植物同源异型基因及同源异型盒基因的研究进展

植物同源异型基因及同源异型盒基因是涉及植物个体发育调节的两类重要转录因子编码基因.近10年来的研究表明,这两类基因及其产物的结构与功能具有明显的差异.深入研究这两类基因的结构与功能对揭示植物的发育机制具有重要意义.     

同源盒蛋白与人类白血病

同源盒蛋白是一类具有特定的时空表达模式的转录调控因子,本对造血细胞内同源盒基因的表达特点及因同源盒蛋白表达异常所致白血病的各种分子机制加以综述,提出同源盒基因的结构与功能异常是人类种瘤发生的重要原因之一。     

同源异形盒基因和肿瘤

最近,美国哈佛药学院的Ｆｏｒｄ发现同源异形盒(ｈｏｍｅｏｂｏｘ)基因在细胞周期、发育以及癌症发展中起着重要的链接作用[1]同源异形盒基因是与细胞正常分化、发育相关的转录因子,最初作为果蝇同源异形突变中的重要座位而得名。此后,陆续有170多个同源异形盒基因在各类物种中被发现。同源异形盒基因的共同点是具有183个核苷酸长度的同源区,编码61个氨基酸。同源异形盒基因同源区表达蛋白通过其ＤＮＡ结合活性及其下游基因转录活性发挥作用。Ｌａｗｒｅｎｃｅ等[2]推测哺乳动物同源异形盒表达蛋白的作用目标为编码细胞外层蛋白质的基因,粘…     

水稻基因组MADS盒DNA的克隆和分析

利用来自金鱼草Squamosa基因的MADS盒序列作为异源探针 ,从水稻基因组Cosmid文库中筛选获得了 1个含MADS盒保守序列的DNA片段(RgMADS1 ) ,对RgMADS1进行的结构及功能研究表明 :RgMADS1中含有与已报道的MADS盒基因高度同源的区段 ;水稻基因组中存在多拷贝的含MADS盒的基因族 ;将RgMADS1与 35S启动子构成嵌合基因 ,转化拟南芥 ,转基因植株表型异常 ,主要是花型结构改变、花数目减少和花着生部位异常 .由以上分析初步认为 ,RgMADS1可能是水稻MADS盒基因家族中的一员 ,它们可能参与了花形态建成和发育过程中的功能调控     

高等植物的同源异型基因

最近几年,对植物中同源异型基因的研究正日益引人注目,并且取得了很大进展。以一些模式植物（例如拟南芥和金鱼草）局部组织的形态发育过程为研究系统,将传统经典遗传学方法和现代分子遗传学技术相结合,已经分离了许多在植物器官发育中起重要作用的同源异型基因,并初步阐述了这类基因的功能和分子之间相互调控的概约作用框架。     

植物同源异型枢基因的研究进展

植物同源异型枢基因是涉及到植物个体发育的一类重要转录因子编码基因.这类基因及其编码蛋白的结构具有明显的保守性,在植物中广泛存在,研究这类基因,对于揭示植物的发育机制具有重要意义.     

同源盒基因和肿瘤

同源盒基因是一族含有共同的183个核苷酸序列的调节基因,在生物的发育分化中起重要的作用,具有高度保守性,是转录过程的主控基因,本文结合有关文献,探讨同源盒基因在各种恶性肿瘤中的表达与肿瘤发生,发展相关的分子机制及其常用的分子生物学研究方法。     

癌基因PPO及其同源性基因的结构分析

目的 采用PPO（proliferation and phosphorylation oncogene）基因与其同源性基因的结构分析,推测PPO并验证其功能。方法 利用PPO的蛋白序列寻找同源基因,比较其结构并利用蛋白免疫杂交方法证实其功能。结果 克隆了PPO基因,找到了PPO基因与小鼠、果蝇、蚊子、线虫以及酵母等的同源基因,比较发现PPO在进化上非常保守。人和小鼠的氨基酸序列有许多与磷酸化有关的功能域,并发现其中某些氨基酸在进化上非常保守。进一步研究表明PPO能使ERK2和MEK磷酸化。结论 PPO基因在进化上非常保守,与磷酸化功能有关。     

LEAFY同源基因研究进展

LEAFY(LFY)同源基因存在于所有的陆生植物中,在植物花发育早期表达,并在花发育过程中抑制茎端分生组织的营养生长,调控花分生组织和花器官的形成,使转LFY基因植株提前开花,LFY同源基因与其上下游基因共同调控花发育过程.LFY同源基因的蛋白质结构在不同物种间保守性很高,但它们的表达部位差异很大.该文总结了近年来国内外已经克隆到的LFY同源基因的表达、功能及其在果树、花卉、粮食作物上的应用,以期为植物花发育的深入研究提供参考.     

蒺藜苜蓿花器官特异基因的表达分析

蒺藜苜蓿(Medicago truncatula G)花器官特异表达基因是参与其花器官形成与发育的重要基因。筛选蒺藜苜蓿的花器官特异表达基因,寻找这类基因在其他模式植物中的直系同源基因,并将其表达模式在不同植物间进行比较,有利于深入的理解这类基因在蒺藜苜蓿花器官发育中的功能。根据蒺藜苜蓿表达谱,并以其PISTILLAZA(PI)基因为模板,文章筛选了97个蒺藜苜蓿花器官特异表达基因(Ratio≥10,且Z≥7.9).通过同源比对,确定了这类基因在拟南芥(Arabidopsis thaliana L.)、大豆(Glycinemax L.)、百脉根(Lotusjaponicus L.)和水稻(Oryzasativa L.)中的直系同源基因。对这类基因在5种植物中的表达量、表达部位和功能进行比较,发现进化关系较近的植物,直系同源基因的表达变异较小,而进化关系较远的植物,直系同源基因的表达变异较大。进一步对表达分化较大的直系同源基因进行启动子分析,发现不同植物中直系同源基因表达模式的变化与启动子中调控元件的特性有关。     

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.