Crustacean cardioactive peptide receptor (CCAPR), a G protein-coupled receptor, is critical for pupal ecdysis in Drosophila melanogaster and Acyrthosiphon pisum, both of which possess a single ccapr gene. In this study, we identified two ccapr genes in Henosepilachna vigintioctomaculata, a potato-defoliating ladybird widely distributed in Asia, and found that the two receptors have diverged functionally in their requirement for pupal ecdysis. Bayesian phylogenetic analysis recovered well-supported within-lineage relationships and placed HvCCAPR1 and HvCCAPR2 as a sister pair within the coleopteran clade. Spatiotemporal expression analysis showed that Hvccapr2 was upregulated immediately before the onset of pupal ecdysis and exhibited a stronger bias toward neural and muscular tissues. Injection of in vitro-synthesized dsRNA or oral administration of bacterially expressed dsRNA targeting the common region shared by both genes, as well as dsccapr2 but not dsccapr1, impaired larval-pupal transition. Moreover, knockdown of Hvccapr1 + Hvccapr2 or Hvccapr2, but not Hvccapr1, markedly prolonged the durations of ecdysis and postecdysis behavioral sequences. As a consequence, most Hvccapr1 + Hvccapr2 and Hvccapr2 RNAi prepupae failed to shed the old larval cuticle. In contrast, pupal cuticles beneath the retained larval exoskeleton became pigmented in developmentally arrested Hvccapr1 + Hvccapr2 and Hvccapr2 RNAi beetles. Together, these findings demonstrate that CCAPR2, rather than CCAPR1, plays the predominant role in coordinating pupal ecdysis behavior in H. vigintioctomaculata.
Wu et al. (Mon,) studied this question.