Gluconeogenic compensation renders glycogen phosphorylase non-essential as an insecticidal target in <i>Plutella xylostella</i>

Gluconeogenic compensation renders the enzyme glycogen phosphorylase (GP) unnecessary as a target for insecticides in the insect known as Plutella xylostella, according to a recent study. GP plays a crucial role in glycogenolysis and chitin biosynthesis in insects. The research reveals that acyl urea compounds, structurally similar to benzoylphenylurea (BPU) insecticides, effectively inhibit mammalian GP, leading researchers to inquire if insect GP could function as an independent insecticide target.

In their study, they discovered that a mammalian GP inhibitor (GPI) efficiently suppresses recombinant GP from Plutella xylostella (PxGP) with an IC 50 value of 2.96 nM, unlike BPU. Molecular docking and MM/GBSA analysis suggest this selectivity is due to differentiated side-chain interactions. Despite the potent in vitro inhibition, GPI fails to exhibit any insecticidal effects, and RNAi-mediated suppression of PxGP does not negatively impact insect development or survival.

The researchers provide evidence that insects adapt by upregulating gluconeogenic enzymes (PEPCK, G-6-Pase) and increasing protein catabolism, resulting in a ~29% decrease in GP-a activity following RNAi. The fitness assessment shows transient larval weight loss, followed by full recovery of pupal weight, adult morphology, and fecundity.

These findings demonstrate that GP is functionally non-essential under the tested conditions, likely due to gluconeogenic compensation and alternative carbon sources. This study underscores the significance of metabolic network redundancy in the design of insecticide-targeted treatments.