F331Y was found in one clone of SAMB and GSS reference strains. It could play a role in carbaryl sensivity. The position is 439 in the protein corresponding to 331 in Torpedo
Kinetic parameters
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References:
Title: Geographical distribution and origin of acetylcholinesterase mutations conferring acaricide resistance in Tetranychus urticae populations from Turkey Inak E Ref: Exp Appl Acarol, :, 2021 : PubMed
Two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a cosmopolitan pest species that can feed on more than 1000 host plant species. Historically, organophosphate (OP) and carbamate insecticides have been used to control this extremely polyphagous pest. However, its ability to develop acaricide resistance rapidly has led to failure in control. Mutations in acetylcholinesterase gene (ace), the target-site of OP and carbamate insecticides, have been reported to be one of the major mechanisms underlying this developing resistance. In this study, mutations previously associated with resistance (G119S, A201S, T280A, G328A, F331W/Y) in ace have been screened in 37 T. urticae populations collected across Turkey. All mutations were found in various populations, except G119S. Almost all populations had F331W/Y mutation (being fixed in 32 populations), whereas only two populations harboured A201S mutation, but not fixed. On the other hand, more than half of the populations contained T280A and G328A mutations. In addition, the presence of same haplotypes in populations originating from distinct geographic locations and a wide variety of ace haplotypes might indicate multiple origins of F331W and F331Y mutations; however, this needs further investigation. The results of area-wide screening showed that ace mutations are widely distributed among T. urticae populations. Therefore, the use of this group of insecticides should be limited or only rotational use might be regarded as a resistance management tool due to its different mode of action from other main acaricide groups in T. urticae control across Turkey.
BACKGROUND: Tetranychus urticae is a notorious crop pest with world-wide distribution that has developed resistance to a wide range of acaricides. Here, we investigated the resistance levels of a T. urticae population collected from an ornamental greenhouse in Peloponnese, Greece, and analyzed its resistance mechanisms at the molecular level. RESULTS: Toxicological assays showed resistance levels against compounds with different mode of action, with resistance ratios scaling at: 89-fold for abamectin, >1000-fold for clofentezine, >5000-fold etoxazole, 27-fold for fenpyroximate and pyridaben, 20- and 36-fold for spirodiclofen and spirotetramat, respectively and 116- and >500-fold for cyenopyrafen and cyflumetofen, respectively. Bioassays with synergists indicated the involvement of detoxification enzymes in resistance to abamectin but not to cyflumetofen and spirodiclofen. RNAseq analysis showed significant over-expression of several genes encoding detoxification enzymes such as cytochrome P450 monooxygenases and UDP-glycosyltransferases, which have been previously associated with acaricide resistance. Known target-site resistance mutations were identified in acetyl-choline esterase, chitin synthase 1 and NDUFS7/psst, but also discovered putative novel resistance mutations in targets such as the glutamate-gated chloride channel subunit 3. Interestingly, target site resistance mutations against pyrethroids or bifenazate were not identified possibly indicating a recent reduced selection pressure in Greece, as well as a possible opportunity to rotate these chemistries. CONCLUSION: We identified and characterized a striking case of multiple acaricide resistance in a field population of T. urticae. Exceptionally strong resistance phenotypes, with accumulation of multiple resistance mutations and over-expression of P450s and other detoxification genes in the same field population is reported. This article is protected by copyright. All rights reserved.
BACKGROUND: In Tetranychus urticae Koch, acetylcholinesterase insensitivity is often involved in organophosphate (OP) and carbamate (CARB) resistance. By combining toxicological, biochemical and molecular data from three reference laboratory and three OP selected strains (OP strains), the AChE1 mutations associated with resistance in T. urticae were characterised. RESULTS: The resistance ratios of the OP strains varied from 9 to 43 for pirimiphos-methyl, from 78 to 586 for chlorpyrifos, from 8 to 333 for methomyl and from 137 to 4164 for dimethoate. The insecticide concentration needed to inhibit 50% of the AChE1 activity was, in the OP strains, at least 2.7, 55, 58 and 31 times higher for the OP pirimiphos-methyl, chlorpyrifos oxon, paraoxon and omethoate respectively, and 87 times higher for the CARB carbaryl. By comparing the AChE1 sequence, four amino acid substitutions were detected in the OP strains: (1) F331W (Torpedo numbering) in all the three OP strains; (2) T280A found in the three OP strains but not in all clones; (3) G328A, found in two OP strains; (4) A201S found in only one OP strain. CONCLUSIONS: Four AChE1 mutations were found in resistant strains of T. urticae, and three of them, F331W, G328A and A201S, are possibly involved in resistance to OP and CARB insecticides. Among them, F331W is probably the most important and the most common in T. urticae. It can be easily detected by the diagnostic PCR-RLFP assay developed in this study.