An amino acid substitution on the second acetylcholinesterase in the pirimicarb-resistant strains of the peach potato aphid, Myzus persicae

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Mechanisms of resistance to pirimicarb were surveyed in Iranian populations of the peach-potato aphid, Myzus persicae. Insecticide bioassays were carried out using topical application on three different populations collected from Karaj and Rasht in the Northern provinces. Results of the bioassays indicated that Rasht and Karaj-S populations were susceptible to pirimicarb. A population collected from the college greenhouse (Karaj-R) was resistant to pirimicarb. LD 50 (Ͼ100 ng/insect) of pirimicarb was not calculated for the Karaj-R population due to limited solubility of this insecticide. The activity and PAGE patterns of esterase in resistant (Karaj-R) and susceptible populations showed that one mechanism of resistance to pirimicarb was esterase-based resistance. Esterase activity of the Karaj-R population was 3.25-fold higher than the susceptible population (Karaj-S), and one of the two esterase bands with higher activity in the Karaj-R population showed strong susceptibility to pirimicarb. The acetylcholinesterase (AChE) of the Karaj-R population had lower affinity to artificial substrates, acetylthiocholine, propionylthiocholine and butyrylthiocholine, than Rasht and Karaj-S populations. The I 50 of pirimicarb for Karaj-R, Karaj-S and Rasht populations was 1.89ϫ 10 Ϫ5 M, 1.37ϫ10 Ϫ8 M and 1.37ϫ10 Ϫ8 M, respectively. These results suggest that AChE of the Karaj-R population is insensitive to pirimicarb. Ratios of AChE insensitivity of the Karaj-R population to the Karaj-S population were 1,384.6, 11.8 and 2.7 for pirimicarb, monocrotophos and aldicarb, respectively; however, the ratios were 0.32, 0.15 and 0.10 for carbofuran, propoxure and MTMC, respectively, showing negatively correlated sensitivity to pirimicarbinsensitive AChE.

Section: Discussionmentioning

confidence: 99%

Studies on pirimicarb resistance mechanisms in Iranian populations of the peach-potato aphid, Myzus persicae

Ghadamyari

Mizuno

et al. 2008

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“…In wild types of AP-AChE from aphid species, M. persicae and A. gossypii, the amino acid at position 331 is exceptionally Ser, and 331Ser is replaced with Phe in the pirimicarb resistant strains (Nabeshima et al, 2003;Andrews et al, 2004;Toda et al, 2004). The acyl pocket of AP-AChE with 331Ser seems larger and less hydrophobic than that with 331Phe.…”

Section: Discussionmentioning

confidence: 99%

“…albimanus (Weill et al, 2004); Phe331Trp at the acyl pocket in Cx. tritaeniorhynchus (Nabeshima et al, 2004) and Tetranychus kanzawai (Aiki et al, 2005); Ser331Phe in Myzus persicae (Nabeshima et al, 2003) and Aphis gossypii (Li and Han, 2002;Andrews et al, 2004;Toda et al, 2004) and Phe290Val at the acyl pocket in Nephotettix cincticeps (Terada et al, un- (Weill et al, 2003;Oh et al, 2006). In the present study, therefore, 6 substitutions known to cause insensitivity in various species including positions of 119Gly and 331Phe were designed in the AP-AChE cDNA of Cx.…”

Section: Introductionmentioning

confidence: 97%

“…D. melanogaster has a single AChE gene in its genome (Adams et al, 2000). In other insect species that have two AChE genes in the genome, the amino acid substitution responsible for insensitivity has been found in a second type of AChE paralogous to Ace (AP-AChE) (Nabeshima et al, 2003(Nabeshima et al, , 2004Weill et al, 2003). Several amino acid substitutions causing insensitivity have been found in the active site of AP-AChE; Gly119Ser (indicates a substitution from Gly to Ser, numbering of amino acid position follows the equivalent number of Torpedo californica AChE without notice) at the oxyanion hole in Culex pipiens (Weill et al, 2003), Anopheles gambiae (Weill et al, 2003) and An.…”

Section: Introductionmentioning

confidence: 99%

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Biochemical properties of recombinant acetylcholinesterases with amino acid substitutions in the active site

Kozaki²,

Tomita³

et al. 2007

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Several amino acid substitutions causing insensitivity have been found in the active site of Ace-paralogous acetylcholinesterase (AP-AChE); Gly119Ser (Culex pipiens, Anopheles gambiae), Ala201Ser (Aphis gossypii), Phe290Val (Nephotettix cincticeps), Ser331Phe (Myzus persicae, A. gossypii), Phe331Cys (Tetranychus urticae) and Phe331Trp (Cx. tritaeniorhynchus). To confirm the responsibility of these substitutions to the insensitivity, the six substitutions were introduced into the AP-AChE cDNA of Cx. tritaeniorhynchus resistant strain (Toyama), and their biochemical properties were examined by using a baculovirus-insect cell system. The substitution Gly119Ser gave the enzyme a high level of insensitivity to carbamate insecticides but a slight insensitivity to organophosphates. On the other hand, an amino acid substitution Phe331Trp located in the acyl pocket induced a very high level of insensitivity to organophosphates and ten times lower insensitivity to carbamates. The amino acid replacement appear to render the acyl pocket less hydrophobic and smaller, and then alter the accessibility of the substrates and inhibitors to this site.

“…gambiae (Weill et al, 2003), An. albimanus (Weill et al, 2004), C. tritaeniorhynchus (Nabeshima et al, 2004), M. persicae (Nabeshima et al, 2003), Aphis gossypii (Andrews et al, 2004;Toda et al, 2004) and Plutella xylostella (Baek et al, 2005). Recent studies of several insect species have shown that the expression level of the AP-AChE gene was much higher than that of the AO-AChE gene, and suggest that AP-AChE plays a main role in terminating synaptic transmission.…”

Section: Introductionmentioning

confidence: 99%

cDNA identification and gene expression of two types of acetylcholinesterases in a cultured cell line of Aedes albopictus, compared to mosquito whole body extracts

Mizuno

Tomita

Kasai

et al. 2006

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Two cDNA sequences containing open reading frames encoding two types of acetylcholinesterase (AChE) precursors, Ace-orthologous AChE (AO-AChE) and Ace-paralogous AChE (AP-AChE), with 635 residues and 702 residues, respectively, were determined in Aedes albopictus by PCR-based techniques. The partial and whole cDNAs for AOAChE and AP-AChE, respectively, were also sequenced from a cultured cell line of mosquito, NIAS-AeAl-2, derived from Ae. albopictus neonatal larvae. Comparing the sequences of the respective AChEs between cultured cells and mosquito whole body extracts, many nucleotide polymorphisms were found in both AChE cDNAs but only one amino acid substitution. The expression level of AChE genes in the cultured cells was low, 1/2 and 1/7 that of the mosquito body for AO-AChE and AP-AChE, respectively. The expression ratio of AO-AChE/AP-AChE was 1/2 in the cultured cells. AP-AChE genes was more highly expressed than AO-AChE genes in both cultured cells and the mosquito body. In an enzyme assay, the activity of AChE per protein in the cultured cells was 1/8 that of the mosquito body. The function of AChE in cultured cells is discussed based on the present and previous papers.