GABA_B receptor modulates responses to sweet substances by regulating sugar metabolism in Spodoptera frugiperda larvae

Previous studies have found that the metabotropic γ-aminobutyric acid (GABA) B receptor (GABA_B receptor, GABA_B R) is highly expressed in the fat body of Spodoptera frugiperda larvae and significantly affects their feeding behavior in response to sucrose. However, the mechanism by which GABA_B receptors regulate the feeding behavior of S. frugiperda larvae remains unclear.

In this study, single sensillum recording (SSR) of taste, transcriptomics, physiological and biochemical assays, and behavioral tests were used to investigate the effect of GABA_B receptor-mediated sugar metabolism on larval sugar-feeding behavior.

The results showed that after knockdown of the GABA_B R gene, the sensitivity of the lateral styloconic sensilla on the larval mouthparts to sucrose decreased, the expression of sugar metabolism-related genes in the larvae changed, and the concentrations of glucose and trehalose in the larvae increased. Additionally, after separate injections of glucose or trehalose into larvae, the sensitivity of the lateral styloconic sensilla on the larval mouthparts to sucrose decreased, and the larvae no longer preferred to feed on sucrose-treated leaf discs.

These findings indicate that GABA_B receptors affect larval sugar-feeding behavior by regulating sugar metabolism in larvae. This study further reveals the mechanism by which the neurotransmitter GABA regulates chemosensation and feeding behavior in insects, and provides theoretical support for the use of GABA in managing agricultural pests such as S. frugiperda.