| Budget Amount *help |
¥12,500,000 (Direct Cost: ¥12,500,000)
Fiscal Year 2001: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2000: ¥9,200,000 (Direct Cost: ¥9,200,000)
|
|---|
| Research Abstract |
The AChE of the toyama strain of Culex tritaenlorhynchus showed extremely low sensitivity to various kinds of organophosphates (OP) and carbamates compared to a susceptible strain, Taiwan. An open reading frame encoding 633 residues of AChE precursor was determined from cDNA sequence. The deduced protein sequences of AChE were identical among Toyama and Taiwan. A cloned AChE cDNA was introduced to BmNPV-BmN4 expression system and AChE sensitive to OP was produced regardless of cDNA sources; susceptible or resistant strains.
To the contrary, AChE of OP resistant strains of the house fly has 2 amino acids replacement in the structure. Expression experiments of AChE gene of resistant strains confirmed mat the insensitivity to the insecticides was caused by the replacement of the amino acids.
Therefore, there are two different molecular mechanism to produce insensitive AChE. The one is merely expression of the structural gene which maps insensitive AChE in it. This type of insensitive AChE was observed in D. melanogaster and M. domestica. The other is a production of two different structured AChEs from the same DNA map. The post translational modification of the protein is inevitable by other factors. According to our results, this type of insensitive AChE seems to distribute widely in insect species, C. tritaeniorhynchua, Nephotettix cincticepus, Qulema oryzae, Myzus persicae, Aphis gossipii, Tetranychtis ulticae, Plutella xyllostella. Linkage analysis of AChE atructure gene, the gene relating insensitivity of AChE and other molecular marker genes was conducted in C. tritaeniorhynchus, and indicated that the gene concerning the insensitivity located on chromosome 2 which was not the same chromosome loaded with AChE structure, gene. This result suports the existance of the second mechanism.
Purification of sensitive and insensitive AChE were tried to provide the materials for furthere studies on the mechanism of insensitive AChE production in insects.
|
