Gene_locus Report for: cydpo-ACHE1

Changes in genome architecture often have a significant effect on ecological specialization and speciation. This effect may be further enhanced by involvement of sex chromosomes playing a disproportionate role in reproductive isolation. We have physically mapped the Z chromosome of the major pome fruit pest, the codling moth, Cydia pomonella (Tortricidae), and show that it arose by fusion between an ancestral Z chromosome and an autosome corresponding to chromosome 15 in the Bombyx mori reference genome. We further show that the fusion originated in a common ancestor of the main tortricid subfamilies, Olethreutinae and Tortricinae, comprising almost 700 pest species worldwide. The Z-autosome fusion brought two major genes conferring insecticide resistance and clusters of genes involved in detoxification of plant secondary metabolites under sex-linked inheritance. We suggest that this fusion significantly increased the adaptive potential of tortricid moths and thus contributed to their radiation and subsequent speciation.

In southern Brazilian apple (Malus spp.) orchards, predominantly organophosphates are used to control the oriental fruit moth, Cydia molesta (Busck) (Lepidoptera: Tortricidae), but control failures often occur. Therefore the susceptibility of three C. molesta Brazilian populations was investigated to five insecticides of different groups and modes of action, in comparison with a susceptible laboratory strain mass reared in southern France for >10 yr. At the same time, comparative biochemical and genetic analysis were performed, assessing the activities of the detoxification enzymatic systems and sequencing a gene of insecticide molecular target to find out markers associated with resistance. The three Brazilian populations were significantly resistant to chlorpyrifos ethyl compared with the reference strain. One of the field populations that had been frequently exposed to deltamethrin treatments showed significant decreasing susceptibility to this compound, whereas none of the three populations had loss of susceptibility to tebufenozide and thiacloprid compared with the reference strain. All three populations had slight but significant increases of glutathione transferase and carboxylesterases activities and significant decrease of specific acetylcholinesterase activities compared with the reference. Only the most resistant population to chlorpyriphos exhibited a significantly higher mixed function oxidase activity than the reference. The acetylcholinesterase of females was significantly less inhibited by carbaryl in the Brazilian populations than in the reference strain (1.7-2.5-fold), and this difference was not expressed in the male moth. However, no mutation in the MACE locus was detected. These biological and molecular characterizations of adaptive response to insecticides in C. molesta provide tools for early detection of insecticide resistance in field populations of this pest.

Two strains of Cydia pomonella (L.) (Lepidoptera: Tortricidae) were selected in the lab by exposure to increasing concentrations of diflubenzuron (Rdfb strain) or azinphos-methyl (Raz strain). Insecticide bioassays showed that the adults of the Rdfb strain exhibited a 2.6-fold and a 7.7-fold resistance ratio to azinphos-methyl and carbaryl, respectively compared to a susceptible strain (S) whereas the adults of the Raz strain exhibited a 6.7-fold resistance ratio to azinphos-methyl and a 130-fold resistance ratio to carbaryl. In the Raz strain, a target site resistance mechanism was suggested by the inhibition of acetylcholinesterase (AChE) activity. In fact the ki values did not discriminate the S and Rdfb strains, while the Raz strain exhibited a 1.7-fold and a 14-fold increase in ki value compared to the S strain for azinphos-methyl oxon and carbaryl, respectively. To verify this hypothesis, two cloned AChE cDNAs sequences (named cydpom-ace2 e cydpom-ace1) were compared between the susceptible and the resistant strains. No difference in the deduced amino acid sequence was found in cydpom-ace2 (orthologous to the Drosophila melanogaster AChE). In the putative cydpom-ace1 (paralogous to the Drosophila AChE), a single amino acid substitution F399V was exclusively present in the Raz strain. The F399 lined the active site of the enzyme and the F399V substitution likely could influence the accessibility of different types of inhibitors to the catalytic site of the insensitive cydpom-ace1.

Changes in genome architecture often have a significant effect on ecological specialization and speciation. This effect may be further enhanced by involvement of sex chromosomes playing a disproportionate role in reproductive isolation. We have physically mapped the Z chromosome of the major pome fruit pest, the codling moth, Cydia pomonella (Tortricidae), and show that it arose by fusion between an ancestral Z chromosome and an autosome corresponding to chromosome 15 in the Bombyx mori reference genome. We further show that the fusion originated in a common ancestor of the main tortricid subfamilies, Olethreutinae and Tortricinae, comprising almost 700 pest species worldwide. The Z-autosome fusion brought two major genes conferring insecticide resistance and clusters of genes involved in detoxification of plant secondary metabolites under sex-linked inheritance. We suggest that this fusion significantly increased the adaptive potential of tortricid moths and thus contributed to their radiation and subsequent speciation.

In southern Brazilian apple (Malus spp.) orchards, predominantly organophosphates are used to control the oriental fruit moth, Cydia molesta (Busck) (Lepidoptera: Tortricidae), but control failures often occur. Therefore the susceptibility of three C. molesta Brazilian populations was investigated to five insecticides of different groups and modes of action, in comparison with a susceptible laboratory strain mass reared in southern France for >10 yr. At the same time, comparative biochemical and genetic analysis were performed, assessing the activities of the detoxification enzymatic systems and sequencing a gene of insecticide molecular target to find out markers associated with resistance. The three Brazilian populations were significantly resistant to chlorpyrifos ethyl compared with the reference strain. One of the field populations that had been frequently exposed to deltamethrin treatments showed significant decreasing susceptibility to this compound, whereas none of the three populations had loss of susceptibility to tebufenozide and thiacloprid compared with the reference strain. All three populations had slight but significant increases of glutathione transferase and carboxylesterases activities and significant decrease of specific acetylcholinesterase activities compared with the reference. Only the most resistant population to chlorpyriphos exhibited a significantly higher mixed function oxidase activity than the reference. The acetylcholinesterase of females was significantly less inhibited by carbaryl in the Brazilian populations than in the reference strain (1.7-2.5-fold), and this difference was not expressed in the male moth. However, no mutation in the MACE locus was detected. These biological and molecular characterizations of adaptive response to insecticides in C. molesta provide tools for early detection of insecticide resistance in field populations of this pest.

Two strains of Cydia pomonella (L.) (Lepidoptera: Tortricidae) were selected in the lab by exposure to increasing concentrations of diflubenzuron (Rdfb strain) or azinphos-methyl (Raz strain). Insecticide bioassays showed that the adults of the Rdfb strain exhibited a 2.6-fold and a 7.7-fold resistance ratio to azinphos-methyl and carbaryl, respectively compared to a susceptible strain (S) whereas the adults of the Raz strain exhibited a 6.7-fold resistance ratio to azinphos-methyl and a 130-fold resistance ratio to carbaryl. In the Raz strain, a target site resistance mechanism was suggested by the inhibition of acetylcholinesterase (AChE) activity. In fact the ki values did not discriminate the S and Rdfb strains, while the Raz strain exhibited a 1.7-fold and a 14-fold increase in ki value compared to the S strain for azinphos-methyl oxon and carbaryl, respectively. To verify this hypothesis, two cloned AChE cDNAs sequences (named cydpom-ace2 e cydpom-ace1) were compared between the susceptible and the resistant strains. No difference in the deduced amino acid sequence was found in cydpom-ace2 (orthologous to the Drosophila melanogaster AChE). In the putative cydpom-ace1 (paralogous to the Drosophila AChE), a single amino acid substitution F399V was exclusively present in the Raz strain. The F399 lined the active site of the enzyme and the F399V substitution likely could influence the accessibility of different types of inhibitors to the catalytic site of the insensitive cydpom-ace1.

Resistance of the codling moth Cydia pomonella (L.) to azinphos-methyl is not based on enhanced detoxifying enzymes like oxidation mediated by mixed function oxidases or by glutathione S-transferases. Synergism by S,S,S-tributylphosphoro-trithioate was evident, but the overall activity of general esterases using p-nitrophenyl acetate as the substrate was similar in resistant and susceptible insects. In comparison to acetylcholinesterase (AChE) from susceptible adult codling moth, the enzyme of insects resistant to azinphos-methyl has low affinities (higher K(m) values) to the substrates acetylthiocholine (ATCh) and propionylthiocholine. This difference indicates a possible amino acid alteration at the catalytic or anionic binding sites of the resistant enzyme. Inhibition studies revealed no apparent differences in sensitivity of AChE enzymes from resistant and susceptible moths to organophosphorus compounds (OPs), carbamate insecticides and quaternary ammonium ligands. MEPQ (7-Methylethoxyphosphinyloxy)-1-methylquinolinium) is the most powerful OP inhibitor acting at a nM range, while chlopyrifos oxon, azinphos-methyl oxon and paraoxon are less inhibitory by 22.9, 82.3 and 475 fold, respectively. The codling moth AChE is a typical enzyme that displays substrate inhibition by ATCh, negligible hydrolysis of butyrylthiocholine, very high sensitivity to the bisquaternary ammonium compound BW284c51 and it is not inhibited by the powerful butyrylcholinesterase inhibitor iso-OMPA. Of the three carbamates examined, only carbaryl was inhibitory at the mM range while pirimicarb and aldicarb were inactive. Of the quaternary ammonium ligands (except for the powerful BW284c51), edrophonium and decamethonium displayed appreciable inhibition rates, while d-tubocuraine was practically inactive.