Identification,Expression Pattern,and Antioxidant Function Of Superoxide Dismutase Genes From Pieris Rapae

The small white butterfly,Pieris rapae(Lepidoptera:Pieridae),is one of the most important insect pests of cruciferous vegetables.The accumulation of reactive oxygen species(ROS)might be induced by insecticide,and could be removed by the antioxidant enzymes.Superoxide dismutase(SOD)is one of the most important member of antioxidant enzyme system and plays a key role in scavenging ROS and protect the cells from oxidative stress.Lambda-cyhalothrin is a commonly used chemical insecticide in controlling P.rapae.However,it's still unclear whether it can cause the increase of ROS in P.rapae.In addition,the reports on SOD in P.rapae are limited.In this case,we identified and studied the expression profiles and function of the SOD genes from P.rapae.Our results may pave the way for revealing the antioxidant mechanisms in P.rapae at the molecular level,and provide theoretical basis for developing reasonable chemical control strategies to manage P.rapae.The main findings are as follows:(1)Three PrSOD genes were identified from the P.rapae transcriptome dataset,namely,PrSOD1,PrSOD2 and PrSOD3.PrSOD1 and PrSOD3 contained the signature sequence and the metal binding sites of CuZnSOD,while PrSOD2 contained the signature sequence and the metal binding sites of MnSOD.Sequence and phylogenetic analysis showed that PrSOD1 and PrSOD3 belonged to intracellular CuZnSOD and extracellular CuZnSOD,respectively,whereas PrSOD2 belonged to mitochondrial MnSOD.(2)Three pET-30a-PrSOD vectors were constructed,and the recombinant proteins for PrSOD1,PrSOD2 and PrSOD3 were successfully expressed in Escherichia coli.Enzymatic activity assay results showed that the three PrSODs have the ability to remove superoxide anion,indicating that the three PrSOD genes encode functional proteins.(3)The relative expression levels of three PrSOD genes in different tissues and developmental stages were analyzed.The highest mRNA levels of PrSOD1 and PrSOD3 were found in midgut while PrSOD2 in fat body.PrSOD1 showed the highest expression level in male adult stage,by contrast,the highest PrSOD2 and PrSOD2 levels were observed in female adult stage.(4)The concentration of superoxide anion was significantly increased in P.rapae larvae after exposure to lambda-cyhalothrin.And this oxidative stress upregulates the expression level and enzyme activity of PrSODs.The results suggested that PrSODs are involved in the removal of ROS induced by lambda-cyhalothrin.