Sorbitol Suppression in Spodoptera frugiperda Enhances Parasitoid Development and Fitness

Parasitoid parasitism reprograms host metabolism to nourish the developing offspring, yet its impact on alternative carbohydrate pathways, such as the polyol pathway, is poorly understood. Here, we demonstrate that a generalist parasitoid wasp, Meteorus pulchricornis, suppresses sorbitol contents in the larvae of Spodoptera frugiperda by downregulating polyol metabolism in the fat body. Two aldose reductase genes of S. frugiperda, AKR1B1-1 and AKR1B1-2, responsible for catalyzing glucose-to-sorbitol conversion, are identified as key mediators of this metabolic shift. Furthermore, sorbitol restoration in hosts disrupts parasitoid larval development and reduces its fitness, including a decrease in pupation rate, reduced cocoon weight, smaller adult size, and lower parasitism rates. Transcriptomic analysis and the fluctuating reactive oxygen species level suggest that the elevated host-circulating sorbitol may disrupt redox homeostasis in developing wasp larvae. These findings provide new insights into host-parasite metabolic interactions centered on polyol metabolism and lay the groundwork for enhancing parasitoid-based biological control strategies.