Sun_2026_Proc.Biol.Sci_293_

Many parasitoid wasps do not accumulate triacylglycerols (TAGs) as adults, yet recent studies have shown that they can convert sugars into fatty acids (FAs) and TAGs. Whether lipogenesis is fitness-relevant, and which fatty acid synthase (FAS) genes mediate it, remain unclear. Using RNAi-mediated knockdown and stable isotope labelling in the parasitic wasp Nasonia vitripennis, we demonstrate that the FAS gene Nvfas1 is required not only for TAG biosynthesis in females, but also for ovarian development and male pheromone production. Nvfas1 knockdown females exhibited significantly reduced de novo synthesis of TAGs and underdeveloped ovarioles with few or no mature oocytes. These females completely lost the ability to produce offspring, while their lifespan remained unaffected. In males, Nvfas1 knockdown led to a reduced de novo biosynthesis of the FA-derived sex pheromone. Our study provides the first evidence of a single FAS gene exerting such pleiotropic and far-reaching effects on both males and females of a parasitoid wasp. Although the absolute contribution of Nvfas1-mediated de novo FA and TAG synthesis is quantitatively minor, it is indispensable for reproductive success, highlighting the essential role of lipogenesis in the fitness of N. vitripennis.