江西山药种质资源遗传多样性及其组培苗遗传稳定性的RAPD检测

目的 对来自江西的11份山药种质资源进行遗传多样性分析,并对其组培苗的遗传稳定性进行检测。方法 采用RAPD-PCR技术。结果 试验筛选出20条引物,共扩增出238个条带,其中234个为多态性带,平均每个引物扩增出多态性带11.7条,多态性条带比率为98.32%,材料间遗传相似系数为0.575 6~0.970 6,平均相似系数为0.723 1。根据UPGMA聚类分析结果,可在0.634 8的遗传相似系数上,将11份山药种质资源聚成5大类群(类群I~V)。其中第I类群只包含黄独;第II类群只包含瑞昌山药;第III类群包括南城淮山药1、千金薯、信州山药、永丰淮山药和铁棍山药,说明南城淮山药1、千金薯、信州山药、永丰淮山药与来源于河南焦作市温县的铁棍山药亲缘关系较近;第IV类包括南城山药、南城淮山药2、广丰药薯;第V类只包括泰和竹篙薯。这个结果表明江西山药种质资源遗传多样性还是比较丰富的。同时,江西山药带芽茎段连续继代6次后的组培苗(处理组)及其微型块茎实生苗(对照组)的RAPD分析结果也表明,11份山药品种均扩出126~179条可辨认的条带,每个品种的处理组和对照组均出现了5~18条变异条带数,表明江西山药各个品种带芽茎段连续继代6次后的组培苗存在着一定的体细胞无性系变异,但它们与微型块茎萌发实生苗的遗传相似系数还是比较高,说明它们的遗传性状还是比较稳定的,并未影响到其基因型。结论 本实验结果可为江西山药引种育种、资源改良、品种鉴定、种质保存及其种苗培育提供可靠依据。     

月季花、玫瑰及其近缘种ISSR分析与鉴定

目的基于ISSR分子标记技术研究药用植物月季花、玫瑰及其同属近缘种的遗传多样性,构建它们之间系统发育关系,为蔷薇属种质资源分子鉴定及育种提供参考。方法应用ISSR分子标记技术对药用植物月季花、玫瑰及其同属近缘种的15个种33个样品进行分析,利用POPGEN软件分析Nei’s基因遗传多样性指数(H)等遗传信息参数,应用NTSYS软件构建亲缘关系UPGMA聚类图。结果 6条引物共检测到110个位点,其中多态性位点109个,多态位点百分率(PPB)为99.09%。药用植物月季花、玫瑰及其同属近缘种的种群间H平均值为0.370 5,Shannon’s多样性信息指数(I)的平均值为0.546 4,种群间基因分化系数(Gst)的平均值为0.886 8,基因流(Nm)的平均值为0.063 8,遗传距离(D)的变化范围为0.169 1~0.730 2,聚类分析结果显示蔷薇属15个种,在遗传相似系数(GS)0.60处分成6个组。结论药用植物月季花、玫瑰及其同属近缘种具有丰富的遗传多样性,聚类分析与基于形态特征的蔷薇属属下的分类学研究结果相吻合,ISSR分子标记可以有效鉴别药用植物月季花、玫瑰及其同属近缘种,为蔷薇属植物资源的收集和种间分类提供理论依据。     

Genotypic diversity of oral Actinomyces naeslundii genospecies 1 and 2 in caries-active preschool children

A total of 991 isolates of Actinomyces naeslundii were obtained from sound approximal tooth sites in either caries-active (n = 35) or caries-free (n = 20) preschool children. From this group of isolates, 101 strains were chosen to study the genotypic diversity of A. naeslundii genospecies 1 (n = 30), catalase-positive (n = 30), and catalase-negative genospecies 2 (n = 41). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), with a pair of primers targeting the 16S ribosome RNA gene (16S rDNA), and MnlI digestion together with randomly amplified polymorphic DNA (RAPD) with eight arbitrary, single 10-mer primers were performed to generate genetic profiles of selected Actinomyces isolates. The hierarchic relationships of genetic profiles were finally analyzed using computerized dendrograms. There was no significant difference in the prevalence rates and proportions of either genospecies 1 or 2 between the caries-free and caries-active groups, although a higher prevalence of genospecies 2 was noted in the total population. Dendrogram analyses of the 16S rDNA PCR-RFLP profiles revealed that all strains belonging to A. naeslundii genospecies 1 could be subgrouped into three genotypes (T7, T18, and T19), with a single predominant genotype, T18 (27/30). Catalase-positive strains for genospecies 2 fell into three subtypes (T4, T7, and T17), whereas the catalase-negative counterparts were distributed amongst 16 subtypes. No specific genotype was significantly associated with caries activity. We conclude that heterogeneous subgroups of A. naeslundii genospecies 1 and 2, particularly the latter, are the constituent flora of dental plaque in children and may contribute to the pathogenesis of childhood caries.     

涎腺腺样囊性癌患者口腔微生物多样性研究

目的 探讨涎腺腺样囊性癌（SACC）患者口腔微生物的多样性和群落差异。方法 采集13例SACC患者与10例健康人的唾液样本,提取其口腔菌群的总DNA,经通用引物扩增16s rRNA基因,利用高通量测序平台进行细菌16S rRNA基因（V3-V4）区高通量测序分析后,利用Mothur软件分析微生物的多样性和群落结构。结果 SACC组优势种群有16种（相对丰度>1%）,依次是:链球菌属（36.68%）,奈瑟菌属（8.55%),普雷沃菌属_7（7.53%）,韦荣球菌属（6.37%）等。对照组优势种群有15种,依次有:链球菌属（18.41%）,奈瑟菌属（18.20%）,普雷沃菌属_7（8.89%）,卟啉单胞菌属（6.20%）,梭杆菌属（5.86%）,韦荣球菌属（5.82%）等。2组间有统计学差异的菌门包括厚壁菌门、变形菌门、梭杆菌门（P<0.05）。有统计学差异的菌属包括链球菌属、奈瑟菌属和卟啉单胞菌属（P<0.05）,而嗜二氧化碳噬细胞菌属仅在SACC患者中检出。结论 SACC患者的唾液微生物与健康人群唾液微生物的种群结构存在明显差异。     

Molecular epidemiology reveals genetic diversity among 363 isolates of the Cryptococcus neoformans and Cryptococcus gattii species complex in 61 Ivorian HIV‐positive patients

Cryptococcal meningitis is a severe opportunistic infection in HIV‐infected patients. In Ivory Coast, despite the availability of antiretroviral treatment (ART), this infection is still prevalent. The study investigates the genetic diversity of 363 clinical isolates of Cryptococcus from 61 Ivorian HIV‐positive patients, the occurrence of mixed infections and the in vitro antifungal susceptibility of the isolates. Serotyping was performed via LAC1 and CAP64 gene amplification. Genotyping was performed using the phage M13 core (GACA)₄ and (GTG)₅ primers and restriction fragment length polymorphism analysis of the URA5 gene. By PCR fingerprinting, the presence of the three serotypes were demonstrated among the 363 isolates in the population studied: A (n=318; 87.6%), AD (n=40; 11%) and B (n=4; 1.1%). Using PCR fingerprinting with primers M13 (GACA)₄ and (GTG)₅, we grouped the isolates into 56 molecular subtypes. We observed a high frequency (39.3%) of mixed infections, with up to two different genotypes per sample. None of the isolates were resistant to amphotericin B. Only 0.3% and 1.1% of the isolates were resistant to fluconazole and flucytosine respectively. This study revealed the high genetic diversity among Cryptococcus isolates, the occurrence of mixed infections and a high antifungal susceptibility for the majority of Ivorian cryptococcal isolates.     

Competition between cryptic species explains variations in rates of lineage evolution

Gradual evolution is a common phenomenon in the fossil record of marine microplankton, yet no theoretical model has so far been presented to explain the observed pattern of unidirectionality in trait evolution lasting over tens of millions of generations. Recent molecular genetic data show that the majority of microfossil-producing plankton groups harbors substantial cryptic diversity. Here, we examine the effect of cryptic diversity on apparent rates of lineage evolution. By using a theoretical approach, we show that under resource competition, an increasing number of sibling species within a hypothetical lineage leads to an exponential slowdown of the apparent rate of evolution. This mechanism explains both the remarkable variation in apparent rates of evolution observed in marine plankton, as well as the presence of long gradual evolutionary trends.     

A crop population perspective on maize seed systems in Mexico

Improvement of local germplasm through artificial selection is regarded as the main force behind maize evolution and diversity in Mexico, the crop's center of origin. This perspective neglects the larger social context of maize evolution. Using a theoretical approach and Mexico-wide data, we show that farmer-led evolution of maize is largely driven by a technological diffusion and appropriation process that selectively integrates nonlocal germplasm into local seed stocks. Our approach construes farmer practices as events in the life history of seed to build a demographic model. The model shows how random and systematic differences in management combine to structure maize seed populations into subpopulations that can spread or become extinct, in some cases independently of visible agronomic advantages. The process involves continuous population bottlenecks that can lead to diversity loss. Nonlocal germplasm thus might play a critical role in maintaining diversity in individual localities. Empirical estimates show that introduction of nonlocal seed in Central and Southeastern Mexico is rarer than previously thought; prompt replacement further prevents new seed from spreading. Yet introduced seed perceived as valuable diffuses rapidly, contributing variation in the form of type diversity or through introgression into local seed. Maize seed dynamics and evolution are thus part of a complex social process driven by farmers' desire to appropriate the value in maize farming, not always achieved by preserving or improving local seed stocks.     

口腔微生物群落结构的影响因素

口腔微生物群落作为人体最多样化的微生物群落之一,其生态失衡不仅可以诱发多种口腔疾病,如龋病、牙髓根尖周病、牙周病等,还与心血管疾病、糖尿病等多种系统性疾病紧密相关。口腔微生物群落结构受多种因素影响,本文就口腔微生物群落结构的影响因素作一综述,文献复习结果表明:环境因素在口腔微生物群落的塑造中起重要作用,而遗传和饮食因素的影响目前尚有争议;此外,系统性疾病也可能影响口腔微生物群落结构。目前,高通量测序研究已确定一些“核心微生物群”,不同环境、不同遗传背景下的“核心微生物群”将是下一步的研究方向。     

新疆民族药多伞阿魏挥发油成分与遗传多样性相关性研究

目的:通过对多伞阿魏挥发油成分与其遗传多样性相关性研究,为多伞阿魏种质资源与品质评价提供重要科学依据。方法:测定不同产地多伞阿魏挥发油成分含量,采用ISSR分子标记技术和聚类分析对来自省内8个县的176份多伞阿魏样品的遗传多样性进行研究,运用灰色关联法分析多伞阿魏遗传多样性对挥发油成分含量的影响。结果:用所筛选的15条引物对多伞阿魏样品进行ISSR分析,共扩增出126条清晰的条带,其中多态性位点93个。8个居群中遗传多样性水平最高的是裕民县[多态性位点百分率(PPB)=29.37%,Nei’s多样性指数(H)=0.110 4,Shannon’s信息指数(I)=0.164 3)],最低的是青河县(PPB=19.05%,H=0.070 5,I=0.105 4)。其中沙湾县与富蕴县的多伞阿魏居群间遗传距离最大(0.219 9),两者的遗传一致度最低(0.802 6),表明两者之间的亲缘关系最远,遗传差异较大。由H,I,PPB计算的多伞阿魏居群间的遗传多样性与人参新萜醇、龙脑、γ-桉叶油醇及挥发油成分总含量关联性较大。结论:多伞阿魏居群间的遗传变异为63.08%,居群内的遗传变异为36.92%,多伞阿魏地理分布与遗传多样性具有显著关系,多伞阿魏3个遗传多样性因子中的Nei’s多样性指数对多伞阿魏挥发性成分含量有着较大的影响。     

对叶百部遗传多样性的ISSR分析

目的分析不同居群对叶百部Stemona tuberosa的亲缘关系和遗传多样性。方法应用ISSR分子标记技术研究长江流域以南各省对叶百部的遗传多样性;采用POPGENE32进行亲缘关系分析,NTSYSpc-2.10E进行UPGMA聚类分析。结果 7条ISSR引物共检测到74个清晰的扩增位点,多态性位点74个,多态性位点百分率100%;有效等位基因数(Ne)为1.524 4,平均Nei’s基因多样性指数(He)为0.314 6,平均Shannon多样性指数(I)为0.478 6,各居群间的遗传距离介于0~0.950 2,平均值为0.416 3。结论从分子角度揭示了对叶百部具有较高的遗传多样性,其居群间亲缘关系与地理环境有一定的相关性,实验结果将为后续对叶百部引种栽培及根用药植物资源的持续利用,特异生物碱的筛选及其运用于化学分类,以及对叶百部道地药材产区的科学选择奠定理论基础。