RNA interference of MDR genes in L. decemlineata and T. ni by ingestion of double-stranded RNA


Favell, G., Donly, C. (2017) RNA interference of MDR genes in L. decemlineata and T. ni by ingestion of double-stranded RNA. Insect Biotech Conference, St. Catharines, Ontario. 14-16 June 2017, oral presentation.


Colorado potato beetle (Leptinotarsa decemlineata) and cabbage looper (Trichoplusia ni) are
two species of insects that are significant agricultural pests around the world. Numerous
populations of these insects have developed resistances to various pest control techniques
including chemical insecticides. Of these populations, many exhibit a multi-drug resistance
phenotype whereby they are resistant to multiple, often unrelated insecticides. Overexpression of multidrug resistance (MDR) genes which code for transmembrane ATP-binding cassette efflux
transporters has been associated with this multi-drug resistance phenotype in many other
organisms, but not yet in L. decemlineata or T. ni, as their MDR genes have not been closely
studied. In this project, three MDR genes in L. decemlineata and one MDR gene in T. ni are
investigated. First, relative expression of these genes was measured in nerve, Malpighian tubule,
and midgut tissue to determine their localization across tissues related to insecticide
detoxification. Then, RNA interference mediated knockdown of each gene was attempted
through ingestion of double-stranded RNA (dsRNA) to evaluate the effectiveness of this delivery
method for dsRNA in each species. Finally, for successfully down-regulated genes, their relation
to insecticide susceptibility was assessed by exposing the insects to an insecticide and measuring differences in mortality caused by the knockdown. This research provides valuable knowledge of MDR gene expression in L. decemlineata and T. ni, the relationship between that expression and insecticide susceptibility; and the potential of RNA interference as a control method for these pests.

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