Iron-sulfur protein in mitochondrial complexes of Spodoptera litura as potential site for ROS generation

- The ISCU2 and ISCU8 genes were cloned from Spodoptera litura.
- The developmental expression patterns of ISCUs in the S. litura were examined.
- RNA interference of ISCUs could result in declining of the ROS in Sf9 cells.
- Rotenone and azadirachtin treatment could increase Sf9 ISCUs and ROS levels.
- SOD and POD were increased by rotenone and azadirachtin and declined by ISCU-siRNA.

Mitochondrial complex I is the main source of reactive oxygen species (ROS) production, but the exact site of superoxide generation or their relative contribution is not clear. This study aims to determine the function of iron-sulfur clusters (ISCU) in the initiation of ROS generation. ISCU2 and ISCU8 were cloned from Spodoptera litura which shared the conserved amino acid sequence with other insects. The expressions of the two genes were ubiquitous throughout the whole development stages and tissues. Knockdown of ISCU2 and ISCU8 resulted in the decline of the ROS, whereas rotenone and azadirachtin treatment up-regulated ROS levels by increasing mRNA expression. Furthermore, antioxidant enzyme activity of SOD and POD were up-regulated by rotenone and azadirachtin treatment and then declined after ISCU was silenced. Our results suggest the possibility that the molecules of ISCU2 and ISCU8 in complex I may serve as potential sites in the initiation of ROS generation.