Resistance mechanisms in Lycopersicon spp. to tomato powdery mildew (Oidium neolycopersici)

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S141-S144 ◽  
Author(s):  
A. Lebeda ◽  
B. Mieslerová ◽  
L. Luhová ◽  
K. Mlíčková
Keyword(s):  
Germ Tube ◽  
Leaf Surface ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Host Tissue ◽  
Tissue Response ◽  
Limited Information ◽  
Oidium Neolycopersici ◽  
Conidium Germination ◽  
Tomato Powdery Mildew

Limited information on the resistance mechanisms in Lycopersicon spp. to Oidium neolycopersici is still available. Macroscopically the resistance is characterized by a very low amount of mycelium development and a lack of sporulation. The leaf surface did not effectively inhibite conidium germination, however significant differences in germ tube and appressorium development were recorded. A large variation was observed in host tissue response. The prevailing resistance mechanism was hypersensitivity (HR). Considerable changes of peroxidase and catalase activities during pathogenesis were detected among tested wild Lycopersicon spp. There was positive correlation between increasing of peroxidase activity and extent of necrosis. Histochemistry showed large differences in production of superoxid ions, H<sub>2</sub>O<sub>2</sub> and peroxidase in Lycopersicon spp. with various level of resistance.

scholarly journals Antimicrobial Susceptibility and Clonality of Clinical Ureaplasma Isolates in the United States

2016 ◽  
Vol 60 (8) ◽  
pp. 4793-4798 ◽  
Author(s):  
Javier Fernández ◽  
Melissa J. Karau ◽  
Scott A. Cunningham ◽  
Kerryl E. Greenwood-Quaintance ◽  
Robin Patel
Keyword(s):  
United States ◽  
Antimicrobial Susceptibility ◽  
Antimicrobial Agents ◽  
Ureaplasma Urealyticum ◽  
Resistance Mechanism ◽  
The United States ◽  
Resistance Mechanisms ◽  
Resistant Isolate ◽  
Limited Information ◽  
Content Type

ABSTRACTUreaplasma urealyticumandUreaplasma parvumare pathogens involved in urogenital tract and intrauterine infections and also in systemic diseases in newborns and immunosuppressed patients. There is limited information on the antimicrobial susceptibility and clonality of these species. In this study, we report the susceptibility of 250 contemporary isolates ofUreaplasma(202U. parvumand 48U. urealyticumisolates) recovered at Mayo Clinic, Rochester, MN. MICs of doxycycline, azithromycin, ciprofloxacin, tetracycline, erythromycin, and levofloxacin were determined by broth microdilution, with MICS of the last three interpreted according to CLSI guidelines. Levofloxacin resistance was found in 6.4% and 5.2% ofU. parvumandU. urealyticumisolates, respectively, while 27.2% and 68.8% of isolates, respectively, showed ciprofloxacin MICs of ≥4 μg/ml. The resistance mechanism of levofloxacin-resistant isolates was due to mutations inparC, with the Ser83Leu substitution being most frequent, followed by Glu87Lys. No macrolide resistance was found among the 250 isolates studied; a singleU. parvumisolate was tetracycline resistant.tet(M) was found in 10U. parvumisolates, including the single tetracycline-resistant isolate, as well as in 9 isolates which had low tetracycline and doxycycline MICs. Multilocus sequence typing (MLST) performed on a selection of 46 isolates showed high diversity within the clinicalUreaplasmaisolates studied, regardless of antimicrobial susceptibility. The present work extends previous knowledge regarding susceptibility to antimicrobial agents, resistance mechanisms, and clonality ofUreaplasmaspecies in the United States.

scholarly journals Tomato Defense to Oldium neolycopersici: Dominant OI Genes Confer Isolate-Dependent Resistance Via a Different Mechanism Than Recessive oI-2

2005 ◽  
Vol 18 (4) ◽  
pp. 354-362 ◽  
Author(s):  
Yuling Bai ◽  
Ron van der Hulst ◽  
Guusje Bonnema ◽  
Thierry C. Marcel ◽  
Fien Meijer-Dekens ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Resistance Genes ◽  
Resistance Mechanism ◽  
Recessive Gene ◽  
Defense Responses ◽  
Oidium Neolycopersici ◽  
Mechanism Of Resistance ◽  
Tomato Chromosome ◽  
Tomato Powdery Mildew ◽  
Important Disease

Tomato powdery mildew caused by Oidium neolycopersici has become a globally important disease of tomato (Lycopersicon esculentum). To study the defense responses of tomato triggered by tomato powdery mildew, we first mapped a set of resistance genes to O. neolycopersici from related Lycopersicon species. An integrated genetic map was generated showing that all the dominant resistance genes (Ol-1, Ol-3, Ol-4, Ol-5, and Ol-6) are located on tomato chromosome 6 and are organized in three genetic loci. Then, near-isogenic lines (NIL) were produced that contain the different dominant Ol genes in a L. esculentum genetic background. These NIL were used in disease tests with local isolates of O. neolycopersici in different geographic locations, demonstrating that the resistance conferred by different Ol genes was isolate-dependent and, hence, may be race-specific. In addition, the resistance mechanism was analyzed histologically. The mechanism of resistance conferred by the dominant Ol genes was associated with hypersensitive respo-nse, which varies in details depending on the Ol-gene in the NIL, while the mechanism of resistance governed by the recessive gene ol-2 on tomato chromosome 4 was associated with papillae formation.

scholarly journals Characterization of resistance mechanisms of Enterobacter cloacae Complex co-resistant to carbapenem and colistin

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Shixing Liu ◽  
Renchi Fang ◽  
Ying Zhang ◽  
Lijiang Chen ◽  
Na Huang ◽  
...  
Keyword(s):  
Lipid A ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Carbapenem Resistance ◽  
Enterobacter Cloacae ◽  
Resistance Mechanisms ◽  
Colistin Resistance ◽  
Carbapenem Resistant ◽  
Horizontal Spread

Abstract Background The emergence of carbapenem-resistant and colistin-resistant ECC pose a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in Enterobacter cloacae Complex (ECC) strains. Results This study showed that the mechanisms of carbapenem resistance in this study are: 1. Generating carbapenemase (7 of 19); 2. The production of AmpC or ESBLs combined with decreased expression of out membrane protein (12 of 19). hsp60 sequence analysis suggested 10 of 19 the strains belong to colistin hetero-resistant clusters and the mechanism of colistin resistance is increasing expression of acrA in the efflux pump AcrAB-TolC alone (18 of 19) or accompanied by a decrease of affinity between colistin and outer membrane caused by the modification of lipid A (14 of 19). Moreover, an ECC strain co-harboring plasmid-mediated mcr-4.3 and blaNDM-1 has been found. Conclusions This study suggested that there is no overlap between the resistance mechanism of co-resistant ECC strains to carbapenem and colistin. However, the emergence of strain co-harboring plasmid-mediated resistance genes indicated that ECC is a potential carrier for the horizontal spread of carbapenems and colistin resistance.

scholarly journals Formation of Conidial Pseudochains by Tomato Powdery Mildew Oidium neolycopersici

Plant Disease ◽  
2006 ◽  
Vol 90 (7) ◽  
pp. 915-919 ◽  
Author(s):  
W. Oichi ◽  
Y. Matsuda ◽  
T. Nonomura ◽  
H. Toyoda ◽  
L. Xu ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Powdery Mildew ◽  
Critical Level ◽  
Oidium Neolycopersici ◽  
Ambient Relative Humidity ◽  
Digital Microscope ◽  
Tomato Powdery Mildew ◽  
A Chain ◽  
Weak Wind ◽  
Generative Cells

The formation of conidial pseudochains by the tomato powdery mildew Oidium neolycopersici on tomato leaves was monitored using a high-fidelity digital microscope. Individual living conidiophores that formed mature conidial cells at their apex were selected for observation. The conidial cells were produced during repeated division and elongation by the generative cells of the conidiophores. Under weak wind conditions (0.1 m/s), these conidial cells did not separate from each other to produce a chain of conidial cells (pseudochain). The pseudochains dropped from the conidiophores once four conidial cells were connected. The conidiophores resumed conidium production, followed by another cycle of pseudochain formation. The formation of pseudochains by tomato powdery mildew was not influenced by the ambient relative humidity. On the other hand, the conidial cells produced were easily wind dispersed without forming pseudochains when conidiophores were exposed to stronger winds (1.0 m/s). The present study successfully demonstrated that the pathogen required wind to disperse progeny conidia from the conidiophores and produced conidial pseudochains when the wind was below a critical level, independent of high relative humidity as reported previously.

scholarly journals Black Queen Evolution and Trophic Interactions Determine Plasmid Survival after the Disruption of the Conjugation Network

mSystems ◽  
2018 ◽  
Vol 3 (5) ◽  
Author(s):  
Johannes Cairns ◽  
Katariina Koskinen ◽  
Reetta Penttinen ◽  
Tommi Patinen ◽  
Anna Hartikainen ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Bacterial Communities ◽  
Resistance Mechanism ◽  
Real Life ◽  
Ecological Factors ◽  
Mobile Genetic Elements ◽  
Resistance Mechanisms ◽  
Antibiotics Resistance ◽  
Bacterial Populations ◽  
Genetic Elements

ABSTRACTMobile genetic elements such as conjugative plasmids are responsible for antibiotic resistance phenotypes in many bacterial pathogens. The ability to conjugate, the presence of antibiotics, and ecological interactions all have a notable role in the persistence of plasmids in bacterial populations. Here, we set out to investigate the contribution of these factors when the conjugation network was disturbed by a plasmid-dependent bacteriophage. Phage alone effectively caused the population to lose plasmids, thus rendering them susceptible to antibiotics. Leakiness of the antibiotic resistance mechanism allowing Black Queen evolution (i.e. a “race to the bottom”) was a more significant factor than the antibiotic concentration (lethal vs sublethal) in determining plasmid prevalence. Interestingly, plasmid loss was also prevented by protozoan predation. These results show that outcomes of attempts to resensitize bacterial communities by disrupting the conjugation network are highly dependent on ecological factors and resistance mechanisms.IMPORTANCEBacterial antibiotic resistance is often a part of mobile genetic elements that move from one bacterium to another. By interfering with the horizontal movement and the maintenance of these elements, it is possible to remove the resistance from the population. Here, we show that a so-called plasmid-dependent bacteriophage causes the initially resistant bacterial population to become susceptible to antibiotics. However, this effect is efficiently countered when the system also contains a predator that feeds on bacteria. Moreover, when the environment contains antibiotics, the survival of resistance is dependent on the resistance mechanism. When bacteria can help their contemporaries to degrade antibiotics, resistance is maintained by only a fraction of the community. On the other hand, when bacteria cannot help others, then all bacteria remain resistant. The concentration of the antibiotic played a less notable role than the antibiotic used. This report shows that the survival of antibiotic resistance in bacterial communities represents a complex process where many factors present in real-life systems define whether or not resistance is actually lost.

scholarly journals Playing the Whack-A-Mole Game: ERK5 Activation Emerges Among the Resistance Mechanisms to RAF-MEK1/2-ERK1/2- Targeted Therapy

2021 ◽  
Vol 9 ◽  
Author(s):  
Alessandro Tubita ◽  
Ignazia Tusa ◽  
Elisabetta Rovida
Keyword(s):  
Tyrosine Kinases ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Mitogen Activated Protein Kinase ◽  
Cancer Therapies ◽  
New Era ◽  
Mitogen Activated Protein ◽  
The Impact ◽  
The Ideal

Molecularly tailored therapies have opened a new era, chronic myeloid leukemia being the ideal example, in the treatment of cancer. However, available therapeutic options are still unsatisfactory in many types of cancer, and often fail due to the occurrence of resistance mechanisms. With regard to small-molecule compounds targeting the components of the Mitogen-Activated Protein Kinase (MAPK) cascade RAF-MEK1/2-ERK1/2, these drugs may result ineffective as a consequence of the activation of compensatory pro-survival/proliferative signals, including receptor tyrosine kinases, PI3K, as well as other components of the MAPK family such as TPL2/COT. The MAPK ERK5 has been identified as a key signaling molecule in the biology of several types of cancer. In this review, we report pieces of evidence regarding the activation of the MEK5-ERK5 pathway as a resistance mechanism to RAF-MEK1/2-ERK1/2 inhibitors. We also highlight the known and possible mechanisms underlying the cross-talks between the ERK1/2 and the ERK5 pathways, the characterization of which is of great importance to maximize, in the future, the impact of RAF-MEK1/2-ERK1/2 targeting. Finally, we emphasize the need of developing additional therapeutically relevant MEK5-ERK5 inhibitors to be used for combined treatments, thus preventing the onset of resistance to cancer therapies relying on RAF-MEK1/2-ERK1/2 inhibitors.

scholarly journals IDENTIFICATION OF THE kdr MUTATIONS IN VGSC GENE OF THE DENGUE MOSQUITOES AEDES ALBOPICTUS COLLECTED FROM HANOI AND HAIPHONG

2018 ◽  
Vol 16 (2) ◽  
pp. 273-278
Author(s):  
Nguyen Thi Kim Lien ◽  
Nguyen Thu Hien ◽  
Nguyen Huy Hoang ◽  
Nguyen Thi Hong Ngoc ◽  
Nguyen Thi Huong Binh
Keyword(s):  
Sodium Channel ◽  
Aedes Albopictus ◽  
Novel Mutation ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Resistance Mutations ◽  
Well Control ◽  
Voltage Gated ◽  
Activity Of Enzymes ◽  
Dengue Epidemic

Vietnam is one of the countries that is affected by dengue fever in Southeast Asia. The dengue epidemic is becoming increasingly more complex so it is necessary to have a well control to vectors in order to limit the spread of the disease. The Aedes albopictus mosquito is determined as one of the two major vectors that transmitted the dengue. Recent research shows that A. albopictus is present in some parts of Hanoi and Haiphong. In order to control the vector as well as the disease, it is necessary to understand the level of resistance and the resistance mechanism of the vector. Two important resistance mechanisms of insect were known as the mutations in the target protein of the insecticides and enhancing the activity of enzymes that participate in the resolution of the insecticides. In this study, the mosquito samples were collected from Hanoi and Haiphong to identify the level of resistance and detect the knock down resistance mutations in voltage gated sodium channel (VGSC) in membrane of nervecell of mosquito. The results of insecticide susceptibility test showed that A. albopictus in Hanoi and Haiphong were still sensitive to organophosphate but resistant to DDT, carbamate and pyrethroid. Ser989Pro, Ile1011Met, Val1016Gly and Phe1534Cys mutations were not deteced in A. albopictus in Hanoi and Haiphong. However, we detected a novel mutation Tyr986His in VGSC protein.

Distribution and validation of genotypic and phenotypic glyphosate and PPO-nhibitor resistance in Palmer amaranth (Amaranthus palmeri) from southwestern Nebraska

2020 ◽  
pp. 1-12 ◽  
Author(s):  
Maxwel C Oliveira ◽  
Darci A Giacomini ◽  
Nikola Arsenijevic ◽  
Gustavo Vieira ◽  
Patrick J Tranel ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Gene Amplification ◽  
Cropping Systems ◽  
Resistance Mechanism ◽  
Geographic Area ◽  
Glyphosate Resistance ◽  
Resistance Mechanisms ◽  
Palmer Amaranth ◽  
Resistance Evolution ◽  
Inhibitor Resistance

Abstract Failure to control Palmer amaranth with glyphosate and protoporphyrinogen IX oxidase (PPO)-inhibitor herbicides was reported across southwestern Nebraska in 2017. The objectives of this study were to 1) confirm and 2) validate glyphosate and PPO-inhibitor (fomesafen and lactofen) resistance in 51 Palmer amaranth accessions from southwestern Nebraska using genotypic and whole-plant phenotypic assay correlations and cluster analysis, and 3) determine which agronomic practices might be influencing glyphosate resistance in Palmer amaranth accessions in that location. Based on genotypic assay, 88% of 51 accessions contained at least one individual with amplification (>2 copies) of the 5-enolypyruvyl-shikimate-3-phosphate synthase (EPSPS) gene, which confers glyphosate resistance; and/or a mutation in the PPX2 gene, either ΔG210 or R128G, which endows PPO-inhibitor resistance in Palmer amaranth. Cluster analysis and high correlation (0.83) between genotypic and phenotypic assays demonstrated that EPSPS gene amplification is the main glyphosate resistance mechanism in Palmer amaranth accessions from southwestern Nebraska. In contrast, there was poor association between genotypic and phenotypic responses for PPO-inhibitor resistance, which was attributed to segregation for PPO-inhibitor resistance within these accessions and/or the methodology that was adopted herein. Genotypic assays can expedite the process of confirming known glyphosate and PPO-inhibitor resistance mechanisms in Palmer amaranth from southwestern Nebraska and other locations. Phenotypic assays are also a robust method for confirming glyphosate resistance but not necessarily PPO-inhibitor resistance in Palmer amaranth. Moreover, random forest analysis of glyphosate resistance in Palmer amaranth indicated that EPSPS gene amplification, county, and current and previous crops are the main factors influencing glyphosate resistance within that geographic area. Most glyphosate-susceptible Palmer amaranth accessions were found in a few counties in areas with high crop diversity. Results presented here confirm the spread of glyphosate resistance and PPO-inhibitor resistance in Palmer amaranth accessions from southwestern Nebraska and demonstrate that less diverse cropping systems are an important driver of herbicide resistance evolution in Palmer amaranth.

scholarly journals Persistent Bacteremia fromPseudomonas aeruginosawithIn VitroResistance to the Novel Antibiotics Ceftolozane-Tazobactam and Ceftazidime-Avibactam

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Louie Mar Gangcuangco ◽  
Patricia Clark ◽  
Cynthia Stewart ◽  
Goran Miljkovic ◽  
Zane K. Saul
Keyword(s):  
Susceptibility Testing ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Blood Cultures ◽  
The Novel ◽  
First Case ◽  
Persistent Bacteremia ◽  
Novel Antibiotics

Ceftazidime-avibactam and ceftolozane-tazobactam are new antimicrobials with activity against multidrug-resistantPseudomonas aeruginosa. We present the first case of persistentP.aeruginosabacteremia within vitroresistance to these novel antimicrobials. A 68-year-old man with newly diagnosed follicular lymphoma was admitted to the medical intensive care unit for sepsis and right lower extremity cellulitis. The patient was placed empirically on vancomycin and piperacillin-tazobactam. Blood cultures from Day 1 of hospitalization grewP.aeruginosasusceptible to piperacillin-tazobactam and cefepime identified using VITEK 2 (Biomerieux, Lenexa, KS). Repeat blood cultures from Day 5 grewP.aeruginosaresistant to all cephalosporins, as well as to meropenem by Day 10. Susceptibility testing performed by measuring minimum inhibitory concentration byE-test (Biomerieux, Lenexa, KS) revealed that blood cultures from Day 10 were resistant to ceftazidime-avibactam and ceftolozane-tazobactam. The Verigene Blood Culture-Gram-Negative (BC-GN) microarray-based assay (Nanosphere, Inc., Northbrook, IL) was used to investigate underlying resistance mechanism in theP.aeruginosaisolate but CTX-M, KPC, NDM, VIM, IMP, and OXA gene were not detected. This case report highlights the well-documented phenomenon of antimicrobial resistance development inP.aeruginosaeven during the course of appropriate antibiotic therapy. In the era of increasing multidrug-resistant organisms, routine susceptibility testing ofP. aeruginosato ceftazidime-avibactam and ceftolozane-tazobactam is warranted. Emerging resistance mechanisms to these novel antibiotics need to be further investigated.

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