A fructose-sensitive gustatory receptor links nutrient sensing to lipid metabolism in the red imported fire ant

Abstract

Fructose is an important energy source for many insects, yet its perception and physiological roles in the red imported fire ant, Solenopsis invicta, remain unclear. Here, we show that S. invicta workers strongly prefer sucrose and glucose but demonstrate only weak attraction for fructose. Using Ca²⁺ imaging and intracellular Ca²⁺ assays, we identified SinvGr43a as a fructose-responsive gustatory receptor. While its expression is low in the antennae, reverse transcription-quantitative PCR (RT-qPCR) revealed high levels in the brain and gut, suggesting an internal sensing role. RNA interference-mediated knockdown of SinvGr43a led to reduced production and secretion of short neuropeptide F (sNPF) in the gut and insulin-like peptide (ILP) in both the brain and gut. Moreover, this silencing also downregulated key fatty acid metabolic regulators, including sterol regulatory element-binding protein (SREBP) and fatty acid synthase (FAS), in the fat body, resulting in decreased lipid storage. Our findings demonstrate that SinvGr43a functions primarily as an internal fructose sensor, linking nutrient detection with neuropeptide signaling and lipid metabolism to maintain energy homeostasis in S. invicta.