SIFamide Signaling regulates energy mobilization during phototactic behavior in the Asian Citrus psyllid, Diaphorina citri.

Phototactic behavior is an energy-intensive visually guided behavior critical for insect survival and dispersal. The central neuromodulatory mechanisms underlying this oriented response remain poorly understood, particularly with respect to peptidergic regulation. To address this knowledge gap, we conducted a study on the Asian citrus psyllid, Diaphorina citri, a vector of citrus huanglongbing, whose adults exhibit robust positive phototaxis. The SIFamide (SIFa) neuropeptide (DcSIFa) and its cognate receptor (DcSIFaR) were identified, both of which showed the highest expression levels in the head. Immunofluorescence analysis revealed two pairs of SIFa-producing neurons in the pars intercerebralis with widespread brain-wide arborizations. Expression of both genes was dynamically upregulated in phototactic individuals. RNAi-mediated knockdown of either gene substantially reduced phototactic behavior, downregulated energy metabolism genes, disrupted mitochondrial respiratory function, and altered nitrogen metabolism and circadian rhythm. Physiologically, gene silencing led to reduced heart rate, lower oxygen consumption, and decreased production of adenosine triphosphate and citric acid. These findings demonstrate that SIFamide signaling acts as a central neuromodulatory hub regulating energy mobilization during phototactic behavior in D. citri, and indicate that DcSIFa or DcSIFaR may serve as promising candidate targets for pest control strategies.