Heavy Metal Tolerance in Lymantria dispar Larvae: Essential Roles of ABC Transporters in Resisting Heavy Metal Toxicity.

Heavy metals are transported and accumulated along the food chain, exposing phytophagous insects to high risks of contamination. This study investigated the mechanisms underlying Pb and Cd tolerance in Lymantria dispar by focusing on the ABC transporter family. Multiple ABC genes in the larval midgut were significantly upregulated under Pb and Cd stress, respectively. Among them, LdABC7 showed the most prominent positive response to Pb stress, and LdABC12 to Cd stress. Following silencing of LdABC7 or LdABC12, larval growth inhibition under heavy metal stress was significantly exacerbated and the expression of apoptosis-related genes was markedly up-regulated. Genes associated with the mitochondrial pathway shifted further toward pro-apoptosis after silencing of either LdABC7 or LdABC12. At the cellular level, both LdABC7 and LdABC12 proteins were localized to the cell membrane. Sf9 cells overexpressing these genes exhibited significantly increased cell viability, reduced apoptosis rates, restored mitochondrial membrane potential, reduced opening of the mitochondrial permeability transition pore (MPTP), and decreased levels of reactive oxygen species and calcium ions under heavy metal stress. Taken together, LdABC7 and LdABC12 serve as key detoxification components in L. dispar larvae in response to Pb and Cd stress, respectively, with the ability to maintain mitochondrial homeostasis and inhibit apoptosis.