Characterization of Elicitor-inducible Tobacco Genes Isolated by Differential Hybridization

Inducible responses in plants against pathogen attack play a major role in resistance to disease. The defense responses are mostly associated with the expression of various kinds of inducible genes. We employed differential hybridization to isolate elicitor-inducible genes (EIGs) of tobacco (Nicotiana tabacum cv. Samsun NN) using the tobacco-fungal elicitor system. A cDNA library was constructed from tobacco leaves treated for 12 hr with hyphal wall components (HWC) prepared from Phytophthora infestans, and six EIGs were identified. Expression of all EIGs was induced after inoculation with the soybean pathogen Pseudomonas syringae pv. glycinea (nonpathogenic on tobacco) or treatment with salicylic acid, and a variety of expression patterns of EIG mRNAs was observed. Sequence analysis of EIG cDNAs revealed similarities to genes for SAR8.2 (EIG-B39 and EIG-D14), glycine-rich protein (EIG-G7), extensin (EIG-I30), acyltransferase (EIG-I24) and unknown protein (EIG-J7). Possible roles of EIG products in disease resistance are discussed. Received 30 August 2000/ Accepted in revised form 30 November 2000     

大豆细菌性斑点病侵染大豆品种叶片的超微结构观察

大豆细菌性斑点病是严重危害大豆生产的叶部病害。本研究采用针刺法,对高抗大豆细菌性斑点病4号生理小种的大豆品种绥农8和高感品种合丰25分别接种大豆细菌性斑点病4号生理小种后,进行透射电镜观察。结果表明,随着接种时间的增加,抗感大豆品种叶片超微结构出现了明显差异,接种120h后,抗病品种叶片细胞内部结构基本上比较完整,而感病品种叶片细胞内部结构发生了较大的变化,细胞质膜、核膜、核质及叶绿体均受到严重的破坏;叶绿体基粒片层消失,大部分叶绿体膜也逐渐解体,线粒体的空泡化严重,说明大豆细菌性斑点病引起细胞结构病变在抗感品种间的表现不同。研究为揭示大豆细菌性斑点病病原菌的致病机理奠定一定的理论基础。     

Patterns of interaction between isolates of three pathovars of Pseudomonas syringae and accessions of a range of host and nonhost legume species

Isolates of three pathovars of Pseudomonas syringae were tested against 10 legume species. Some isolates of all pathovars showed cultivar-specific interactions with at least one legume species outside the expected host range. Lablab purpureus and Phaseolus lunatus were found to be hosts to isolates of both P. syringae pv. glycinea and P. syringae pv. phaseolicola, while Lathyrus latifolius was host to isolates of P. syringae pv. pisi and P. syringae pv. glycinea . Lens culinaris showed patterns of interaction with isolates of all three pathovars. Gene models based on mathematical estimates of minimum gene numbers agreed with those previously published for the interactions of P. syringae pv. pisi with Pisum sativum and P. syringae pv. phaseolicola with Phaseolus vulgaris. Two different gene-for-gene models based on five resistance/avirulence gene pairs were proposed to explain observed interactions between Glycine max and P. syringae pv . glycinea . Pathogen isolates which contained no known avirulences defined on their respective host species were found to carry cryptic avirulences recognized by other plant species. Estimates of minimum gene numbers required to explain the interactions of a plant species with all pathogen isolates or to explain the interactions of the isolates of one pathovar with all plant accessions were consistently lower than the sum of the minimum gene numbers required to explain the interactions of each individual component.     

The possibility of factors other than phytoalexin accumulation preventing fungal growth in the incompatible interactions of soybean with Phytophthora megasperma f. sp. glycinea

Soybean ( Glycine max ) cv. Harosoy 63 is resistant to race 1 and susceptible to race 9 of Phytophthora megasperma f. sp. glycinea (Pmg). In detached primary leaves inoculated with zoospores, growth of race 1 was completely suppressed 16 h after inoculation, while race 9 was unaffected. The amount of the phytoalexin glyceollin that accumulated, however, was not significantly different in either the incompatible or compatible interaction 16 h after inoculation. At the circumference of the inoculated area, a slight accumulation of phytoalexin was observed only in the incompatible interaction 20 h or more after inoculation. Tolerance of race 9 to the phytoalexin was significantly higher than that of race 1 when the phytoalexin was added to agar. Moreover, race 9 degraded glyceollin faster than race 1. On leaves inoculated at separate points with either race, the lesion associated with race 9 never colonized areas inoculated with race 1. These results suggest that factor(s) other than the accumulation of phytoalexin in soybean tissue might cause cessation of growth of Pmg.     

吉林省大豆细菌性斑点病菌(Pseudomonas syringae pv.glycinea)生理小种鉴定结果初报

自1989年至1992年的四年间,在吉林省的长春、公主岭、吉林、白城、通化等地区的各大豆品种上分离到大豆细菌性斑点病菌的菌株146个,接种在7个国际鉴别寄主上,即Aeme,Chippwwa,Flambeau,Harosoy,Lindarin,Merit,Norchief,观察其抗感反应。将测定结果与国际上已鉴定的9个生理小种在这7个鉴别寄主上的反应相对照,发现有98个菌株属4号生理小种,占总菌株数的67.1％,为主要菌株;4个菌株属2号生理小种;1个菌株属7号生理小种。经反复测定,发现两个新的生理小种,定名为10号和11号生理小种。     

大豆细菌性斑点病抗性品种和种质资源筛选

近年我国东北大豆产区细菌性斑点病发生严重,影响大豆品质和产量。采用室内高压喷雾接种法,利用分离的假单胞杆菌Psgneau001菌株接种黑龙江省主栽品种211份和东北大豆核心种质192份材料,进行抗性鉴定。结果表明,黑龙江省主栽品种抗性材料占34%,感病材料占51%,中间材料占15%;东北大豆核心种质抗性材料占57%,感病材料占26%,中间材料占17%。试验所获抗病种质资源可为大豆抗病育种提供优质候选材料。     

大豆细菌性斑点病菌hrpZPsg12基因增强病原菌对大豆的致病性并引起烟草过敏性反应

[目的]明确hrpZPsg12基因对大豆细菌性斑点病菌致病性的影响。[方法]采用PCR方法从大豆细菌性斑点病菌中克隆hrpZPsg12基因,利用具有自杀特性的敲除质粒pKNOCK-Cm和具有功能互补作用的粘粒pUFR034,构建了hrpZPsg12基因的突变载体pKNOCK477-7和互补载体pUFR1026-68,并筛选出hrpZPsg12基因的突变体477-1及其功能互补子1026-5。进一步将野生型Psg12、突变体477-1和互补子反应斑。但是,反应斑的大小有差异,Psg12菌株接种的病斑较大,477-1的较小,互补子1026-5的接近野生型菌株Psg12。病斑中细菌繁殖量分析表明,野生型菌株Psg12繁殖量最高,突变体477-1的最低,互补子1026-5的接近野生型菌株Psg12的繁殖量。[结论]hrpZ-Psg12基因能够增强大豆细菌性斑点病菌对大豆的致病性,并且能够在烟草上产生过敏性反应。     

大豆接种细菌性斑点病菌后叶片中SOD、POD活性和可溶性糖含量的变化

对6个不同抗性的大豆品种接种细菌性斑点病菌后12、24、36、48和60 h分别测定叶片中SOD、POD活性以及可溶性糖含量.结果表明:抗感品种接种细菌性斑点病菌后叶片中SOD和POD活性在病程的大部分较对照增加,总体而言抗病品种叶片中SOD活性总体增加幅度高于感病品种.而感病品种叶片中可溶性糖的含量较对照均有一定幅度的增加,抗病品种相反.     

大豆细菌性斑点病菌生理小种分布的研究

采用中国的一套鉴别寄主体系对来源于全国各地的42个大豆细菌性斑点病菌菌株进行了测定。吉林省共存在13个小种：C2，C3，C4，C5，C6，C7，C8，C9，C10，C11，C12，C13和C14；辽宁省存在5个小种；C1，C4，C9，C10和C14；黑龙江省存在8个小种：C1，C3，C7，C8，C11，C13和C14。湖北省存在1个小种C10。属于小种C10，C11，C12，C13和C14的菌株数分别占分离菌株数的9.5%；属于小种C1，C2，C5和C6的菌株数分别占分离菌株数的7.1%，属于小种C3，C4，C7，C8和C9的菌株数分别占分离菌株数的4.8%。     

乙烯合成酶基因的克隆及其在大肠杆菌中的表达

通过PCR的方法从丁香假单胞菌大豆致病变种(Pseudomonas syringae pv.glycinea)ICMP2189中克隆到了乙烯形成酶基因efe,并且在大肠杆菌(Escherichia coli)BL21中利用T7强启动子进行了高效表达,表达蛋白占总蛋白的45%。气相色谱分析表明,含有efe基因的大肠杆菌可以高效地产生乙烯。