Molecular cloning, characterization, and antioxidant function of catalase in Lymantria dispar asiatic (Lepidoptera: Lymantriidae) under avermectin stress

The critical antioxidant catalase(CAT)breaks down hydrogen peroxide induced by environmental stresses.Here we cloned full length catalase cDNA from Lymantria dispar asiatic(LdCAT).Bioinformatic analyses showed that open reading frames of LdCAT contains 1524 bp,encoding 507 amino acids with molecular weight of 126.99 kDa,theoretical pI of 5.00,aliphatic index of 29.92,grand average of hydropathicity of 0.764,and instability index(II)of 46.56.Protein BLAST and multiple sequence alignment indicated that LdCAT had high identity with CAT from other insects,especially lepidopterans.In a phylogenetic analysis,LdCAT was most similar to CAT from Spodoptera litura and S.exigua.Quantitative realtime polymerase chain reaction showed that LdCAT transcripts in all instar larvae and the five tissues tested,verifying the ubiquity of LdCAT in L.disapr.Moreover,LdCAT of third instar larvae was significantly upregulated after they fed on avermectin at sublethal and LC10 doses.The highest relative transcript levels were found 2 h after an avermectin spray at LC90,and in the cuticula,rather than heads,fat bodies,malpighian tubes,and midguts after a spray avermectin at a sublethal concentration.The expression level of LdCAT under pesticide stresses here suggested that CAT is an important antioxidant enzyme of L.disapr defensing against pesticide stress and may be a good target for controlling this pest.

Role of c-Jun NH_(2)-terminal kinase-mediated mitogen-activated protein kinase pathway in response to pesticides in Apis cerana cerana

The mitogen-activated protein kinase(MAPK)cascade pathway plays an important role in regulating stress responses.The function of the c-Jun NH_(2)-terminal kinase(JNK),a component of the MAPK cascade pathway,in Apis cerana cerana(Acc)remains unclear.Here,JNK was isolated and identified from Acc.Bioinformatics analyses revealed there is a typical serine/threonine protein kinase catalytic domain in the AccJNK protein.An expression profile analysis showed that AccJNK was significantly induced by pesticide treatments.To further explore the functional mechanisms of AccJNK,a yeast 2-hybrid screen was performed,activator protein-1(AP-1)was screened as the interaction partner of AccJNK,and the interaction relationship was further verified by pull-down assay.Quantitative real-time polymerase chain reaction showed the expression pattern of AccAP-I was similar to that of AccJNK.After a knockdown of AccJNK or AccAP-I by RNA interference,the survival rate of Acc after pesticide treatments increased.Additionally,the expression levels of antioxidant-related genes and the activities of antioxidant enzymes increased,suggesting that the knockdown of AccJNK or AccAP-I increased the antioxidant capacity of bees.Our study revealed that the JNK-mediated MAPK pathway responds to pesticide stress by altering the antioxidant capacity of Acc.