In vivo functional analysis of Fatty-acyl desaturase 3 in sex pheromone biosynthesis and courtship behavior of Plutella xylostella.

Moths rely on sex pheromones for long-distance mate attraction and recognition. The biosynthesis of moth sex pheromones involves multiple enzymatic steps, among which desaturases play a pivotal role in introducing carbon-chain unsaturation. However, the specific desaturases involved in sex pheromone biosynthesis in the diamondback moth, Plutella xylostella, remain largely unexplored. In this study, we identified a Δ11-desaturase gene, PxylDES3, from the pheromone gland transcriptome and generated a homozygous mutant line using the CRISPR/Cas9 system. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that the three major sex pheromone components (Z11-16:Ald, Z11-16:OH, and Z11-16:Ac) were significantly reduced, but not completely abolished, in homozygous mutant females compared with wild-type females. Behavioral assays demonstrated that the loss of PxylDES3 led to a significant reduction in female mating success, impaired male orientation preference, and attenuated male wing-fanning and hair-pencil responses. Notably, the residual pheromone components detected in mutant females suggest potential functional redundancy within the desaturase gene family. Collectively, these findings establish PxylDES3 as an important contributor to sex pheromone biosynthesis and courtship behavior in P. xylostella, and provide a potential target for pheromone-based pest management strategies.