Integrative transcriptomic and functional analysis reveals fatty acyl elongases involved in sex pheromone biosynthesis in rice leaffolder, Cnaphalocrocis medinalis (Lepidoptera: Pyraloidea).

Elongases are essential enzymes in the biosynthesis of sex pheromones in many lepidopteran species, where together with desaturases they determine pheromone precursor carbon skeletons and contribute to species-specific chemical communication. Despite their presumed importance, no fatty acyl elongase involved in lepidopteran sex pheromone biosynthesis has been functionally characterized to date. The rice leaffolder, Cnaphalocrocis medinalis, utilizes a blend of C18 monounsaturated aldehydes and alcohols as its sex pheromone, implying a critical elongation step from C16 precursors. Here, transcriptome analysis of the pheromone gland identified 45 candidate genes potentially involved in pheromone biosynthesis. Functional assays in Nicotiana benthamiana established a desaturation-elongation pathway in which the Δ11 desaturase Cmed070400 produces (Z)-11-hexadecenoic acid, which serves as the substrate for elongation. Multiple elongases, including Cmed092440, Cmed063180 and Cmed153360 catalyzed the conversion to (Z)-13-octadecenoic acid, the direct precursor of the major pheromone component. These findings provide the first experimental evidence for elongase-mediated formation of C18 pheromone precursors in C. medinalis. The identification of a minimal set of functionally active enzymes enables reconstruction of this pathway in plant systems, offering a basis for sustainable production of pheromone precursors for pest management applications.