BdNOX5 mediates gut microbiota homeostasis via ROS regulation in Bactrocera dorsalis

BACKGROUND: Reactive oxygen species (ROS) serve as crucial signaling molecules in maintaining intestinal microbial homeostasis. The NADPH oxidase gene family represents the primary source of controlled ROS production in metazoans. Although it is known that insect intestinal epithelial cells primarily generate ROS via dual oxidase (DUOX), the potential involvement of other NADPH oxidases in this process remains unclear. RESULTS: This study identified a NADPH oxidase gene, BdNOX5, in Bactrocera dorsalis. The gene features an open reading frame of 4470 bp, encoding a 1489-amino acid protein containing typical NADPH oxidase domains, and is highly expressed in the adult midgut and foregut in B. dorsalis. Functional studies revealed that interference with BdNOX5 expression significantly reduced midgut ROS activity and H₂O₂ levels, leading to disrupted microbiota structure, an effect that was reversible upon exogenous H₂O₂ supplementation. Furthermore, knockdown of BdNOX5 induced a compensatory upregulation of BdDUOX, which subsequently contributed to the restoration of microbial homeostasis. CONCLUSION: These findings demonstrate that BdNOX5 acts as a key gene in maintaining intestinal ROS levels and coordinates with BdDUOX to regulate microbial balance, providing novel insights into the host's regulation of gut microbiota via ROS signaling pathways. © 2026 Society of Chemical Industry.