Targeting octopamine synthesis genes LsTDC and LsTβH impairs reproduction, feeding and virus transmission in the small brown planthopper Laodelphax striatellus.

BACKGROUND

Octopamine (OA) is an important biogenic amine in insects, and regulates multiple physiological and behavioral processes. Tyrosine decarboxylase (TDC) and tyramine β-hydroxylase (TβH) are critical enzymes in the biosynthesis of OA. The small brown planthopper Laodelphax striatellus is a major rice pest and causes serious damage by transmitting plant viruses, such as rice stripe virus (RSV). However, the functions of TDC and TβH remain largely unknown in rice planthoppers.

RESULTS

We cloned LsTDC and LsTβH from L. striatellus. LsTDC was significantly enriched in the 4th instar nymphs, and LsTβH was highly expressed in eggs. LsTDC and LsTβH were predominantly expressed in the brain. RNA interference (RNAi) targeting-mediated knockdown of LsTDC and LsTβH in female L. striatellus significantly reduced the fecundity and egg hatchability. Moreover, LsTDC and LsTβH knockdown markedly decreased the transcript levels of vitellogenin (LsVg) in the fat body and ovary, and Vg receptor (LsVgR) in the ovary, as well as changed the expressions of genes involved in juvenile hormone (JH) and 20-hydroxyecdysone (20E) pathways. Additionally, targeting LsTDC and LsTβH significantly reduced the honeydew excretion and body weight of both female and male adults. Notably, the expressions of LsTDC and LsTβH were significantly higher in RSV-viruliferous L. striatellus, while LsTDC and LsTβH knockdown affected the expressions of capsid protein (CP), and vertical transmission rate of RSV.

CONCLUSION

These results provide valuable insights into the roles of LsTDC and LsTβH in reproduction, feeding, and virus transmission in L. striatellus, highlighting their potential as promising targets for developing new pest control strategies. © 2026 Society of Chemical Industry.