Cloning and induction patterns of Cu/Zn superoxide dismutase in responses to immune elicitors and nucleopolyhedrovirus in the beet armyworm Spodoptera exigua

Abstract

Superoxide dismutase (SOD) is a metalloenzyme that catalyzes the dismutation of the superoxide anion to oxygen and hydrogen peroxide, and has accordingly been known to play an important role in reducing oxidative stresses induced by various stresses and infection. In an attempt to investigate whether it is involved in antiviral immune responses in insects, the full-length cDNA of SeCu/ZnSOD was obtained from the cDNA library of Spodoptera exigua. It is 1,008 bp long (excluding poly-A tail) with the open reading frame of 459 bp encoding 152 amino acids. Sequence analysis with BLAST shows identities to various insects such as Bombyx mori (80%), Hyphantria cunea (80%), Plutella xylostella (77%), Aedes aegypti (73%), Apis mellifera (71%), Lasius niger (70%), Drosophila melanogaster (69%) and Gryllotalpa orientalis (67%). During development, S. exigua expressed SeCu/ZnSOD predominantly at embryonic stage, pupal stage and adult female stage, whereas it was slightly expressed in larvae and adult male. In addition, SeCu/ZnSOD was highly expressed in the fat body, hemocyte, silk gland and Malpighian tubule, although the levels of SeCu/ZnSOD transcripts were very low in the gut. Furthermore, SeCu/ZnSOD mRNA was slightly induced in response to either lipopolysaccharide or laminarin. Finally, SeCu/ZnSOD mRNA was induced in carcass in response to S. exigua nucleopolyhedrovirus (SeNPV) infection, whereas it was not strikingly induced in the gut. The precise roles of SeCu/ZnSOD in antiviral immune response remains to be further studied.