Knockdown of CYP9A9 increases the susceptibility to lufenuron, methoxyfenozide and a mixture of both in Spodoptera exigua

A Malpighian Tubule-Specific P450 Gene SlCYP9A75a Contributes to Xenobiotic Tolerance in Spodoptera litura

Phytophagous insects are more predisposed to evolve insecticide resistance than other insect species due to the "preadaptation hypothesis". Cytochrome P450 monooxygenases have been strongly implicated in insecticide and phytochemical detoxification in insects. In this study, RNA-seq results reveal that P450s of Spodoptera litura, especially the CYP3 clan, are dominant in cyantraniliprole, nicotine, and gossypol detoxification. The expression of a Malpighian tubule-specific P450 gene, SlCYP9A75a, is significantly upregulated in xenobiotic treatments except α-cypermethrin. The gain-of-function and loss-of-function analyses indicate that SlCYP9A75a contributes to cyantraniliprole, nicotine, and α-cypermethrin tolerance, and SlCYP9A75a is capable of binding to these xenobiotics. This study indicates the roles of inducible SlCYP9A75a in detoxifying man-made insecticides and phytochemicals and may provide an insight into the development of cross-tolerance in omnivorous insects.

Identification and characterization of both cis- and trans-regulators mediating fenvalerate-induced expression of CYP6B7 in Helicoverpa armigera

As we known, inducibility is an important feature of P450 genes. Previous studies indicated that CYP6B7 could be induced and involved in fenvalerate detoxification in Helicoverpa armigera. However, the regulatory mechanism of CYP6B7 induced by fenvalerate is still unclear. In this study, CYP6B7 promoter of H. armigera was cloned and the cis-acting element of fenvalerate was identified to be located between -84 and - 55 bp of CYP6B7 promoter. Subsequently, 33 candidate transcription factors (CYP6B7-fenvalerate association proteins, CAPs) that may bind to the cis-acting element were screened and verified by yeast one-hybrid. Among them, the expression levels of several CAPs were significantly induced by fenvalerate. Knockdown of juvenile hormone-binding protein-like (JHBP), RNA polymerase II-associated protein 3 (RPAP3), fatty acid synthase-like (FAS) and peptidoglycan recognition protein LB-like (PGRP) resulted in significant expression inhibition of CYP6B7, and increased sensitivity of H. armigera to fenvalerate. Co-transfection of reporter gene p (-84/-55) with pFast-CAP showed that JHBP, RPAP3 and PGRP could significantly increase the activity of CYP6B7 promoter. These results suggested that trans-acting factors JHBP, RPAP3 and PGRP may bind with cis-acting elements to regulate the expression of CYP6B7 induced by fenvalerate, and play an important role in the detoxification of H. armigera to fenvalerate.

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

A Comparative Study of Transcriptional Regulation Mechanism of Cytochrome P450 CYP6B7 between Resistant and Susceptible Strains of Helicoverpa armigera

Cytochrome P450 CYP6B7 has previously been proved to be associated with fenvalerate-resistance in Helicoverpa armigera. Here, how CYP6B7 is regulated and involved in the resistance of H. armigera is studied. Seven base differences (M1-M7) were found in CYP6B7 promoter between a fenvalerate-resistant (HDTJFR) and a susceptible (HDTJ) strain of H. armigera. M1-M7 sites in HDTJFR were mutated into the corresponding base in HDTJ, and pGL3-CYP6B7 reporter genes with different mutation sites were constructed. Fenvalerate-induced activities of reporter genes mutated at M3, M4, and M7 sites were significantly reduced. Transcription factors Ubx and Br, whose binding sites contain M3 and M7, respectively, were overexpressed in HDTJFR. Knockdown of Ubx and Br results in significant expression inhibition of CYP6B7 and other resistance-related P450 genes, and increase of sensitivity of H. armigera to fenvalerate. These results indicate that Ubx and Br regulate the expression of CYP6B7 to mediate the fenvalerate-resistance in H. armigera.