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.