Date of Award


Degree Type


Degree Name

Master of Science




Cam Donly

Second Advisor

Stan Caveney

Third Advisor

Dr. Anthony Percival-Smith


Three genes encoding multidrug resistance proteins were identified in Trichoplusia ni larvae, named trnMDRl, trnMDR2 and trnMDR3. Their open reading frames were sequenced, and the translated sequences were compared to each other as well as to multidrug resistance proteins from other species. Quantification of their expression in various tissues of caterpillars fed on either artificial diet or organically- grown cabbage revealed upregulation of trnMDRl in Malpighian tubules, integument and fat body, trnMDR2 in fat body and trnMDR3 in brain in response to the plant diet. Sf9 cells stably transformed with either trnMDRl or trnMDR3 were used to assay MDR protein transport of calceinAM and vinblastine, as well as to test the inhibitory effect of cyclosporin A and verapamil on MDR protein activity. No significant calceinAM transport or inhibition of MDR activity by cyclosporin A or verapamil was observed. Cell lines stably transformed with trnMDRl demonstrated increased resistance to vinblastine toxicity. This study suggests that tissue-specific upregulation of MDR protein expression may contribute to caterpillar defences against toxic plant secondary metabolites, and that inhibitors of MDR proteins could be exploited as synergists with pesticides that are detoxified in a similar fashion. The assay system of Sf9 cells transformed with T. ni MDR genes could be used to screen for such potential MDR inhibitors.



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