The Pb tolerance initiated by LdZIP8 in Lymantria dispar larvae: An effective defense against heavy metal stress

Pb is a prevalent heavy metal contaminant in the habitats of herbivorous insects. This study investigated the tolerance level of Lymantria dispar larvae to Pb and its corresponding mechanism focusing on the role of ZIP genes. The detrimental impacts of Pb on larval growth and survival exhibited a dose-dependent relationship, with a survival rate of 48 % even at the extreme concentration of 3424 mg/kg. Among the 11 ZIP family genes analyzed, only LdZIP8 showed a significant up-regulation in response to Pb treatment. Localization studies revealed that LdZIP8 was situated on the cell membrane in Sf9 cells. Under Pb stress, silencing LdZIP8 led to a marked reduction in larval body weight and extended developmental duration. This gene silencing exacerbated Pb-induced activation of mitochondrial apoptosis pathways, evidenced by elevated expression of apoptotic genes and increased disorder of mitochondrial pathway compared to non-silenced controls. At the cellular level, LdZIP8 overexpression in Sf9 cells mitigated the adverse effects of Pb on cell viability, apoptosis, mitochondrial membrane potential, mitochondrial permeability transition pore opening, reactive oxygen species levels, and calcium ion homeostasis. Taken together, L. dispar larvae exhibit considerable Pb tolerance, with LdZIP8 identified as a critical regulator of this resilience.