拟南芥芥子酸酯对UV-B辐射的响应

芥子酸酯(sinapate esters)是拟南芥和其他十字花科植物中大量存在的一类具有紫外吸收作用的羟基肉桂酸衍生物,有研究表明其紫外吸收能力甚至强于类黄酮。以模式植物拟南芥(Arabidopsis thaliana)为实验材料,通过施加低强度(40 μW/cm²)、相对长时间(7 d)的UV-B辐射,考察了拟南芥幼苗和成苗芥子酸酯组分(芥子酰葡萄糖、芥子酰苹果酸)和含量及合成途径关键酶编码基因表达水平对UV-B辐射的响应。经过7 d的UV-B辐射处理,拟南芥幼苗和成苗的芥子酰葡萄糖、芥子酰苹果酸含量均高于对照植株,芥子酸酯表现为响应UV-B辐射而积累。无论是幼苗还是成苗,叶片中芥子酰苹果酸的含量都要比芥子酰葡萄糖高出一个数量级,而且在UV-B处理过程中观察到芥子酰葡萄糖含量减少而芥子酰苹果酸含量增加,催化芥子酰葡萄糖生成芥子酰苹果酸的芥子酰葡萄糖苹果酸转移酶编码基因的表达水平也显著提高,说明芥子酰苹果酸在拟南芥叶片响应UV-B辐射过程中起重要作用并优先合成。另外,拟南芥幼苗中两种芥子酸酯的含量是成苗中的数十倍之多,芥子酸酯合成途径关键酶编码基因fah1和sng1的相对表达量也显著高于成苗。同时,在响应UV-B辐射的过程中,幼苗中芥子酰葡萄糖、芥子酰苹果酸含量的变化幅度(分别是7.01％、6.05％)远远低于成苗叶片中芥子酰葡萄糖、芥子酰苹果酸含量的变化幅度(分别是21.88％、70.63％),这可能意味着拟南芥叶片中芥子酸酯对于UV-B辐射的防护作用,幼苗属于组成型防御(constitutive defense),而到成苗则转变为诱导型防御(inducible defense)。     

金属离子及保护剂对深绿木霉T155产芥子酶的活性影响及芥子酶的分离纯化

【目的】探求金属离子及保护剂对深绿木霉T155产生的粗芥子酶液活性的影响以及芥子酶的分离纯化方法。【方法】通过添加不同浓度的金属离子及保护剂研究对芥子酶活性的影响并通过细胞破壁、硫酸铵沉淀、透析、Sephadex G-100柱层析、DEAE-52离子交换层析、Sephadex G-200柱层析等方法提取到纯的芥子酶,最后通过电泳检测芥子酶的纯度和分子量。【结果】研究发现Ag+、Zn2+、Pb2+、Mg2+、Hg2+、Fe3+等金属离子在低浓度时对芥子酶均表现为一定的促进作用,但达到一定浓度后则起抑制作用,Ca2+浓度在0.069–17.000 g/L范围内均对酶活性起到促进作用,且促进效果基本与Ca2+浓度成正比;添加1 mmol/L EDTA和3 mmol/L DTT对芥子酶的保护作用最好,4°C保存26 d后芥子酶能够保持85%活性;电泳分析该芥子酶的分子量大约在150 kD左右,并且是一个二聚体。【结论】Ca2+在实验浓度内主要是提高芥子酶活性,而其他金属离子对芥子酶活性主要起抑制作用;EDTA或者EDTA与DTT协同能够较好保持芥子酶活性的稳定性;通过一系列分离纯化步骤得到了纯的二聚体芥子酶,研究结果为挖掘产芥子酶的微生物资源提供了新的途径和思路。     

植物芥子酶研究进展

芥子酶防御系统为白花菜目植物特有．由芥子酶及其底物硫代葡萄糖苷组成．芥子酶和硫代葡糖苷分别储藏在不同的细胞中,在受到病虫侵袭时,底物和酶相遇,硫代葡糖苷被降为有毒化合物,起防御作用．对植物芥子酶防御系统研究进展进行了综述,包括基因家族的结构、基因的表达调控、芥子酶的细胞定位、植物以外其它生物的芥子酶、硫代葡糖苷／芥子酶系统起源进化以及其可能功能等．     

芥子碱硫氰酸盐清除超氧阴离子自由基作用的研究

目的:研究芥子碱硫氰酸盐清除超氧阴离子自由基的作用。方法:用化学发光法测定芥子碱硫氰酸盐清除超氧阴离子自由基的能力,并以抗坏血酸的清除能力做为对照,以IC50值(清除率为50%时的浓度值)作为评价指标。结果:芥子碱硫氰酸盐和抗坏血酸的IC50值分别为0.135 mmol/L和18.74 mmol/L,后者的IC50值约为前者的140倍。结论:芥子碱硫氰酸盐具有良好的抗氧化作用,可以作为天然抗氧化剂进行开发。     

果蝇伴性隐性致死突变试验中芥子碱的辐射保护作用

过去的工作证明一些十字花科植物的抗辐射性与其体内存在的天然辐射保护物质有关。芥子碱是存在于十字花科植物中的一种天然辐射保护物质。它对大麦和小麦以及小鼠均有辐射保护作用。本文报道芥子碱在果蝇伴性隐性致死(SLRL)突变试验系统中的辐射保护作用。供试果蝇并不拒食芥子碱水溶液。10 mg/ml芥子碱对果蝇无生理毒性,对生育力亦无不良影响。40 Gy X 射线诱发8.96% SLRL 突变。而40 Gy 辐照前喂10 mg/ml芥子碱的果蝇其SLRL 突变率降为0.4%。Oregon K 果蝇的自发突变率为0-0.4%。可见喂芥子碱后辐射诱发的SLRL 突变不复出现,说明芥子碱对果蝇有很强的辐射保护作用。也讨论了芥子碱作为潜在抗癌物质的可能性。     

藏药菥蓂中黑芥子苷对黄嘌呤致小鼠高尿酸作用的研究北大核心CSCD

采用黄嘌呤致小鼠高尿酸模型,将昆明种小鼠随机分为模型组、空白对照组、阳性组、未灭活水提液(WMHSTY)组、灭活水提液(MHSTY)组、醇提液(CTY)组和水提醇沉浓缩液(STCCNSY)组并分别给药,以提取液对尿酸降低程度与提取液中黑芥子苷含量的关系阐明黑芥子苷与菥蓂治疗痛风作用的关系。结果,MHSTY和WMHSTY对黄嘌呤致小鼠高尿酸模型有显著的降低尿酸作用,两者间无明显差异,但黑芥子苷含量差异显著;CTY中黑芥子苷含量最高,但对本模型无明显作用;STCCNSY中无法检测出黑芥子苷,但对本模型有极显著作用。表明,藏药菥蓂中黑芥子苷的含量与菥蓂对黄嘌呤致小鼠高尿酸模型的作用无明显关系。     

拟南芥芥子酶基因TGG6是花特异表达的假基因

芥子酶是一类催化硫代葡萄糖苷水解的同工酶．TGG6是在拟南芥中新发现的芥子酶基因．从拟南芥几个不同生态型中克隆了他G6基因的全长核基因和cDNA片段．序列分析结果表明,所有供斌的生态型的他G6基因都与拟南芥第3个芥子酶基因彤G3类似,在编码区存在1个以上移码突变,不能编码完整多肽．生态型Col-0第10个内含子的剪切边界还发生了缺失,导致内含子不能被切除．初步确定TGG6是一个假基因．然而,RT-PCR结果却表明TGG6在花器中特异性表达,说明TGG6在进化的某个阶段可能是有功能的基因,由于某种原因。该基因在进化过程中被失活．     

辐射及活性氧对DNA的损伤以及芥子碱的保护作用

在Ｘ射线照射下,小牛胸腺ＤＮＡ的碱基损伤及链断裂随着剂量升高而增加,其损伤主要集中于链断裂;活性氧可以引起ＤＮＡ损伤,Ｈ２Ｏ２仅造成少量伤害,当在含有Ｈ２Ｏ２的体系中加入微量的Ｃｕ＾２＋、Ｆｅ＾２＋时损伤急剧增加,这是由反应产生的．ＯＨ所致,Ｃｕ＾２＋的致损伤效果明显高于Ｆｅ＾２＋。ＯＨ清除剂芥子碱具有很强的抗辐射及抗氧化作用,且对ＤＮＡ无伤害。这说明ＯＨ在ＤＮＡ的氧化损伤中起重要作用。     

油菜花粉单倍体苗形成过程中硫甙含量和芥子酶活性变化的研究

在油菜（Brassica uncea)花粉胚状体及幼苗的形成过程中,经分析测定表明,花粉胚状体中硫甙含量较高,随着胚状体的生长发育,含量有所下降,并在20天内基本保持稳定,由花粉胚状体形成的无定形培养物再生次生胚状体时,硫苷含量迅速增加,在对各种样品的硫苷含量进行测定的同时,分析测定了其芥子酶活性,从实验结果看,硫苷含量与芥子酶活性之间有一定的相关性,在整个单倍体苗形成过程中,它们的变化模式相近。     

辐射及活性氧对DNA的损伤以及芥子碱的保护作用

在X射线照射下,小牛胸腺DNA的碱基损伤及链断裂随着剂量升高而增加,其损伤主要集中于链断裂;活性氧可以引起DNA损伤,H2O2仅造成少量伤害,当在含有H2O2的体系中加入微量的Cu2＋、Fe2＋时损伤急剧增加,这是由反应产生的·OH所致,Cu2＋的致损伤效果明显高于Fe2＋。·OH清除剂芥子碱具有很强的抗辐射及抗氧化作用,且对DNA无伤害。这说明·OH在DNA的氧化损伤中起重要作用。     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

Identification and Characterization of the First Equine Parainfluenza Virus 5

正Dear Editor,Parainfluenza virus 5 (PIV5), known as canine parainfluenza virus in the veterinary field, is a negative-sense,nonsegmented, single-stranded RNA virus belonging to the Paramyxoviridae family (Chen 2018). The virus was first reported in primary monkey kidney cells in 1954 (Hsiung1972), then it has been frequently discovered in various