Cytochromes P450 and insecticide resistance

The cytochrome P450-dependent monooxygenases (monooxygenases) are an extrem ely important metabolic system involved in the catabolism and anabolism of xenobiotics and endogenous compounds. Monooxygenase-mediated metabolism is a common mechanism by which insects become resistant to insecticides;as evi denced by the numerous insect species and insecticides affected. This revie w begins by presenting background information about P450s, the role of mono oxygenases in insects, and the different techniques that have been used to isolate individual insect P450s. Next, insecticide resistance is briefly de scribed, and then historical information about monooxygenase-mediated insec ticide resistance is reviewed. For any case of monooxygenase-mediated resis tance, identification of the P450(s) involved, out of the dozens that are p resent in an insect, has proven very challenging. Therefore, the next secti on of the review focuses on the minimal criteria for establishing that a P4 50 is involved in resistance. This is followed by a comprehensive examinati on of the literature concerning the individual P450s that have been isolate d from insecticide resistant strains. In each case, the history of the stra in and the evidence for monooxygenase-mediated resistance are reviewed. The isolation and characterization of the P450(s) from the strain are then des cribed, and the evidence of whether or not the isolated P450(s) is involved in resistance is summarized. The remainder of the review summarizes our cu rrent knowledge of the molecular basis of monooxygenase-mediated resistance and the implications for the future. The importance of these studies for d evelopment of effective insecticide resistance management strategies is dis cussed. (C) 1999 Elsevier Science Ltd. All rights reserved.