Insights into Temperature and Hypoxia Tolerance in Cowpea Weevil via HIF-1

Cowpea weevil (Callosobruchus maculatus) is a major pest that leads to severe damage of the stored leguminous grains. Several management approaches, including physical barriers, biological or chemical methods, are used for controlling bruchid in cowpea. These methods usually target the metabolically active state of weevil. However, it becomes less effective at early stages as egg, larva, or pupa under low temperature and oxygen conditions. Since hypoxia-inducible factor-1 (HIF-1) is known to coordinate multiple gene responses to low oxygen or low temperature signals, we examined the HIF-1 alpha gene expression under low temperature and hypoxic treatments. At -20 degrees C, it took 4 h to reduce the survival rate for eggs, larvae, and pupae down to 10%, while at 4 degrees C and 15 degrees C, the survival rate remained higher than 50% even after 128 h as HIF-1 alpha gene expression peaked at 15 degrees C. Moreover, HIF-1 protein offers a valuable target for early stage pest control complementary to traditional methods. In particular, HIF-1 inhibitor camptothecin (CPT), one of the five HIF-1 inhibitors examined, achieved a very significant reduction of 96.2% and 95.5% relative to the control in weevil survival rate into adult at 4 degrees C and 30 degrees C, respectively. Our study can be used as one model system for drug development in virus infections and human cancer.