Functional identification of three new genes involved in resistance to Bacillus thuringiensis in Plutella xylostella

The widespread and sustained exploitation of the entomopathogen Bacillus thuringiensis (Bt) in the control of insects, pests and disease vectors is threatened by the evolution of resistance. In the present work, the construction of subtractive libraries and analysis of gene function by RNA interference-mediated gene silencing (RNAi) were combined to determine the molecular basis of resistance to DiPel® bio-insecticide in the KarUK6 population of the model insect Plutella xylostella. DiPel® is the commercial product of its type most used for the control of different insect pests, based on a mixture of spores and insecticidal toxins of Bt subspecies kurstaki HD1 strain (Btk-HD1), with a broad action spectrum. A population susceptible to DiPel®, genetically similar to KarUK6, was used as a control. The ontological analysis of the subtractive libraries showed a multitude of altered biological processes in the resistant strain; and gene expression analysis in the presence of DiPel® evidenced the pre-induced nature of the transcriptional response in the KarUK6 strain. By their regulation, three genes stood out: SDF2L1, CDKAL1 and HEL-1, the first two had never before been described in invertebrates, whose vertebrate orthologues are critical to regulate cellular homeostasis under different types of stress. Gene silencing via RNAi of all three genes suppressed DiPel® resistance in KarUK6 larvae, demonstrating that these genes or the cellular mechanisms in which they participate are crucial for resistance, and their potential use as targets to minimize the risk of resistance to Bt products and increase their effectiveness. This research granted the 2015 Award of the Cuban National Academy of Sciences.