抗甜菜坏死黄脉病毒单抗轻链可变区基因的克隆及全序列测定

甜菜是温带地区主要糖料作物,甜菜丛根病是其一种毁灭性病害,在世界范围内广泛蔓延,发病田块可以造成２０％—５０％以上的减产,甚至绝收,糖度可以降低４—８度。甜菜坏死黄脉病毒（ＢＮＹＶＶ）是丛根病的主要病源,目前没有好的防治方法。为了探索用基因工程抗体技术与植物转化技术防治丛根病的可行性,首先要把抗ＢＮＹＶＶ的单克隆抗体的可变区基因扩增和克隆出来,本文报道轻链可变区基因的扩增、克隆和全序列分析的结果。材料和方法抗甜菜坏死黄脉病毒的单抗杂交瘤（３Ｃ４）由北京农业大学植物病毒研究室制备［１］。细胞培养于…     

云南红豆杉培养细胞系的建立

紫杉醇(Taxol)最初是从红豆杉属植物短叶红豆杉(Taxus brevifolia)树皮中分离出的一种二萜类化合物^[1]．对卵巢癌,转移性乳腺癌和恶性黑色寮瘤等患者疗效显著^[2],全世界红豆杉属植物有近11种,都含紫杉醇成分．但含量很低,加之现存数量很少,生长极为缓慢．造成了紫杉醇原料供应的危机^[3]。紫杉醇化学合成已经成功^[4-6],但繁杂的反应过程及前体化合物来源的限制使得它们无法实现商业化生产。最近从短叶红豆杉中分离出一种生产紫杉醇的内寄生真菌Tgromyer andreanae^[7]．由于紫杉醇含量仅为24～50ng/L．没有实用价值。植物细胞和组织培养可能是解决天然抗肿瘤药物长期供应的有效方法之一^[8]。自1991年Christen等人申请利用红豆杉细胞培养物生产紫杉醇专利以来^[9]．有关红豆杉细胞培养的研究已有不少报^[10-12]。但云南红豆杉(T.yunnanensis)仅见愈伤组织诱导的报道^[13]。本文报道云南红豆杉愈伤组织诱导和细胞培养的初步结果,并分析了细胞培养物中紫杉醇含量。     

甜菜多粘菌形态发育过程研究

甜菜多粘菌(Polymyxa betae)是一种专性寄生于甜菜根部的低等真菌,可作为甜菜坏死黄脉病毒(BNYVV)的传播介体并与甜菜丛根病的产生有关。对甜菜多粘菌的研究有助于了解其与所传病毒的生物学关系及其在引致甜菜丛根病中所起的作用。本文观察记录了甜菜多粘菌侵染甜菜根系及其在甜菜根细胞中的发育过程,对甜菜多粘菌各主要发育阶段进行了显微镜观察并发现在其游动孢子中有BNYVV粒体存在。根据观察结果并提出了甜菜多粘菌生活史模式图。     

摇瓶的体积氧传递系数和氧通透率的测定

通过设计特殊摇瓶,用亚硫酸钠法测出摇瓶的体积氧传递系数和氧透过纱布层的通透率。以氧电极测其内外氧的分压降后,可以算出摇瓶表观体积氧传递系数(k_La)app及真实体积氧传递系数k_La,并进一步求出氧通透率。由实验得出：氧分压降低6．1％,氧传递系数增加一倍;在37c、220r／min、500m1摇瓶(内盛液50m1)8层纱布的氧通透率Pm=43．7moI／m²·h·arm;并且关联出摇瓶容积V、装液量VL、转速n、摄氏温度t之间的模型式：(k_La)_app=1．84×10^-7[t]1.8479·[n]2.3906.(VLV]-0.6360(kLa)=2．02×10^-7[t]1.8525·[n]2.39441·[VLV]-0.6370     

枯草杆菌中性蛋白酶基因在大肠杆菌中的表达

蛋白酶是枯草杆菌(Bacillus subtilis)产生的具有重要工业价值的水解酶。对蛋白酶基因的分离与高效率表达一直是基因工程研究领域的重要内容之一^[1-4]。蛋白酶基因的筛选可采用不同的方法,如“免疫法”、“DNA 杂交法”、“遗传互补法”等。大肠杆菌(Escherichia coli)是基因工程中最常用的宿主菌, 若能以E．Coli作为筛选蛋白酶基因的宿主苗,那么使用E．Coli的常规载体,便可直接获得完整的蛋白 酶基因。枯草杆菌的蛋白酶基因能否在大肠杆菌中表达．则是实现这一目标的关键。Koide等人^[5]报道过枯草杆菌的胞内丝氨酸蛋白酶基因在大肠杆菌中的表达。转化细胞在含有脱脂牛奶的平板上可产生十分微弱的水解圈。Ikeraara等人^[6]将Subtilisin E(枯草杆菌蛋白酶E)插人大肠杆菌的表达载体,具有活性的Subtilisin E便可分泌到大肠杆菌的细胞周质中。吴汝平撰文指出^[7]。克隆的枯草杆菌蛋白酶基因不能在大肠杆菌中表达。是因为大肠杆菌不能转录枯草杆菌的促使生长调节基因。Wang等人^[8]则认为,在大肠杆菌中观察不到野生型的中性蛋白酶基因E(nprE)的表达。是因为nprE的表达产物对大肠杆菌有致死作用．除去该基因上的核糖体结合位点,nprE便能在大肠杆菌中低水平表达,并能将表达产 物分泌至胞外。由上可知．枯草杆菌的蛋白酶基因能否在大肠杆菌中表达以及表达的位置仍然是一个众说纷纭的问题,这一问题也正是能否用大肠杆菌作为宿主菌筛选蛋白酶基因的关键。     

盘梗霉属一新种——甜菜盘梗霉

本文报道了寄生于藜科(Chenopodiaccae)甜菜(Beta. Vulgaris L．)上的盘梗霉属一新种——甜菜盘梗霉(Bremia betae sp. Nov.)。对此新种作了汉文和拉丁文描述．     

PVA固定化的生黑醋菌生产L-山梨糖的研究

生黑醋菌可以将D-山梨醇转化为L-山梨塘,用微生物将D-山梨醇氧化为L-山梨糖是维生素C生产的一个重要部分,目前工业上用的都是游离菌批式生产工艺。由于固定化活细胞作为生物催化剂具有生产的连续性和稳定性．操作简便．产物易于分离纯化等优点^[1],已有不少实验室研究甩固定化微生物细胞将D-山梨醇转化为L-山梨糖^[1-6],国内也有用海藻酸固定化生黑醋菌Acetobacteriummelanogenum的报道^[2,3]。用海藻酸钙^[1-3]、聚丙烯酰胺^[4]、铝处理的海藻酸钙^[5]、水合聚丙烯酰胺与海藻酸钙混合固定化的微生物细胞^[6]转化D-山梨醇成为L-山梨糖,都有因机械强度差,而不适合在搅拌式发酵罐中生产的弱点。聚乙烯醇制备的固定化微生物细胞具有机械强度好、类似于橡皮的弹性、成低等特性^[7]。因此,我们选择聚乙烯醇作为固定化生黑醋菌的材料。     

云南红豆杉愈伤组织培养及其生产紫杉醇的研究

从红豆杉科红豆杉属植物如短叶红豆杉（Ｔａｘｕｓｂｒｅｖｉｆｏｌｉａ）等的树皮或枝叶提取到的紫杉醇（Ｔａｘ-ｏｌ）是一种具有强抗癌活性的二萜烯类化合物^[1].作为一种治疗晚期卵巢癌、乳腺癌的新药已经在欧美等一些国家被批准上市,成为迄今从植物中提取的最有效的抗癌药之一^[2].但由于紫杉树皮来提取紫杉醇的方法如紫杉醇的化学合成、半合成,从真菌中提取紫杉醇以及改善红豆杉的栽培措施等等均已取得了较大进展,但离实际应用还相差太远^[5,6].而利用组织和细胞培养方法替代砍伐天然红豆杉树皮来提取紫杉醇,也已成为近几年来红豆杉研究的一个重要课题之一并已取得了较大进展^[7].云南红豆杉（Taxus yunnanensis）主要分布于我国云南省,是分布于我国的主要品种之一,其含量在我国现有的几种红豆杉植物中属于较高的一种^[3],在我国,近些年来亦有不少实验室在红豆杉细胞培养方面取得了较好的成绩,但文献报道的较少^[8-10].本文报道利用云南红豆杉细胞培养方法来生产紫杉醇,以最终取代从天然来源的树皮和枝叶中提取的可能性,对云南红豆杉进行的愈伤组织的诱导和培养研究的进展。     

甘蓝与菜心中间杂种F1代花药培养初报

花药培养和小孢子培养是大量获得单倍体和纯合二倍体的主要方法之一。在芸苔属中,花药培养和小孢子培养已在白菜(　B．Pekinensis)、甘蓝(B．Oleracea)、油菜(B．Napus)、芥菜(B．Juncea)和阿比西尼亚芥(B．Carinata)等蔬菜中有许多成功的报道,并在培养条件、基因型作用、培养基选择和供体植株选择等方面有较深入的研究^{[2,3,5,7－11]},但种间杂种F1代的花药培养尚未见报道。为了探讨芸苔属种间杂种花药培养的可能性,获得有价值的异源染色体杂种,我们开展了本研究工作。     

丹参冠瘿组织高产株系选择和丹参酮的产生

丹参(Salvia miltiorrhiza)是治疗心血管系统疾病的重要中草药。前文我们已报道了丹参冠瘿组织培养的部分研究结果^[1].利用根癌农杆菌(Agrobacterium tumefaciens)Ti 质粒转化产生的冠瘿组织进行高产株系选择的研究还很少,本文报道丹参冠瘿组织高产株系选择和丹参酮产生的研究结果。     

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.