MCE activities and malathion resistances in field populations of the australian sheep blowfly (Lucilia cuprina).
Malathion resistance has been shown to be the result of a single point mutation in the LcalphaE7 gene in four independently isolated chromosomes of Lucilia cuprina. The resultant amino acid substitution specifies high malathion carboxylesterase (MCE) activity. We have assayed MCE activities and resistance to malathion in three sets of field-derived samples, two sets of isogenic lines and five mass populations, and show that resistance to malathion in these samples is associated with high MCE activity in both sets of isogenic lines and four of the five mass populations. Additional mechanisms contributing to MCE activity or malathion resistance may be present in one of the mass populations. A second point mutation in LcalphaE7 is responsible for conferring diazinon resistance by encoding an increased organophosphate (OP) hydrolase activity. We also assayed diazinon resistances from the same three samples and show that diazinon and malathion resistances were in complete disequilibrium, with two exceptions. One exception involves the mass population with additional resistance mechanism(s) and the other involves three isogenic lines that are resistant to both insecticides. The molecular data for these lines suggest that they carry a duplication of the LcalphaE7 gene.
Smyth
K A
KA
CSIRO Division of Entomology, GPO Box 1700, Canberra, ACT 2601, Australia. ksmyth@mail.utexas.edu
Boyce
T M
TM
Russell
R J
RJ
Oakeshott
J G
JG
D019943:Amino Acid Substitution; D000818:Animals; D001315:Australia; D002265:Carboxylic Ester Hydrolases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003976:Diazinon / Q000494:pharmacology; D004175:Diptera / Q000187:drug effects* / Q000502:physiology*; D014644:Genetic Variation; D006720:Homozygote; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology; D008294:Malathion / Q000494:pharmacology; D017354:Point Mutation
D002800:Cholinesterase Inhibitors; D007306:Insecticides; D002265:Carboxylic Ester Hydrolases; C021528:malathion esterases; D008294:Malathion; D003976:Diazinon