Accumulation and metabolism of di(n-butyl) phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in mature wheat tissues and their effects on detoxification and the antioxidant system in grain

Abstract

Di(2-ethylhexyl) phthalate (DEHP) and di(n-butyl) phthalate (DBP) are the major phthalic acid esters to be used during the plastic manufacturing process; they have emerged as pollutants that result in serious environmental problems. However, their impacts on wheat at the reproductive stage remain unclear. Here, we examined the distribution of DEHP and DBP and their respective metabolites mono(2-ethylhexyl) phthalate (MEHP) and mono-n-butyl phthalate (MBP) in mature wheat, along with the mechanism of detoxification and oxidative burst in wheat grains under DBP and DEHP stress conditions in a pot experiment. High-performance liquid chromatography showed that the contents of DBP and DEHP, as well as their metabolites, i.e., MBP and MEHP, presented the highest values in the grain, followed by the stem, leaf, and root. Entry of DBP and DEHP into the grain from the soil induced the production of reactive oxygen species, accompanied by the upregulated expression and activity of the antioxidant enzymes (e.g., cytochrome P4503A4 and peroxidase). The metacaspase type I gene was also upregulated in response to DBP and DEHP stress in grains, which is indicative of programmed cell death to maintain normal physiological activities and to resist cell damage. DBP and DEHP stress-damaged cells in the grains underwent programmed cell death by upregulating the expression levels of the metacaspase type I gene. These results provide a new perspective for improving wheat tolerance to DBP and DEHP through the use of genetic engineering strategies.