scholarly journals Application of computational methods in the analysis of pesticide target-site and resistance mechanisms

2021 ◽  
Vol 46 (3) ◽  
pp. 283-289
Author(s):  
Shinichi Banba
Keyword(s):  
Computational Methods ◽  
Resistance Mechanisms ◽  
Target Site

Functional Genomics Analysis of Horseweed (Conyza canadensis) with Special Reference to the Evolution of Non–Target-Site Glyphosate Resistance

Weed Science ◽  
2010 ◽  
Vol 58 (2) ◽  
pp. 109-117 ◽  
Author(s):  
Joshua S. Yuan ◽  
Laura L. G. Abercrombie ◽  
Yongwei Cao ◽  
Matthew D. Halfhill ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Functional Genomics ◽  
Molecular Mechanisms ◽  
Glyphosate Resistance ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Environmentally Benign ◽  
Conyza Canadensis ◽  
Target Site Resistance ◽  
Weedy Species ◽  
Heterologous Microarray

The evolution of glyphosate resistance in weedy species places an environmentally benign herbicide in peril. The first report of a dicot plant with evolved glyphosate resistance was horseweed, which occurred in 2001. Since then, several species have evolved glyphosate resistance and genomic information about nontarget resistance mechanisms in any of them ranges from none to little. Here, we report a study combining iGentifier transcriptome analysis, cDNA sequencing, and a heterologous microarray analysis to explore potential molecular and transcriptomic mechanisms of nontarget glyphosate resistance of horseweed. The results indicate that similar molecular mechanisms might exist for nontarget herbicide resistance across multiple resistant plants from different locations, even though resistance among these resistant plants likely evolved independently and available evidence suggests resistance has evolved at least four separate times. In addition, both the microarray and sequence analyses identified non–target-site resistance candidate genes for follow-on functional genomics analysis.

Target and Non–target site Mechanisms Confer Resistance to Glyphosate in Canadian Accessions ofConyza canadensis

Weed Science ◽  
2017 ◽  
Vol 66 (2) ◽  
pp. 234-245 ◽  
Author(s):  
Eric R. Page ◽  
Christopher M. Grainger ◽  
Martin Laforest ◽  
Robert E. Nurse ◽  
Istvan Rajcan ◽  
...  
Keyword(s):  
Ssr Markers ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Conyza Canadensis ◽  
Weed Species ◽  
Target Site Resistance ◽  
Selection For ◽  
Simple Sequence ◽  
Growing Region ◽  
Selection Of

Glyphosate-resistant populations ofConyza canadensishave been spreading at a rapid rate in Ontario, Canada, since first being documented in 2010. Determining the genetic relationship among existing Ontario populations is necessary to understand the spread and selection of the resistant biotypes. The objectives of this study were to: (1) characterize the genetic variation ofC. canadensisaccessions from the province of Ontario using simple sequence repeat (SSR) markers and (2) investigate the molecular mechanism (s) conferring resistance in these accessions. Ninety-eightC. canadensisaccessions were genotyped using 8 SSR markers. Germinable accessions were challenged with glyphosate to determine their dose response, and the sequences of 5-enolpyruvylshikimate-3-phosphate synthase genes 1 and 2 were obtained. Results indicate that a majority of glyphosate-resistant accessions from Ontario possessed a proline to serine substitution at position 106, which has previously been reported to confer glyphosate resistance in other crop and weed species. Accessions possessing this substitution demonstrated notably higher levels of resistance than non–target site resistant (NTSR) accessions from within or outside the growing region and were observed to form a subpopulation genetically distinct from geographically proximate glyphosate-susceptible and NTSR accessions. Although it is unclear whether other non–target site resistance mechanisms are contributing to the levels of resistance observed in target-site resistant accessions, these results indicate that, at a minimum, selection for Pro-106-Ser has occurred in addition to selection for non–target site resistance and has significantly enhanced the levels of resistance to glyphosate inC. canadensisaccessions from Ontario.

scholarly journals Some approaches to new antibacterial agents

2007 ◽  
Vol 79 (12) ◽  
pp. 2143-2153 ◽  
Author(s):  
John B. Bremner
Keyword(s):  
Bacterial Resistance ◽  
Efflux Pump ◽  
Transmembrane Protein ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Resistant Bacteria ◽  
General Strategy ◽  
Dual Action ◽  
Hybrid Drugs

Bacteria use a number of resistance mechanisms to counter the antibacterial challenge, and one of these is the expression of transmembrane protein-based efflux pumps which can pump out antibacterials from within the cells, thus lowering the antibacterial concentration to nonlethal levels. For example, in S. aureus, the NorA pump can pump out the antibacterial alkaloid berberine and ciprofloxacin. One general strategy to reduce the health threat of resistant bacteria is to block a major bacterial resistance mechanism at the same time as interfering with another bacterial pathway or target site. New developments of this approach in the context of dual-action prodrugs and dual-action (or hybrid) drugs in which one action is targeted at blocking the NorA efflux pump and the second action at an alternative bacterial target site (or sites) for the antibacterial action are discussed. The compounds are based on a combination of 2-aryl-5-nitro-1H-indole derivatives (as the NorA efflux pump blocking component) and derivatives of berberine. General design principles, syntheses, antibacterial testing, and preliminary work on modes of action studies are discussed.

scholarly journals Widespread occurrence of both metabolic and target-site herbicide resistance mechanisms inLolium rigidumpopulations

2015 ◽  
Vol 72 (2) ◽  
pp. 255-263 ◽  
Author(s):  
Heping Han ◽  
Qin Yu ◽  
Mechelle J Owen ◽  
Gregory R Cawthray ◽  
Stephen B Powles
Keyword(s):  
Herbicide Resistance ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Widespread Occurrence

Quinolone-resistant uropathogenic E. coli: is there a relation between qnr genes, gyrA gene target site mutation and biofilm formation?

2021 ◽  
Vol 70 (10) ◽  
Author(s):  
Amira M. Sultan ◽  
Ghada F. Amer ◽  
Yasmin Nabiel
Keyword(s):  
Gene Mutation ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Quinolone Resistance ◽  
Urine Samples ◽  
Gyra Gene ◽  
Gene Target ◽  
Transfer Resistance ◽  
Biofilm Production ◽  
Tract Infections

Introduction. The resistance to quinolone reported in uropathogenic Escherichia coli (UPEC) is commonly caused by mutations in the target site encoding genes such as the gyrA gene. Bacterial plasmids carrying resistance genes such as qnr genes can also transfer resistance. Biofilms produced by UPEC can further aid the development of resistant urinary tract infections (UTIs). Hypothesis. Biofilm production is associated with higher prevalence of quinolones resistance genetic determinants. Aim. To detect the prevalence of qnr genes and gyrA gene mutation among quinolone-resistant UPEC and to investigate the relation between these genetic resistance determinants and biofilm production. Methodology. Catheterized urine samples were collected from 420 patients with evidence of UTIs and processed using standard techniques. Isolated UPEC were screened for quinolone resistance using an antimicrobial susceptibility test. Biofilm production among quinolone-resistant isolates was detected using the tissue culture plate method. All quinolone-resistant isolates were screened for qnr genes (qnrA, qnrB and qnrS) by multiplex PCR and for gyrA gene mutation by PCR-RFLP. Results. Two hundred and sixty-four UPEC isolates were detected from 420 processed urine samples. Out of the identified 264 UPEC, 123 (46.6 %) isolates were found to be quinolone-resistant, showing resistance to 1 or more of the tested quinolones. Of the 123 quinolone-resistant UPEC detected, 71(57.7 %) were biofilm producers. The qnr genes were detected among 62.6 % of the quinolone-resistant UPEC, with an estimated prevalence of 22.8, 32.5 and 37.4 % for qnrA, qnrB and qnrS genes, respectively. Additionally, the gyrA gene mutation was identified among 53.7 % of the quinolone-resistant isolates. We reported a significant association between biofilm production and the presence of qnrA, qnrB and qnrS genes. Furthermore, the gyrA gene mutation was significantly associated with biofilm-producing isolates. The coexistence of qnr genes, gyrA gene mutation and biofilm production was demonstrated in almost 40 % of the quinolone-resistant isolates. Conclusions. A significantly higher prevalence of qnr genes (qnrA, qnrB and qnrS) as well as the gyrA gene mutation was found among biofilm-forming UPEC. The reported coexistence of these different resistance mechanisms could aggravate quinolone resistance. Therefore, monitoring of resistance mechanisms and a proper stewardship programme are necessary.

scholarly journals Target-Site Resistances to ALS and PPO Inhibitors Are Linked in Waterhemp (Amaranthus tuberculatus)

Weed Science ◽  
2016 ◽  
Vol 65 (1) ◽  
pp. 4-8 ◽  
Author(s):  
Patrick J. Tranel ◽  
Chenxi Wu ◽  
Ahmed Sadeque
Keyword(s):  
Resistance Mechanism ◽  
Acetolactate Synthase ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Recurrent Parent ◽  
Common Waterhemp ◽  
Independent Assortment ◽  
Resistance Evolution ◽  
Amaranthus Tuberculatus ◽  
Molecular Marker Analysis

It is generally expected that, in the case of multiple herbicide resistance, different resistance mechanisms within a weed will follow Mendel’s law of independent assortment. Research was conducted to investigate anecdotal observations suggesting that target site–based resistances to inhibitors of acetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO) did not follow independent assortment in common waterhemp. Cosegregation of the two resistances was observed in backcross lines (population sensitive to both herbicides as recurrent parent). Specifically, whereas 52% of backcross plants were resistant to a PPO inhibitor, this percentage increased to 92% when the backcross plants were preselected for resistance to an ALS inhibitor. Molecular marker analysis confirmed that the corresponding genes (ALSandPPX2) were genetically linked. When data from all plants analyzed were pooled, the genetic distance between the two genes was calculated to be 7.5 cM. The two genes were found to be about 195 kb apart in the recently published grain amaranth genome, explaining the observed genetic linkage. There is likely enough recombination that occurs between the linked genes to prevent the linkage from having significant implications in terms of resistance evolution. Nevertheless, documentation of the happenstance linkage between target-site genes for resistance to ALS and PPO inhibitors in waterhemp is a reminder that one should not assume distinct resistance mechanism will independently assort.

Aerobic Metabolism Alterations as an Evidence of Underlying Deltamethrin Resistance Mechanisms in Triatoma infestans (Hemiptera: Reduviidae)

2020 ◽  
Vol 57 (6) ◽  
pp. 1988-1991
Author(s):  
Carmen Rolandi ◽  
Gonzalo Roca-Acevedo ◽  
Pablo E Schilman ◽  
Mónica D Germano
Keyword(s):  
Resistance Mechanism ◽  
Resistance Management ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Triatoma Infestans ◽  
Co2 Production ◽  
Mechanisms Of Resistance ◽  
Metabolic Resistance ◽  
Open Flow ◽  
Deltamethrin Resistance

Abstract Triatoma infestans (Klug, 1834), the main vector of Chagas disease in Latin America, is regularly controlled by spraying the pyrethroid deltamethrin, to which some populations have developed resistance. The three main mechanisms of resistance are 1) metabolic resistance by overexpression or increased activity of detoxifying enzymes, 2) target site mutations, and 3) cuticle thickening/modification. We use open-flow respirometry to measure real-time H2O loss rate (V˙H2O) and CO2 production rate (V˙CO2), on nymphs from susceptible and resistant populations before and after exposure to the insecticide to understand the underlying mechanisms of resistance in live insects. Lack of differences in V˙H2O between populations suggested that cuticular thickness/composition is not acting as a relevant resistance mechanism. Similarly, there was no difference in resting V˙CO2, suggesting a trade-off between resistance mechanisms and other physiological processes. The increment in V˙CO2 after application of deltamethrin was similar in both populations, which suggested that while enhanced enzymatic detoxification may play a role in resistance expression in this population, the main mechanism involved should be a passive one such as target site mutations. Open-flow respirometry provided useful evidence for evaluating the mechanisms involved in deltamethrin resistance. Using this technique could improve efficiency of scientific research in the area of insecticide resistance management, leading to a faster decision making and hence improved control results.

A Decade of Glyphosate-ResistantLoliumaround the World: Mechanisms, Genes, Fitness, and Agronomic Management

Weed Science ◽  
2009 ◽  
Vol 57 (4) ◽  
pp. 435-441 ◽  
Author(s):  
Christopher Preston ◽  
Angela M. Wakelin ◽  
Fleur C. Dolman ◽  
Yazid Bostamam ◽  
Peter Boutsalis
Keyword(s):  
Weed Management ◽  
Single Gene ◽  
Glyphosate Resistance ◽  
Resistance Mechanisms ◽  
Target Site ◽  
Italian Ryegrass ◽  
Shoot Meristem ◽  
Agronomic Management ◽  
Translocation Mechanism ◽  
Rigid Ryegrass

Glyphosate resistance was first discovered in populations of rigid ryegrass in Australia in 1996. Since then, glyphosate resistance has been detected in additional populations of rigid ryegrass and Italian ryegrass in several other countries. Glyphosate-resistant rigid ryegrass and Italian ryegrass have been selected in situations where there is an overreliance on glyphosate to the exclusion of other weed control tactics. Two major mechanisms of glyphosate resistance have been discovered in these two species: a change in the pattern of glyphosate translocation such that glyphosate accumulates in the leaf tips of resistant plants instead of in the shoot meristem; and amino acid substitutions at Pro 106 within the target site, 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). There are also populations with both mechanisms. In the case of glyphosate resistance, the target site mutations tend to provide a lower level of resistance than does the altered translocation mechanism. Each of these resistance mechanisms is inherited as a single gene trait that is largely dominant. As these ryegrass species are obligate outcrossers, this ensures resistance alleles can move in both pollen and seed. Some glyphosate-resistant rigid ryegrass populations appear to have a significant fitness penalty associated with the resistance allele. Field surveys show that strategies vary in their ability to reduce the frequency of glyphosate resistance in populations and weed population size, with integrated strategies—including alternative weed management and controlling seed set of surviving plants—the most effective.

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