Cytochrome P450 monooxygenase specific activity reduction in wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis> induced by soil roxithromycin stress

Roxithromycin, as widely used medicine and livestock growth promoter, arouses concern because its occurrence and persistence in soil environments. However, effects of roxithromycin in higher plants are still vague. Accordingly, we hypothesized that roxithromycin-contaminated soil may exhibits ecotoxicological effects in wheat (Triticum aestivum). In this study, effects induced by a gradient concentration of roxithromycin stress (0.01, 0.1, 1, 10, and 100 mg·kg^–1) was investigated in a 7-d soil test in T. aestivum. Results indicated that the specific activity of cytochrome P450 (CYP450) monooxygenase was decreased dramatically with the concentration of roxithromycin in soil. The IC₅₀ value was 8.78 mg·kg^–1 of roxithromycin. On the contrary, the growth related endpoints (i.e., the germination percentage, the biomass and the height), the content related endpoints (i.e., soluble protein content and CYP450 content), and the superoxide dismutase (SOD) activity failed to reveal the roxithromycin-induced effects. Further analysis revealed that the CYP450 monooxygenase specific activity reduction was enzymatic mechanism mediated, other than oxidative stress induced. We conclude that the soil roxithromycin declined the CYP450 monooxygenase activity in T. aestivum by the inhibition of the enzymatic mechanism. Further efforts can include, but are not limited to, investigation of joint effects induced by combined exposure of roxithromycin and the pesticides and evaluation of the similar effects in other higher plants.