Effects of Amino Acid Mutation in Cytochrome P450 (CYP96A146) of Descurainia sophia on the Metabolism and Resistance to Tribenuron-Methyl

Cytochrome P450 monooxygenases (P450s) play important roles in herbicide resistance. In this study, there are four amino acid mutations (F39Y, H163Y, S203A, and V361E) between CYP96A146-S and CYP96A146-R, which were cloned, respectively, from susceptible (S) and tribenuron-methyl-resistant (TR) Descurainia sophia. The Arabidopsis expressing CYP96A146-S or CYP96A146-R showed resistance to tribenuron-methyl, carfentrazone-ethyl, and oxyfluorfen, while Arabidopsis transformed with CYP96A146-R or CYP96A146 with any two or three mutations of H163Y, S203A, or V361E exhibited significantly higher resistance to tribenuron-methyl than Arabidopsis expressing CYP96A146-S. The metabolic rates of tribenuron-methyl were significantly faster in Arabidopsis expressing CYP96A146-R than that with CYP96A146-S. The molecular dynamics simulation demonstrated that amino acid mutations did not affect the domain of the HEM ring, which could significantly enhance the volume of the catalytic pocket in P450 (CYP96A146), thereby increasing the collision rate between the catalytic pocket and tribenuron-methyl. Hence, the amino acid mutations may be one of the mechanisms underlying P450-mediated herbicide resistance.