利用分子标记18S rDNA对天牛高阶元进化关系的研究

【目的】构建天牛总科高阶元的进化关系,为解决天牛各亚科之间进化关系和归属提供依据。【方法】本研究采用18S rDNA(V4、V7区)分子标记,分析和测定了49种天牛基因序列,并结合GenBank数据库中3科2亚科21种天牛的18S rDNA基因序列,采用邻近法(Neighbor Jointing,NJ)、贝叶斯推论法(Bayesian Inference,BI)和最大似然法(Maximum Likelihood),对天牛总科3科6亚科的70种天牛基因序列构建进化树,探讨天牛高阶元类群的进化关系。【结果】研究表明:序列分析比对后得到序列为703 bp,碱基A、T、C、G的含量分别为21.1%、26.3%、23.6%和28.9%;变异位点(Variable sites)98个占全部位点的13.9%,简约信息位点(Parsimony informative sites)45个占全部位点的6.4%;转换(Transition)/颠换(Transversion)的平均值R值为2.79,转换大于颠换。进化树结果显示沟胫天牛亚科Lamiinae、天牛亚科Cerambycinae、锯天牛亚科Prioninae和瘦天牛科Disteniidae为单系性进化群,这与传统形态学分类结果相似。【结论】本研究成功构建了天牛总科高阶元的系统发育树,研究证明18S rDNA(V4、V7区)是探讨天牛高级阶元分类有效的分子标记。     

广义飞蛾藤属(旋花科)的分支系统学分析

基于33个广义的形态学性状,对广义飞蛾藤属Porana s．l．进行了分支系统学分析。经过简约性分析,得到了10个同等简约的分支树。10个同等简约树的严格一致化树表明,广义飞蛾藤属是一较为自然的分类群。与广义飞蛾藤属的孢粉学、种皮微形态学研究结果一致,分支分析的结果不支持将广义飞蛾藤属拆分为4个或5个独立的属,应在属内划分分类等级。在整个形态分支树中广义飞蛾藤属4个亚属呈并列2个分支,其中飞蛾藤亚属(subg．Porana)和白花叶亚属(subg．Poranopsis)形成姐妹群构成一分支,三翅藤亚属(subg．Tridynamia)和棒状亚属(subg．Dinetus)以姐妹群的关系构成另一支。鉴于分支分析的Bootstrap支持率不高,广义飞蛾藤属范畴的最后界定和属内等级的划分仍有待于进一步研究。     

Mitochondrial genome size variation and restriction fragment length polymorphisms in threePhaseolus species

Summary Restriction patterns of mitochondrial DNA (mtDNA) from threePhaseolus species were examined to estimate their relative genome sizes and to determine the level of interspecific variability and relatedness. Three restriction endonucleases that produced relatively simple profiles were identified and used to determine the genome size of the three species. Taking into account fragment stoichiometries, the average estimates across enzymes were 456, 324, and 400 kb, respectively, forP. vulgaris, P. coccineus, andP. acutifolius. Restriction fragment length polymorphisms (RFLPs) differentiated the species when the mtDNAs were digested with seven endonucleases and hybridized with five cosmid clones covering ca. 200 kb of mtDNA sequences. Proportions of shared restriction fragments between every two species were computed as F-values and demonstrated thatP. vulgaris andP. coccineus are more related to each other than either is toP. acutifolius, and that the latter has a similar degree of relationship to the other two species.     

Quorum Sensing Is a Language of Chemical Signals and Plays an Ecological Role in Algal-Bacterial Interactions

Algae are ubiquitous in the marine environment, and the ways in which they interact with bacteria are of particular interest in the field of marine ecology. The interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape microbial diversity. Although algal-bacterial interactions are well known and studied, information regarding the chemical-ecological role of this relationship remains limited, particularly with respect to quorum sensing (QS), which is a system of stimuli and response correlated to population density. In the microbial biosphere, QS is pivotal in driving community structure and regulating behavioral ecology, including biofilm formation, virulence, antibiotic resistance, swarming motility, and secondary metabolite production. Many marine habitats, such as the phycosphere, harbor diverse populations of microorganisms and various signal languages (such as QS-based autoinducers). QS-mediated interactions widely influence algal-bacterial symbiotic relationships, which in turn determine community organization, population structure, and ecosystem functioning. Understanding infochemicals-mediated ecological processes may shed light on the symbiotic interactions between algae host and associated microbes. In this review, we summarize current achievements about how QS modulates microbial behavior, affects symbiotic relationships, and regulates phytoplankton chemical-ecological processes. Additionally, we present an overview of QS-modulated co-evolutionary relationships between algae and bacterioplankton, and consider the potential applications and future perspectives of QS.     

StructureActivity Relationships of Antimicrobial Gallic Acid Derivatives from Pomegranate and Acacia Fruit Extracts against Potato Bacterial Wilt Pathogen

Bacterial wilts of potato, tomato, pepper, and or eggplant caused by Ralstonia solanacearum are among the most serious plant diseases worldwide. In this study, the issue of developing bactericidal agents from natural sources against R. solanacearum derived from plant extracts was addressed. Extracts prepared from 25 plant species with antiseptic relevance in Egyptian folk medicine were screened for their antimicrobial properties against the potato pathogen R. solancearum by using the disc‐zone inhibition assay and microtitre plate dilution method. Plants exhibiting notable antimicrobial activities against the tested pathogen include extracts from Acacia arabica and Punica granatum. Bioactivity‐guided fractionation of A. arabica and P. granatum resulted in the isolation of bioactive compounds 3,5‐dihydroxy‐4‐methoxybenzoic acid and gallic acid, in addition to epicatechin. All isolates displayed significant antimicrobial activities against R. solanacearum (MIC values 0.5–9 mg/ml), with 3,5‐dihydroxy‐4‐methoxybenzoic acid being the most effective one with a MIC value of 0.47 mg/ml. We further performed a structure–activity relationship (SAR) study for the inhibition of R. solanacearum growth by ten natural, structurally related benzoic acids.     

青藏高原东缘林线杜鹃-岷江冷杉原始林的空间格局

为深入理解高山林线原始林中优势树种的空间结构特征和种间关系,以青藏高原东缘林线杜鹃-岷江冷杉原始林1 hm²样地调查数据为基础,采用成对相关函数g(r)函数,分析了优势种岷江冷杉(Abies faxoniana)和凝毛杜鹃(Rhododendron agglutinatum)各径级的空间分布格局和各径级间的空间关联性。结果表明:岷江冷杉和凝毛杜鹃径级分布连续,呈倒"J"型,均为进展种群。小尺度上,对于岷江冷杉活立木(小树+中树+大树)、小树、中树为显著聚集分布,大树为均匀分布,死树则为随机分布;凝毛杜鹃活立木(小树+中树+大树)、小树、中树、大树、死树均为显著聚集分布。小尺度上随径级增大岷江冷杉的分布格局从聚集分布趋于均匀分布。岷江冷杉大树与其小树的空间关联验证了Janzen-Connell假说中的距离制约效应。通过验证接受了随机死亡假说,发现种内的密度制约效应不明显。两个树种的枯立木对凝毛杜鹃小树均表现为排斥关系,而对岷江冷杉小树表现为相互独立的关系。两个优势种总体表现为相互独立,但种间不同径级间的空间关联性各异。     

五株纤毛虫遗传关系的ISSR分析

采用ISSR分子标记技术,尝试对四种五株纤毛虫(褶累枝虫(Epistylis plicatilis)、绿草履虫(Paramecium bursaria)、多态喇叭虫(Stentor polymorphus)、嗜热四膜虫BF1株(Tetrahymena thermophilaBF1)和嗜热四膜虫BF5株(T.ther-mophilaBF5))进行遗传关系研究。用13个ISSR引物对五株纤毛虫进行扩增,六个ISSR引物获得多态片段。根据Nei s遗传距离矩阵构建了五株纤毛虫的遗传关系树状图。UPGMA,NJ聚类图表明:两株嗜热四膜虫最先聚在一起;其次是褶累枝虫和多态喇叭虫聚在一起,然后再与嗜热四膜虫聚在一起;咽膜亚纲的绿草履虫形成独立的一枝。结果显示:①缘毛亚纲纤毛虫可能是寡膜纲中较独特的一个类群,建议提升缘毛亚纲纤毛虫的分类地位;②缘毛亚纲褶累枝虫与膜口亚纲嗜热四膜虫的亲缘关系近于咽膜亚纲绿草履虫,在寡膜纲中绿草履虫处于原始地位;③五株纤毛虫基因组中均含有微卫星DNA序列:(GTG)4(、GACA)4(、AG)8(、CAA)6和(GAA)6。     

A dynamic, architectural plant model simulating resource-dependent growth

BACKGROUND AND AIMS: Physiological and architectural plant models have originally been developed for different purposes and therefore have little in common, thus making combined applications difficult. There is, however, an increasing demand for crop models that simulate the genetic and resource-dependent variability of plant geometry and architecture, because man is increasingly able to transform plant production systems through combined genetic and environmental engineering. MODEL: GREENLAB is presented, a mathematical plant model that simulates interactions between plant structure and function. Dual-scale automaton is used to simulate plant organogenesis from germination to maturity on the basis of organogenetic growth cycles that have constant thermal time. Plant fresh biomass production is computed from transpiration, assuming transpiration efficiency to be constant and atmospheric demand to be the driving force, under non-limiting water supply. The fresh biomass is then distributed among expanding organs according to their relative demand. Demand for organ growth is estimated from allometric relationships (e.g. leaf surface to weight ratios) and kinetics of potential growth rate for each organ type. These are obtained through parameter optimization against empirical, morphological data sets by running the model in inverted mode. Potential growth rates are then used as estimates of relative sink strength in the model. These and other 'hidden' plant parameters are calibrated using the non-linear, least-square method. KEY RESULTS AND CONCLUSIONS: The model reproduced accurately the dynamics of plant growth, architecture and geometry of various annual and woody plants, enabling 3D visualization. It was also able to simulate the variability of leaf size on the plant and compensatory growth following pruning, as a result of internal competition for resources. The potential of the model's underlying concepts to predict the plant's phenotypic plasticity is discussed.