Cloning and RNAi-mediated functional characterization of two Monochamus alternatus chitinase genes

Insect chitinases play essential roles in molting and immune defense, however their specific functions in the Japanese pine sawyer (Monochamus alternatus), the primary vector of pine wilt disease, remain poorly understood. Existing control strategies are non-eco-friendly and inefficient, indicating the need for sustainable alternatives. This study was designed to at characterize two chitinase genes, (MaCht-3 and MaIDGF-4) and evaluate their roles in M. alternatus development to identify novel RNAi-based control targets.

MaCht-3 and MaIDGF-4 exhibited peak expression during the late larval (L5) and early pupal stages. RNAi-mediated silencing of MaCht-3 resulted in molting defects (80% deformity at 15 μg dsRNA), developmental delays (25-50% prolongation of the larval-pupal transition), and cuticle wrinkling. Silencing MaIDGF-4 compromised immune function, leading to 33.33% mortality due to infection and structural disruption of the tracheal and abdominal cuticle integrity. Transmission electron microscopy revealed abnormal epidermal thinning in MaCht-3-silenced individuals and thickening in those treated with dsMaIDGF-4.

MaCht-3 and MaIDGF-4 regulate distinct chitin remodeling pathways essential for M. alternatus development and immunity. RNAi-mediated disruption of these genes presents targeted, environmentally friendly strategy to reduce vector populations and limit pine wilt disease transmission. These findings serve as a reference for the development of molecular pest control approaches by linking gene-specific dysfunction to actionable practical biocontrol solutions, reducing dependence on traditional insecticides. © 2025 Society of Chemical Industry.