmacokinetics between horses.     

Molecular characterization of Ascaridia galli from Bangladesh and development of a PCR method for distinguishing A. galli from Heterakis spp.

We analyzed the nuclear ribosomal internal transcribed spacer (ITS) 1 and ITS2 sequences for Bangladesh isolates of Ascaridia galli, and we determined that the sequences were unreliable as molecular markers for distinguishing A. galli from other Ascaridia species, because the sequences showed high identity with that of A. columbae. However, the ITS1 sequences were available for designing PCR primers distinguishable between Ascaridia galli and Heterakis spp. Bangladesh isolates of A. galli constituted a monophyletic clade along with other geographical isolates in the cytochrome c oxidase subunit I (COI) phylogenetic tree, however, we could not clarify the phylogenetic relationships between A. galli and other Ascaridia spp., because their available sequences in GenBank were very few. The developed PCR method using DNA from A. galli and Heterakis spp. eggs would enable differential diagnosis of the individual infections in the future.     

红三叶多酚氧化酶特性的研究

红三叶(Trifolium pretense L.)多酚氧化酶仅作用于邻苯酚,与对苯酚、间苯酚和一元酚无作用,而且对不同的邻苯酚其活性也表现很大差异,其中以咖啡酸作底物时活性最大.红三叶多酚氧化酶反应的最适pH值为6.5～7.0,最适温度为25～30℃,50℃时热稳定性相对较好.     

软儿梨冷冻贮藏过程酚类物质与多酚氧化酶的区域化分布

为研究冷冻贮藏中不同部位酚类物质和多酚氧化酶的分布特征,以青海省地方梨优良品种‘软儿梨’果实为研究材料,采用高效液相色谱法和比色法测定软儿梨果实后熟(室温)、冻藏(-18℃)和解冻(室温)3个时期的果皮、果肉中总多酚、绿原酸的含量和多酚氧化酶活性。结果表明:软儿梨果实后熟后,酚类物质果肉?果皮,多酚氧化酶则果皮?果肉;冷冻贮藏过程中,不同部位的酚类物质和多酚氧化酶均呈现不同程度的升高,但绿原酸在果皮急剧下降、果肉中略有增加。解冻后总体呈下降趋势,2个部位总酚、多酚氧化酶下降明显,而果皮中的绿原酸变化不大。研究表明:软儿梨果实后熟后,酚类物质和多酚氧化酶分布呈现区域化,冷冻贮藏加剧了酚类物质和多酚氧化酶活性的积累,导致了软儿梨冷冻贮藏后果皮先于果肉发生了褐变。     

肾型传染性支气管炎病毒对鸡嘌呤代谢的影响研究

用T株肾型传染性支气管炎病毒(IBV)人工感染14日龄非免疫土种鸡建立感染模型,于攻毒前、攻毒后48 h、72 h、96 h、120 h 采集血样,测定血浆黄嘌呤氧化酶(xanthine oxidase, XOD)活性,探索鸡嘌呤代谢变化与肾型IBV致病机理之间的关系.结果表明,与攻毒前相比较, 攻毒后48 h和72 h血浆XOD活性明显增强, 差异显著(P<0.01,P<0.05).结果提示,XOD活性升高引起的嘌呤代谢紊乱可能是鸡肾型IB的病理机制之一.     

Interaction of benzimidazole-N-sulfonamides with the cytochrome b/c1 complex of Pythium aphanidermatum

Experiments with intact cells and submitochondrial fractions of Pythium aphanidermatum (Edson) Fitz. indicated an interference of benzimidazole-N-sulfonamides with the NADH- or succinate-driven electron transport system between cytochromes b and c. Comparison with Ustilago maydis (DC) Corda and Botrytis cinerea Pers. ex Fr. revealed that this effect is Oomycetes specific. The molecular interaction between benzimidazole-N-sulfonamides and the mitochondrial cytochrome b/c₁ complex from P. aphanidermatum has been investigated. Binding assays with [¹⁴C]52232 RP (dimefluazole) indicated a time- and dose-dependent labelling of two proteins. The molecular mass of one labelled protein and the competition of the binding with antimycin A suggest that benzimidazole-N-sulfonamides interact with the Q₁-centre of cytochrome b. Furthermore, experiments with doubly labelled [³H][¹⁴C]CGA 323103 revealed a possible irreversible inactivation of the b/c₁ complex leading to covalent linkage of the dimethylsulfonamoyl moiety to the target site.     

原卟啉原氧化酶抑制剂类除草剂进展概况

本文对近期开发的原卟啉氧化酶抑制剂按用途进行了简要的介绍。文中涉及原卟啉氧化酶抑制剂的化学结构、生物活性、登记与专利和开发公司等。     

细胞色素P450s酶系催化除草剂代谢的研究进展

综述了细胞色素P450s酶系催化的单加氧反应机理,细胞色素P450s酶系在酰胺类、三氮苯类、磺酰脲类、脲类、苯氧羧酸类等除草剂的活性或降解代谢中的催化反应。讨论了研究细胞色素P450s酶系代谢作用在除草剂选择性、抗药性机理,抗除草剂作物的培育以及除草剂安全剂的解毒机理等方面的意义。