丛枝菌根(AM)对根瘤菌趋化作用研究

对紫穗槐非接种(AM-+Rh-)、单接种根瘤菌(Rh+)、单接种AM真菌(AM+)和双接种(AM++Rh+)处理, 研究AM真菌、根瘤菌对宿主植物紫穗槐侵染情况, 并采用经过改良的根部微生物趋化试验手段研究AM真菌侵染根系后分泌物对根瘤菌的趋化性。实验结果表明：在接种AM++ Rh+情况下, 使宿主先于AM+、Rh+处理形成根瘤, 且双接种能够显著提高菌根侵染率; 在共生体形成期间, AM真菌与根瘤菌之间存在着识别互动反应和一定的信号物质, 接种AM真菌对根瘤菌有正趋化作用; 同时, 外界温度对AM真菌-宿主植物---根瘤菌三者共生体初始信号识别也起到一定的调控作用。     

植物与丛枝菌根真菌在共生早期的信号交流

摘要:丛枝菌根真菌(Arbuscular Mycorrhizal Fungi,AMF)与大多数陆生植物互利共生具有广泛的生理生态学意义,而这一生态学功能背后的共生机制我们知之甚少。已探明AM形成前宿主植物根分泌的独脚金内酯促进AMF菌丝分支,分泌的角质单体促进AMF 在宿主根中定植;同时,菌根真菌的分支菌丝释放出脂质几丁糖(lipochitooligosaccharides,LCOs)和短链几丁质寡聚物(short-chain chitin oligomers,COs)信号分子诱导宿主基因表达、侧根发育以及形成Ca2+振荡,它们相互作用共同促进AM形成。在能同时形成菌根和根瘤的蒺藜苜蓿(Medicago truncatula)和日本百脉根(Lotus corniculatus)植物中,根瘤共生体形成过程所需的若干基因与菌根形成所需的基因有关。这些研究成果为全面揭示菌根共生体发生过程的信号转导奠定了基础。本文对目前国内外宿主植物与AM真菌之间的信号物质及其功能、相关基因及其调控功能等进行了综述,旨在为AM真菌共生早期的信号交流研究提供有价值的参考。     

不同水分处理下双接种丛枝菌根真菌和根瘤菌对疏叶骆驼刺生长及氮素转移的影响

以疏叶骆驼刺为研究对象,设定3个水分梯度正常水分(土壤相对含水量(70±5)%)、干旱胁迫(土壤相对含水量(20±5)%)和复水处理(干旱胁迫60天后恢复至正常水分)与四组接种处理(单接种丛枝菌根真菌(AMF)、单接种根瘤菌、双接种AMF+根瘤菌和不接种),分析不同水分条件下双接种丛枝菌根真菌和根瘤菌对疏叶骆驼刺的生长以及供、受体疏叶骆驼刺之间氮素转移的影响。结果表明,正常水分处理时,双接种疏叶骆驼刺的AMF侵染率、地上生物量、地下生物量、总生物量以及氮含量均要高于单接种处理;根瘤数量、最大荧光(Fm)、初始荧光(Fo)、最大光化学效率(Fv/Fm)与单接种处理之间无差异;在遭遇干旱胁迫时,双接种疏叶骆驼刺的AMF侵染率、总生物量、Fv/Fm均小于单接种处理;地上生物量、地下生物量、根瘤数、Fm、Fo以及氮含量与单接种之间无差异。复水后,双接种疏叶骆驼刺的地上生物量、地下生物量、总生物量、根瘤数均优于单接种;AMF侵染率、氮含量低于单接种;Fm、Fo、Fv/Fm均与单接种之间无差异。在氮素转移方面,正常水分时,双接种与单接种的氮素转移率无差异,在遭遇干旱胁迫时,双接种疏叶骆驼刺的氮素转...     

丛枝菌根真菌诱导植物信号物质研究进展

丛枝菌根(AM)真菌侵染植物根系形成菌根共生体过程中能诱导植物合成多种信号物质,如水杨酸(SA)、茉莉酸(JA)、类黄酮、一氧化氮(NO)和过氧化氢(H2O2)等。这些信号分子的传导途径和作用机制备受关注。本文从AM真菌诱导植物信号物质的种类和数量入手,探讨这些信号分子在植物体内的传导途径、生理效应和可能的作用机制,旨在为研究AM真菌与植物之间的共生关系、功能与进化等提供依据。     

丛枝菌根共生建成的信号识别机制

丛枝菌根(Arbuscular mycorrhiza,AM)共生是自然界中普遍存在的一种互惠共生现象,对促进土壤生态系统物质循环及维持生态系统稳定具有重要的意义。AM共生体的建立需要AM真菌和宿主植物间一系列复杂的信号识别、交换和传导。本文总结近年来相关文献,从AM共生体形成前期及AM共生体形成期两个阶段,分别综述了信号物质的生物合成过程、调控过程及其作用机制,希望有助于进一步认识AM共生体建成过程,同时通过分析当前研究工作的不足及未来研究动向,期望推动相关研究工作。     

丛枝菌根真菌-豆科植物-根瘤菌共生体系的研究进展

丛枝菌根真菌（Arbuscular Mycorrhizal Fungi,AMF）-豆科植物-根瘤菌（Rhizobia）三者形成的共生体。是植物与微生物共生中的一种特殊类型。本文对这种共生体中微生物与植物之间的营养关系;AMF和根瘤菌双接种豆科植物的效应以及影响双接种效应的因素;AMF和根瘤菌在与豆科植物形成共生过程中的分子互作机制等进行了综述。同时对这种共生体还需进一步研究的问题及其在基础研究和实践应用方面的前景进行了讨论。     

VA菌根真菌、根瘤菌双接种对大豆增产效果的影响

本文论述了在自然状态下的土壤里,VA菌根真菌、根瘤菌双接种对大豆结瘤、菌根真菌侵染率、固氮酶活性及植株养分吸收状况的影响.研究结果表明,VA菌根真菌、根瘤菌双接种明显提高大豆结瘤能力与固氮酶活性,并可促进植物对养分的吸收,双接种比单接种VA菌根真菌处理提高产量140%,比单接种根瘤菌处理提高55.84%.     

干旱及复水条件下接种AMF和根瘤菌对疏叶骆驼刺根系生长的影响北大核心CSCD

疏叶骆驼刺为塔里木河下游优势草本植物,对下游地区防风固沙,涵养水源具有重要的生态价值。该试验以疏叶骆驼刺为研究对象,设定正常水分(土壤相对含水量70%±5%)、干旱胁迫(土壤相对含水量20%±5%)和复水处理(干旱胁迫60 d后恢复至正常水分)3个水分梯度,以及单接种丛枝菌根真菌、单接种根瘤菌、双接种丛枝菌根真菌+根瘤菌和不接种4组接种处理,分析不同水分条件下各接种处理对疏叶骆驼刺根系生长的影响。结果表明:(1)双接种丛枝菌根真菌+根瘤菌处理的疏叶骆驼刺根系AMF侵染率在干旱胁迫、复水条件下均显著降低,且低于单接种AMF处理。(2)随着正常水分→干旱胁迫→复水的水分变化,双接种处理疏叶骆驼刺根系根瘤数量先降低后增加,复水后显著高于单接种根瘤菌处理。(3)双接种处理扩大了疏叶骆驼刺的根系吸收范围,提高了根系的吸收能力,并随着正常水分→干旱胁迫→复水的水分变化,呈现先降低后增加的变化趋势。(4)双接种处理显著提高了疏叶骆驼刺根系SOD和POD活性,并随着正常水分→干旱胁迫→复水的水分变化而逐渐升高。研究发现,双接种AMF+根瘤菌处理可以显著促进疏叶骆驼刺根系的生长,增强其抗逆性,而干旱胁迫会降低AMF和根瘤菌的协同促进作用,复水后双接种AMF+根瘤菌处理的疏叶骆驼刺能及早地做出响应,对其根系生长表现出一定的补偿效应。     

丛枝菌根（AM）真菌-豆科植物-根瘤菌共生识别信号研究概况

<正>植物与微生物共生是自然界中普遍存在的一种生物学现象,其中高等植物和丛枝菌根(arbuscular mycorrhiza,AM)真菌共生形成的菌根、以及豆科植物和根瘤菌(rhizobia)形成的根瘤与农林牧业生产和生态系统的稳定性密切相关。豆科植物形成根瘤的同时还能与AM真菌形成菌根,最终建立三位一体     

菌丝桥介入枳根系间抗溃疡病的信号物质响应

对两室根箱试验装置中一分室(供体室)定植的枳Poncirus trifoliata实生苗接种丛枝菌根(AM)真菌Paraglomus occultum,另一分室(受体室)不作任何处理。定植17周后,将溃疡病病菌Xanthomonas axonopodis(Xac)接种于供体植株,研究不同处理受体植株间的信号物质响应差异,揭示菌丝桥的功能。与不接种处理相比,单接种AM真菌、预先接种AM真菌后再接种Xac均显著提高了供体根系一氧化氮(NO)含量,单接种AM真菌只显著提高了受体根系NO含量;单接种Xac显著降低了供体根系脱落酸(ABA)含量,而单接种AM真菌、双接种(AM真菌+Xac)均增加了供体根系ABA含量。双接种处理显著提高了受体ABA含量;与不接种对照相比,接种处理均降低了供体根系玉米素核苷(ZR)含量,同时单接种AM真菌、双接种处理也降低了受体根系ZR含量;AM真菌显著降低了供体和受体根系茉莉酸(JA)含量,但双接种却显著提高了供体和受体根系JA含量;与不接种对照相比,单接种AM真菌或Xac、双接种处理均显著下调供体根系JA合成基因(PtLOX、PtAOS和PtAOC)的表达,单接种Xac显著下调了受体根系PtLOX和Pt AOC的表达,单接种AM真菌显著下调了受体根系PtAOC的表达,而双接种显著上调了受体根系PtAOS基因的表达。表明菌根真菌的菌丝桥传导JA并诱导受体植株中NO、ABA和ZR含量改变以抵御溃疡病菌危害。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

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.