Cytochrome P450 Monooxygenases as a Tool for Metabolizing of Herbicides in Plants

ABSTRACT

Plants like most other organisms evolved a remarkable battery of metabolic reactions to metabolize many different xenobiotics. In recent years the use of biochemical and molecular technics associated with enzymatic techniques have greatly advanced our understanding of the metabolic reactions (oxidation, reduction, hydrolysis, conjugation, etc.) not only in plants. In addition recombinant DNA techniques allowed the isolation, cloning and expression in plants of a number of foreign genes, including foreign detoxification genes for tolerance to xenobiotic compounds. Cytochrome P450 are one of the major plant enzyme classes which mediate the oxidative degradation of xenobiotic chemicals, including herbicides._The transgenic tobacco and potato plants expressing CYP1A1 and its fused enzyme with yeast reductase showed tolerance to the herbicide chlorotoluron. Some of them are tolerant to the herbicides diuron and atrazine. The tolerance of the obtained transgenic plants seem to be due to the one and the same mechanism. Our results related to the bulgarian tobacco transgenic plants expressing cytochrome P450 monooxygenase genes showed tolerance to the herbicides chlorotoluron and chlorosulfuron. The herbicide chlorotoluron delayed the germination and development of Orobanche ramosa seeds in case of use of transgenic plants tolerant to the herbicide. New data were obtained about the state of photosystem II by measurement of chlorophyll fluorescence. The lower PSII activity in the control and transgenic plants after application of the herbicide chlorotoluron, increase more rapidly in transgenic plants after the nineth day. Its recovery is due to the better metabolization of the herbicide in the transgenic plants. The transgenic CytP450 plants with increased cyt monooxigenase activity tolerate better oxidative stress after herbicide treatment.