Physiological role and application potential of HcCAT2 in multi-host adaptability of Hyphantria cunea revealed by RNA...

The antioxidant defence system is crucial for herbivorous insects to adapt to various host plants. This study focused on catalase 2 gene (HcCAT2) to investigate the antioxidant mechanisms that underlie the ability of Hyphantria cunea to adapt to a wide range of hosts and to develop a disruptor for its polyphagous behaviour. Results indicated that, compared to larvae fed on the highly preferred host plant Morus alba, HcCAT2 expression increased 33.19- to 47.25-fold in larvae reared on Betula platyphylla and Tilia amurensis with moderate and low preference, respectively. Silencing HcCAT2 consistently reduced larval body weight and downregulated growth-related genes (e.g., Cyclin A2 and Decapentaplegic) across all host plant groups. Moreover, HcCAT2 silencing significantly downregulated key glycolytic genes (Hexokinase and Pyruvate kinase), the tricarboxylic acid cycle gene (Isocitrate Dehydrogenase 2) and lipid metabolism genes (e.g., Acetyl-CoA Carboxylase) in larvae fed on all three host plants. The redox response in larvae was complex, as HcCAT2 silencing led to a marked downregulation of negative regulators of oxidative damage and key ROS-producing genes. The nucleic acid pesticide CS-dsHcCAT2, designed to target HcCAT2 expression, demonstrated potent silencing efficacy. Treatment with CS-dsHcCAT2 suppressed larval body weight on all host plants. Collectively, the HcCAT2-mediated antioxidant defence system is critical to the host plant adaptation of H. cunea, and CS-dsHcCAT2, by inhibiting HcCAT2 expression, holds promise as an effective agent to disrupt the polyphagous behaviour of H. cunea.