Detrimental impacts of concomitant application of cadmium and pesticides are ameliorated by 24-epibrassinolide through alteration in oxidative status and CYP genes expression in Zea mays L.

Abstract

The ameliorative impact of 24-epibrassinolide (EBL) was assessed under toxicity of cadmium (Cd) and three different pesticides including diazinon (DZ), imidacloprid (IMI), and chlorpyrifos (CPS) in maize plants. Maize seeds were pre-treated with 0.01 μM of EBL and grown in soil contaminated with 100 μM Cd for one month. Then, at five fully expanded leaf stage, plants received DZ, IMI, and CPS pesticides separately by foliar spray and were harvested five days later. The EBL seed primed plants, grown in soil contaminated with Cd and exposed to pesticides, exhibited higher deleterious photosynthesis (Pn) and stomatal conductivity (Gs) compared to un-EBL-treated plants. A considerable decrease was observed in the pesticide's residue and Cd, MDA and H2O2 contents of EBL + Cd + Pesticide treated plants compared to the Cd + Pesticide groups plants. Higher phenol, flavonoid and protein contents, as well as increment in SOD, CAT, POD, APX, PAL, GST, and GR enzymes activity were detected in EBL + Cd + Pesticide groups compared to the plants imposed with Cd + Pesticides. The expression analyses of four CYP family members including CYP71C1, CYP71C3v2, CYP72A5, and CYP81A9 revealed downregulation under Cd and Cd + pesticides treatments, while EBL seed priming highly induced transcript abundance of CYP71C1 (EBL + Cd + IMI); CYP71C3v2 (EBL + Cd + DZ & EBL + Cd + IMI) and CYP81A9 (EBL + Cd + DZ & EBL + Cd + CPS), specifically. The higher mRNA accumulation of CYP72A5 gene was exhibited under all three different EBL + Cd + pesticides treatments. The 24-epibrassinolide alleviates the adverse impacts of Cd and pesticides via the activation of enzymatic and non-enzymatic components to eliminate ROS through the up-regulation of CYP genes. This facilitates conjugation of glutathione to pesticides residue, leading to their rapid transportation into the vacuole or out of the membrane.