Functions of keratin-associated protein genes in reproduction of Nilaparvata lugens

As a notorious rice pest, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) inflicts severe damage owing to its exceptionally high reproductive potential. Previous ovarian transcriptome analyses have revealed that the insect Keratin-associated protein (KAP) gene is potentially implicated in vitelline secretion and eggshell sclerotization, and it holds promise as a novel target for the suppression of pest reproduction. In this study, KAP5-2(LOC111045913, XP_039288177.1) and KAP5-4 (LOC111045916, XP_022187086.1) genes' function were studied by RNA interference technology. The results showed that gene silencing significantly suppressed female fecundity, and the pre-oviposition period extended from 3 days to 4 days. The total number of eggs laid within 10 days was significantly reduced, with only 113.2 and 101.3 eggs in the dsKAP5-2 and dsKAP5-4 groups, respectively, representing decreases of 49.3 % and 56.0 % compared to the control group. In addition, the hatching rates of offspring were significantly reduced by 60.1 % and 63.78 %, with many malformed unhatched eggs remaining. Molecular mechanism studies revealed that silencing KAP genes led to significant downregulation of vitellogenin (Vg) and its receptor (VgR, vitellogenin receptor). Additionally, it affected the expression of key genes in the juvenile hormone (Juvenile Hormone Acid Methyltransferase (JHAMT), Methoprene-tolerant (Met)) and nutrient signaling pathways. This study indicates the critical role of KAP genes in regulating female reproductive processes and embryonic development in N. lugens, thereby providing a theoretical foundation for the rational design of eco-friendly insecticides targeting these KAP genes.