The neuropeptide pigment-dispersing factor enhanced food intake and alleviated antifeedant effects by azadirachtin in <i>Spodoptera frugiperda</i> larvae

The neuropeptide pigment-dispersing factor (PDF) is essential for the circadian rhythm of Drosophila and other insects. Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) is a transcontinental pest that threatens the global agricultural supply. However, the functional study of PDF in S. frugiperda larvae remains unexamined. The study demonstrated that the Sf-PDF coding sequence spans 330 bp, and a highly conserved mature peptide sequence was found in the predicted protein. A spatiotemporal expression analysis revealed that Sf-PDF was predominantly expressed in female adults and 1st instars, with the lowest expression level noted during the pupal stage. Sf-PDF exhibited significant expression in the larval head and midgut tissues. A marked reduction in the expression of Sf-PDF was also noted in the larval midgut following azadirachtin treatments. The Sf-PDF mature peptide injection enhanced larval food consumption and weight gain during 2 days of treatment, while also mitigating the antifeedant impact caused by 1.0 μg/g azadirachtin. Our research indicates that Sf-PDF is associated with feeding behavior in S. frugiperda larvae and modulates the antifeedant effects caused by azadirachtin. These findings elucidate a novel understanding of the role of PDF protein and enhance comprehension of the antifeedant mechanism of azadirachtin in insect larvae.