VdToxD1和VdToxD3调控大丽轮枝菌微菌核的萌发

大丽轮枝菌Verticillium dahliae是一种土传性植物病原真菌,可侵染660多种植物,引发黄萎病。微菌核是大丽轮枝菌在侵染后期形成的特殊休眠结构,可在土壤中存活14年,是黄萎病的主要初侵染来源。本研究在前期大丽轮枝菌萌发与休眠微菌核转录组分析的基础上,选择微菌核休眠状态高表达的VdToxD1和VdToxD3基因进行功能研究。结果发现,VdToxD1和VdToxD3敲除突变体菌株的微菌核萌发率分别为87.3%和86.0%,显著高于野生型菌株的64.0%;负调控微菌核萌发的转录因子VdCrz1与VdToxD1上游的-937 bp到-349 bp中的特定基序结合,与VdToxD3上游的-752 bp到-496 bp中的特定基序结合,结合位点均位于2个基因的启动子区。     

大丽轮枝菌致病及微菌核形成相关基因研究进展

大丽轮枝菌(Verticillium dahliae)致病力强且宿主范围广,能以微菌核的形式在土壤中存活多年,当遇到合适的宿主就萌发,因此极难防控,对农业生产造成巨大危害。目前已经发现多种影响大丽轮枝菌致病力的基因,最为重要的发现为大丽轮枝菌能够形成侵入钉入侵植物,许多效应因子也是由侵入钉颈环处分泌出大丽轮枝菌并最终调控植物的免疫防御。同时,研究也表明黑色素对于形成成熟的微菌核非常关键,并且许多与微菌核形成相关的基因也与大丽轮枝菌致病相关。但目前的研究尚未完全阐明大丽轮枝菌如何导致植物萎蔫坏死以及微菌核形成的分子机理。综述了近年来有关大丽轮枝菌致病及微菌核相关基因的研究进展,以期为大丽轮枝菌致病及微菌核形成机理的进一步研究奠定理论基础。     

大丽轮枝菌 VdCPMO基因克隆与功能分析

大丽轮枝菌 Verticillium dahliae是一种典型的土传病原真菌,可侵染400多种植物引致黄萎病,造成巨大的经济损失。微菌核是大丽轮枝菌的特殊休眠结构,能够在土壤中存活14年之久,是病害的主要初侵染来源。本研究在前期微菌核萌发表达谱的基础上,选择上调倍数最高的环戊酮1,2-单加氧酶基因（ VDAG_03943）,进行克隆与功能分析。结果表明,该基因全长1 929bp,cDNA序列全长1 668bp,编码555个氨基酸组成的蛋白,命名为 VdCPMO。与野生型菌株JY相比,敲除突变体菌株的菌落生长减慢,微菌核萌发率显著降低,芽管平均长度明显较短,而互补突变体菌株与野生型菌株JY间无显著性差异。致病力测定结果显示,敲除突变体菌株的微菌核丧失了对棉花的致病力。     

雪腐核盘菌菌核的萌发条件与致死温度

菌核是核盘菌Sclerotinia spp.在土壤中的主要存活形式和菌核病的主要初侵染源,在土壤中可存活8年以上,其数量和存活状况直接影响着菌核病的发生和危害程度。本研究以雪腐核盘菌Sclerotinia nivalis菌株SS-TB为材料,分析了菌核萌发的影响因素、致死温度以及土壤温度对菌核存活的影响。结果表明,未成熟菌核较成熟菌核更容易萌发;菌核萌发的最佳温度为20-25℃、pH为3.0-4.0、土壤含水量为20%-45%。菌核长时间浸泡水中对其存活不利,浸泡30d以后,存活率开始急剧下降,至47d时存活率为0。雪腐核盘菌菌核具有较强的耐高温特性,随着温度和处理时间的增加,菌核萌发率呈下降趋势。菌核在水浴中85℃ 5min、80℃ 10min、75℃ 10min、70℃ 30min、65℃ 120min、60℃ 180min时全部丧失活力。在土壤温度30℃和35℃处理5周、40℃和45℃处理4周时菌核全部失去活力。该研究结果为通过水旱轮作和土壤高温处理来防治西洋参菌核病提供了理论基础。     

大丽轮枝孢微菌核的形成条件

以棉花黄萎病菌Verticillium dahliae XJ2008菌株为试材,研究了培养基类型、pH值、温度等因素对棉花黄萎病菌微菌核形成的影响,确立了微菌核形成的最佳培养条件,并对采自新疆、江苏、河南、陕西、山东等地的15个棉花黄萎病菌菌株进行了测试。结果表明,适合于棉花黄萎病菌微菌核大量产生的培养基为基础改良培养基（BMM）、pH值为9.5－11.5、温度为20℃。在该条件下,15个大丽轮枝孢菌株在接种后第12天即可产生大量的微菌核,不同菌株产生微菌核的数量及大小间存在着显著差异,但均与病菌的致病性     

黄萎病不同发生程度棉田中土壤微生物多样性

作物根际土壤微生物群落对土壤生态及作物健康至关重要。以棉花黄萎病不同发生程度棉田的土壤为研究对象,采用理化分析、微生物纯培养及高通量测序技术对土壤理化性质及微生物数量、细菌丰度多样性进行综合分析。结果表明:在纯培养条件下,大丽轮枝菌无菌发酵滤液对细菌生长有明显的抑制作用;棉田接种大丽轮枝菌对土壤中细菌、真菌、放线菌的数量及细菌菌群丰度多样性未产生明显影响,不同采样时间的土壤中细菌菌群结构差异更大。土壤中大丽轮枝菌微菌核数量与棉花黄萎病的发生程度呈显著正相关。土壤肥力对土壤中微生物数量起主导作用,而水稻-棉花轮作能够使棉田有效降盐、减病、改善土壤肥力。通过生物防治、作物轮作、深翻等调控措施增加土壤中有益菌群数量、改善土壤生态、降低棉田土壤中大丽轮枝菌菌源数量是减轻棉花黄萎病危害的基础。     

大丽轮枝菌黑色素合成相关基因与微菌核形成的关系

大丽轮枝菌是一种重要的土传植物病原真菌,以休眠结构微菌核作为初始接种体,可侵染660多种植物引致黄萎病。微菌核是致密的多细胞结构,表面附着大量的DHN黑色素。许多报道指出,在微菌核发育过程中,传统的DHN黑色素合成途径中有5种催化酶编码基因Vd PKS、Vd T4HR、Vd SCD、Vd T3HR和Vd LAC均被诱导表达,但这些基因与微菌核形成的关系目前尚无报道。本研究通过基因敲除技术,系统研究了传统DHN黑色素合成通路上这5种关键酶编码基因及一种缩链催化酶编码基因Vayg1在大丽轮枝菌黑色素合成及微菌核形成中的作用。结果表明,大丽轮枝菌DHN黑色素合成需要Vayg1基因的参与,且Vayg1和Vd T3HR基因还参与微菌核的形成过程。因此,Vayg1基因和Vd T3HR基因可作为黄萎病防治的新靶标。     

过量表达GhPFN2基因增强棉花对大丽轮枝菌的抗性

越来越多的研究表明,微丝骨架参与植物先天免疫过程,但是其作用机制尚不明确.本研究发现,棉花(Gossypium spp.)的profilin基因(GhPFN2)在大丽轮枝菌(Verticillium dahliae)侵染条件下表达水平上调,推测GhPFN2可能参与棉花应答黄萎病过程.当棉花根部侵染大丽轮枝菌后,根表皮细胞中微丝的密度和成束度显著增加.与野生型相比,过量表达GhPFN2棉花对黄萎病的耐受性提高,并且棉花根部微丝骨架高级结构与野生型受到大丽轮枝菌侵染后的表型一致.这些结果表明,GhPFN2能够介导微丝骨架的重排,进而参与棉花抵御大丽轮枝菌的侵染过程.     

从功能基因到生物学性状:大丽轮枝菌致病性形成的分子基础

大丽轮枝菌为典型的土传维管束病原真菌,针对其致病相关基因的挖掘与功能解析一直是植物病理学研究的热点.大丽轮枝菌具有定殖维管束、"毒素"致萎、形成微菌核、种群分化多元化等特征,这些性状最终支撑或决定了病原对寄主的致病性基础.从进化角度来说,功能基因决定生物学性状.截至目前,在大丽轮枝菌中已鉴定出上百个功能基因;但针对其与...     

大丽轮枝菌假定蛋白VDAG＿07165的功能

土传病原真菌大丽轮枝菌寄主范围广,引起的黄萎病危害程度重、防控难度大。对病菌重要致病蛋白的挖掘和功能研究有望为病害防治提供新思路。本研究通过前期蛋白质组测序鉴定到一个未知功能结构域DUF1620家族蛋白VDAG＿07165在大丽轮枝菌对马铃薯根部初侵染阶段高表达。缺失VDAG＿07165基因导致大丽轮枝菌产孢量、分生孢子萌发率和穿透力均显著降低,对马铃薯植株的致病力显著减弱。由此说明,假定蛋白VDAG＿07165可在侵染早期通过调控大丽轮枝菌分生孢子的产生、萌发和穿透能力参与该菌对寄主的致病过程。本研究首次探明了DUF1620家族蛋白在土传病原真菌大丽轮枝菌分生孢子产生和侵染中的作用,为挖掘未知功能的新基因及其在真菌发育和致病过程中的功能研究提供了借鉴和参考。     

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.