Tian-yi Zhang,Chang-wei Gong,Jian Pu,An-chun Peng,Xu-yang Li,Yu-meng Wang,Xue-gui Wang
Solenopsis invicta is a main issue in southern China and is causing significant damage to the local ecological environment. The extensive use of insecticides has resulted in the development of tolerance in S. invicta . In our study, ten S. invicta colonies from Sichuan Province exhibited varying degrees of tolerance against flonicamid, with LC 50 values from 0.49 mg/L to 8.54 mg/L. The sensitivity of S. invicta to flonicamid significantly increased after treatment with the P450 enzyme inhibitor piperonyl butoxide (PBO). Additionally, the activity of P450 in S. invicta was significantly enhanced after being treated with flonicamid. Flonicamid induced the expression levels of CYP4aa1 , CYP9e2 , CYP4C1 , and CYP6A14 . The expression levels of these P450 genes were significantly higher in the tolerant colonies compared to the sensitive colonies, and the relative copy numbers of CYP6A14 in the tolerant colonies were 2.01–2.15 fold. RNAi feeding treatment effectively inhibited the expression of P450 genes, thereby reducing the tolerance of S. invicta against flonicamid. In addition, the overexpression of CYP6A14 in D. melanogaster resulted in reduced sensitivity to flonicamid. Our investigations revealed hydrophobic interactions between flonicamid and seven amino acid residues of CYP6A14, along with the formation of a hydrogen bond between Glu306 and flonicamid. Our findings suggest that flonicamid can effectively control S. invicta and P450 plays a pivotal role in the tolerance of S. invicta against flonicamid. The overexpression of CYP6A14 also increased tolerance to flonicamid.
Haolin Li,Xue Kong,Han Yang,Dongyu Yang,Jiguang Wei,Xuesheng Li
Juvenile hormones (JHs) play a crucial role in regulating development and reproduction in insects. In the cowpea aphid ( Aphis craccivora ), JH Ⅲ acid (JH ⅢA) can be converted into JH Ⅲ skipped bisepoxide (JHSB 3 ); however, the enzymes and pathways involved in this conversion remain elusive. In this study, we identified Ac -CYP6A14 as a key JH epoxidase and characterized its role in the JHSB 3 biosynthetic pathway in A. craccivora . In addition, we found that JHSB 3 titers were significantly higher in embryonic tissues than in maternal tissues. Transcriptomic analysis revealed six upregulated genes in the embryo. Temporal expression pattern analysis revealed that only Ac - CYP6A14 showed concordance with JHSB 3 titers. Silencing Ac - CYP6A14 decreased JHSB 3 titers. In vitro catalytic experiments demonstrated that Ac -CYP6A14 catalyzes the conversion of JH Ⅲ into JHSB 3 . Furthermore, we found that the “epoxidation then esterification” sequence is not feasible. Collectively, our findings elucidated the JHSB 3 biosynthetic pathway, in which JH ⅢA is first esterified to form JH Ⅲ, followed by epoxidation to JHSB 3 by Ac -CYP6A14.
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