What was it all about? 

The diamondback moth is considered the most economically important pest of cruciferous crops in many parts of the world, including Australia. It has an unrivalled ability to develop resistance to all classes of insecticides, and its sustainable management relies on the adoption of flexible integrated pest management strategies. In many instances, the mechanism of resistance is metabolic ‘detoxification’ of insecticides and is heritable.

‘MicroRNAs’ are small ribonucleic acids (the building blocks of genetic material) that play significant roles in various physiological and developmental processes in all plants and animals, by regulating expression of genes.

In this project, researchers explored the effect of insecticide resistance and insecticide exposure on the microRNA profile of diamondback moth larvae. Using next generation sequencing, results showed changes in the microRNA profile of Deltamethrin-resistance and Chlorantraniliprole-exposed moth larvae, with the abundance of a number of microRNAs being affected.

Subsequently, a short-listed number of microRNAs were tested in bioassays in which Deltamethrin-resistant moth larvae were fed on synthetic ‘mimic’ microRNAs and then exposed to the insecticide. Results showed that one of the microRNAs, miR-2b-3p, can significantly enhance mortality in Deltamethrin-resistant moth larvae, presumably by decreasing the production of a key protein involved in the larval detoxification pathway.

In order to move towards practical application of the findings of the proposed research, this microRNA is currently in the process of being artificially produced in a model plant, Arabidopsis, to test larval mortality in insecticide-resistant larvae when treated with the insecticide.