RNAi Targeting MhieJHEH Disrupts Hormonal Homeostasis and Induces Systemic Metabolic Dysregulation in Monolepta Hieroglyphica.

Juvenile hormone epoxide hydrolase (JHEH) plays a crucial role in insect development by degrading juvenile hormone (JH). While functionally characterized in some leaf beetle species (e.g., Leptinotarsa), its molecular mechanisms and physiological roles in many agriculturally important Chrysomelids remain poorly understood. This study provides the first comprehensive functional analysis of MhieJHEH in the maize pest Monolepta hieroglyphica. We cloned and sequenced the gene, which encodes a 454-amino acid protein classified within the Coleoptera JHEH clade. Structural modeling revealed a binding pocket for JH III by key residues Thr250 and Arg379, confirmed by enzymatic assays showing the protein catalyzes JH III conversion. Expression analysis indicated significantly higher transcript levels in the female abdomen, thorax, cuticle, and intestine, implying a sex-biased regulatory function. RNAi-mediated knockdown of MhieJHEH disrupted JH III homeostasis and caused severe adult mortality, establishing its essential role in survival. Integrated transcriptomic and proteomic analyses following knockdown revealed extensive dysregulation of genes and proteins enriched in metabolic pathways, oxidative phosphorylation, and energy derivation, with strong correlations in mitochondrial and nucleoside metabolism components. These findings establish MhieJHEH as a critical regulator of JH degradation, adult survival, and systemic metabolism in M. hieroglyphica, supporting its potential as a target for novel pest management strategies.