A ventral nerve cord enriched major allergen family gene maintains muscle function under heat stress in Bactrocera dorsalis.

Heat stress threatens insect survival by disrupting tissue homeostasis and physiological performance, yet how insects preserve tissue function under high temperature remains poorly understood. Members of the major allergen gene family are widely distributed in insects, but whether and how they contribute to heat stress adaptation remains unclear. Here, using the tropical and subtropical horticultural pest Bactrocera dorsalis, a species capable of surviving temperatures above 40 °C, as a model, we identified a previously uncharacterized heat-responsive gene, matl2, which encodes a secreted lipid-binding protein and serves as a key regulator of muscle function during heat stress. Matl2 protein is secreted and targets the thoracic muscles. Under heat stress, the downregulation of matl2 maintains muscle protein homeostasis, potentially through autophagy and lysosome system, which might involve modulation of the PIP3-Akt signaling pathway. Moreover, Matl2 preserves locomotor performance under heat stress. Together, these findings uncover a lipid-mediated signaling axis that safeguards muscle proteostasis, providing insight into a strategy insects employ to cope with heat stress.