Multiple Cytochrome P450 Genes: Their Constitutive Overexpression and Permethrin Induction in Insecticide Resistant Mosquitoes, Culex quinquefasciatus

Abstract

Four cytochrome P450 cDNAs, CYP6AA7, CYP9J40, CYP9J34, and CYP9M10, were isolated from mosquitoes, Culex quinquefasciatus. The P450 gene expression and induction by permethrin were compared for three different mosquito populations bearing different resistance phenotypes, ranging from susceptible (S-Lab), through intermediate (HAmCqG0, the field parental population) to highly resistant (HAmCqG8, the 8th generation of permethrin selected offspring of HAmCqG0). A strong correlation was found for P450 gene expression with the levels of resistance and following permethrin selection at the larval stage of mosquitoes, with the highest expression levels identified in HAmCqG8, suggesting the importance of CYP6AA7, CYP9J40, CYP9J34, and CYP9M10 in the permethrin resistance of larva mosquitoes. Only CYP6AA7 showed a significant overexpression in HAmCqG8 adult mosquitoes. Other P450 genes had similar expression levels among the mosquito populations tested, suggesting different P450 genes may be involved in the response to insecticide pressure in different developmental stages. The expression of CYP6AA7, CYP9J34, and CYP9M10 was further induced by permethrin in resistant mosquitoes. Taken together, these results indicate that multiple P450 genes are up-regulated in insecticide resistant mosquitoes through both constitutive overexpression and induction mechanisms, thus increasing the overall expression levels of P450 genes.

A cis-regulatory sequence driving metabolic insecticide resistance in mosquitoes: Functional characterisation and signatures of selection

“…Our estimate of >20-fold higher expression of CYP9M10 in ISOP450 relative to CqSF (from qPCR) is similar in magnitude to the estimate of 11-fold over expression (vs. S-LAB) in a North American strain selected for permethrin resistance (Liu et al, 2011) but less than the 264-fold change found for JPAL vs Ogasawara . It is however incompatible with the 1800-fold over-expression reported by Hardstone et al (2010) for ISOP450 vs S-LAB.…”

“…It is however incompatible with the 1800-fold over-expression reported by Hardstone et al (2010) for ISOP450 vs S-LAB. Whilst CYP9M10 can be induced by recent exposure (Liu et al, 2011) this cannot explain the levels estimated by Hardstone et al (2010) which are much higher even than for tandemly duplicated genes e.g. esterase E4 in aphids which exhibit fold changes of >60 (Puinean et al, 2010).…”

Pyrethroid Resistance in Insects: Genes, Mechanisms, and Regulation

“…They are also involved in metabolizing endogenous compounds such as hormones, fatty acids, and steroids. Insect cytochrome P450s are known to play an important role in the detoxification and/or activation of xenobiotics such as insecticides (Scott 1999;Feyereisen, 2005) and plant toxins (Berenbaum 1991;Schuler 1996), leading to the development of resistance to insecticides (Carino et al 1994;Liu and Scott 1997;Feyereisen 2005;Zhu et al 2008a;Komagata et al 2010;Liu et al 2011) and tolerance to plant toxins (Li et al 2002;Wen et al 2003). Basal and up-regulation of P450 gene expression can significantly affect the disposition of xenobiotics or endogenous compounds in the tissues of organisms and thus alter their pharmacological/toxicological effects (Pavek and Dvorak 2008).…”

“…Insecticide resistance is a pre-adaptive phenomenon, in the sense that prior to an organism's (e.g., a mosquito's) exposure to insecticides, rare individuals (resistant individuals) carrying one or more possible resistance genes (or an altered [varied] genome) already exist, allowing the organism to survive exposure to the insecticides (WHO 1957). A large number of studies have indicated that multiple resistance mechanisms or genes are involved in the development of insecticide resistance in many insect species, including mosquitoes and house flies (Raymond et al 1989;Hemingway et al 2002;2004;Liu and Scott 1995;1997;Liu and Yue 2000;2001;Ranson et al 2002;Liu et al 2005;Vontas et al 2005;Xu et al 2005;Liu et al 2007;Zhu and Liu 2008;Zhu et al 2008a;b;Liu et al 2011). Characterization of the molecular mechanisms and genes involved in insecticide resistance has therefore been fundamental in understanding the development of resistance and in practical applications such as designing novel strategies to prevent or minimize the spread and evolution of resistance development and control insect pests.…”

Effect of isodillapiole on the expression of the insecticide resistance genes GSTE7 and CYP6N12 in Aedes aegypti from central Amazonia

“…Several studies using qRT-PCR have shown that genes of the GST and CYP families of Anopheles gambiae, Culex quinquefasciatus, and A. albopictus are super expressed, especially when induced by xenobiotic compounds (Edi et al, 2014;Hao et al, 2014;Liu et al, 2014). The genes GSTE7 and CYP6N12 have been linked to resistance to synthetic insecticides, such as DDT, temephos and pyrethroids (Lumjuan et al, 2011;Strode et al, 2012).…”