<b>Identification and functional characterization of carboxypeptidase Q in the ovarian development of parthenogenetic </b><b><i>Haemaphysalis longicornis</i></b>

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 expression analysis revealed that CPQ transcript levels peak in the midgut and salivary glands at 96 hours post-blood feeding, 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 suppresses transmembrane transport, and mitochondrial energy conversion, thereby 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 demonstrate that CPQ is a critical metabolic regulator linking midgut nutrient mobilization to ovarian development, maintaining reproductive efficiency in H. longicornis by modulating metabolic homeostasis and interacting with the antioxidant defense.