UV辐射对植物多酚代谢的影响

植物多酚是紫外线防御物质,是植物体中重要的次生代谢产物,参与植物的生长发育,赋予植物抗紫外线、抗病害等生理功能。紫外线辐射作为一种逆境因子,与植物多酚间存在着相互制约而又相辅相成的关系。文章综述了植物多酚的合成途径,着重阐述了紫外线辐射对植物生长发育及贮藏品质、植物多酚的种类及含量以及多酚合成相关基因表达的影响,旨为揭示植物多酚合成与紫外辐射的关系及调控植物多酚合成提供更多信息。     

甘蓝多酚氧化酶的生物化学性质及其杀虫剂的诱导作用

采用时间动力学法,在研究了甘蓝多酚氧化酶的最适反应条件的基础上,对有机溶剂和杀虫剂对多酚氧化酶活性的影响进行了研究。结果表明:甘蓝多酚氧化酶反应的最适pH值为6.4,最适反应温度为55℃;丙酮和乙醇对多酚氧化酶活性有明显的激活作用;高效氯氰菊酯、灭多威和辛硫磷以及小菜蛾和桃蚜取食的胁迫会对多酚氧化酶的活性产生影响。     

Calcium and magnesium interactions in browning of ‘Golden Delicious’ apples with bitter pit

The role of Ca and Mg in the enzymatic browning of ‘Golden Delicious’ apples was explored. Enzymatic browning due to polyphenol oxidase (PPO) was stimulated with the addition of 0.8–10 mM MgCl₂ to the reaction mixture, whereas 0.8–10 mM CaCl₂ had little effect or decreased the rate of enzymatic browning. Within a week after vacuum infiltration with MgCl₂, treated fruits exhibited browning symptoms that were similar to bitter pit. Six months after vacuum infiltration, when analyzed for enzyme activity, MgCl₂-treated fruits exhibited higher rates of PPO activity, whereas CaCl₂-treated fruits had lower activity than the MgCl₂-treated fruits and the controls. A hypothesis is advanced that the initial visible symptoms of bitter pit, i.e. the localized browning, is caused by PPO, its activity being stimulated by the localized Mg/Ca imbalance present in the tissue. The results indicate that Ca is predominant in the prevention of this disorder, whereas a deficiency of Ca is involved in its induction.     

茶叶多酚氧化酶的序列分析与结构预测

调用生物信息学方法对已在国际互联网上的生物数据库(DDBJ、Uni-Prot)注册的茶树多酚氧化酶基因的核酸及氨基酸序列进行分析,并对其组成成分、信号肽、跨膜拓扑结构域、疏水性/亲水性、蛋白质二级及三级结构进行预测与推断。结果表明:茶多酚氧化酶不具有信号肽,存在卷曲螺旋,为位于细胞质中的无跨膜的亲水性不稳定蛋白,无规则卷曲是其蛋白质结构的主要结构元件,α-螺旋与β-折叠分散于整个多肽链中,并存在2个结构功能域。     

Effects of including bioactive legumes in grass silage on digestion parameters,nitrogen balance and methane emissions in sheep

The aim of this work was to investigate the effects of feeding sheep with silage mixtures containing bioactive legumes on intake and digestive parameters. The bioactive legumes used were sainfoin (SF, Onobrychis viciifolia) and red clover (RC, Trifolium pratense), which contain condensed tannins (CT) and polyphenol oxidase respectively. Five treatments were assigned to two groups of sheep according to a replicated 5 × 5 Latin square design. The five types of silages tested were, on a dry matter (DM) basis: pure timothy grass silage (Phleum pratense, control, T), three binary mixtures of T‐SF, T‐RC and RC‐SF (500 g/kg each) and a ternary mixture of T‐RC‐SF (500, 250 and 250 g/kg respectively). The daily voluntary DM intake of silage mixtures containing both SF and RC was greater than for pure T silage, while the presence of SF resulted in lower organic matter digestibility compared to pure T. The rumen disappearance rate measured in situ increased linearly with the presence of SF and RC in silage. The nitrogen (N) digestibility was greater for pure T and T‐RC than for T‐SF, and the amount of N retained daily by the animals was greater for RC‐containing silages than for T and T‐SF. The methane (CH₄) yield was greater for pure T than for the silage mixtures containing SF. We conclude that the presence of RC in silage could boost performances through intake and N retention, while SF‐based mixtures appear to have reduced negative environmental impacts through the reduction of CH₄ emissions.     

灰斑病菌对大豆叶片总多酚和总黄酮的诱导研究

利用大豆灰斑病菌不同致病力的生理小种接种抗感不同的大豆品种,结果表明:大豆叶片内总黄酮类物质的含量与品种的抗病性呈明显正相关;感病品种叶片内总多酚含量变化显著降低,抗病品种总体变化不大.接种致病力强的生理小种能够大幅度提高抗病品种体内总黄酮含量,这一结果可以作为筛选和鉴定抗病品种的一种生化指标;大豆灰斑病菌弱毒菌株能够诱导感病品种体内总黄酮含量提高,进而提高大豆的抗病性,这一结果为大豆灰斑病的生物防治提供了依据.     

槲皮素和硫脲对野桑蚕多酚氧化酶的抑制类型

多酚氧化酶(Polyphenol oxidase,PPO)在昆虫的变态发育和免疫防御中起着非常重要的作用,为开发以该酶为靶标的新型害虫抑制剂提供理论依据,以野桑蚕(Bombyx mandarina)五龄幼虫为材料提取多酚氧化酶,探讨了槲皮素和硫脲对该酶的抑制作用。结果表明,这两种抑制剂分别属于竞争性和非竞争性抑制剂。     

红茶发酵中pH调控对多酚氧化酶活性及茶黄素形成的影响

利用悬浮发酵模拟试验研究了酸处理调控红碎茶发酵．结果表明,发酵系统pH值与茶黄素（TF）和茶红素（TR）呈极显著负相关（r=-0．967,p〈0．001;r=-0．864,p〈0．005）,而与茶褐素（TB）呈极显著正相关（r=＋0．826,p〈0．005）;TF形成主要受二羟基多酚氧化酶（DPPO）与三羟基多酚氧化酶（TPPO）相对活性影响;酸处理可促进PP向TF的有效转化,TF转化率比对照提高71．2％．通过综合分析研究,提出了红茶发酵中pH调控提高TF含量的作用机制．     

山核桃仁多酚提取工艺及其抗氧化活性研究

以山核桃(Carya cathayensis)仁为材料,采用单因素试验和正交试验辅助超声波提取其中的多酚,确定多酚提取的最佳工艺,采用FRAP、DPPH和ABTS 3种方法测定了山核桃仁多酚的抗氧化能力并用Folin-Ciocalteu法测定其总酚含量。结果表明,多酚提取的最佳工艺组合为料液比1∶50(g∶m L),乙醇体积分数30%,超声时间20 min,提取温度35℃。FRAP、DPPH和ABTS法测得山核桃仁多酚的抗氧化活性分别为108.94、184.71和175.92μmol Trolox/g。山核桃仁多酚是较好的抗氧化剂。     

长春花感染黄龙病菌多酚氧化酶基因的表达及活性分析

【目的】分析长春花Catharanthus roseus受黄龙病菌Candidatus Liberibacter asiaticus侵染后多酚氧化酶(PPO)基因的表达及活性变化。【方法】根据不同作物多酚氧化酶基因PPO序列的相似性,筛选出长春花多酚氧化酶基因Pw PPO引物,PCR扩增得Pw PPO基因片段,运用qRT-PCR和生理生化方法分析长春花嫁接黄龙病芽后,不同时间长春花叶、主茎和根中Pw PPO基因的表达量和酶活性变化。【结果】长春花受黄龙病菌侵染后,叶、主茎和根中Pw PPO基因的表达分别在嫁接后30、35和40 d上调表达4.23、12.64和33.80倍,不同组织中Pw PPO基因上调表达的时间和幅度不同。染病长春花的叶、主茎和根中PPO活性分别在嫁接后30、35和45 d为对照的2.87、2.10和1.89倍。【结论】Pw PPO基因表达量与PPO活性成正比,与长春花抵抗黄龙病菌侵染的能力密切相关。