Regulation of eight avr genes by hrpG and hrpX in Xanthomonas campestris pv. campestris and their role in pathogenicity

Eight putative avirulence genes in Xanthomonas campestris pv. campestris (Xcc) strain 8004 were characterized by Tn5gusA5 mutagenesis and gene expression analysis. The virulence test of mutants on Chinese radish showed that all mutants in individual avr genes except avrBs2 mutant were not significantly different from the wild type in virulence. The avrBs2 mutant showed reduced virulence and bacterial growth in planta. Gene expression analysis using β-glucuronidase as reporter indicated that avrBs1.1，avrBs1，avrXccB，avrXccC，avrXccE1 were regulated by hrpG, whereas avrXccA1, avrXccA2 and avrBs2 were not. RT-PCR analysis showed that all hrpG-regulated genes except avrBs1 were also regulated by hrpX. In addition, it was demonstrated that avrBs1　 was responsible for elicitation of a type III dependent hypersensitive reaction (HR) on nonhost plant pepper ECW-10R, and wild type Xcc 8004 was unable to cause HR on pepper ECW-20R.     

Widespread distribution and fitness contribution of Xanthomonas campestris avirulence gene avrBs2

Disease-resistance genes introduced into cultivated plants are often rendered ineffective by the ability of pathogen populations to overcome host resistance. The bacterial pathogen Xanthomonas campestris pathovar vesicatoria causes bacterial spot disease of tomato and pepper, and this pathogen has been shown to overcome disease resistance in pepper (Capsicum annuum) by evading the recognition and defence response of the host plant. Numerous resistance genes to bacterial spot have been identified in pepper and its wild relatives, each providing resistance to specific races of X.c. vesicatoria. The resistance gene Bs1, for example, provides resistance to X.c. vesicatoria strains expressing the avirulence gene avrBs1; Bs2 provides resistance to stains expressing avrBs2 and so on. We now report that avr Bs2 is highly conserved among strains of X.c. vesicatoria, and among many other pathovars of X. campestris. Furthermore, we find that avrBs2 is in fact needed for full virulence of the pathogen on susceptible hosts. This implies that plants carrying Bs2 can recognize an essential gene of the bacterial pathogen, which may explain why Bs2 confers the only effective field resistance to X.c. vesicatoria in pepper.     

水稻白叶枯病菌1个毒性相关基因的鉴定

我们曾报道了来自水稻白叶枯病菌真基文库的重级质粒ｐＧＸＮ３０００中含有一个能互补甘蓝黑腐病菌ｒｐｆＧ致病因子调控基因突变全的基因，并通过转座子诱变获得子转座子插在ｐＧＸＮ３０００中的这一基因的转座子插重组质粒，本研究利用这些转座子插入重组质粒，通过标记置换方法构建了不稻白叶枯病菌这一基因的突变菌株，植株试验结果表明，突变株虽然在水稻中仍能正常生长繁殖，但毒性严重降低，说明水稻白叶枯病菌的这一基因在     

磁处理土壤对油菜抗旱性影响及其机理研究

应用室外盆栽试验的方法，将土壤磁效应与生物磁效应相结合，研究了磁处理土壤对油菜抗旱特性的影响．研究结果表明，磁处理土壤增加了在干旱胁迫条件下油菜根、叶的过氧化物酶活性，促使其叶片中相对含水量、自由水和束缚水含量也相应增加，还提高了叶片中脯氨酸的含量水平，并使叶片相对电导率降低，从而增强了油菜的抗逆能力．     

真空渗入对菜薹叶表面扫描结构的影响

利用扫描电镜研究了真空渗入处理对菜薹(Brassica campestris)叶片表面结构的影响.结果表明,在吸力为14.4 m3/h的真空泵下断续处理1 min+30 s后,菜薹叶片形成不规则水浸状斑,顶端幼叶完全水浸状,同时叶片外部形态发生显著变化.与对照相比,叶片未形成水浸状部分气孔处于关闭或半关闭状态,气孔形状则由长梭形变为细长形;水浸状部分气孔处于过度开放状态,呈近圆形,局部叶表面蜡质、脂质等疏水结构破坏,呈碎斑状分散于叶片表面.     

重金属铜对红菜苔(Brassica campestris L.var.purpurea Baileysh)的生态毒理效应

通过盆栽实验研究了不同浓度铜对红菜苔的生态毒理效应．结果表明：低浓度的铜促进红菜苔的生长,使苗高、生物量增大;其生理生化指标,如叶绿素含量、POD、SOD的活性均有不同程度的升高．红菜苔在高浓度的铜中出现叶片黄化失绿、植株矮化、开花抽苔延长,烂根等中毒现象,叶绿素含量、POD、SOD的活性明显低于对照．另外,高浓度铜下植物体内矿质养分的缺失,进一步加深了植物的铜毒害．当铜离子浓度达到500mg/kg时,大多数植株死亡．     

重庆地区玉米圆斑病菌(Bipolaris carbonum Wilson)的分离鉴定

试验对重庆地区玉米圆斑病病原菌进行了分离、纯化和鉴定，同时进行了病原菌的致病性测定．病原菌的致病性测定结果表明：病原菌可直接侵入玉米的叶片，并于1周后表现出玉米圆斑病的典型症状．病原菌的培养性状及其分生孢子和分生孢子梗等形态特征的观察结果表明：重庆地区玉米圆斑病菌属半知菌亚门平脐蠕孢属炭色长孺孢（Bipolaris carbonum Wilson）．     

家茸天牛生物学特征的研究

着重对家茸天牛Ｔｒｉｃｈｏｆｅｒｕｓｃａｍｐｅｓｔｒｉｓ（Ｆａｌｄｅｒｍａｎｎ）在我国的分布、为害范围进行论述，对其分布、习性进行了调查、实验和饲养研究。认为该幼虫期为能休眠和连续蜕皮缩小的虫体以减少其能量消耗适应环境，它不仅为害林木，也是一种由野生向食储演化的害虫。     

野油菜黄单胞菌8004胞外酶及多糖合成正负调控基因在X.c.NK01菌中功能初探

利用野油菜黄单胞菌（Xanthomonascompestris）8004正、负调控胞外酶及多糖合成的基因片断分别经三亲本接合方法导入黄单胞菌NK01抗性突变株中，测定接合于四种胞外酶活力和多糖合成能力，确定该正、负调控基因对NK01的作用．结果表明，负调控基因作用明显，使NK01胞外多糖及胞外酶产量显著降低，正调控基因未见明显的胞外酶及多糖合成的增强作用．本文并对正、负调控基因的作用方式作了初步探讨．     

野油菜黄单胞菌色素的分离与稳定性研究

液体发酵野油菜黄单胞菌,生产大量菌液,通过离心、浓缩获得野油菜黄单胞菌色素干品,进行热、光照、酸碱度对色素稳定性的影响试验。结果表明,野油菜黄单胞菌黄色素在高温、长时间光照、强酸碱度条件下,性状稳定,吸收波长稳定在330 nm。     

田野菟丝子Cuscuta campestris的研究

本文描述了田野菟丝子的形态特征,研究了田野菟丝子的生物学特性与危害性,提出了检疫防治的对策.     

烟草赤星病菌孢子萌发和侵染条件的研究

用烟草赤星病菌两个菌株进行测定,孢子在烟草叶面萌发能力最强;其次是在1％的葡萄糖溶液中;在蒸馏水中萌发最弱。在侵染试验中,用丙酮和70％酒精清洗的幼苗叶片发病加重;露天放置的烟苗较生长在温室内的烟苗发病重。在3种接种方法中,以孢子悬滴法效果最好。侵染和接种方法中的幼苗,其叶面微生物在种类和数量上均以处理的不同而有差别。     

紫菜苔Ogura细胞质雄性不育系花药发育的细胞形态学研究

通过甘蓝型油菜Ogura细胞质雄性不育材料与紫菜苔的种间杂交和连续回交,获得了稳定的紫菜苔Ogura细胞质雄性不育系,细胞形态学研究表明,该不育系的花药发育兼有无花粉囊型和单核败育型的特征,由于没有造孢细胞的形成或造孢细胞退化,不育系最多只有1－2个花粉囊,而可育系都是4个花粉囊,发育起来的不育系花粉囊里面的小孢子到单核期后不再向前继续发育,而是迅速退化以至解体,开花前彻底败育,在减数分裂前期,不育系绒毡层细胞中已经出现液泡,有肥大趋势,在单核小孢子退化以后绒毡层还很发达,而正常花药绒毡层的发育在减数分裂过程中达到高峰,四分体时出现退化迹象,开花前已完全解体。     

镉对油菜花粉细胞内钙离子浓度的影响

应用激光扫描共聚焦显微系统(LSCM)和fluo-3 AM荧光探针标记技术,观察了不同浓度Cd2+对油菜花粉细胞内游离Ca2+的影响。发现油菜花粉经水合培养后,胞内Ca2+呈极性分布,萌发沟附近浓度较高,花粉管萌生部位浓度最高;胞外环境中Cd2+可使细胞内游离Ca2+的浓度升高,表明油菜花粉受重金属Cd2+毒害后,可通过调动胞质内游离Ca2+的变化而做出对外界刺激的应答。这一实验结果为探索重金属对植物的毒害机理提供了新的证据。     

甘蔗黑腐病病原菌的鉴定

在云南开远6根发病的甘蔗茎上分离到甘蔗黑腐病病原菌,鉴定了该病害的病原菌,以期为防治和控制该病害提供一定的理论依据.基于致病性测定,ITSI-5.8S-ITS2 rDNA序列的系统发病分析和形态学观察结果,甘蔗黑腐病是由多脂长喙壳菌(Ceratocystis adiposa(Butl.)Moreau)引起的,该病菌导致甘蔗黑腐病在中国属首次报道.     

甘蔗黑腐病病原菌的鉴定

 在云南开远6根发病的甘蔗茎上分离到甘蔗黑腐病病原菌,鉴定了该病害的病原菌,以期为防治和控制该病害提供一定的理论依据.基于致病性测定,ITSI-5.8S-ITS2 rDNA序列的系统发病分析和形态学观察结果,甘蔗黑腐病是由多脂长喙壳菌（Ceratocystis adiposa(Butl.)Moreau）引起的,该病菌导致甘蔗黑腐病在中国属首次报道.     

Isolation and characterization of rice lesion mimic mutants from a T-DNA tagged population

A rice ( Oryza sativa L. ssp. japonica cv. Nipponbare) T-DNA tagged population consisting of about 7000 individual lines was generated and screened for rice lesion mimic mutants in the T1 generation. Ten lines were found to develop spontaneous lesions in the absence of pathogen infection and displayed distinct lesion phenotypes. These mutants were tentatively designated as lm1 -lm10 (for lesion mimic), respectively. Lesion formation of lm mutants was developmentally regulated, and all the mutants showed stunted growth and reduced fertility. Genetic analysis demonstrated that all the mutations were recessive, and five partially fertile mutants (lm4-lm8) were derived from different loci. Mimic lesions occurring on the leaves of lm mutants resulted from cell death as revealed by trypan blue staining. Six of them ( lm3 -lm8 ) exhibited enhanced resistance to five bacterial blight isolates, indicating their wide-spectrum resistance to this pathogen. These results imply that some lesion mimic mutations of rice might be involved in disease resistance signaling pathways,and that isolation of these mutated genes may be useful for elucidating molecular mechanisms of plant disease resistance. Among the mutants, only one mutant, lm6, was preliminarily shown to cosegregate with the inserted T-DNA in its T1 generation, making it feasible to isolate the gene responsible for the phenotype of this mutant.     

萝卜过氧化物酶对番茄幼苗生长发育的影响

为了研究萝卜过氧化物酶对植物生长的影响.用萝卜过氧化物酶对番茄种子浸种和幼苗叶面喷洒后;分别于番茄幼苗3叶1心期和4叶1心期测量番茄幼苗的株高、鲜质量和干质量等形态指标,测定幼苗根部的可溶性蛋白含量和过氧化物酶的活性;并用活性电泳和PCR检测萝卜过氧化物酶和番茄过氧化物酶的差异.结果表明:萝卜过氧化物酶能显著促进番茄幼苗的生长,并且使番茄幼苗根部的蛋白含量有明显地增加,显著提高其过氧化物酶活性.由此可见,外源过氧化物酶对番茄幼苗的生理和形态指标均有一定的影响.     

Release of active oxygen from phytopathogenic bacteria and their regulation

Some phytopathogenic bacteria including Xanthomonas oryzae pv. oryzae (a rice leaf bacterial blight pathogen) and its virulent gene mutant XooM3105, Xanthomonas campestris pv. campestris, Erwinia carotovora subsp. carotovora and so on, could release active oxygen such as O2 and H2O2 by themselves. Ca2+ , NADPH and O2 concentration regulated the response. The response is sensitive to heat and proteinase. These results show that the component releasing active oxygen in the bacterial plant pathogen may involve special protein and enzyme and be secreted to culture liquid. Various components of rice tissue can significantly induce the release of active oxygen in Xan-thomonas oryzae pv. oryzae.     

中国烟草赤星病菌致病力在地理上和品种中分化状况的研究

从来自全国6大烟区11个主产烟省的烤烟和晒晾烟的14个品种上获得300多个分离物,从中鉴定出168个烟草赤星病菌;经接种测定研究了病菌致病力的组成及其地理分化和在不同品种中的发生情况。病菌致病力的地理分布有3种类型,广东、吉林2省为强致病力分布型;川、陕、鄂、皖、鲁5省为中致病力分布型;闽、豫、湘3省为弱致病力分布型。结合品种抗性测定分析提出,强致病力菌株主要发生在抗病性较强的品种中,而弱致病力菌株则主要发生在抗病性较弱的品种中。