The GPCR A35 regulates fecundity of Nilaparvata lugens Stål via juvenile hormone signaling

The brown planthopper, <i>Nilaparvata lugens</i> is a major rice pest in Asia, with its high fecundity contributing to recurrent outbreaks. G protein-coupled receptors (GPCRs) are a critical class of transmembrane proteins in insects that sense diverse extracellular and intracellular signals and regulate a wide range of physiological processes. In this study, we characterized GPCR A35 and its function in <i>N. lugens</i> fecundity. Expression profiling revealed that GPCR A35 was highly enriched in female heads and fat bodies, with peak levels in females at 4 days post-eclosion. RNAi-mediated the silencing of <i>GPCR A35</i> in fifth-instar nymphs by 57-60%, and was effectively delivered to female adults, resulting in a 14.8% reduction in juvenile hormone (JH) titer and marked downregulation of JH biosynthetic and signaling genes, including <i>HMGCR</i> (-60.1%), <i>FPPS</i> (-57.0%), <i>JHAMT</i> (-52.7%), <i>Met</i> (-24.2%), and <i>Kr-h1</i> (-78.3%). Silencing of <i>GPCR A35</i> further decreased <i>Vg</i> and <i>VgR</i> expression by 82.1% and 72.9% in females at 4 days post-eclosion, reduced protein contents in fat body and ovaries, and impaired ovarian development with fewer mature oocytes. Consequently, female fecundity declined by 51.3%, oviposition duration shortened by 18.5%, and the F1 population growth index decreased by 46.8%. These results demonstrate that GPCR A35 regulates fecundity in <i>N. lugens</i> by modulating JH-mediated vitellogenesis and oogenesis, providing a novel molecular target for RNAi-based green pest control.