Identification and functional characterization of carboxypeptidase Q in the ovarian development of parthenogenetic Haemaphysalis longicornis

Carboxypeptidase Q (CPQ), a member of the M28 family of metalloproteases, remains functionally uncharacterized in tick species. In this study, we identified a CPQ gene from Haemaphysalis longicornis that is significantly upregulated during ovarian development. Spatiotemporal transcription profiling analysis revealed that CPQ transcript levels showed a relative increasing trend in the midgut and salivary glands at rapid engorgement phase, suggesting its involvement in nutrient processing. Although RNAi-mediated knockdown of CPQ did not induce gross morphological abnormalities in the ovaries, it significantly prolonged the oviposition and incubation period, while markedly reducing egg production and weight. To explore the underlying mechanism, DIA-based proteomic analysis was performed on ovaries, revealing that CPQ silencing altered the abundance of proteins related to transmembrane transport, and mitochondrial energy conversion, thereby potentially disrupting ovarian cellular homeostasis. Furthermore, GST pull-down and yeast two-hybrid assays confirmed a specific interaction between CPQ and a GST-like protein, indicating a link between proteolytic processing and antioxidant defense. In conclusion, our findings suggest that CPQ may serve as a critical metabolic regulator linking midgut nutrient mobilization to ovarian development in H. longicornis, potentially modulating metabolic homeostasis and interacting with the antioxidant defense.