RNAi assay in the 28-spotted ladybeetle Henosepilachna vigintioctopunctata suggests nuclear receptor HR3 as a potential molecular target for pest control

BACKGROUND: Nuclear hormone receptors play crucial roles in embryonic development, neural regulation, metabolism, and organogenesis in insects. This study aimed to investigate the expression and function of the nuclear hormone receptor 3 (HR3) in the 28-spotted ladybeetle, Henosepilachna vigintioctopunctata. RESULTS: Our findings revealed that HvHR3 was expressed at all developmental stages, with the highest expression levels in the 1st instar larvae, 3rd instar larvae, and pupa. HvHR3 silencing in both the 1st and 3rd instar larvae resulted in high mortality rates. Reduced HvHR3 expression in the 3rd instar larvae led to developmental arrest and failure to molt, accompanied by a down-regulation of 20E-related genes. Furthermore, HvHR3 silencing in the 3rd instar larvae resulted in a decrease in the 20E titer. Silencing HvHR3 in adult females significantly impaired ovarian development, resulting in reduced ovary size and absence of mature oocytes. Additionally, the eggs produced by these females had partially ruptured shells and failed to maintain normal spindle shape. CONCLUSION: These findings indicate that HvHR3 is a critical regulator of development, molting, and reproduction, underscoring its potential as a molecular target for RNA interference-based biopesticides aimed at controlling this pest.