Pyrethroid Resistance in Insects: Genes, Mechanisms, and Regulation

Insecticides are the most important component in insect pest-control efforts worldwide. Pyrethroids are among the insecticides that have been most widely used for this purpose for many years because of their safe, cheap, effective and long-lasting nature (Bulter et al. 2011). However, the widespread development of insecticide resistance, especially pyrethroid resistance, and the fact that resistance to an insecticide generally confers cross-resistance to other insecticides has become an immense practical problem challenging the control of agriculturally, economically, and medically important insect pests and resulting in the rise of insect vector-borne diseases in many parts of the world (Zaim 2002; Bulter 2011). 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; 1996; 1997; 1998; 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. Three major mechanisms are involved in insecticide resistance: (1) increased metabolic detoxification of insecticides; (2) decreased sensitivity of the target proteins on which an insecticide acts, known as target site insensitivity; and (3) decreased cuticular penetration/or increased sequestration/storage. Gene overexpression, amplification, and structural mutations have been linked to insecticide resistance mechanisms in some insects, while transcriptional overexpression of genes in resistant insects appears to be a common determining event in the evolution of resistance in insects generally. Regulatory interaction