| As the insecticides resistance of S.exigua is increasing seriously,and aslobring huge losses on agricultural production,further understanding of the mechanisms of insecticide resistance is needed,and understanding insecticide resistance mechanisms is essential for insect control strategies.Above all,metabolic resistance plays an important role among them.Detoxification enzymes such as cytochrome P450 monooxygenases(P450s or CYPs),glutathione S-transferases(GSTs)and carboxy/choline esterases(CCEs)which enhance metabolism of insecticides are well known for their role in the resistance to insecticides in insects.UGT plays an important role in the detoxification of mammals,but whether the UGTs of insects participate in detoxification and metabolism of pesticides,which lead to insecticide resistance has never mentioned.Our study is the first time to conduct system research on UGT from S.exigua,to provide the basis for further understanding of the mechanisms of insecticide resistance of S.exigua.1.The characteristics of UGTs from S.exigua32 new UGT sequences of larva of S.exigua were cloned for the first time.The deduced amino acid sequence of each UGTs reported here showed homology to a range of UGTs and included the UGT signature:(FVA)-(LIVMF)-(TS)-(HQ)-(SGAC)-G-X(2)-(STG)-X(2)-(DE)-X(6)-P-(LIVMFA)-(LIVMFA)-X(2)-P-(LMVFIQ)-X(2)-(DE)-Q(all amino acids that can occur at a given position are listed inside brackets;X indicated any amino acid).The presence of this sequence strongly improved the identification of this protein is a member of the UGT superfamily,and all the new UGTs of S.exigua have a high amino acid identity with H.armigera and B.mori UGTs.All UGTs possess an N-terminal signal peptide which is used to remove following insertion of the proteins into endoplasmic reticulum,and in the C-terminal of these UGTs contains a hydrophobic transmembrane(TM)domain that anchors the protein to the ER membrane with catalytic sites facing the lumen and a tail exposed to cytosol.And UGTs of S.exigua showed high amino acid homology compared with H.armigera and B.mori.2 Phylogenetic analysisA consensus phylogenetic tree constructed with deduced amino acid sequences from the Lepidoptera S.exigua(32),H.armigera(40)and B.mori(42),revealed patterns of inter-specific conservation and of the gene families,and S.exigua UGT showed high homology and similarity evolution compared with H.armigera and B.mori.UGT33 is the largest UGTs family,which contains13 UGTs of S.exigua which contain UGT33B14,UGT33B15,UGT33B16,UGT33F5,UGT33F6,UGT33F7,UGT33F8,UGT33J3,UGT33T3,UGT33V1,UGT33V2,UGT33V3,UGT33V4.The second largest family UGT40,which composed 11 UGTs of S.exigua include UGT40D3,UGT40D5,UGT40F3,UGT40F4,UGT40F5,UGT40L3,UGT40M2,UGT40M3,UGT40Q2,UGT40R4,UGT40U2.While others are belong to different small families which only contains two or one UGT.3 The effects of insecticide on expression levels of UGTsThe expression of UGT genes from fat body were rapidly respond when treat with insecticides.Compare the influence of UGT expression by five insecticides treatment,only UGT33T3,UGT40D5 were significant up-regulated in each insecticides and UGT33V1 was prominent down-regulated in every pesticides,implicated that these three UGTs has a strong related with metabolize insecticides.Contrast indoxacarb,metaflumizone,chlorantraniliprole and lambda-cyhalothrin,the tendency of expression revealed similar,UGT33T3,UGT33J3,UGT40D5 and UGT42B5 were significant up-regulated,while UGT33V1 was prominent down-regulated.However abamectin showed striking imparity compared with them,which most of the UGTs showed down-regulated,only UGT33T3 and UGT40D5 were significant up-regulated.Obvious,the response mechanisms of fat body cell had striking difference between abamectin and other four insecticides.This means the metabolic detoxification mechanisms of fat body were distinct among abamectin and other four insecticides,but indoxacarb,metaflumizone,chlorantraniliprole and lambda-cyhalothrin may be shared the similar metabolic detoxification mechanisms. |
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