Noorda blitealis is a major defoliating pest of moringa, causing severe damage to this tree and constraining its sustainable production. Plant volatiles play a crucial role in insect host location and recognition, which is mediated by odorant binding proteins (OBPs) in the insect olfactory system. However, the molecular mechanisms underlying the olfactory recognition of moringa volatiles by N. blitealis remain unclear. In this study, gas chromatography-mass spectrometry (GC-MS) was used to identify 39 volatile compounds from M. oleifera leaves and tender shoots, and gas chromatography-electroantennographic detection (GC-EAD) revealed seven volatiles that elicited significant electrophysiological responses in N. blitealis antennae, including α-pinene, 2-methylcyclopentanone, hexyl acrylate, 2,2,4,6,6-pentamethylheptane, 4-allylanisole, 4-ethylacetophenone, and n-hexanol. We identified 32 NbOBP genes from the high-quality genome of N. blitealis. They were classified them into three classes (Classical, Minus-C, Plus-C) and six subfamilies. All of them contained complete open reading frames that are encoding proteins exhibited typical insect OBP structural features. Transcriptomic analysis and qPCR validation showed that sixteen NbOBP genes were highly expressed in the antennae, and significantly upregulated in response to M. oleifera volatiles. Of them, six NbOBPs (NbOBP1, NbOBP2, NbOBP3, NbOBP12, NbOBP21, NbOBP29) were recombinantly expressed and purified. Fluorescence competitive binding assays demonstrated that NbOBP1, NbOBP12, NbOBP21, and NbOBP29 can bind to the seven EAD-active volatiles, with NbOBP1 showing the broadest and strongest binding affinity. These findings provide insights into the molecular basis of olfactory recognition of M. oleifera volatiles by N. blitealis, and valuable targets for the development of eco-friendly behavior-regulating agents for the integrated management of this pest.
Ge et al. (2026) studied this question.