Abstract
Both exogenous and endogenous compounds can induce the expression of cytochrome P450 genes. The insect cytochrome P450 genes related to insecticide resistance are likely to be expressed as the “first line of defense” when challenged with insecticides. In this study, four cytochrome P450 genes, SinvCYP6B1, SinvCYP6A1, SinvCYP4C1, and SinvCYP4G15, were firstly isolated from workers of the red imported fire ant (Solenopsis invicta) through rapid amplification of cDNA ends (RACE) and sequenced. The fipronil induction profiles of the four cytochrome P450 genes and the two previously isolated CYP4AB1 and CYP4AB2 were characterized in workers. The results revealed that the expression of SinvCYP6B1, SinvCYP6A1, CYP4AB2, and SinvCYP4G15, increased 1.4-fold and 1.3-fold more than those of acetone control, respectively, after 24 h exposure to fipronil at concentrations of 0.25 μg mL−1 (median lethal dose) and 0.56 μg mL−1 (90% lethal dose), while no significant induction of the expression of CYP4AB1 and SinvCYP4C1 was detected. Among these genes, SinvCYP6B1 was the most significantly induced, and its maximum expression was 3.6-fold higher than that in acetone control. These results might suggest that multiple cytochrome P450 genes are co-up-regulated in workers of the fire ant through induction mechanism when challenged with fipronil. These findings indicated that cytochrome P450 genes play an important role in the detoxification of insecticides and provide a theoretical basis for the mechanisms of insecticide metabolism in the fire ant.
Highlights
The red imported fire ant (RIFA; Solenopsis invicta, Hymenoptera, Formicidae, Myrmicinae, Solenopsis) is recognized as the most invasive and destructive alien species because of the complexity of its diet and its aggressive nature, rapid reproduction and strong competitive abilityPLOS ONE | DOI:10.1371/journal.pone.0150915 March 16, 2016Expression of Multiple Cytochrome P450 monooxygenases (P450s) Genes Induced by Fipronil [1]
The sequences of the cDNA fragments amplified using the SMART rapid amplification of cDNA ends (RACE) technique perfectly overlapped with the sequences of the clones #12H3 (SinvCYP6B1), #24E8 (SinvCYP6A1), #9E4 (SinvCYP4C1), and #C423 (SinvCYP4G15), which indicated that the fragments were the 5' and 3' ends of the putative P450 genes
We investigated the evolutionary relationships of SinvCYP6B1 with the other insect CYP6 family sequences, SinvCYP4C1 and SinvCYP4G15 with the other insect CYP4 family sequences, and SinvCYP6B1 and SinvCYP6A1 with the other insect CYP6 family sequences doi:10.1371/journal.pone.0150915.g002 (Fig A in S1 File)
Summary
The red imported fire ant (RIFA; Solenopsis invicta, Hymenoptera, Formicidae, Myrmicinae, Solenopsis) is recognized as the most invasive and destructive alien species because of the complexity of its diet and its aggressive nature, rapid reproduction and strong competitive abilityPLOS ONE | DOI:10.1371/journal.pone.0150915 March 16, 2016Expression of Multiple Cytochrome P450 Genes Induced by Fipronil [1]. Many methods have been used to control the fire ant, but none have permanently eradicated this species from an area. A phenylpyrazole insecticide, exhibits neurotoxic activity by blocking the GABA-regulated chloride channels of neurons [5,6]. Formulation of fipronil into granules or bait has been demonstrated to be effective against RIFA [7]. These insecticides are widely used to control crop pests, and the development of resistance among many pests has been reported [8,9,10,11,12]. The tolerance of the fire ant to insecticides has not been reported
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