RNA-Seq identification of candidate defense genes targeted by endophytic Bacillus cereus-mediated induced systemic resistance against Meloidogyne incognita in tomato. - Related Documents




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873201.0000RNA-Seq identification of candidate defense genes targeted by endophytic Bacillus cereus-mediated induced systemic resistance against Meloidogyne incognita in tomato. BACKGROUND: The endophytic bacteria Bacillus cereus BCM2 has shown great potential as a defense against the parasitic nematode Meloidogyne incognita. Here, we studied endophytic bacteria-mediated plant defense against M. incognita and searched for defense-related candidate genes using RNA-Seq. RESULTS: The induced systemic resistance of BCM2 against M. incognita was tested using the split-root method. Pre-inoculated BCM2 on the inducer side was associated with a dramatic reduction in galls and egg masses on the responder side, but inoculated BCM2 alone did not produce the same effect. In order to investigate which plant defense-related genes are specifically activated by BCM2, four RNA samples from tomato roots were sequenced, and four high-quality total clean bases were obtained, ranging from 6.64 to 6.75 Gb, with an average of 21 558 total genes. The 34 candidate defense-related genes were identified by pair-wise comparison among libraries, representing the targets for BCM2 priming resistance against M. incognita. Functional characterization revealed that the plant-pathogen interaction pathway (ID: ko04626) was significantly enriched for BCM2-mediated M. incognita resistance. CONCLUSION: This study demonstrates that B. cereus BCM2 maintains a harmonious host-microbe relationship with tomato, but appeared to prime the plant, resulting in more vigorous defense response toward the infection nematode. © 2018 Society of Chemical Industry.201829737595
878310.9988Characterization and potential of plant growth promoting rhizobacteria isolated from native Andean crops. Bacteria isolated from soil and rhizosphere samples collected in Peru from Andean crops were tested in vitro and in vivo to determine their potential as plant growth promoters and their ability to induce systemic resistance to Alternaria alternata in tomato plants. The isolates were identified by sequencing their 16S ribosomal RNA gene. Test for phosphate solubilization, and indolacetic acid were also carried out, together with in vitro antagonism assays in dual cultures towards the plant pathogens Fusarium solani, A. alternata and Curvularia lunata. The three most promising isolates (Pa15, Ps155, Ps168) belonged to the genus Pseudomonas. Further assays were carried out with tomato plants to assess their plant protection effect towards A. alternata and as growth promoters. Inoculation of tomato seeds with all isolates significantly enhanced seed germination, plantlets emergence and plant development. Bacterial inoculation also reduce damage level caused by A. alternata. The expression levels of three tomato genes involved in the jasmonate (AOS), ethylene responsive (ERF-2) and pathogenesis related (PR-P2) pathways were determined in plants challenged with A. alternata, alone or with each bacterial isolate, respectively. Results showed that at 24 h after infection, in absence of the pathogen, the expression level of the tested genes was very low. The presence of A. alternata alone and in combination with bacteria increased the transcripts of all genes. Data showed a potential of best performing isolate Ps168 to sustain tomato plants nutrition and activate defense-related genes for protection by pathogenic fungi.201729079927
875820.9986Genome-wide association mapping for resistance to bacterial blight and bacterial leaf streak in rice. Using genome-wide SNP association mapping, a total of 77 and 7 loci were identified for rice bacterial blight and bacterial leaf streak resistance, respectively, which may facilitate rice resistance improvement. Bacterial blight (BB) and bacterial leaf streak (BLS) caused by Gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two economically important diseases negatively affecting rice production. To mine new sources of resistance, a set of rice germplasm collection consisting of 895 re-sequenced accessions from the 3000 Rice Genomes Project (3 K RGP) were screened for BB and BLS resistance under field conditions. Higher levels of BB resistance were observed in aus/boro subgroup, whereas the japonica, temperate japonica and tropical japonica subgroups possessed comparatively high levels of resistance to BLS. A genome-wide association study (GWAS) mined 77 genomic loci significantly associated with BB and 7 with BLS resistance. The phenotypic variance (R(2)) explained by these loci ranged from 0.4 to 30.2%. Among the loci, 7 for BB resistance were co-localized with known BB resistance genes and one for BLS resistance overlapped with a previously reported BLS resistance QTL. A search for the candidates in other novel loci revealed several defense-related genes that may be involved in resistance to BB and BLS. High levels of phenotypic resistance to BB or BLS could be attributed to the accumulation of the resistance (R) alleles at the associated loci, indicating their potential value in rice resistance breeding via gene pyramiding. The GWAS analysis validated the known genes underlying BB and BLS resistance and identified novel loci that could enrich the current resistance gene pool. The resources with strong resistance and significant SNPs identified in this study are potentially useful in breeding for BB and BLS resistance.202133830376
845430.9986Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus x domestica) with Erwinia amylovora. BACKGROUND: The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceae species, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora. RESULTS: cDNA were isolated from M.26 (susceptible) and G.41 (resistant) apple tissues collected 2 h and 48 h after challenge with a virulent E. amylovora strain or mock (buffer) inoculated. To identify differentially expressed transcripts, electrophoretic banding patterns were obtained from cDNAs. In the AFLP experiments, M.26 and G.41 showed different patterns of expression, including genes specifically induced, not induced, or repressed by E. amylovora. In total, 190 ESTs differentially expressed between M.26 and G.41 were identified using 42 pairs of AFLP primers. cDNA-AFLP analysis of global EST expression in a resistant and a susceptible apple genotype identified different major classes of genes. EST sequencing data showed that genes linked to resistance, encoding proteins involved in recognition, signaling, defense and apoptosis, were modulated by E. amylovora in its host plant. The expression time course of some of these ESTs selected via a bioinformatic analysis has been characterized. CONCLUSION: These data are being used to develop hypotheses of resistance or susceptibility mechanisms in Malus to E. amylovora and provide an initial categorization of genes possibly involved in recognition events, early signaling responses the subsequent development of resistance or susceptibility. These data also provided potential candidates for improving apple resistance to fire blight either by marker-assisted selection or genetic engineering.201020047654
845340.9986In silico analysis of gene content in tomato genomic regions mapped to the Ty-2 resistance gene. Tomato yellow leaf curl virus is one of the main diseases affecting tomato production worldwide. Previous studies have shown that Ty-2 is an important resistance gene located between molecular markers C2_At2g28250 (82.3 cM) and T0302 (89.0 cM), and exhibits strong resistance to tomato yellow leaf curl virus in Asia. In this study, Ty-2 candidate genes were subjected to bioinformatic analysis for the sequenced tomato genome. We identified 69 genes between molecular markers C2_At2g28250 and T0302, 22 of which were disease-related resistant genes, including nucleotide binding site-leucine-rich repeat disease resistance genes, protease genes (protein kinase, kinase receptor, and protein isomerase), cytochromes, and transcription factors. Expressed sequence tag analysis revealed that 77.3% (17/22) of candidate disease-resistance genes were expressed, involving 143 expressed sequence tags. Based on full-length cDNA sequence analysis, 7 candidate genes were found, 4 of which were involved in tomato responses to pathogens. Microarray expression analysis also showed that most candidate genes were involved in the tomato responses to multiple pathogens, including fungi, viruses, and bacteria. RNA-seq expression analysis revealed that all candidate genes participated in tomato growth and development.201526214476
878450.9986Bacillus firmus Strain I-1582, a Nematode Antagonist by Itself and Through the Plant. Bacillus firmus I-1582 is approved in Europe for the management of Meloidogyne on vegetable crops. However, little information about its modes of action and temperature requirements is available, despite the effect of these parameters in its efficacy. The cardinal temperatures for bacterial growth and biofilm formation were determined. The bacteria was transformed with GFP to study its effect on nematode eggs and root colonization of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) by laser-scanning confocal microscopy. Induction of plant resistance was determined in split-root experiments and the dynamic regulation of genes related to jasmonic acid (JA) and salicylic acid (SA) by RT-qPCR at three different times after nematode inoculation. The bacteria was able to grow and form biofilms between 15 and 45°C; it degraded egg-shells and colonized eggs; it colonized tomato roots more extensively than cucumber roots; it induced systemic resistance in tomato, but not in cucumber; SA and JA related genes were primed at different times after nematode inoculation in tomato, but only the SA-related gene was up-regulated at 7 days after nematode inoculation in cucumber. In conclusion, B. firmus I-1582 is active at a wide range of temperatures; its optimal growth temperature is 35°C; it is able to degrade Meloidogyne eggs, and to colonize plant roots, inducing systemic resistance in a plant dependent species manner.202032765537
878560.9985Mechanism of resistance to Cucumber mosaic virus elicited by inoculation with Bacillus subtilis subsp. subtilis. BACKGROUND: Systemic resistance stimulated by rhizosphere bacteria is an important strategy for the management of plant viruses. The efficacy of Bacillus subtilis subsp. subtilis was assessed for protection of cucumber and Arabidopsis against Cucumber mosaic virus (CMV). Moreover, transcriptomic analysis was carried out for A. thaliana colonized with B. subtilis subsp. subtilis and infected with CMV. RESULTS: Treatment with a cell suspension of Bacillus revealed a significant reduction of CMV severity in comparison to their control. All Arabidopsis mutants treated with B. subtilis showed a clear reduction in CMV accumulation. Disease severity data and virus concentration titer measurements correlated with gene up-regulation in microarray and reverse transcription quantitative polymerase chain reaction (RT-qPCR) experiments. Bacillus treatment increased Arabidopsis growth characteristics (fresh and dry weights and number of leaflets) under pot conditions. The molecular mechanisms by which Bacillus activated resistance to CMV were investigated. Using the microarray hybridization technique, we were able to determine the mechanism of resistance elicited by B. subtilis against CMV. The transcriptomic analysis confirmed the up-regulation of more than 250 defense-related genes in Arabidopsis expressing induced systemic resistance (ISR). RT-qPCR results validated the overexpression of defense genes (YLS9 and PR1 in Arabidopsis and PR1 and LOX in cucumber), implying their important roles in the stimulated defense response. CONCLUSION: Through the study of microarray and RT-qPCR analyses, it can be concluded that the overexpression of pathogenesis-related genes was necessary to stimulate CMV defense in cucumber and Arabidopsis by B. subtilis subsp. subtilis. © 2021 Society of Chemical Industry.202234437749
879470.9985The Enhancement of Potato (Solanum Tuberosum L. Cv. Odyssey) Resistance to Bacterial Soft Rot Disease Through Transformation of the Glyphosate-Resistant Gene from Dickeya Dadanti. OBJECTIVE: An efficient protocol was developed via the Agrobacterium-mediated transformation method with the plasmid, p485, harboring the aroA gene from the bacterial species Dickeya dadantii, to improve resistance to potato bacterial soft rot disease. The study aimed to investigate the relationship between glyphosate application and the enhancement of potatoes' resistance to two bacterial pathogens affecting the plants. MATERIALS AND METHODS: An optimal concentration of 1.8 mg.L(-1) of glyphosate was applied to transgenic potato varieties. The leaves of the Odyssey cultivar demonstrated resistance to two pathogenic strains, Pectobacterium atrosepticum 21A and D. dadantii ENA49. Polymerase chain reaction (PCR) and reverse transcription-PCR (RT-PCR) validation demonstrated the successful integration and heterologous expression of the aroA gene in the potato genome. Additionally, the transcriptional analysis revealed the expression of pathogenesis-related genes and genes associated with the potato defence response. RESULTS: The study revealed a significant increase in the expression of pathogenesis-related genes (PR-2, PR-3, and PR-5) and defence response genes (HSR-203j and HIN1 in transgenic potato leaves after glyphosate treatment and subsequent exposure to pathogenic bacterial infection, with a particular emphasis on the upregulation of HSR-203j. A comparative analysis assessed the average expression levels of these genes in both experimental and control samples. In contrast, minimal changes in gene expression were observed in plants infected with bacteria but not treated with glyphosate. CONCLUSION: The study suggests that glyphosate treatment in potatoes can enhance systemic acquired resistance to bacterial pathogens by upregulating pathogenesis-related and defence response genes. This approach shows potential for addressing bacterial diseases in potatoes, including soft bacterial rot.202440225297
609580.9984Isolation and characterization of plant growth promoting endophytic diazotrophic bacteria from Korean rice cultivars. We have isolated 576 endophytic bacteria from the leaves, stems, and roots of 10 rice cultivars and identified 12 of them as diazotrophic bacteria using a specific primer set of nif gene. Through 16S rDNA sequence analysis, nifH genes were confirmed in the two species of Penibacillus, three species of Microbacterium, three Bacillus species, and four species of Klebsiella. Rice seeds treated with these plant growth-promoting bacteria (PGPB) showed improved plant growth, increased height and dry weight and antagonistic effects against fungal pathogens. In addition, auxin and siderophore producing ability, and phosphate solubilizing activity were studied for the possible mechanisms of plant growth promotion. Among 12 isolates tested, 10 strains have shown higher auxin producing activity, 6 isolates were confirmed as strains with high siderophore producing activity while 4 isolates turned out to have high phosphate-solubilizing activity. These results strongly suggest that the endophytic diazotrophic bacteria characterized in this study could be successfully used to promote plant growth and inducing fungal resistance in plants.201423871145
2790.9984In silico comparison of transcript abundances during Arabidopsis thaliana and Glycine max resistance to Fusarium virguliforme. BACKGROUND: Sudden death syndrome (SDS) of soybean (Glycine max L. Merr.) is an economically important disease, caused by the semi-biotrophic fungus Fusarium solani f. sp. glycines, recently renamed Fusarium virguliforme (Fv). Due to the complexity and length of the soybean-Fusarium interaction, the molecular mechanisms underlying plant resistance and susceptibility to the pathogen are not fully understood. F. virguliforme has a very wide host range for the ability to cause root rot and a very narrow host range for the ability to cause a leaf scorch. Arabidopsis thaliana is a host for many types of phytopathogens including bacteria, fungi, viruses and nematodes. Deciphering the variations among transcript abundances (TAs) of functional orthologous genes of soybean and A. thaliana involved in the interaction will provide insights into plant resistance to F. viguliforme. RESULTS: In this study, we reported the analyses of microarrays measuring TA in whole plants after A. thaliana cv 'Columbia' was challenged with fungal pathogen F. virguliforme. Infection caused significant variations in TAs. The total number of increased transcripts was nearly four times more than that of decreased transcripts in abundance. A putative resistance pathway involved in responding to the pathogen infection in A. thaliana was identified and compared to that reported in soybean. CONCLUSION: Microarray experiments allow the interrogation of tens of thousands of transcripts simultaneously and thus, the identification of plant pathways is likely to be involved in plant resistance to Fusarial pathogens. Dissection of the set functional orthologous genes between soybean and A. thaliana enabled a broad view of the functional relationships and molecular interactions among plant genes involved in F. virguliforme resistance.200818831797
8458100.9984A PCR-based approach for isolating pathogen resistance genes from potato with potential for wide application in plants. Plant genes for pathogen resistance can be used to engineer disease resistant crops. Oligonucleotides were designed from sequence motifs conserved between resistance genes of tobacco and Arabidopsis thaliana and used as PCR primers in potato DNA. Amplification products were obtained that were homologous to known resistance genes and linked without recombination with the nematode resistance locus Gro1 and the Phytophthora infestans resistance locus R7 of potato. Map positions of PCR-derived potato gene fragments were also correlated with resistance loci of the related tomato and tobacco genomes. Our results indicate that plant resistance genes that are effective against nematodes, fungi, viruses and bacteria may be isolated based on common sequence motifs and PCR methodology.19968944022
327110.9984Natural variation in RPS2-mediated resistance among Arabidopsis accessions: correlation between gene expression profiles and phenotypic responses. Natural variation in gene expression (expression traits or e-traits) is increasingly used for the discovery of genes controlling traits. An important question is whether a particular e-trait is correlated with a phenotypic trait. Here, we examined the correlations between phenotypic traits and e-traits among 10 Arabidopsis thaliana accessions. We studied defense against Pseudomonas syringae pv tomato DC3000 (Pst), with a focus on resistance gene-mediated resistance triggered by the type III effector protein AvrRpt2. As phenotypic traits, we measured growth of the bacteria and extent of the hypersensitive response (HR) as measured by electrolyte leakage. Genetic variation among accessions affected growth of Pst both with (Pst avrRpt2) and without (Pst) the AvrRpt2 effector. Variation in HR was not correlated with variation in bacterial growth. We also collected gene expression profiles 6 h after mock and Pst avrRpt2 inoculation using a custom microarray. Clusters of genes whose expression levels are correlated with bacterial growth or electrolyte leakage were identified. Thus, we demonstrated that variation in gene expression profiles of Arabidopsis accessions collected at one time point under one experimental condition has the power to explain variation in phenotypic responses to pathogen attack.200718083910
8791120.9984Synergistic biocontrol of Bacillus subtilis and Pseudomonas fluorescens against early blight disease in tomato. Early blight of tomato caused by Alternaria solani results in significant crop losses. In this study, Bacillus subtilis J3 and Pseudomonas fluorescens J8 were co-cultured as a synthetic microbial community (BCA) for synergistic biocontrol of A. solani, and the inhibition mechanism was investigated. BCA presented an inhibition ration against A. solani at 94.91%, which lowered the disease incidence by 38.26-42.87%; reduced peroxidase, catalase, superoxide dismutase activity of tomatoes by 73.11-90.22%; and promoted the biomass by 66.91-489.21%. With BCA protection, the relative expression of tomato resistance genes (including gPAL2, SWRKY, PR-10, and CHI) in roots and leaves was 12.83-90.70% lower than without protection. BCA also significantly altered the rhizosphere and phyllosphere microbial community. The abundance of potentially beneficial bacteria, including Bacillus, Pseudomonas, Arthrobacter, Lysobacter, and Rhizobium, elevated by 6.58-192.77%. They were negatively correlated with resistance gene expression, indicating their vital involvement in disease control. These results provided essential information on the synergistic biocontrol mechanism of bacteria against pathogens, which could contribute to developing novel biocontrol strategies. KEY POINTS: • Bacillus and Pseudomonas present a synergistic biocontrol effect against A. solani. • Biocontrol prevents pathogen damage and improves tomato growth and systemic resistance. • Beneficial bacteria thrive in the rhizosphere is the key to microbial regulation.202337540249
8457130.9984Molecular profiling of bacterial blight resistance in Malaysian rice cultivars. Bacteria blight is one of the most serious bacterial diseases of rice worldwide. The identification of genetic potential against bacterial blight in the existing rice resources is a prerequisite to develop multigenic resistance to combat the threat of climate change. This investigation was conducted to evaluate alleles variation in 38 Malaysian cultivars using thirteen Simple Sequences Repeats markers and one Sequence Tagged Sites (STS) marker which were reported to be linked with the resistance to bacterial blight. Based on molecular data, a dendrogram was constructed which classified the rice cultivars into seven major clusters at 0.0, 0.28 and 0.3 of similarity coefficient. Cluster 5 was the largest group comprised of ten rice cultivars where multiple genes were identified. However, xa13 could not be detected in the current rice germplasm, whereas xa2 was detected in 25 cultivars. Molecular analysis revealed that Malaysian rice cultivars possess multigenic resistance.202236541981
8445140.9984A genome-wide association study in catfish reveals the presence of functional hubs of related genes within QTLs for columnaris disease resistance. BACKGROUND: Columnaris causes severe mortalities among many different wild and cultured freshwater fish species, but understanding of host resistance is lacking. Catfish, the primary aquaculture species in the United States, serves as a great model for the analysis of host resistance against columnaris disease. Channel catfish in general is highly resistant to the disease while blue catfish is highly susceptible. F2 generation of hybrids can be produced where phenotypes and genotypes are segregating, providing a useful system for QTL analysis. To identify genes associated with columnaris resistance, we performed a genome-wide association study (GWAS) using the catfish 250 K SNP array with 340 backcross progenies derived from crossing female channel catfish (Ictalurus punctatus) with male F1 hybrid catfish (female channel catfish I. punctatus × male blue catfish I. furcatus). RESULTS: A genomic region on linkage group 7 was found to be significantly associated with columnaris resistance. Within this region, five have known functions in immunity, including pik3r3b, cyld-like, adcyap1r1, adcyap1r1-like, and mast2. In addition, 3 additional suggestively associated QTL regions were identified on linkage groups 7, 12, and 14. The resistant genotypes on the QTLs of linkage groups 7 and 12 were found to be homozygous with both alleles being derived from channel catfish. The paralogs of the candidate genes in the suggestively associated QTL of linkage group 12 were found on the QTLs of linkage group 7. Many candidate genes on the four associated regions are involved in PI3K pathway that is known to be required by many bacteria for efficient entry into the host. CONCLUSION: The GWAS revealed four QTLs associated with columnaris resistance in catfish. Strikingly, the candidate genes may be arranged as functional hubs; the candidate genes within the associated QTLs on linkage groups 7 and 12 are not only co-localized, but also functionally related, with many of them being involved in the PI3K signal transduction pathway, suggesting its importance for columnaris resistance.201525888203
6172150.9984Resistance and susceptibility of mice to bacterial infection. IV. Genetic and cellular basis of resistance to chronic infection with Brucella abortus. The number of Brucella abortus strain 19 organisms in the spleens of CBA/H mice peaked two weeks after intravenous injection of 5 X 10(6) organisms. With the onset of specific cell-mediated immunity, 90% of the bacteria were killed, but approximately 10(6) bacteria persisted up to seven weeks after infection. In contrast, in BALB/c, C57BL/10, and B10Br mice, bacterial numbers peaked at two weeks but decreased steadily with the onset of bactericidal activity. In all strains, clearance of bacteria from the liver was relatively efficient. The course of infection in (CBA/H X BALB/c) F1 mice was similar to that in CBA/H mice, indicating that the mechanism(s) leading to slower recovery from infection was dominant. The H-2 haplotype of the mice did not influence the rate of recovery from infection. The use of backcross mice showed that multiple genes were involved. In bone marrow-chimeric mice, resistance was determined by the genome of the bone marrow donor, not that of the host.19826809847
6162160.9983The resistance of BALB/cJ mice to Yersinia pestis maps to the major histocompatibility complex of chromosome 17. Yersinia pestis, the causative agent of plague, has been well studied at the molecular and genetic levels, but little is known about the role that host genes play in combating this highly lethal pathogen. We challenged several inbred strains of mice with Y. pestis and found that BALB/cJ mice are highly resistant compared to susceptible strains such as C57BL/6J. This resistance was observed only in BALB/cJ mice and not in other BALB/c substrains. Compared to C57BL/6J mice, the BALB/cJ strain exhibited reduced bacterial burden in the spleen and liver early after infection as well as lower levels of serum interleukin-6. These differences were evident 24 h postinfection and became more pronounced with time. Although a significant influx of neutrophils in the spleen and liver was exhibited in both strains, occlusive fibrinous thrombi resulting in necrosis of the surrounding tissue was observed only in C57BL/6J mice. In an effort to identify the gene(s) responsible for resistance, we measured total splenic bacteria in 95 F(2) mice 48 h postinfection and performed quantitative trait locus mapping using 58 microsatellite markers spaced throughout the genome. This analysis revealed a single nonrecessive plague resistance locus, designated prl1 (plague resistance locus 1), which coincides with the major histocompatibility complex of chromosome 17. A second screen of 95 backcrossed mice verified that this locus confers resistance to Y. pestis early in infection. Finally, eighth generation backcrossed mice harboring prl1 were found to maintain resistance in the susceptible C57BL/6J background. These results identify a novel genetic locus in BALB/cJ mice that confers resistance to Y. pestis.200818573896
8787170.9983Improved resistance against Botrytis cinerea by grapevine-associated bacteria that induce a prime oxidative burst and phytoalexin production. Bacteria such as Pantoea agglomerans (Pa-AF2), Bacillus subtilis (Bs-271), Acinetobacter lwoffii (Al-113), and Pseudomonas fluorescens (Pf-CT2), originating from the vineyard, can induce defense responses and enhance resistance of grapevine against the fungal pathogen Botrytis cinerea. The perception of these bacteria by plant cells or tissues in relation to their activities remains unknown. In this study, we examined the relationships between the activity of each bacterium to induce or prime some defense responses, and its effectiveness to induce resistance in grapevine against B. cinerea. We showed that all selected bacteria are capable of inducing early oxidative burst and phytoalexin (trans-resveratrol and trans-ε-viniferin) production in grapevine cells and leaves. Pf-CT2 and Al-113 induced higher H(2)O(2) and trans-resveratrol accumulations, and were able to further prime plants for accelerated phytoalexin production after B. cinerea challenge. These two bacteria were also the most effective in inducing local and systemic resistance. A similar level of induced resistance was observed with live Pa-AF2 which also induced but not primed a greater accumulation of trans-resveratrol. However, Bs-271, which was less effective in inducing resistance, induced a lower trans-resveratrol synthesis, without priming activity. Treatment of grapevine cells with growing medium or crude extract of the bacteria quickly and strongly enhanced oxidative burst compared with the live bacteria. However, both treatments resulted in comparable amounts of phytoalexins and induced local and systemic resistance to B. cinerea as compared with those induced by living bacteria, with extracts from Pf-CT2 and Al-113 being the most effective. Together, these results indicate that induced resistance can be improved by treatment with bacteria or derived compounds which induced or primed plants for enhanced phytoalexin accumulation.201121425931
253180.9983The Rxo1/ Rba1 locus of maize controls resistance reactions to pathogenic and non-host bacteria. Infiltration of different maize lines with a variety of bacterial pathogens of maize, rice and sorghum identified qualitative differences in resistant reactions. Isolates from two bacterial species induced rapid hypersensitive reactions (HR) in some maize lines, but not others. All isolates of the non-host pathogen Xanthomonas oryzae pv. oryzicola (bacterial leaf streak disease of rice) and some isolates of the pathogenic bacterium Burkholderia andropogonis induced HR when infiltrated into maize line B73, but not Mo17. Genetic control of the HR to both bacteria segregated as a single dominant gene. Surprisingly, both phenotypes mapped to the same locus, indicating they are either tightly linked or controlled by the same gene. The locus maps on the short arm of maize chromosome six near several other disease-resistance genes. Results indicate the same type of genes may contribute to both non-host resistance and resistance to pathogens.200415114472
436190.9983The capsule is a virulence determinant in the pathogenesis of Pasteurella multocida M1404 (B:2). Capsules from a range of pathogenic bacteria are key virulence determinants, and the capsule has been implicated in virulence in Pasteurella multocida. We have previously identified and determined the nucleotide sequence of the P. multocida M1404 (B:2) capsule biosynthetic locus (J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121-134, 2000). The cap locus consists of 15 genes, which can be grouped into three functional regions. Regions 1 and 3 contain genes proposed to encode proteins involved in capsule export, and region 2 contains genes proposed to encode proteins involved in polysaccharide biosynthesis. In order to construct a mutant impaired in capsule export, the final gene of region 1, cexA, was disrupted by insertion of a tetracycline resistance cassette by allelic replacement. The genotype of the tet(M) OmegacexA mutant was confirmed by Southern hybridization and PCR. The acapsular phenotype was confirmed by immunofluorescence, and the strain could be complemented and returned to capsule production by the presence of a cloned uninterrupted copy of cexA. Wild-type, mutant, and complemented strains were tested for virulence by intraperitoneal challenge of mice; the presence of the capsule was shown to be a crucial virulence determinant. Following intraperitoneal challenge of mice, the acapsular bacteria were removed efficiently from the blood, spleen, and liver, while wild-type bacteria multiplied rapidly. Acapsular bacteria were readily taken up by murine peritoneal macrophages, but wild-type bacteria were significantly resistant to phagocytosis. Both wild-type and acapsular bacteria were resistant to complement in bovine and murine serum.200010816499