hrpZ_(Psg12) Gene of Pseudomonas syringae pv.glycinea can Enhance Pathogenicity of the Pathogen on Soybean and Cause the Hypersensitive Response of Tobacco

[ Objective ] The paper was to confirrm the effect of hrpZpsg12 gene on the pathogenicity of Pseudomonas syringae pv. glycinea. [ Method ] hrpZpsg12 gene was cloned from P. syringae using PCR method. The knockout plasmid pKNOCK-Cm with suicide characteristics and cosmid pUFR034 with complementation func- tion were used to construct the mutation vector pKNOCK477-7 and complementary vector pUFR1026-68 of hrpZpsg12 gene, the mutant 477-1 and the functional com- plementation unit 1026-5 of the gene was also screened out. Three strains including wild-type Psg12, mutant 477-1 and complementary unit 1026-5 were simultane- ously inoculated into soybean leaves and tobacco leaves, then pathogenicity determination and hypersensitive reaction analysis were carried out. [ Result] All the inoculated leaves of soybean and tobacco produced reaction lesion. However, the sizes of reaction lesion were different. The lesion in the leaves inoculated with Psgl2 was relatively large, while the lesion in the leaves inoculated with 477-1 was relatively small; the lesion of complementary unit 1026-5 was similar to wild- type Psgl2. Analysis of reproduction quantity of bacteria in lesions showed that the reproduction quantity of wild-type Psg12 was the highest, while that of mutant 477-1 was the lowest. The reproduction quantity of complementary unit 1026-5 was similar to that of wild-type Psg12. [ Conclusion] hrpZpsg12 gene could enhance the pathogenicity of P. syrimgae on Soybean and produce hypersensitive response in tobacco.

Functional identification of phenazine biosynthesis genes in plant pathogenic bacteria Pseudomonas syringae pv. tomato and Xanthomonas oryzae pv. oryzae

Phenazines are secondary metabolites with broad spectrum antibiotic activity and thus show high potential in biological control of pathogens. In this study, we identified phenazine biosynthesis （phz） genes in two genome-completed plant pathogenic bacteria Pseudomonas syringae pv. tomato （Pst） DC3000 and Xanthomonas oryzae pv. oryzae （Xoo） PXO99A. Unlike the phz genes in typical phenazine-producing pseudomonads, phz homologs in Pst DC3000 and Xoo PXO99A consisted of phzC/D/E/F/G and phzC/E1/E2/F/G, respectively, and the both were not organized into an operon. Detection experiments demonstrated that phenazine-l-carboxylic acid （PCA） of Pst DC3000 accumulated to 13.4 IJg L-1, while that of Xoo PXO99A was almost undetectable. Moreover, Pst DC3000 was resistant to 1 mg mL-1 PCA, while Xoo PXO99A was sensitive to 50 IJg mL ~ PCA. Furthermore, mutation of phzF blocked the PCA production and significantly reduced the pathogenicity of Pst DC3000 in tomato, while the complementary strains restored these phenotypes. These results revealed that Pst DC3000 produces low level of and is resistant to phenazines and thus is unable to be biologically controlled by phenazines. Additionally, phz-mediated PCA production is required for full pathogenicity of Pst DC3000. To our knowledge, this is the first report of PCA production and its function in pathogenicity of a plant pathogenic P. syringae strain.

Pear Blossom Blast Caused by Pseudomonas syringae pv. syringae in China

This study was done to determine the causal organism of the pear blossom and bud blast in China. It was identified by a bacteriological test, electro-microscopic observation, Koch＇s postulate test, Biolog, fatty acid methyl esters （FAMEs）, and a polymerase chain reaction （PCR） test, and compared with the standard reference strains. Six representative strains out of 20 pathogenic bacterial isolates from 16 diseased samples showed characteristics similar to three standard strains of Pseudomonas syringae pv. syringae from Belgium. They were identified as P. syringae pv. syringae with a Biolog similarity of 0.57-0.86 and FAMEs similarity of 0.58-0.81. The bacterium was reisolated from the symptomatic plants and blossoms. Identification as P. syringae pv. syringae was confirmed by using PCR primers and sequence tests, and compared with the above-mentioned results. The data supported the fact that the pear blossom and bud blast in China could be caused by P. syringae pv. syringae.

Identification of QTLs Associated with Resistance to Pseudomonas syringae pv.Glycinea in Soybean(Glycine max(L.)Merr)

Soybean bacterial spot disease caused by Pseudomonas syringae pv.Glycinea which is a bacterial disease seriously affects soybean yield.Ten soybean germplasms and recombinant inbred lines(RILs)population were used to identify the resistant trait after inoculated with P.sg(P.sgneau001)in this study.High-density genetic mapping was obtained by specific length amplified fragment sequencing(SLAF-seq)of 149 RILs population which was derived from the crossing between Charleston and Dongnong594.The results indicated that 10 germplasm resources had four resistant germplasms included highly resistant cultivar Charleston,four susceptible varieties included Dongnong594 and two moderately resistant cultivars.Five quantitative trait locus(QTLs)were detected in RILs population by the composite interval mapping(CIM)method,and located on Linkage Group(LG)D1b(chromosome two),LG C2(chromosome six)and LG H(chromosome 12),respectively.LOD scores ranged from 2.68 to 4.95 and the phenotypic variation percentage was from 6%to 11%.Six candidate genes were detected,according to the result of gene annotation information.Four of them had relationship with protein kinase activity,protein phosphorylation and leucine rich repeat(LRR)transmembrane protein,which had high expression after inoculated with P.sg by qRT-PCR.

Two plant NLR proteins confer strain-specific resistance conditioned by an effector from Pseudomonas syringae pv.actinidiae

Pseudomonas syringae pv.actinidiae(Psa)causes bacterial canker,a devastating disease threatening the Actinidia fruit industry.In a search for non-host resistance genes against Psa,we find that the nucleotidebinding leucine-rich repeat receptor(NLR)protein ZAR1 from both Arabidopsis and Nicotiana benthamiana(Nb)recognizes Hop Z5 and triggers cell death.The recognition requires ZED1 in Arabidopsis and JIM2 in Nb plants,which are members of the ZRK pseudokinases and known components of the ZAR1 resistosome.Surprisingly,Arabidopsis ZAR1 and RPM1,another NLR known to recognize Hop Z5,confer disease resistance to Hop Z5 in a strain-specific manner.Thus,ZAR1,but not RPM1,is solely required for resistance to P.s.maculicola ES4326(Psm)carrying hop Z5,whereas RPM1 is primarily required for resistance to P.s.tomato DC3000(Pst)carrying hop Z5.Furthermore,the ZAR1-mediated resistance to Psm hop Z5 in Arabidopsis is insensitive to SOBER1,which encodes a deacetylase known to suppress the RPM1-mediated resistance to Pst hop Z5.In addition,hop Z5 enhances P.syringae virulence in the absence of ZAR1 or RPM1 and that SOBER1 abolishes such virulence function.Together the study suggests that ZAR1 may be used for improving Psa resistance in Actinidia and uncovers previously unknown complexity of effectortriggered immunity and effector-triggered virulence.

Establishment of a Loop-mediated Isothermal Amplification Method for Rice Bacterial Leaf Brown Spot Disease

Rice bacterial leaf brown spot disease caused by Pseudomonas syringae pv.syringae(Pss)is a major disease on rice.In recent years,Pss has emerged worldwide,seriously affecting rice production.It is very important to establish a rapid detection method of Pss for the diagnosis and prevention of this disease.In order to robust and accurately diagnose the rice bacterial leaf brown spot disease in the field and laboratory,an assay system for the Pss was developed in this study,and the specific sequence of hrcN was used as the target,based on loop-mediated isothermal amplification(LAMP).The best detection system was MgSO 48 mmol·L^(-1),Bst DNA polymerase 8 U,dNTP 1.4 mmol·L^(-1),the ratio of internal and outer primers was 2:1,the reaction temperature was 63℃,the reaction time was 45 min,and the lowest sensitivity was 104 CFU·mL^(-1).This results provided an accurate and robust method for laboratory and field diagnosis of bacterial leaf brown spot disease of rice.

Integrated Green Prevention and Control Techniques for Kiwifruit Canker Disease in "Guichang" Kiwifruit in Xiuwen County, Guizhou Province

Kiwifruit canker disease seriously affects the yield and quality of"Guichang"kiwifruit in Xiuwen County,Guizhou Province.In order to scientifically,safely,greenly and efficiently prevent and control the disease,theory was combined with prevention and control techniques to optimize existing prevention and control techniques,so as to improve the production yield and quality of kiwifruit.Specifically,biocontrol strains targeting local kiwifruit canker disease were screened,and reduced and mixed use of agrochemicals with improved efficiency was studied;and the effects and application techniques of disease resistance inducers and bioorganic fertilizers in inducing systemic disease resistance in kiwifruit trees were explored,and finally,an integrated green prevention and control scheme for kiwifruit canker disease that is suitable for kiwifruit production areas in Guizhou Province and has strong operability was proposed.This study provides technical support for green,efficient,standardized production technical services and sustainable and healthy development of kiwifruit industry.

Construction of Lescpth5 Bait Vector and Detection of Its Self-activated Activity

[ Objective ] The paper was to construct bait vector pGBKTT-Lescpth5, and detect its self-activated transcription activity and the toxicity on yeast cells. [ Method] Lescpth5 was amplified by PCR technique, and connected into bait vector pGBKTT. The recombined vector was transformed into yeast competent ceils AH109 and carried out self-activated detection and toxicity detection in the au.xotrephic medium. [ Result] Digestion and sequencing results showed that bait vector pGBKT7-Lescpth5 was suecessfully constructed with correct reading frame. Self-activated activity and toxicity detection results showed that bait vector had no self- activated activity on yeast strain AH109, which also had no toxicity on yeast. [Condusion] Bait vector successfully constructed could be used in yeast two-hybrid system, which laid the foundation for screening of cDNA library in the next step.

猕猴桃溃疡病菌Ⅲ型效应蛋白HopAZ1功能研究与互作蛋白鉴定

细菌Ⅲ型分泌系统可向寄主植物细胞分泌多种效应蛋白,在丁香假单胞菌猕猴桃致病变种(Psa)侵染猕猴桃致病中发挥关键作用。但是,尚不清楚Psa如何利用这些效应蛋白与寄主互作。Psa的5个生物型群体具有不同种类的效应子,但其中共有的14个效应子可能是参与病菌与寄主亲和互作的关键因子。本研究系统调查了其中HopAZ1的功能。结果显示,HopAZ1广泛分布于丁香假单胞菌的不同类群,在Psa不同生物型群体遗传分化前已经存在,且可能由于在致病中具有重要功能而被纯化选择;HopAZ1在Psa侵染猕猴桃早期被诱导表达,敲除突变体对不同猕猴桃枝条的致病力均显著上升;进而通过构建猕猴桃酵母文库和酵母双杂交筛选,发现HopAZ1可能与猕猴桃抗病相关蛋白Cp1(Acc23383)、PR5(Acc28852)互作。这表明HopAZ1是Psa与猕猴桃互作的重要因子,可能通过与Cp1或PR5互作激发一定程度的抗病反应。这为深入解析HopAZ1的作用机制及猕猴桃抗病基因的挖掘提供了重要依据。