Modulation of MnSOD protein in response to different experimental stimulation in Hyphantria cunea

A manganese superoxide dismutase (MnSOD) gene was cloned from the fall webworm, Hyphantria cunea. MnSOD cDNAs encode precursor proteins of 215 amino acid residues. H. cunea MnSOD possesses the metal binding ligands of 3 histidines and 1 aspartic acid common to MnSODs. The deduced amino acid sequences of the H. cunea MnSOD cDNA showed 76% identity to Bombyx mori MnSOD and 56–62% identity to MnSOD sequences from other species. MnSOD and copper/zinc superoxide dismutase (Cu/ZnSOD) is expressed in all tissues of H. cunea. MnSOD expression changed at a trace-level in infected larvae, while Cu/ZnSOD expression strongly changed against Gram-positive and Gram-negative bacteria, and fungi. Environmental stresses such as different artificial photoperiods (24L:0D), ultraviolet irradiation (312 nm), and starvation condition increased Cu/ZnSOD expression, MnSOD expression, on the other hand, was increased by starvation. Moreover, MnSOD and Cu/ZnSOD expression showed no significant change in the 0L:24D condition. MnSOD and Cu/ZnSOD expression in H. cunea also significantly increased at high (37 °C) and low (4 °C) temperature. Oxidative stress induced by 10% H2O2 reduced the expression levels of MnSOD and Cu/ZnSOD. However, paraquat-induced oxidative stress reduced MnSOD expression but increased Cu/ZnSOD expression. These results suggest that Cu/ZnSOD may play a larger role than MnSOD as a superoxide anion scavenger against oxidative stress in H. cunea.