Abstract: The frequent and extensive use of insecticides leads to the evolution of insecticide resistance. It is well recognized that over-expression of cytochrome P450s involved in insecticide detoxification is one common and major mechanism of resistance to
various classes of insecticides in insects. However, the molecular mechanisms for overexpression of insecticide resistance-related P450 genes in insects have not been well identified until now. In the recent decade, with the development of biological science and technology, many significant advances have been achieved in this direction. In this article, an overview of the current knowledge with respect to expression regulation of insect cytochrome P450 genes was provided. In addition to gene duplication and amplification, up-regulation of P450s at the transcriptional level can be ascribed to the interaction between the cis-regulatory elements and the trans-acting factors. Transcription factors such as CncC, CREB and AhR directly regulate the expression of P450s. The G-protein-coupled receptors and their downstream effectors play indirect roles in the transcriptional regulation of P450 genes. The universality of the role of CncC:Maf/Keap1 in the expression regulation of P450s is supported by studies on a variety of insect species. Increasing reports confirm the involvement of microRNAs in the regulation of P450 expression. Current findings reveal the diversity of regulatory factors and signal transduction pathways, and the complexity of underlying mechanisms in the regulation of P450 expression.

Key words:  Insecticide resistance, cytochrome P450, transcription factor, regulatory pathway; cis-regulatory element, microRNA