Metabolism and subcellular distribution of anthracene in tall fescue (Festuca arundinacea Schreb.)

Abstract

Understanding the uptake processes of organic contaminants by plants is essential when assessing crop contamination and subsequent human exposure. Unfortunately, limited information is available on plant metabolism and subcellular distribution of polycyclic aromatic hydrocarbons (PAHs), a group of highly toxic organic contaminants with carcinogenic, mutagenic, and teratogenic properties. Thus we seek to investigate the metabolism and intracellular distribution of PAH in tall fescue (Festuca arundinacea Schreb.). This work was conducted utilizing greenhouse hydroponical experiments. Seedlings of tall fescue were firstly cultured in half-strength Hoagland solution with anthracene (ANT). Then treated plants were removed from the ANT-spiked solution, and transplanted into solutions free of ANT. After 0–16 days, the seedlings were sampled and prepared for ANT analysis. Seedlings were washed using Milli-Q water and then separated into different parts to measure ANT distributions at the subcellular level. ANT concentrations and dissipation amounts in root and shoot of tall fescue decreased in 0–16 days after transplantation from an ANT-spiked culture solution to a solution free of PAH, revealing ANT metabolism in the plant. The accumulation of the examined primary metabolites of ANT, i.e., anthrone and anthraquinone, against time also supported plant metabolism of ANT. About 10 % of ANT resided in the plants at 8–16 days due to the formation of ANT-bound residues with plant tissues. ANT concentrations in the cell walls and organelles of plant roots and shoots decreased significantly during the 16-day period. Cell walls and organelles were the dominant storage compartments for ANT and anthraquinone in plants at 16 days, whereas the distribution of anthrone at 16 days in root cells was ordered as cell organelles >cell soluble fraction >cell wall and in shoot cells as cell soluble fraction >> cell organelle ≅ cell wall. Although the organelle content is smaller, the concentrations of ANT and metabolites in the organelle fraction were much higher than those in cell walls. This was a primary investigation into the metabolism and intracellular distribution of PAH in plant. We demonstrated the metabolism of ANT in tall fescue based on the observed reduced concentrations, dissipated amounts, and detected metabolites. ANT and its metabolites were distributed into the cell water-soluble fraction, cell walls, and organelles. Results of this work will enhance the understanding of PAH transfer and transformation in plants and will be valuable for risk assessments of plant contamination at polluted sites.