Differential expression of CYP6A5 and CYP6A5v2 in pyrethroid‐resistant house flies, Musca domestica

Abstract

Two cytochrome P450 alleles, CYP6A5 and CYP6A5v2, were isolated from a pyrethroid-resistant house fly stain, ALHF. The two alleles shared 98% similarity in amino acid sequence. To understand the importance of these two alleles in resistance and examine the expression profile of the two alleles between resistant and susceptible strains, quantitative real-time PCR (qRT-PCR) was performed and compared with the Northern blot analysis. We found that qRT-PCR was an efficient method to characterize the expression profiles between these two sequence-closely-related P450 genes between resistant and susceptible houses flies. One of them, CYP6A5v2, was constitutively overexpressed in ALHF house flies compared with susceptible house fly strains. Moreover, this gene was predominantly expressed in the abdominal tissues of ALHF, in which the primary detoxification organs of insects are located. However, there was no significant difference in the expression of CYP6A5 between ALHF and susceptible house flies. The genetic linkage analysis was conducted to determine the possible link between the constitutively overexpressed CYP6A5v2 and insecticide resistance. CYP6A5v2 was mapped on autosome 5, which is correlated with the linkage of resistance in ALHF. Taken together, the study suggests the importance of CYP6A5v2 in increasing metabolic detoxification of insecticides in ALHF. The distinct expression of CYP6A5 and CYP6A5v2 in resistant and susceptible house flies implies the functional difference of theses two genes in house flies and suggests that they are two recently diverged P450 genes presented in a single organism.

Pyrethroid Resistance in Insects: Genes, Mechanisms, and Regulation

“…quinquefasciatus was examined because these genes overexpressed not only in resistant insects but also in adult stages. Although the expression of CYP6A5v2 was observed to be significantly higher in the abdominal tissue in both the susceptible CS and aabys flies and the resistant ALHF flies compared with their head+thorax tissues, this overexpression was far greater in both sets of tissues for resistant ALHF flies than in the tissues of susceptible flies (Zhu and Liu 2008). The expression of CYP6A36 was not significantly different between the head+thorax and abdomen tissues of the CS strain; lower in the head+thorax tissue than in the abdomen tissue of ALHF; and significantly higher in both tissues of the ALHF strain than in the CS strain (Zhu et al 2008a).…”

“…In addition, some insect P450 genes can be induced by exogenous compounds. Recently, our group has identified that multiple P450 genes are overexpressed in insecticide resistant house flies Musca domestica and mosquitoes Culex quinquefasciatus through both constitutive overexpression and induction by pyrethroids ( (Zhu and Liu 2008;Zhu et al 2008a;b;Liu et al 2011), suggesting that constitutive overexpression and induction are key factors for increased levels of detoxification of insecticides and insecticide resistance. Nevertheless, although their importance in insect physiology and toxicology is widely recognized, there are enormous gaps in our knowledge of insect P450s.…”

“…quinquefasciatus, comparing susceptible and resistant populations and the field parental population and their permethrin selected offspring. The differential expression patterns of all eight P450 genes, CYP4G13v1, CYP4D4v2, CYP4G2, CYP6A5v2, CYP6A36, CYP6A37, CYP6A38, and CYP28B1, were characterized for resistant ALHF and susceptible CS house fly strains and for different types of tissues using Northern blot analyses and quantitative real-time PCR (qRT-PCR) (Zhu and Liu 2008;Zhu et al 2008a;b). No significant difference in the expression of CYP4G13v1, CYP4D4v2, CYP4G2, CYP6A37, CYP6A38, and CYP28B1 between resistant ALHF and susceptible CS and aabys flies was observed, but CYP6A5v2 and CYP6A36 showed significant constitutive overexpression in the resistant ALHF strain.…”

“…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.…”

Allelic variants of cytochrome P450 monooxygenases: Constitutive and insecticide-mediated expression in a Malaysian strain of the dengue vector, Aedes aegypti (Diptera: Culicidae)

“…However, variants of the same P450 gene could also respond differently to insecticide pressure. The genes CYP6A5 and CYP6A5v2 have a protein sequence identity of 99% and according to Zhu & Liu (2008), while CYP6A5v2 was over-expressed in a pyrethroid resistant strain of house fl y compared to a susceptible strain, there was no signifi cant difference in expression of CYP6A5 in both strains. There was also a remarkable difference in the expression levels of two genes, CYP4D42v1 (3.2-fold) and CYP4D42v2 (7.0-fold) in permethrin selected Culex quinquefasciatus assessed using qPCR (Reid et al, 2012).…”