地黄SCoT分子标记体系的建立和指纹图谱的构建

该研究采用L_(25)(5~6)正交设计和单因素两种方法,对影响地黄SCoT-PCR反应的5个因素(模板DNA浓度,引物浓度,ddH_2O和Mix的用量以及退火温度)进行了优化。结果表明:优化后的反应体系总体积为25μL,含有8μL ddH_2O,1μL模板DNA(80 ng·μL~(-1)),1μL引物(8μmol·L~(-1))和15μL Mix,退火温度为45℃。运用30份地黄种质材料,对优化的SCoT-PCR正交体系进行多次重复验证,获得了多态性丰富、条带清晰的扩增图谱,证明该反应体系稳定可靠。利用该体系对32条SCoT引物进行两次筛选,得到14个扩增产物清晰、重复性好且多态性条带相对较高的引物。利用SCoT_4等5条引物构建了上述地黄2个种共30份种质的SCoT指纹图谱。利用这5个SCoT引物指纹图谱可将7个地黄常用栽培品种区分开。这表明SCoT分子标记体系适用于地黄主要品种亲缘关系及遗传多样性的研究,所构建的指纹图谱也为地黄常见的7个栽培品种的区分提供参考依据。     

油茶SRAP-PCR反应体系的建立和优化

为了建立油茶SRAP-PCR扩增体系,本研究使用单因素试验设计,对反应体系的Taq酶、Mg2+、模板DNA、dNTP和引物浓度5个主要影响因子各设10个不同的水平梯度,筛选出适宜的因子范围;在此基础上,进一步采用L16(45)正交设计,对影响油茶SRAP-PCR反应体系的5个因素在4水平上进行优化,建立了油茶SRAP-PCR最佳反应体系,即25μL体积中包含模板DNA30ng,Mg2+2.8mmol/L,引物0.44μmol/L,dNTP0.2mmol/L和Taq酶1.0U。该SRAP-PCR体系的建立为油茶种质资源遗传多样性分析、品种鉴定及指纹图谱构建等研究提供了一个标准化的程序。     

葡萄SRAP反应体系优化及引物筛选

本试验利用L16(45)正交试验设计探寻葡萄SRAP-PCR反应体系中的关键因子,同时结合单因素试验简单、快捷的特点逐个对PCR反应体系的主要成分进行优化.充分利用两种方法的优点并降低试验工作量取得了较好的效果,建立了适于葡萄的SRAP反应体系.结果表明Mg2+浓度为影响葡萄SRAP-PCR反应的关键因素:优化的20 μL SRAP-PCR反应体系中各组分的最适含量为:10×Buffer 2.0μL,Mg2+2.5mmol/L,dNTPs 0.3 mmol/L,引物0.4 μmol/L,DNA聚合酶1.0 U,模板DNA 1.0 ng/L.利用SRAP反应体系,从100对SRAP引物组合中筛选出扩增稳定,条带清晰,多态性好的引物19对.本研究建立的适于葡萄SRAP-PCR扩增的反应体系,将为葡萄种质遗传多样性评价、基因组分析、指纹图谱构建,分子标记辅助育种和遗传改良研究提供基础.     

红曲菌基因组DNA提取及RAPD反应体系优化

为了建立一套适合红曲属真菌RAPD反应的优化体系,用改进的CTAB法提取红曲菌基因组DNA,采用单因素试验探讨RAPD反应体系中模板DNA、随机引物、Taq酶、Mg^2＋、dNTPs对扩增结果的影响。结果在20μL体积中,模板DNA20 ng、随机引物0、2μmol/L、Taq酶、Mg^2＋1.5mmol/L,dNTPs 1mmol/L的反应体系可得到稳定清晰的RAPD扩增图谱,为采用RAPD技术进行红曲菌种质资源遗传多样性研究奠定基础。     

节瓜ISSR-PCR反应体系的建立与正交优化

旨在开展节瓜种质资源分类鉴定与遗传多样性研究。通过正交试验设计与单因素分析相结合的方法,对节瓜ISSR-PCR反应体系5个因素(模板DNA浓度、dNTP浓度、Mg2+浓度、引物浓度与Taq聚合酶浓度)在4个水平上进行优化分析,建立了节瓜稳定可靠且具丰富多态性的最佳反应体系,进而对引物退火温度进行梯度试验分析。结果表明,20μL节瓜ISSRPCR最佳反应体系为70 ng模板DNA、0.2 mmol/L dNTP、1.2 mmol/L Mg2+浓度、0.96μmol/L引物、0.8 U Taq DNA聚合酶和2.0μL10×buffer;引物IS807最佳退火温度为53℃。以此为基础,利用4条引物对4份节瓜种质进行最佳反应体系稳定性验证,证明该体系稳定可靠、扩增谱带清晰、多态性丰富且重复性较好。     

新疆枸杞种质资源遗传多样性分析及DNA指纹图谱构建

利用SCoT分子标记对新疆枸杞种质资源进行遗传多样性分析和DNA指纹图谱构建,为杂交育种和种质鉴定提供理论依据。结果显示:9条SCoT引物扩增出条带256条,其中219条为多态性条带,多态性比率达85.62%,多态性信息含量(PIC)值变化范围在0.77~0.91之间,平均值为0.85,观测等位基因数(Na)、有效等位基因数(Ne)、Nei's基因多样性指数(H)和Shannon信息指数(I)的平均值分别为1.8562、1.4350、0.2611、0.3989,聚类分析表明,遗传相似系数变化范围在0.5938~0.8398之间,在遗传相似系数为0.66和0.71处,可将30份材料分别分为2大类和4个亚类,主坐标分析结果和聚类结果基本一致,同时利用5条多态性SCoT引物构建了30份材料的DNA指纹图谱。新疆枸杞种质资源遗传多样性水平较高,且SCoT分子标记适于新疆枸杞种质资源遗传多样性分析和DNA指纹图谱构建,该研究结果为新疆枸杞种质资源评价、鉴定和新品种选育奠定了基础。     

芋ISSR-PCR扩增反应体系的建立

目的:获得清晰可靠、重复性较好的ISSR-PCR扩增反应体系,应用于芋种质资源进行遗传多样性的研究中.方法:以芋的幼叶提取基因组DNA为材料,采用正交试验设计L16(45),从模板DNA浓度、引物浓度、Mg2+浓度、dNTPs浓度及TaqDNA聚合酶的用量5因素4水平出发,构建芋最佳反应体系.结果:芋ISSR-PCR的最佳反应体系为:在25μl的反应体系中,40ng DNA模板、0.4μmol/L引物浓度、2.5 mmol/L Mg2+、0.2 mmol/L dNTPs、1 U Taq DNA聚合酶.结论:利用芋种质资源对最佳反应体系的验证,结果显示该反应体系具有扩增稳定性.     

蚬壳花椒ISSR-PCR反应体系的建立及优化

通过单因素试验及正交设计方法对影响蚬壳花椒ISSR-PCR扩增的主要因素(模板DNA、Mg2+的浓度、引物、dNTPs,TaqDNA聚合酶的用量以及退火温度)进行优化,以建立蚬壳花椒ISSR-PCR反应的最佳体系。结果表明:最佳反应体系(20μL)为模板DNA 60ng、MgCl2 2.5mmol/L、dNTPs 0.15mmol/L、引物0.6μmol/L、TaqDNA聚合酶2.4U。在此基础上,从100条引物中筛选出18条扩增稳定、多态性好的ISSR引物并经过10份蚬壳花椒种质检验,证明该体系具有扩增条带清晰、稳定、重复性好等优点。该反应体系的建立为蚬壳花椒种质资源分类、遗传多样性分析提供了更客观可靠的方法。     

海南特有极小种群植物文昌锥的SCoT-PCR体系建立及有效引物评价

为了应用SCoT分子标记研究文昌锥种质资源,通过单因素试验和正交试验2种方法,分析DNA、引物、dNTPs、Taq DNA聚合酶这4种因素对文昌锥SCoT-PCR扩增结果的影响,优化建立文昌锥SCoT-PCR体系,并对文昌锥SCoT标记引物进行有效性评价。结果表明：各个因子对SCoT-PCR扩增影响大小依次为：DNA > dNTPs > 引物 > Taq DNA聚合酶;最优反应体系为：总体系为20 μL,DNA含量为2.5 ng,引物浓度为0.8 μmol·L^-1,dNTPs浓度为0.2 mmol·L^-1,Taq DNA聚合酶的含量1 U;经验证,该体系获得的扩增产物清晰、稳定;应用该体系筛选出15条多态性好且适合文昌锥扩增的引物,为今后利用SCoT分子标记技术对文昌锥及其他壳斗科植物进行相关研究提供技术支持。     

曼地亚红豆杉RAPD反应体系与程序的优化

以曼地亚红豆杉为研究对象,采用L16(45)正交组合实验和单因素梯度实验对MgCl2、dNTP、随机引物、Taq酶、模板DNA浓度和退火温度、循环次数等影响RAPD扩增的重要因素进行优化,以期建立最优的RAPD反应体系与程序。实验结果表明,各因素最适条件为:25μLPCR反应体系中10×Buffer2.5μL,MgCl21.5mmol/L,dNTP0.2mmol/L,随机引物0.6μmol/L,Taq酶1.0U,模板DNA80ng;退火温度为37℃,循环次数为45次。     

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     

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.     

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.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.