S-Space College of Agriculture and Life Sciences (농업생명과학대학) Dept. of Food and Animal Biotechnology (식품·동물생명공학부) Theses (Master's Degree_식품·동물생명공학부)
Biochemical and molecular mechanism of prothiofos-resistance in the diamondback moth, Plutella xylostella (L.)
- Issue Date
- 서울대학교 대학원
- 배추좀나방 (Plutella xylostella); Diamondback moth; 저항성 메커니즘; Resistance mechanism; Prothiofos; Prothiofos; AChE; Ache; General esterase; General esterase; Kinetic analysis; Kinetic analysis; Polymorphism; Polymorphism
- 학위논문(석사)--서울대학교 대학원 :농생명공학부,2004.
- A prothiofos-resistant diamondback moth (DBM-R) strain has been established from the susceptible
(DBM-S) strain over 100 generations under the selective pressure of the prothiofos. The
resistance level of the DBM-R strain against prothiofos was 20- to 70-fold greater than that of
the DBM-S strain in the leaf-dipping assay. To determine the resistance mechanism of the DBM-R
strain, enzyme activities of acetylcholinesterase (AChE), general esterase and glutathione Stransferase
(GST), usually responsible for insecticide resistance in arthropods, were examined.
AChE activity in the DBM-R strain showed 1.2-fold higher than that of the DBM-S strain, whereas
there was no significant difference in GST activity. The activity of general esterase in the
midgut of DBM-R strain was 2 times higher than that of the DBM-S strain, but no different
pattern of general esterase was detected in non-denaturing polyacrylamide gel electrophoresis.
In contrast to low affinity of resistant AChE for the substrate, Vmax was 1.2-fold higher than
that of susceptible AChE. In semiquantitative RT-PCR, the transcript level of resistant AChE
gene was approximately 8% more than that of susceptible AChE gene. These suggest that increased
amount of AChE is related to prothiofos-resistance in the DBM.R strain. Kinetic analysis of the
resistant AChE with paraoxon (phenyl organothiophosphate) revealed 7-fold reduced ki, indicating
AChE insensitivity to paraoxon, the same group with prothiofos, was increased. Furthermore, this
result proposes that resistant AChE may result from structural alteration. In order to determine
whether prothiofos- resistance of DBM is attributed to altered AChE (such as point mutation) or
AChE gene amplification, AChE gene (cDNA and genomic DNA) from both strains was cloned and
sequenced. Resistant and susceptible AChE gene showed polymorphism in nucleotide analysis,
resulting in the substitution of amino acids in several positions.
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